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Fahr syndrome discovered in adulthood revealing a rare GNAS mutation in pseudohypoparathyroidism type 1a in a Tunisian family.

ABSTRACT: Pseudohypoparathyroidism (PHP) indicates a rare heterogeneous group of disorders characterized by hypocalcemia, hyperphosphatemia, increased serum concentration of parathyroid hormone (PTH), and insensitivity to the biologic activity of PTH. One of its most common types is PHP-1a. In this report, we present a familial PHP-1a and a novel mutation of the GNAS gene.

SUBMITTER: Debbabi W

PROVIDER: S-EPMC9109644 | biostudies-literature | 2022 May

REPOSITORIES: biostudies-literature

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Fahr syndrome discovered in adulthood revealing a rare GNAS mutation in pseudohypoparathyroidism type 1a in a Tunisian family.

Debbabi Wided W Khelifi Dayssem D Kharrat Issam I Samet Slim S

Clinical case reports 20220516 5

Pseudohypoparathyroidism (PHP) indicates a rare heterogeneous group of disorders characterized by hypocalcemia, hyperphosphatemia, increased serum concentration of parathyroid hormone (PTH), and insensitivity to the biologic activity of PTH. One of its most common types is PHP-1a. In this report, we present a familial PHP-1a and a novel mutation of the GNAS gene. ...[more]

PMID: 35600030

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Pseudohypoparathyroidism type 1a due to a novel mutation in the GNAS gene.

Project description: Not available

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GNAS mutations in Pseudohypoparathyroidism type 1a and related disorders.

Project description:Pseudohypoparathyroidism type 1a (PHP1a) is characterized by hypocalcaemia and hyperphosphatemia due to parathyroid hormone resistance, in association with the features of Albright's hereditary osteodystrophy (AHO). PHP1a is caused by maternally inherited inactivating mutations of Gs-alpha, which is encoded by a complex imprinted locus termed GNAS. Paternally inherited mutations can lead either to pseudopseudohypoparathyroidism (PPHP) characterized by AHO alone, or to progressive osseous heteroplasia (POH), characterized by severe heterotopic ossification. The clinical aspects and molecular genetics of PHP1a and its related disorders are reviewed together with the 343 kindreds with Gs-alpha germline mutations reported so far in the literature. These 343 (176 different) mutations are scattered throughout the 13 exons that encode Gs-alpha and consist of 44.9% frameshift, 28.0% missense, 14.0% nonsense, and 9.0% splice-site mutations, 3.2% in-frame deletions or insertions, and 0.9% whole or partial gene deletions. Frameshift and other highly disruptive mutations were more frequent in the reported 37 POH kindreds than in PHP1a/PPHP kindreds (97.3% vs. 68.7%, P < 0.0001). This mutation update and respective genotype-phenotype data may be of use for diagnostic and research purposes and contribute to a better understanding of these complex disorders.

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Identification of a novel GNAS mutation in a case of pseudohypoparathyroidism type 1A with normocalcemia.

Project description:BackgroundPseudohypoparathyroidism type 1A (PHP1A) is a rare genetic disease primarily characterized by resistance to parathyroid hormone along with hormonal resistance and other features of Albright hereditary osteodystrophy (AHO). It is caused by heterozygous inactivating mutations in the maternal allele of the GNAS gene, which encodes the stimulatory G-protein alpha subunit (Gsα) and regulates production of the second messenger cyclic AMP (cAMP). Herein, we report a case of of PHP1A with atypical clinical manifestations (oligomenorrhea, subclinical hypothyroidism, and normocalcemia) and explore the underlying genetic cause in this patient.MethodsBlood samples were collected from the patient, her family members, and 100 healthy controls. The 13 exons and flanking splice sites of the GNAS gene were amplified by PCR and sequenced. To further assess whether the novel mutation resulted in gain or loss of function of Gsα, we examined the level of cAMP activity associated with this mutation through in vitro functional studies by introducing the target mutation into a human GNAS plasmid.ResultsA novel heterozygous c.715A > G (p.N239D) mutation in exon 9 of the GNAS gene was identified in the patient. This mutation was also found in her mother, who was diagnosed with pseudopseudohypoparathyroidism. An in vitro cAMP assay showed a significant decrease in PTH-induced cAMP production in cells transfected with the mutant plasmid, compared to that in the wild-type control cells (P < 0.01), which was consistent with loss of Gsa activity.ConclusionWe identified a novel GNAS mutation that altered Gsα function, which furthers our understanding of the pathogenesis of this disease. Screening for GNAS mutations should be considered in suspected cases of PHP1A even if the classical signs are not present.

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A Novel GNAS Mutation in a Patient with Ia Pseudohypoparathyroidism (iPPSD2) Phenotype.

Project description:Pseudohypoparathyroidism (PHP) is a heterogeneous orphan disease characterized by multihormonal resistance and several phenotypic features. In some cases, PHP is caused by a mutation in the GNAS that encodes the alpha subunit of the G protein, one of the key transmitters of intracellular signals. A correlation between the genotype and phenotype of patients with GNAS mutations has not yet been described. This often makes diagnosis, drug prescription, and timely diagnosis difficult. Information about GNAS functioning and the impact of specific mutations on the clinical course of the disease is limited. Establishing of the pathogenicity by newly identified GNAS mutations will expand the understanding of this gene functioning in the cAMP signaling pathway and may become the basis for personalized treatment. This paper provides a clinical description of a patient with the Ia PHP phenotype caused by a previously unknown mutation in GNAS (NC_000020.11(NM_000516.7)): c.719-29_719-13delinsACCAAAGAGAGCAAAGCCAAG in the heterozygous state. Verification of the pathogenicity of the detected mutation is also described.

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A novel synonymous variant in exon 1 of GNAS gene results in a cryptic splice site and causes pseudohypoparathyroidism type 1A and pseudo-pseudohypoparathyroidism in a French family.

Project description:IntroductionPseudohypoparathyroidism type 1A (PHP1A) and pseudopseudohypoparathyroidism (PPHP) (Inactivating PTH/PTHrP Signaling Disorders type 2, IPPSD2) are two rare autosomal disorders caused by loss-of-function mutations on either maternal or paternal allele, respectively, in the imprinted GNAS gene, which encodes the α subunit of the ubiquitously-expressed stimulatory G protein (Gαs).Case presentationWe investigated a synonymous GNAS variant NM_001077488.2: c.108C>A / p.(Val36=) identified in a family presenting with IPPSD2 phenotype. In silico splicing prediction algorithms were in favor of a deleterious effect of this variant, by creating a new donor splicing site. The GNAS expression studies in blood suggested haploinsufficiency and showed an alternate splice product demonstrating the unmasking of a cryptic site, leading to a 34 base pairs deletion and the creation of a probable unstable RNA.We present the first familial case of IPPSD2 caused by a pathogenic synonymous variant in GNAS gene.

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Delayed diagnosis of pseudohypoparathyroidism type 1a with rare hypothyroidism since childhood.

Project description:Pseudohypoparathyroidism (PHP) is a rare disorder that associates with resistance to parathyroid hormone (PTH). A 21-year old man visited outpatient clinic to treat previously diagnosed hypothyroidism and vitamin D deficiency. Despite daily 150 mcg of levothyroxine supplement, thyroid-stimulating hormone level was elevated, but thyroid autoantibodies were not detected. He showed features of Albright Hereditary Osteodystrophy and elevated serum PTH level with normal albumin-corrected calcium and phosphorus level. The Ellsworth-Howard test proved the blunted response of urinary phosphorus and cyclic adenosine monophosphate after the infusion of the exogenous PTH, suggesting PTH resistance. DNA analysis revealed a heterozygous mutation in the GNAS gene (c.478C > T). Herein, we report a case of PHP type 1a confirmed by clinical, biochemical and molecular analyses. Establishing correct diagnosis of PHP is necessary for efficient therapeutic management.

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A Novel Splicing Mutation of the GNAS Gene in a Patient with Pseudohypoparathyroidism Ia.

Project description: Not available

| S-EPMC3687632 | biostudies-literature

Intragenic Deletions of GNAS in Pseudohypoparathyroidism Type 1A Identify a New Region Affecting Methylation of Exon A/B.

Project description:Pseudohypoparathyroidism type 1A (PHP1A) and pseudopseudohypoparathyroidism (PPHP) are caused by inactivating mutations in the exons of GNAS that encode the alpha-subunit of the stimulatory G protein (Gsα). In some cases abnormal methylation of exon A/B of GNAS, a hallmark of PHP1B, has been reported. To identify the underlying genetic basis for PHP1A/PPHP in patients in whom molecular defects were not detected by GNAS sequencing and microarray-based analysis of copy number variations. Whole genome sequencing (WGS) and pyrosequencing of differentially methylated regions (DMRs) of GNAS using genomic deoxyribonucleic acid from affected patients. We identified 2 novel heterozygous GNAS deletions: a 6.4 kb deletion that includes exon 2 of GNAS in the first proband that was associated with normal methylation (57%) of exon A/B DMR, and a 1438 bp deletion in a second PHP1A patient that encompasses the promoter region and 5' untranslated region of Gsα transcripts, which was inherited from his mother with PPHP. This deletion was associated with reduced methylation (32%) of exon A/B DMR. WGS can detect exonic and intronic mutations, including deletions that are too small to be identified by microarray analysis, and therefore is more sensitive than other techniques for molecular analysis of PHP1A/PPHP. One of the deletions we identified led to reduced methylation of exon A/B DMR, further refining a region needed for normal imprinting of this DMR. We propose that deletion of this region can explain why some PHP1A patients have reduced of methylation of the exon A/B DMR.

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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.

Project description:ContextSeveral 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.ObjectiveWe 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.MethodsMicrosatellite typing, comparative genome hybridization, and allelic dosage were performed for proband and her parents.ResultsComparative 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.ConclusionWe 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.

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Pseudohypoparathyroidism type Ib associated with novel duplications in the GNAS locus.

Project description:ContextPseudohypoparathyroidism type 1b (PHP-Ib) is characterized by renal resistance to PTH (and, sometimes, a mild resistance to TSH) and absence of any features of Albright's hereditary osteodystrophy. Patients with PHP-Ib suffer of defects in the methylation pattern of the complex GNAS locus. PHP-Ib can be either sporadic or inherited in an autosomal dominant pattern. Whereas familial PHP-Ib is well characterized at the molecular level, the genetic cause of sporadic PHP-Ib cases remains elusive, although some molecular mechanisms have been associated with this subtype.ObjectiveThe aim of the study was to investigate the molecular and imprinting defects in the GNAS locus in two unrelated patients with PHP-Ib.DesignWe have analyzed the GNAS locus by direct sequencing, Methylation-Specific Multiplex Ligation-dependent Probe Amplification, microsatellites, Quantitative Multiplex PCR of Short Fluorescent fragments and array-Comparative Genomic Hybridization studies in order to characterize two unrelated families with clinical features of PHP-Ib.ResultsWe identified two duplications in the GNAS region in two patients with PHP-Ib: one of them, comprising ∼ 320 kb, occurred 'de novo' in the patient, whereas the other one, of ∼ 179 kb in length, was inherited from the maternal allele. In both cases, no other known genetic cause was observed.ConclusionIn this article, we describe the to-our-knowledge biggest duplications reported so far in the GNAS region. Both are associated to PHP-Ib, one of them occurring 'de novo' and the other one being maternally inherited.

| S-EPMC4339194 | biostudies-literature