@article{pmid26439718,

title = {Huntington Disease: Molecular Diagnostics Approach},

author = {Murat Bastepe and Winnie Xin},

doi = {10.1002/0471142905.hg0926s87},

issn = {1934-8258},

year  = {2015},

date = {2015-10-01},

journal = {Curr Protoc Hum Genet},

volume = {87},

pages = {9.26.1--9.26.23},

abstract = {Huntington disease (HD) is caused by expansion of a CAG trinucleotide repeat in the first exon of the Huntingtin (HTT) gene. Molecular testing of Huntington disease for diagnostic confirmation and disease prediction requires detection of the CAG repeat expansion. There are three main types of HD genetic testing: (1) diagnostic testing to confirm or rule out disease, (2) presymptomatic testing to determine whether an at-risk individual inherited the expanded allele, and (3) prenatal testing to determine whether the fetus has inherited the expanded allele. This unit includes protocols that describe the complementary use of polymerase chain reactions (PCR) and Southern blot hybridization to accurately measure the CAG trinucleotide repeat size and interpret the test results. In addition, an indirect linkage analysis that does not reveal the unwanted parental HD status in a prenatal testing will also be discussed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid26307011,

title = {The G protein α subunit variant XLαs promotes inositol 1,4,5-trisphosphate signaling and mediates the renal actions of parathyroid hormone in vivo},

author = {Qing He and Yan Zhu and Braden A Corbin and Antonius Plagge and Murat Bastepe},

doi = {10.1126/scisignal.aaa9953},

issn = {1937-9145},

year  = {2015},

date = {2015-08-01},

journal = {Sci Signal},

volume = {8},

number = {391},

pages = {ra84},

abstract = {GNAS, which encodes the stimulatory G protein (heterotrimeric guanine nucleotide-binding protein) α subunit (Gαs), also encodes a large variant of Gαs termed extra-large α subunit (XLαs), and alterations in XLαs abundance or activity are implicated in various human disorders. Although XLαs, like Gαs, stimulates generation of the second messenger cyclic adenosine monophosphate (cAMP), evidence suggests that XLαs and Gαs have opposing effects in vivo. We investigated the role of XLαs in mediating signaling by parathyroid hormone (PTH), which activates a G protein-coupled receptor (GPCR) that stimulates both Gαs and Gαq/11 in renal proximal tubules to maintain phosphate and vitamin D homeostasis. At postnatal day 2 (P2), XLαs knockout (XLKO) mice exhibited hyperphosphatemia, hypocalcemia, and increased serum concentrations of PTH and 1,25-dihydroxyvitamin D. The ability of PTH to reduce serum phosphate concentrations was impaired, and the abundance of the sodium phosphate cotransporter Npt2a in renal brush border membranes was reduced in XLKO mice, whereas PTH-induced cAMP excretion in the urine was modestly increased. Basal and PTH-stimulated production of inositol 1,4,5-trisphosphate (IP3), which is the second messenger produced by Gαq/11 signaling, was repressed in renal proximal tubules from XLKO mice. Crossing of XLKO mice with mice overexpressing XLαs specifically in renal proximal tubules rescued the phenotype of the XLKO mice. Overexpression of XLαs in HEK 293 cells enhanced IP3 generation in unstimulated cells and in cells stimulated with PTH or thrombin, which acts through a Gq/11-coupled receptor. Together, our findings suggest that XLαs enhances Gq/11 signaling to mediate the renal actions of PTH during early postnatal development.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid25851935,

title = {GNAS Spectrum of Disorders},

author = {Serap Turan and Murat Bastepe},

doi = {10.1007/s11914-015-0268-x},

issn = {1544-2241},

year  = {2015},

date = {2015-06-01},

journal = {Curr Osteoporos Rep},

volume = {13},

number = {3},

pages = {146--158},

abstract = {The GNAS complex locus encodes the alpha-subunit of the stimulatory G protein (Gsα), a ubiquitous signaling protein mediating the actions of many hormones, neurotransmitters, and paracrine/autocrine factors via generation of the second messenger cAMP. GNAS gives rise to other gene products, most of which exhibit exclusively monoallelic expression. In contrast, Gsα is expressed biallelically in most tissues; however, paternal Gsα expression is silenced in a small number of tissues through as-yet-poorly understood mechanisms that involve differential methylation within GNAS. Gsα-coding GNAS mutations that lead to diminished Gsα expression and/or function result in Albright's hereditary osteodystrophy (AHO) with or without hormone resistance, i.e., pseudohypoparathyroidism type-Ia/Ic and pseudo-pseudohypoparathyroidism, respectively. Microdeletions that alter GNAS methylation and, thereby, diminish Gsα expression in tissues in which the paternal Gsα allele is normally silenced also cause hormone resistance, which occurs typically in the absence of AHO, a disorder termed pseudohypoparathyroidism type-Ib. Mutations of GNAS that cause constitutive Gsα signaling are found in patients with McCune-Albright syndrome, fibrous dysplasia of bone, and different endocrine and non-endocrine tumors. Clinical features of these diseases depend significantly on the parental allelic origin of the GNAS mutation, reflecting the tissue-specific paternal Gsα silencing. In this article, we review the pathogenesis and the phenotypes of these human diseases.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid25464124,

title = {Evidence of hormone resistance in a pseudo-pseudohypoparathyroidism patient with a novel paternal mutation in GNAS},

author = {Serap Turan and Susanne Thiele and Olta Tafaj and Bettina Brix and Zeynep Atay and Saygin Abali and Belma Haliloglu and Abdullah Bereket and Murat Bastepe},

doi = {10.1016/j.bone.2014.10.006},

issn = {1873-2763},

year  = {2015},

date = {2015-02-01},

journal = {Bone},

volume = {71},

pages = {53--57},

abstract = {CONTEXT: Loss-of-function GNAS mutations lead to hormone resistance and Albright's hereditary osteodystrophy (AHO) when maternally inherited, i.e. pseudohypoparathyroidism-Ia (PHPIa), but cause AHO alone when located on the paternal allele, i.e. pseudoPHP (PPHP).nnOBJECTIVE: We aimed to establish the molecular diagnosis in a patient with AHO and evidence of hormone resistance.nnCASE: The patient is a female who presented at the age of 13.5years with short stature and multiple AHO features. No evidence for TSH or gonadotropin-resistance was present. Serum calcium and vitamin D levels were normal. However, serum PTH was elevated on multiple occasions (64-178pg/mL, normal: 9-52) and growth hormone response to clonidine or L-DOPA was blunted, suggesting hormone resistance and PHP-Ia. The patient had diminished erythrocyte Gsα activity and a novel heterozygous GNAS mutation (c.328 G>C; p.A109P). The mother lacked the mutation, and the father's DNA was not available. Hence, a diagnosis of PPHP also appeared possible, supported by low birth weight and a lack of AHO features associated predominantly with PHP-Ia, i.e. obesity and cognitive impairment. To determine the parental origin of the mutation, we amplified the paternally expressed A/B and biallelically expressed Gsα transcripts from the patient's peripheral blood RNA. While both wild-type and mutant nucleotides were detected in the Gsα amplicon, only the mutant nucleotide was present in the A/B amplicon, indicating that the mutation was paternal.nnCONCLUSION: These findings suggest that PTH and other hormone resistance may not be an exclusive feature of PHP-Ia and could also be observed in patients with PPHP.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid23956044,

title = {Postnatal establishment of allelic Gαs silencing as a plausible explanation for delayed onset of parathyroid hormone resistance owing to heterozygous Gαs disruption},

author = {Serap Turan and Eduardo Fernandez-Rebollo and Cumhur Aydin and Teuta Zoto and Monica Reyes and George Bounoutas and Min Chen and Lee S Weinstein and Reinhold G Erben and Vladimir Marshansky and Murat Bastepe},

doi = {10.1002/jbmr.2070},

issn = {1523-4681},

year  = {2014},

date = {2014-03-01},

journal = {J Bone Miner Res},

volume = {29},

number = {3},

pages = {749--760},

abstract = {Pseudohypoparathyroidism type-Ia (PHP-Ia), characterized by renal proximal tubular resistance to parathyroid hormone (PTH), results from maternal mutations of GNAS that lead to loss of α-subunit of the stimulatory G protein (Gαs) activity. Gαs expression is paternally silenced in the renal proximal tubule, and this genomic event is critical for the development of PTH resistance, as patients display impaired hormone action only if the mutation is inherited maternally. The primary clinical finding of PHP-Ia is hypocalcemia, which can lead to various neuromuscular defects including seizures. PHP-Ia patients frequently do not present with hypocalcemia until after infancy, but it has remained uncertain whether PTH resistance occurs in a delayed fashion. Analyzing reported cases of PHP-Ia with documented GNAS mutations and mice heterozygous for disruption of Gnas, we herein determined that the manifestation of PTH resistance caused by the maternal loss of Gαs, ie, hypocalcemia and elevated serum PTH, occurs after early postnatal life. To investigate whether this delay could reflect gradual development of paternal Gαs silencing, we then analyzed renal proximal tubules isolated by laser capture microdissection from mice with either maternal or paternal disruption of Gnas. Our results revealed that, whereas expression of Gαs mRNA in this tissue is predominantly from the maternal Gnas allele at weaning (3 weeks postnatal) and in adulthood, the contributions of the maternal and paternal Gnas alleles to Gαs mRNA expression are equal at postnatal day 3. In contrast, we found that paternal Gαs expression is already markedly repressed in brown adipose tissue at birth. Thus, the mechanisms silencing the paternal Gαs allele in renal proximal tubules are not operational during early postnatal development, and this finding correlates well with the latency of PTH resistance in patients with PHP-Ia.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid23392091,

title = {Genetics and epigenetics of parathyroid hormone resistance},

author = {Murat Bastepe},

doi = {10.1159/000342494},

issn = {1662-2979},

year  = {2013},

date = {2013-01-01},

journal = {Endocr Dev},

volume = {24},

pages = {11--24},

abstract = {End-organ resistance to the actions of parathyroid hormone (PTH) is defined as pseudohypoparathyroidism (PHP). Described originally by Fuller Albright and his colleagues in early 1940s, this rare genetic disease is subclassified into two types according to the nephrogenous response to the administration of biologically active PTH. In type I, the PTH-induced urinary excretion of both phosphate and cyclic AMP (cAMP) is blunted. In type II, only the PTH-induced urinary excretion of phosphate is blunted, while the cAMP response is unimpaired. Different subtypes of PHP type I have been described based on the existence of additional clinical features, such as resistance to other hormones and Albright's hereditary osteodystrophy, and underlying molecular defects. Genetic mutations responsible for the different subtypes of PHP type I involve the GNAS complex locus, an imprinted gene encoding the α-subunit of the stimulatory G protein (Gsα) and several other transcripts that are expressed in a parent-of-origin specific manner. Mutations in Gsα-coding GNAS exons cause PHP-Ia and, in some cases, PHP-Ic, while mutations that disrupt the imprinting of GNAS lead to PHP-Ib. PHP type II is less well characterized with respect to its molecular cause. Recently, however, mutations in PRKAR1A, a regulatory subunit of the cAMP-dependent protein kinase, have been identified in several cases of PTH and other hormone resistance and skeletal dysplasia that are considered to be affected by PHP type II due to unimpaired urinary excretion of cAMP following PTH administration.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid24107509,

title = {The GNAS complex locus and human diseases associated with loss-of-function mutations or epimutations within this imprinted gene},

author = {Serap Turan and Murat Bastepe},

doi = {10.1159/000355384},

issn = {1663-2826},

year  = {2013},

date = {2013-01-01},

journal = {Horm Res Paediatr},

volume = {80},

number = {4},

pages = {229--241},

abstract = {GNAS is a complex imprinted locus leading to several different gene products that show exclusive monoallelic expression. GNAS also encodes the α-subunit of the stimulatory G protein (Gsα), a ubiquitously expressed signaling protein that is essential for the actions of many hormones and other endogenous molecules. Gsα is expressed biallelically in most tissues but its expression is silenced from the paternal allele in a small number of tissues. The tissue-specific paternal silencing of Gsα results in different parent-of-origin-specific phenotypes in patients who carry inactivating GNAS mutations. In this paper, we review the GNAS complex locus and discuss how disruption of Gsα expression and the expression of other GNAS products shape the phenotypes of human disorders caused by mutations in this gene.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid23977191,

title = {The β-blocker Nebivolol Is a GRK/β-arrestin biased agonist},

author = {Catherine E Erickson and Rukhsana Gul and Christopher P Blessing and Jenny Nguyen and Tammy Liu and Lakshmi Pulakat and Murat Bastepe and Edwin K Jackson and Bradley T Andresen},

doi = {10.1371/journal.pone.0071980},

issn = {1932-6203},

year  = {2013},

date = {2013-01-01},

journal = {PLoS One},

volume = {8},

number = {8},

pages = {e71980},

abstract = {Nebivolol, a third generation β-adrenoceptor (β-AR) antagonist (β-blocker), causes vasodilation by inducing nitric oxide (NO) production. The mechanism via which nebivolol induces NO production remains unknown, resulting in the genesis of much of the controversy regarding the pharmacological action of nebivolol. Carvedilol is another β-blocker that induces NO production. A prominent pharmacological mechanism of carvedilol is biased agonism that is independent of Gαs and involves G protein-coupled receptor kinase (GRK)/β-arrestin signaling with downstream activation of the epidermal growth factor receptor (EGFR) and extracellular signal-regulated kinase (ERK). Due to the pharmacological similarities between nebivolol and carvedilol, we hypothesized that nebivolol is also a GRK/β-arrestin biased agonist. We tested this hypothesis utilizing mouse embryonic fibroblasts (MEFs) that solely express β2-ARs, and HL-1 cardiac myocytes that express β1- and β2-ARs and no detectable β3-ARs. We confirmed previous reports that nebivolol does not significantly alter cAMP levels and thus is not a classical agonist. Moreover, in both cell types, nebivolol induced rapid internalization of β-ARs indicating that nebivolol is also not a classical β-blocker. Furthermore, nebivolol treatment resulted in a time-dependent phosphorylation of ERK that was indistinguishable from carvedilol and similar in duration, but not amplitude, to isoproterenol. Nebivolol-mediated phosphorylation of ERK was sensitive to propranolol (non-selective β-AR-blocker), AG1478 (EGFR inhibitor), indicating that the signaling emanates from β-ARs and involves the EGFR. Furthermore, in MEFs, nebivolol-mediated phosphorylation of ERK was sensitive to pharmacological inhibition of GRK2 as well as siRNA knockdown of β-arrestin 1/2. Additionally, nebivolol induced redistribution of β-arrestin 2 from a diffuse staining pattern into more intense punctate spots. We conclude that nebivolol is a β2-AR, and likely β1-AR, GRK/β-arrestin biased agonist, which suggests that some of the unique clinically beneficial effects of nebivolol may be due to biased agonism at β1- and/or β2-ARs.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid23087324,

title = {De novo STX16 deletions: an infrequent cause of pseudohypoparathyroidism type Ib that should be excluded in sporadic cases},

author = {Serap Turan and Jaakko Ignatius and Jukka S Moilanen and Outi Kuismin and Helen Stewart and Nicholas P Mann and Agnès Linglart and Murat Bastepe and Harald Jüppner},

doi = {10.1210/jc.2012-2920},

issn = {1945-7197},

year  = {2012},

date = {2012-12-01},

journal = {J Clin Endocrinol Metab},

volume = {97},

number = {12},

pages = {E2314--E2319},

abstract = {CONTEXT: Maternally inherited 3-kb STX16 deletions cause autosomal dominant pseudohypoparathyroidism type Ib (PHP-Ib) characterized by PTH resistance with loss of methylation restricted to the GNAS exon A/B.nnOBJECTIVE: The objective of the study was to search for the 3-kb STX16 deletion and to establish haplotypes for the GNAS region for two PHP-Ib patients and their families.nnSETTING: The study was conducted at a research laboratory and tertiary care hospitals.nnPATIENTS: The index cases presented at the ages 8 and 9.5 yr, respectively, with hypocalcemia, hyperphosphatemia, and elevated PTH.nnINTERVENTIONS: There were no interventions.nnRESULTS: DNA analyses of the index cases revealed an isolated loss of the GNAS exon A/B methylation and the 3-kb STX16 deletion. In the first family, the patient's healthy mother and sister showed no genetic or epigenetic abnormality, yet microsatellite analysis of the GNAS region indicated that both siblings share the same maternal allele, with the exception of an allelic loss for marker 261P9-CA1 (located within STX16), leading to the conclusion that a de novo mutation had occurred on the maternal allele. In the second family, three siblings of the index case are also affected, and an analysis of their DNA revealed the 3-kb STX16 deletion, which was also found in the healthy mother and a maternal uncle. Analysis of the siblings of the deceased maternal grandfather and some of their descendants excluded the 3-kb STX16 deletion, but haplotype analysis of the GNAS region suggested that he had acquired the mutation de novo.nnCONCLUSIONS: De novo 3-kb STX16 deletions, reported only once previously, are infrequent but should be excluded in all cases of PHP-Ib, even when the family history is negative for an inherited form of this disorder.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid22730013,

title = {Relative functions of Gαs and its extra-large variant XLαs in the endocrine system},

author = {M Bastepe},

doi = {10.1055/s-0032-1316331},

issn = {1439-4286},

year  = {2012},

date = {2012-09-01},

journal = {Horm Metab Res},

volume = {44},

number = {10},

pages = {732--740},

abstract = {Gαs is a ubiquitous signaling protein necessary for the actions of many neurotransmitters, hormones, and autocrine/paracrine factors. Loss-of-function mutations within the gene encoding Gαs, GNAS, are responsible for multiple human diseases, including Albright's Hereditary Osteodystrophy, progressive osseous heteroplasia, and pseudohypoparathyroidism. Gain-of-function mutations in the same gene are found in various endocrine and nonendocrine tumors and in patients with McCune-Albright Syndrome and fibrous dysplasia of bone. In addition to Gαs, GNAS gives rise to multiple additional coding and noncoding transcripts. Among those, XLαs is a paternally expressed product that is partially identical to Gαs. This article reviews the cellular actions of Gαs and XLαs, focusing on the significance of XLαs relative to Gαs in mammalian physiology and human disease.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid22496590,

title = {Loss of XLαs (extra-large αs) imprinting results in early postnatal hypoglycemia and lethality in a mouse model of pseudohypoparathyroidism Ib},

author = {Eduardo Fernández-Rebollo and Akira Maeda and Monica Reyes and Serap Turan and Leopold F Fröhlich and Antonius Plagge and Gavin Kelsey and Harald Jüppner and Murat Bastepe},

doi = {10.1073/pnas.1117608109},

issn = {1091-6490},

year  = {2012},

date = {2012-04-01},

journal = {Proc Natl Acad Sci U S A},

volume = {109},

number = {17},

pages = {6638--6643},

abstract = {Maternal deletion of the NESP55 differentially methylated region (DMR) (delNESP55/ASdel3-4(m), delNAS(m)) from the GNAS locus in humans causes autosomal dominant pseudohypoparathyroidism type Ib (AD-PHP-Ib(delNASm)), a disorder of proximal tubular parathyroid hormone (PTH) resistance associated with loss of maternal GNAS methylation imprints. Mice carrying a similar, maternally inherited deletion of the Nesp55 DMR (ΔNesp55(m)) replicate these Gnas epigenetic abnormalities and show evidence for PTH resistance, yet these mice demonstrate 100% mortality during the early postnatal period. We investigated whether the loss of extralarge αs (XLαs) imprinting and the resultant biallelic expression of XLαs are responsible for the early postnatal lethality in ΔNesp55(m) mice. First, we found that ΔNesp55(m) mice are hypoglycemic and have reduced stomach-to-body weight ratio. We then generated mice having the same epigenetic abnormalities as the ΔNesp55(m) mice but with normalized XLαs expression due to the paternal disruption of the exon giving rise to this Gnas product. These mice (ΔNesp55(m)/Gnasxl(m+/p-)) showed nearly 100% survival up to postnatal day 10, and a substantial number of them lived to adulthood. The hypoglycemia and reduced stomach-to-body weight ratio observed in 2-d-old ΔNesp55(m) mice were rescued in the ΔNesp55(m)/Gnasxl(m+/p-) mice. Surviving double-mutant animals had significantly reduced Gαs mRNA levels and showed hypocalcemia, hyperphosphatemia, and elevated PTH levels, thus providing a viable model of human AD-PHP-Ib. Our findings show that the hypoglycemia and early postnatal lethality caused by the maternal deletion of the Nesp55 DMR result from biallelic XLαs expression. The double-mutant mice will help elucidate the pathophysiological mechanisms underlying AD-PHP-Ib.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid21890629,

title = {Extra-long Gαs variant XLαs protein escapes activation-induced subcellular redistribution and is able to provide sustained signaling},

author = {Zun Liu and Serap Turan and Vanessa L Wehbi and Jean-Pierre Vilardaga and Murat Bastepe},

doi = {10.1074/jbc.M111.240150},

issn = {1083-351X},

year  = {2011},

date = {2011-11-01},

journal = {J Biol Chem},

volume = {286},

number = {44},

pages = {38558--38569},

abstract = {Murine models indicate that Gαs and its extra-long variant XLαs, both of which are derived from GNAS, markedly differ regarding their cellular actions, but these differences are unknown. Here we investigated activation-induced trafficking of Gαs and XLαs, using immunofluorescence microscopy, cell fractionation, and total internal reflection fluorescence microscopy. In transfected cells, XLαs remained localized to the plasma membrane, whereas Gαs redistributed to the cytosol after activation by GTPase-inhibiting mutations, cholera toxin treatment, or G protein-coupled receptor agonists (isoproterenol or parathyroid hormone (PTH)(1-34)). Cholera toxin treatment or agonist (isoproterenol or pituitary adenylate cyclase activating peptide-27) stimulation of PC12 cells expressing Gαs and XLαs endogenously led to an increased abundance of Gαs, but not XLαs, in the soluble fraction. Mutational analyses revealed two conserved cysteines and the highly charged domain as being critically involved in the plasma membrane anchoring of XLαs. The cAMP response induced by M-PTH(1-14), a parathyroid hormone analog, terminated quickly in HEK293 cells stably expressing the type 1 PTH/PTH-related peptide receptor, whereas the response remained maximal for at least 6 min in cells that co-expressed the PTH receptor and XLαs. Although isoproterenol-induced cAMP response was not prolonged by XLαs expression, a GTPase-deficient XLαs mutant found in certain tumors and patients with fibrous dysplasia of bone and McCune-Albright syndrome generated more basal cAMP accumulation in HEK293 cells and caused more severe impairment of osteoblastic differentiation of MC3T3-E1 cells than the cognate Gαs mutant (gsp oncogene). Thus, activated XLαs and Gαs traffic differently, and this may form the basis for the differences in their cellular actions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid21713996,

title = {Parathyroid hormone signaling via Gαs is selectively inhibited by an NH(2)-terminally truncated Gαs: implications for pseudohypoparathyroidism},

author = {Svetlana Puzhko and Cynthia Gates Goodyer and Mohammad Amin Kerachian and Lucie Canaff and Madhusmita Misra and Harald Jüppner and Murat Bastepe and Geoffrey N Hendy},

doi = {10.1002/jbmr.461},

issn = {1523-4681},

year  = {2011},

date = {2011-10-01},

journal = {J Bone Miner Res},

volume = {26},

number = {10},

pages = {2473--2485},

abstract = {Pseudohypoparathyroid patients have resistance predominantly to parathyroid hormone (PTH), and here we have examined the ability of an alternative Gαs-related protein to inhibit Gαs activity in a hormone-selective manner. We tested whether the GNAS exon A/B-derived NH(2)-terminally truncated (Tr) αs protein alters stimulation of adenylate cyclase by the PTH receptor (PTHR1), the thyroid-stimulating hormone (TSH) receptor (TSHR), the β(2)-adrenergic receptor (β(2)AR), or the AVP receptor (V2R). HEK293 cells cotransfected with receptor and full-length (FL) Gαs ± Tr αs protein expression vectors were stimulated with agonists (PTH [10(-7) to 10(-9)  M], TSH [1 to 100 mU], isoproterenol [10(-6) to 10(-8)  M], or AVP [10(-6) to 10(-8)  M]). Following PTH stimulation, HEK293 cells cotransfected with PTHR1 + FL Gαs + Tr αs had a significantly lower cAMP response than those transfected with only PTHR1 + FL Gαs. Tr αs also exerted an inhibitory effect on the cAMP levels stimulated by TSH via the TSHR but had little or no effect on isoproterenol or AVP acting via β(2)AR or V2R, respectively. These differences mimic the spectrum of hormone resistance in pseudohypoparathyroidism type 1a (PHP-1a) and type 1b (PHP-1b) patients. In opossum kidney (OK) cells, endogenously expressing the PTHR1 and β(2)AR, the exogenous expression of Tr αs at a level similar to endogenous FL Gαs resulted in blunting of the cAMP response to PTH, whereas that to isoproterenol was unaltered. A pseudopseudohypoparathyroid patient with Albright hereditary osteodystrophy harbored a de novo paternally inherited M1I Gαs mutation. Similar maternally inherited mutations at the initiation codon have been identified previously in PHP-1a patients. The M1I αs mutant (lacking the first 59 amino acids of Gαs) blunted the increase in cAMP levels stimulated via the PTHR1 in both HEK293 and OK cells similar to the Tr αs protein. Thus NH(2)-terminally truncated forms of Gαs may contribute to the pathogenesis of pseudohypoparathyroidism by inhibiting the activity of Gαs itself in a GPCR selective manner.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid21804192,

title = {Gsα enhances commitment of mesenchymal progenitors to the osteoblast lineage but restrains osteoblast differentiation in mice},

author = {Joy Y Wu and Piia Aarnisalo and Murat Bastepe and Partha Sinha and Keertik Fulzele and Martin K Selig and Min Chen and Ingrid J Poulton and Louise E Purton and Natalie A Sims and Lee S Weinstein and Henry M Kronenberg},

doi = {10.1172/JCI46406},

issn = {1558-8238},

year  = {2011},

date = {2011-09-01},

journal = {J Clin Invest},

volume = {121},

number = {9},

pages = {3492--3504},

abstract = {The heterotrimeric G protein subunit Gsα stimulates cAMP-dependent signaling downstream of G protein-coupled receptors. In this study, we set out to determine the role of Gsα signaling in cells of the early osteoblast lineage in vivo by conditionally deleting Gsα from osterix-expressing cells. This led to severe osteoporosis with fractures at birth, a phenotype that was found to be the consequence of impaired bone formation rather than increased resorption. Osteoblast number was markedly decreased and osteogenic differentiation was accelerated, resulting in the formation of woven bone. Rapid differentiation of mature osteoblasts into matrix-embedded osteocytes likely contributed to depletion of the osteoblast pool. In addition, the number of committed osteoblast progenitors was diminished in both bone marrow stromal cells (BMSCs) and calvarial cells of mutant mice. In the absence of Gsα, expression of sclerostin and dickkopf1 (Dkk1), inhibitors of canonical Wnt signaling, was markedly increased; this was accompanied by reduced Wnt signaling in the osteoblast lineage. In summary, we have shown that Gsα regulates bone formation by at least two distinct mechanisms: facilitating the commitment of mesenchymal progenitors to the osteoblast lineage in association with enhanced Wnt signaling; and restraining the differentiation of committed osteoblasts to enable production of bone of optimal mass, quality, and strength.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid21523828,

title = {Exclusion of the GNAS locus in PHP-Ib patients with broad GNAS methylation changes: evidence for an autosomal recessive form of PHP-Ib?},

author = {Eduardo Fernández-Rebollo and Guiomar Pérez de Nanclares and Beatriz Lecumberri and Serap Turan and Emma Anda and Gustavo Pérez-Nanclares and Denice Feig and Serena Nik-Zainal and Murat Bastepe and Harald Jüppner},

doi = {10.1002/jbmr.408},

issn = {1523-4681},

year  = {2011},

date = {2011-08-01},

journal = {J Bone Miner Res},

volume = {26},

number = {8},

pages = {1854--1863},

abstract = {Most patients with autosomal dominant pseudohypoparathyroidism type Ib (AD-PHP-Ib) carry maternally inherited microdeletions upstream of GNAS that are associated with loss of methylation restricted to GNAS exon A/B. Only few AD-PHP-Ib patients carry microdeletions within GNAS that are associated with loss of all maternal methylation imprints. These epigenetic changes are often indistinguishable from those observed in patients affected by an apparently sporadic PHP-Ib form that has not yet been defined genetically. We have now investigated six female patients affected by PHP-Ib (four unrelated and two sisters) with complete or almost complete loss of GNAS methylation, whose healthy children (11 in total) showed no epigenetic changes at this locus. Analysis of several microsatellite markers throughout the 20q13 region made it unlikely that PHP-Ib is caused in these patients by large deletions involving GNAS or by paternal uniparental isodisomy or heterodisomy of chromosome 20 (patUPD20). Microsatellite and single-nucleotide variation (SNV) data revealed that the two affected sisters share their maternally inherited GNAS alleles with unaffected relatives that lack evidence for abnormal GNAS methylation, thus excluding linkage to this locus. Consistent with these findings, healthy children of two unrelated sporadic PHP-Ib patients had inherited different maternal GNAS alleles, also arguing against linkage to this locus. Based on our data, it appears plausible that some forms of PHP-Ib are caused by homozygous or compound heterozygous mutation(s) in an unknown gene involved in establishing or maintaining GNAS methylation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid21488135,

title = {Functional characterization of GNAS mutations found in patients with pseudohypoparathyroidism type Ic defines a new subgroup of pseudohypoparathyroidism affecting selectively Gsα-receptor interaction},

author = {Susanne Thiele and Luisa de Sanctis and Ralf Werner and Joachim Grötzinger and Cumhur Aydin and Harald Jüppner and Murat Bastepe and Olaf Hiort},

doi = {10.1002/humu.21489},

issn = {1098-1004},

year  = {2011},

date = {2011-06-01},

journal = {Hum Mutat},

volume = {32},

number = {6},

pages = {653--660},

abstract = {Pseudohypoparathyroidism type Ia (PHPIa) is caused by GNAS mutations leading to deficiency of the α-subunit of stimulatory G proteins (Gsα) that mediate signal transduction of G protein-coupled receptors via cAMP. PHP type Ic (PHPIc) and PHPIa share clinical features of Albright hereditary osteodystrophy (AHO); however, in vitro activity of solubilized Gsα protein is normal in PHPIc but reduced in PHPIa. We screened 32 patients classified as PHPIc for GNAS mutations and identified three mutations (p.E392K, p.E392X, p.L388R) in four unrelated families. These and one novel mutation associated with PHPIa (p.L388P) were introduced into a pcDNA3.1(-) expression vector encoding Gsα wild-type and expressed in a Gsα-null cell line (Gnas(E2-/E2-) ). To investigate receptor-mediated cAMP accumulation, we stimulated the endogenous expressed β(2) -adrenergic receptor, or the coexpressed PTH or TSH receptors, and measured the synthesized cAMP by RIA. The results were compared to receptor-independent cholera toxin-induced cAMP accumulation. Each of the mutants associated with PHPIc significantly reduced or completely disrupted receptor-mediated activation, but displayed normal receptor-independent activation. In contrast, PHPIa associated p.L388P disrupted both receptor-mediated activation and receptor-independent activation. We present a new subgroup of PHP that is caused by Gsα deficiency and selectively affects receptor coupling functions of Gsα.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid21303955,

title = {Transgenic overexpression of the extra-large Gsα variant XLαs enhances Gsα-mediated responses in the mouse renal proximal tubule in vivo},

author = {Zun Liu and Hiroko Segawa and Cumhur Aydin and Monica Reyes and Reinhold G Erben and Lee S Weinstein and Min Chen and Vladimir Marshansky and Leopold F Fröhlich and Murat Bastepe},

doi = {10.1210/en.2010-1034},

issn = {1945-7170},

year  = {2011},

date = {2011-04-01},

journal = {Endocrinology},

volume = {152},

number = {4},

pages = {1222--1233},

abstract = {XLαs, a variant of the stimulatory G protein α-subunit (Gsα), can mediate receptor-activated cAMP generation and, thus, mimic the actions of Gsα in transfected cells. However, it remains unknown whether XLαs can act in a similar manner in vivo. We have now generated mice with ectopic transgenic expression of rat XLαs in the renal proximal tubule (rptXLαs mice), where Gsα mediates most actions of PTH. Western blots and quantitative RT-PCR showed that, while Gsα and type-1 PTH receptor levels were unaltered, protein kinase A activity and 25-hydroxyvitamin D 1-α-hydroxylase (Cyp27b1) mRNA levels were significantly higher in renal proximal tubules of rptXLαs mice than wild-type littermates. Immunohistochemical analysis of kidney sections showed that the sodium-phosphate cotransporter type 2a was modestly reduced in brush border membranes of male rptXLαs mice compared to gender-matched controls. Serum calcium, phosphorus, and 1,25 dihydroxyvitamin D were within the normal range, but serum PTH was ∼30% lower in rptXLαs mice than in controls (152 ± 16 vs. 222 ± 41 pg/ml; P < 0.05). After crossing the rptXLαs mice to mice with ablation of maternal Gnas exon 1 (E1(m-/+)), male offspring carrying both the XLαs transgene and maternal Gnas exon 1 ablation (rptXLαs/E1(m-/+)) were significantly less hypocalcemic than gender-matched E1(m-/+) littermates. Both E1(m-/+) and rptXLαs/E1(m-/+) offspring had higher serum PTH than wild-type littermates, but the degree of secondary hyperparathyroidism tended to be lower in rptXLαs/E1(m-/+) mice. Hence, transgenic XLαs expression in the proximal tubule enhanced Gsα-mediated responses, indicating that XLαs can mimic Gsα in vivo.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid20965295,

title = {Paternal uniparental isodisomy of the entire chromosome 20 as a molecular cause of pseudohypoparathyroidism type Ib (PHP-Ib)},

author = {Murat Bastepe and Ozge Altug-Teber and Chhavi Agarwal and Sharon E Oberfield and Michael Bonin and Harald Jüppner},

doi = {10.1016/j.bone.2010.10.168},

issn = {1873-2763},

year  = {2011},

date = {2011-03-01},

journal = {Bone},

volume = {48},

number = {3},

pages = {659--662},

abstract = {Pseudohypoparathyoridism type Ib (PHP-Ib) typically defines the presence of end-organ resistance to parathyroid hormone in the absence of Albright's hereditary osteodystrophy. Patients affected by this disorder present with imprinting defects in the complex GNAS locus. Microdeletions within STX16 or GNAS have been identified in familial cases with PHP-Ib, but the molecular cause of the GNAS imprinting defects in sporadic PHP-Ib cases remains poorly defined. We now report a case with sporadic PHP-Ib for whom a SNPlex analysis revealed loss of the maternal GNAS allele. Further analysis of the entire genome with a 100K SNP chip identified a paternal uniparental isodisomy affecting the entire chromosome 20 without evidence for another chromosomal abnormality. Our findings explain the observed GNAS methylation changes and the patient's hormone resistance, and furthermore suggest that chromosome 20 harbors, besides GNAS, no additional imprinted region that contributes to the clinical and laboratory phenotype.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid21062889,

title = {Osteosclerosis in two brothers with autosomal dominant pseudohypoparathyroidism type 1b: bone histomorphometric analysis},

author = {Anne Marie Sbrocchi and Frank Rauch and Margaret L Lawson and Stasia Hadjiyannakis and Sarah Lawrence and Murat Bastepe and Harald Jüppner and Leanne Marie Ward},

doi = {10.1530/EJE-10-0795},

issn = {1479-683X},

year  = {2011},

date = {2011-02-01},

journal = {Eur J Endocrinol},

volume = {164},

number = {2},

pages = {295--301},

abstract = {OBJECTIVE: Pseudohypoparathyroidism (PHP) is a heterogeneous disorder characterized by hypocalcemia and hyperphosphatemia resulting from selective renal resistance to parathyroid hormone (PTH). One autosomal dominant form of PHP type 1b (PHP-Ib) is most frequently caused by a maternally inherited 3-kb deletion within STX16, the gene encoding syntaxin 16. To date, increased bone mineral density (BMD) has been described only in PHP type 1a, and there is a lack of detailed information on bone histomorphometry in PHP-Ib. The objective of this report was to present trans-iliac static and dynamic histomorphometry in two brothers with the 3-kb deletion in the STX16 region and elevated BMD.nnDESIGN: Observational study of two brothers (age 18.0 and 22.7 years) with the 3-kb STX16 deletion and increased BMD.nnRESULTS: The brothers had elevated PTH (146 pg/ml (15.6 pmol/l) and 102 pg/ml (10.9 pmol/l); normal: 10-64 pg/ml (1.1-6.8 pmol/l)) and striking osteosclerosis (lumbar spine areal BMD Z-scores: +5.4 and +4.9). Bone histomorphometry showed marked elevations in cortical width for both brothers (241 and 209% of the mean result expected for age), with elevations in the bone formation rate on the endocortical (119 and 260% of the healthy mean) and trabecular (220 and 190% of mean) surfaces.nnCONCLUSION: Our findings suggest that PTH in this PHP-Ib genotype can increase cortical thickness due to its anabolic effect on endocortical bone, and underscore the heterogeneity in the skeletal phenotype among patients with PHP-Ib.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid20887824,

title = {Potent constitutive cyclic AMP-generating activity of XLαs implicates this imprinted GNAS product in the pathogenesis of McCune-Albright syndrome and fibrous dysplasia of bone},

author = {Virginie Mariot and Joy Y Wu and Cumhur Aydin and Giovanna Mantovani and Matthew J Mahon and Agnès Linglart and Murat Bastepe},

doi = {10.1016/j.bone.2010.09.032},

issn = {1873-2763},

year  = {2011},

date = {2011-02-01},

journal = {Bone},

volume = {48},

number = {2},

pages = {312--320},

abstract = {Patients with McCune-Albright syndrome (MAS), characterized primarily by hyperpigmented skin lesions, precocious puberty, and fibrous dyslasia of bone, carry postzygotic heterozygous mutations of GNAS causing constitutive cAMP signaling. GNAS encodes the α-subunit of the stimulatory G protein (Gsα), as well as a large variant (XLαs) derived from the paternal allele. The mutations causing MAS affect both GNAS products, but whether XLαs, like Gsα, can be involved in the pathogenesis remains unknown. Here, we investigated biopsy samples from four previously reported and eight new patients with MAS. Activating mutations of GNAS (Arg201 with respect to the amino acid sequence of Gsα) were present in all the previously reported and five of the new cases. The mutation was detected within the paternally expressed XLαs transcript in five and the maternally expressed NESP55 transcript in four cases. Tissues carrying paternal mutations appeared to have higher XLαs mRNA levels than maternal mutations. The human XLαs mutant analogous to Gsα-R201H (XLαs-R543H) showed markedly higher basal cAMP accumulation than wild-type XLαs in transfected cells. Wild-type XLαs demonstrated higher basal and isoproterenol-induced cAMP signaling than Gsα and co-purified with Gβ1γ2 in transduced cells. XLαs mRNA was measurable in mouse calvarial cells, with its level being significantly higher in undifferentiated cells than those expressing preosteoblastic markers osterix and alkaline phosphatase. XLαs mRNA was also expressed in murine bone marrow stromal cells and preosteoblastic MC3T3-E1 cells. Our findings are consistent with the possibility that constitutive XLαs activity adds to the molecular pathogenesis of MAS and fibrous dysplasia of bone.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid20499351,

title = {Long-term clinical outcome and carrier phenotype in autosomal recessive hypophosphatemia caused by a novel DMP1 mutation},

author = {Outi Mäkitie and Renata C Pereira and Ilkka Kaitila and Serap Turan and Murat Bastepe and Tero Laine and Heikki Kröger and William G Cole and Harald Jüppner},

doi = {10.1002/jbmr.105},

issn = {1523-4681},

year  = {2010},

date = {2010-10-01},

journal = {J Bone Miner Res},

volume = {25},

number = {10},

pages = {2165--2174},

abstract = {Homozygous inactivating mutations in DMP1 (dentin matrix protein 1), the gene encoding a noncollagenous bone matrix protein expressed in osteoblasts and osteocytes, cause autosomal recessive hypophosphatemia (ARHP). Herein we describe a family with ARHP owing to a novel homozygous DMP1 mutation and provide a detailed description of the associated skeletal dysplasia and carrier phenotype. The two adult patients with ARHP, a 78-year-old man and his 66-year-old sister, have suffered from bone pain and lower extremity varus deformities since early childhood. With increasing age, both patients developed severe joint pain, contractures, and complete immobilization of the spine. Radiographs showed short and deformed long bones, significant cranial hyperostosis, enthesopathies, and calcifications of the paraspinal ligaments. Biochemistries were consistent with hypophosphatemia owing to renal phosphate wasting; markers of bone turnover and serum fibroblast growth factor 23 (FGF-23) levels were increased significantly. Nucleotide sequence analysis of DMP1 revealed a novel homozygous mutation at the splice acceptor junction of exon 6 (IVS5-1G > A). Two heterozygous carriers of the mutation also showed mild hypophosphatemia, and bone biopsy in one of these individuals showed focal areas of osteomalacia. In bone, DMP1 expression was absent in the homozygote but normal in the heterozygote, whereas FGF-23 expression was increased in both subjects but higher in the ARHP patient. The clinical and laboratory observations in this family confirm that DMP1 has an important role in normal skeletal development and mineral homeostasis. The skeletal phenotype in ARHP may be significantly more severe than in other forms of hypophosphatemic rickets.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid20538864,

title = {Recessive versus imprinted disorder: consanguinity can impede establishing the diagnosis of autosomal dominant pseudohypoparathyroidism type Ib},

author = {Serap Turan and Leyla Akin and Teoman Akcay and Erdal Adal and Sevil Sarikaya and Murat Bastepe and Harald Jüppner},

doi = {10.1530/EJE-10-0348},

issn = {1479-683X},

year  = {2010},

date = {2010-09-01},

journal = {Eur J Endocrinol},

volume = {163},

number = {3},

pages = {489--493},

abstract = {Hypocalcemia and hyperphosphatemia with low/normal parathyroid hormone (PTH) levels can be observed in hypoparathyroidism (HP), a disorder that may follow an autosomal dominant (AD) or autosomal recessive (AR) mode of inheritance. Similar biochemical changes are also observed in pseudohypoparathyroidism (PHP) type Ia and Ib, but affected patients usually show elevated PTH levels indicative of hormonal resistance. Features of Albright's hereditary osteodystrophy (AHO) are typically not observed in patients affected by familial forms of PHP-Ib, which are most frequently caused by maternally inherited, heterozygous microdeletions within STX16 and are associated with isolated loss of methylation at GNAS exon A/B. We established the molecular defect in two children of consanguineous Turkish parents, who presented with hypocalcemia, hyperphosphatemia, and low 25-OH vitamin D levels, but initially normal or only mildly elevated PTH levels, i.e. findings that do not readily exclude HP. After normalizing serum magnesium levels, hypocalcemia and hyperphosphatemia persisted, and PTH levels increased, suggesting PTH resistance rather than PTH deficiency. Because of the absence of AHO and parental consanguinity, an AR form of PHP-Ib appeared plausible, which had previously been suggested for sporadic cases. However, loss of GNAS methylation was restricted to exon A/B, which led to the identification of the 3-kb STX16 microdeletion. The same mutation was also detected in the healthy mother, who did not show any GNAS methylation abnormality, indicating that her deletion resides on the paternal allele. Our findings emphasize the importance of considering a parentally imprinted, AD disorder even if consanguinity suggests an AR mode of inheritance.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid20444925,

title = {Deletion of the noncoding GNAS antisense transcript causes pseudohypoparathyroidism type Ib and biparental defects of GNAS methylation in cis},

author = {Smitha Chillambhi and Serap Turan and Daw-Yang Hwang and Hung-Chun Chen and Harald Jüppner and Murat Bastepe},

doi = {10.1210/jc.2009-2205},

issn = {1945-7197},

year  = {2010},

date = {2010-08-01},

journal = {J Clin Endocrinol Metab},

volume = {95},

number = {8},

pages = {3993--4002},

abstract = {CONTEXT: GNAS encodes the alpha-subunit of the stimulatory G protein as well as additional imprinted transcripts including the maternally expressed NESP55 and the paternally expressed XLalphas, antisense, and A/B transcripts. Most patients with pseudohypoparathyroidism type Ib (PHP-Ib) exhibit imprinting defects affecting the maternal GNAS allele, which are thought to reduce/abolish Gsalpha expression in renal proximal tubules and thereby cause resistance to PTH.nnOBJECTIVE: Our objective was to define the genetic defect in a previously unreported family with autosomal dominant PHP-Ib.nnDESIGN AND SETTING: Analyses of serum and urine chemistries and of genomic DNA and lymphoblastoid-derived RNA were conducted at a tertiary hospital and research laboratory.nnPATIENTS: Affected individuals presented with muscle weakness and/or paresthesia and showed hypocalcemia, hyperphosphatemia, and elevated serum PTH. Obligate carriers were healthy and revealed no obvious abnormality in mineral ion homeostasis.nnRESULTS: A novel 4.2-kb microdeletion was discovered in the affected individuals and the obligate carriers, ablating two noncoding GNAS antisense exons while preserving the NESP55 exon. On maternal transmission, the deletion causes loss of all maternal GNAS imprints, partial gain of NESP55 methylation, and PTH resistance. Paternal transmission of the mutation leads to epigenetic alterations in cis, including a partial loss of NESP55 methylation and a partial gain of A/B methylation.nnCONCLUSIONS: The identified deletion points to a unique cis-acting element located telomeric of the NESP55 exon that is critical for imprinting both GNAS alleles. These findings provide novel insights into the molecular mechanisms underlying PHP and GNAS imprinting.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid20427744,

title = {Targeted deletion of the Nesp55 DMR defines another Gnas imprinting control region and provides a mouse model of autosomal dominant PHP-Ib},

author = {Leopold F Fröhlich and Maria Mrakovcic and Ralf Steinborn and Ung-Il Chung and Murat Bastepe and Harald Jüppner},

doi = {10.1073/pnas.0910224107},

issn = {1091-6490},

year  = {2010},

date = {2010-05-01},

journal = {Proc Natl Acad Sci U S A},

volume = {107},

number = {20},

pages = {9275--9280},

abstract = {Approximately 100 genes undergo genomic imprinting. Mutations in fewer than 10 imprinted genetic loci, including GNAS, are associated with complex human diseases that differ phenotypically based on the parent transmitting the mutation. Besides the ubiquitously expressed Gsalpha, which is of broad biological importance, GNAS gives rise to an antisense transcript and to several Gsalpha variants that are transcribed from the nonmethylated parental allele. We previously identified two almost identical GNAS microdeletions extending from exon NESP55 to antisense (AS) exon 3 (delNESP55/delAS3-4). When inherited maternally, both deletions are associated with erasure of all maternal GNAS methylation imprints and autosomal-dominant pseudohypoparathyroidism type Ib, a disorder characterized by parathyroid hormone-resistant hypocalcemia and hyperphosphatemia. As for other imprinting disorders, the mechanisms resulting in abnormal GNAS methylation are largely unknown, in part because of a paucity of suitable animal models. We now showed in mice that deletion of the region equivalent to delNESP55/delAS3-4 on the paternal allele (DeltaNesp55(p)) leads to healthy animals without Gnas methylation changes. In contrast, mice carrying the deletion on the maternal allele (DeltaNesp55(m)) showed loss of all maternal Gnas methylation imprints, leading in kidney to increased 1A transcription and decreased Gsalpha mRNA levels, and to associated hypocalcemia, hyperphosphatemia, and secondary hyperparathyroidism. Besides representing a murine autosomal-dominant pseudohypoparathyroidism type Ib model and one of only few animal models for imprinted human disorders, our findings suggest that the Nesp55 differentially methylated region is an additional principal imprinting control region, which directs Gnas methylation and thereby affects expression of all maternal Gnas-derived transcripts.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid19858129,

title = {Coexistence of two different pseudohypoparathyroidism subtypes (Ia and Ib) in the same kindred with independent Gs{alpha} coding mutations and GNAS imprinting defects},

author = {B Lecumberri and E Fernández-Rebollo and L Sentchordi and P Saavedra and A Bernal-Chico and L F Pallardo and J M Jiménez Bustos and L Castaño and M de Santiago and O Hiort and G Pérez de Nanclares and M Bastepe},

doi = {10.1136/jmg.2009.071001},

issn = {1468-6244},

year  = {2010},

date = {2010-04-01},

journal = {J Med Genet},

volume = {47},

number = {4},

pages = {276--280},

abstract = {BACKGROUND: Pseudohypoparathyroidism (PHP) defines a rare group of disorders whose common feature is resistance to the parathyroid hormone. Patients with PHP-Ia display additional hormone resistance, Albright hereditary osteodystrophy (AHO) and reduced Gsalpha activity in easily accessible cells. This form of PHP is associated with heterozygous inactivating mutations in Gsalpha-coding exons of GNAS, an imprinted gene locus on chromosome 20q13.3. Patients with PHP-Ib typically have isolated parathyroid hormone resistance, lack AHO features and demonstrate normal erythrocyte Gsalpha activity. Instead of coding Gsalpha mutations, patients with PHP-Ib display imprinting defects of GNAS, caused, at least in some cases, by genetic mutations within or nearby this gene.nnPATIENTS: Two unrelated PHP families, each of which includes at least one patient with a Gsalpha coding mutation and another with GNAS loss of imprinting, are reported here.nnRESULTS: One of the patients with GNAS imprinting defects has paternal uniparental isodisomy of chromosome 20q, explaining the observed imprinting abnormalities. The identified Gsalpha coding mutations include a tetranucleotide deletion in exon 7, which is frequently found in PHP-Ia, and a novel single nucleotide change at the acceptor splice junction of intron 11.nnCONCLUSIONS: These molecular data reveal an interesting mixture, in the same family, of both genetic and epigenetic mutations of the same gene.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid19796717,

title = {Identification of a novel dentin matrix protein-1 (DMP-1) mutation and dental anomalies in a kindred with autosomal recessive hypophosphatemia},

author = {Serap Turan and Cumhur Aydin and Abdullah Bereket and Teoman Akcay and Tülay Güran and Betul Akmen Yaralioglu and Murat Bastepe and Harald Jüppner},

doi = {10.1016/j.bone.2009.09.016},

issn = {1873-2763},

year  = {2010},

date = {2010-02-01},

journal = {Bone},

volume = {46},

number = {2},

pages = {402--409},

abstract = {An autosomal recessive form of hypophosphatemia (ARHP) was recently shown to be caused by homozygous mutations in DMP1, the gene encoding dentin matrix protein-1 (DMP-1), a non-collagenous bone matrix protein with an important role in the development and mineralization of bone and teeth. Here, we describe a previously not reported consanguineous ARHP kindred in which the three affected individuals carry a novel homozygous DMP-1 mutation. The index case presented at the age of 3 years with bowing of his legs and showed hypophosphatemia due to insufficient renal phosphate retention. Serum alkaline phosphatase activity was elevated, with initially normal PTH. FGF23 was inappropriately normal at an older age while being treated with oral phosphate and 1,25(OH)(2)D. Similar clinical and biochemical findings, except for elevated FGF23 levels, were present in his 16-month-old brother and his 12.5-year-old female cousin; the parents of the three affected children are first-degree cousins. Nucleotide sequence analysis was performed on PCR-amplified exons encoding DMP-1 and flanking intronic regions. A novel homozygous frame-shift mutation (c.485Tdel; p.Glu163ArgfsX53) in exon 6 resulting in a premature stop codon was identified in all effected individuals. The parents and available unaffected siblings were heterozygous for c.485Tdel. Tooth growth and shape were normal for the index case, his affected brother and cousin, but their permanent and deciduous teeth displayed enlarged pulp chambers. The identified genetic mutation underscores the importance of DMP-1 mutations in the pathogenesis of ARHP. Furthermore, DMP-1 mutations appear to contribute, through yet unknown mechanisms, to tooth development.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid20008020,

title = {Intragenic GNAS deletion involving exon A/B in pseudohypoparathyroidism type 1A resulting in an apparent loss of exon A/B methylation: potential for misdiagnosis of pseudohypoparathyroidism type 1B},

author = {Eduardo Fernandez-Rebollo and Beatriz García-Cuartero and Intza Garin and Cristina Largo and Francisco Martínez and Concepcion Garcia-Lacalle and Luis Castaño and Murat Bastepe and Guiomar Pérez de Nanclares},

doi = {10.1210/jc.2009-1581},

issn = {1945-7197},

year  = {2010},

date = {2010-02-01},

journal = {J Clin Endocrinol Metab},

volume = {95},

number = {2},

pages = {765--771},

abstract = {CONTEXT: Several endocrine diseases that share resistance to PTH are grouped under the term pseudohypoparathyroidism (PHP). Patients with PHP type Ia show additional hormone resistance, defective erythrocyte G(s)alpha activity, and dysmorphic features termed Albright's hereditary osteodystrophy (AHO). Patients with PHP-Ib show less diverse hormone resistance and normal G(s)alpha activity; AHO features are typically absent in PHP-Ib. Mutations affecting G(s)alpha coding exons of GNAS and epigenetic alterations in the same gene are associated with PHP-Ia and -Ib, respectively. The epigenetic GNAS changes in familial PHP-Ib are caused by microdeletions near or within GNAS but without involving G(s)alpha coding exons.nnOBJECTIVE: We sought to identify the molecular defect in a patient who was diagnosed with PHP-Ia based on clinical presentation (hormone resistance and AHO) but displayed the molecular features typically associated with PHP-Ib (loss of methylation at exon A/B) without previously described genetic mutations.nnMETHODS: Microsatellite typing, comparative genome hybridization, and allelic dosage were performed for proband and her parents.nnRESULTS: Comparative genome hybridization revealed a deletion of 30,431 bp extending from the intronic region between exons XL and A/B to intron 5. The same mutation was also demonstrated, by PCR, in the patient's mother, but polymorphism and allele dosage analyses indicated that she had this mutation in a mosaic manner.nnCONCLUSION: We discovered a novel multiexonic GNAS deletion transmitted to our patient from her mother who is mosaic for this mutation. The deletion led to different phenotypic manifestations in the two generation and appeared, in the patient, as loss of GNAS imprinting.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}