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Yang W, Zuo Y, Zhang N, Wang K, Zhang R, Chen Z, He Q. GNAS locus: bone related diseases and mouse models. Front Endocrinol (Lausanne) 2023; 14:1255864. [PMID: 37920253 PMCID: PMC10619756 DOI: 10.3389/fendo.2023.1255864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Accepted: 09/29/2023] [Indexed: 11/04/2023] Open
Abstract
GNASis a complex locus characterized by multiple transcripts and an imprinting effect. It orchestrates a variety of physiological processes via numerous signaling pathways. Human diseases associated with the GNAS gene encompass fibrous dysplasia (FD), Albright's Hereditary Osteodystrophy (AHO), parathyroid hormone(PTH) resistance, and Progressive Osseous Heteroplasia (POH), among others. To facilitate the study of the GNAS locus and its associated diseases, researchers have developed a range of mouse models. In this review, we will systematically explore the GNAS locus, its related signaling pathways, the bone diseases associated with it, and the mouse models pertinent to these bone diseases.
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Affiliation(s)
- Wan Yang
- State Key Laboratory of Oral & Maxillofacial Reconstruction and Regeneration, Key Laboratory of Oral Biomedicine Ministry of Education, Hubei Key Laboratory of Stomatology, School & Hospital of Stomatology, Wuhan University, Wuhan, China
| | - Yiyi Zuo
- State Key Laboratory of Oral & Maxillofacial Reconstruction and Regeneration, Key Laboratory of Oral Biomedicine Ministry of Education, Hubei Key Laboratory of Stomatology, School & Hospital of Stomatology, Wuhan University, Wuhan, China
| | - Nuo Zhang
- School and Hospital of Stomatology, Wuhan University, Wuhan, China
| | - Kangning Wang
- School and Hospital of Stomatology, Wuhan University, Wuhan, China
| | - Runze Zhang
- School and Hospital of Stomatology, Wuhan University, Wuhan, China
| | - Ziyi Chen
- School and Hospital of Stomatology, Wuhan University, Wuhan, China
| | - Qing He
- State Key Laboratory of Oral & Maxillofacial Reconstruction and Regeneration, Key Laboratory of Oral Biomedicine Ministry of Education, Hubei Key Laboratory of Stomatology, School & Hospital of Stomatology, Wuhan University, Wuhan, China
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Fei Y, Liu L, Wu L, Wang O, Xing X, Li A, Huang L. Whole-genome sequencing revealed a novel long-range deletion mutation spanning GNAS in familial pseudohypoparathyroidism. Mol Genet Genomic Med 2023; 11:e2144. [PMID: 36669868 PMCID: PMC10178786 DOI: 10.1002/mgg3.2144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 01/01/2023] [Accepted: 01/10/2023] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND Pseudohypoparathyroidism (PHP) is a series of diseases related to pathological changes and neurocognitive and endocrine abnormalities, mainly due to the GNAS mutation on chromosome 20q13.2, which weakens receptor-mediated hormone signal transduction. Considering its complex genetic and epigenetic characteristics, GNAS may produce complex clinical phenotypes in families or sporadic cases. This study presented a case of familial PHP caused by a deletion mutation in the 20q13.2 region. METHODS AND RESULTS The proband and her second daughter had PHP, and the proband's mother had pseudo-PHP. Whole-genome sequencing revealed that the proband had an 849.81 kb deletion spanning GNAS near the maternal 20q13.2 chromosome. Multiplex ligation-dependent probe amplification methylation analysis indicated that the proband as well as her mother and second daughter had seemingly abnormal GNAS methylation. This is different from the phenotype (feeding difficulty, slow growth, and special facial features) of previously reported cases with the deletion of fragments near the 20q13.2 chromosome. CONCLUSIONS This report demonstrated the variability of 20q13.2 deletion phenotypes and the clinical importance of using multiple molecular genetic detection methods.
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Affiliation(s)
- Yangfan Fei
- Department of Endocrinology and Metabolism, Meishan Municipal People's Hospital, Sichuan, China
| | - Lv Liu
- Department of Endocrinology and Metabolism, Meishan Municipal People's Hospital, Sichuan, China
| | - Lixia Wu
- Department of Endocrinology and Metabolism, Meishan Municipal People's Hospital, Sichuan, China
| | - Ou Wang
- Department of Endocrinology, Key Laboratory of Endocrinology, National Health Commission, Peking Union Medical College Hospital, Chinese Academy of Medical Science & Peking Union Medical College, Beijing, China
| | - Xiaoping Xing
- Department of Endocrinology, Key Laboratory of Endocrinology, National Health Commission, Peking Union Medical College Hospital, Chinese Academy of Medical Science & Peking Union Medical College, Beijing, China
| | - Aiping Li
- Department of Endocrinology and Metabolism, Meishan Municipal People's Hospital, Sichuan, China
| | - Lingyi Huang
- Department of Endocrinology and Metabolism, Meishan Municipal People's Hospital, Sichuan, China
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Bypassing Mendel's First Law: Transmission Ratio Distortion in Mammals. Int J Mol Sci 2023; 24:ijms24021600. [PMID: 36675116 PMCID: PMC9863905 DOI: 10.3390/ijms24021600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 01/10/2023] [Accepted: 01/11/2023] [Indexed: 01/15/2023] Open
Abstract
Mendel's law of segregation states that the two alleles at a diploid locus should be transmitted equally to the progeny. A genetic segregation distortion, also referred to as transmission ratio distortion (TRD), is a statistically significant deviation from this rule. TRD has been observed in several mammal species and may be due to different biological mechanisms occurring at diverse time points ranging from gamete formation to lethality at post-natal stages. In this review, we describe examples of TRD and their possible mechanisms in mammals based on current knowledge. We first focus on the differences between TRD in male and female gametogenesis in the house mouse, in which some of the most well studied TRD systems have been characterized. We then describe known TRD in other mammals, with a special focus on the farmed species and in the peculiar common shrew species. Finally, we discuss TRD in human diseases. Thus far, to our knowledge, this is the first time that such description is proposed. This review will help better comprehend the processes involved in TRD. A better understanding of these molecular mechanisms will imply a better comprehension of their impact on fertility and on genome evolution. In turn, this should allow for better genetic counseling and lead to better care for human families.
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Ohata Y, Kakimoto H, Seki Y, Ishihara Y, Nakano Y, Yamamoto K, Takeyari S, Fujiwara M, Kitaoka T, Takakuwa S, Kubota T, Ozono K. Pathogenic variants of the GNAS gene introduce an abnormal amino acid sequence in the β6 strand/α5 helix of Gsα, causing pseudohypoparathyroidism type 1A and pseudopseudohypoparathyroidism in two unrelated Japanese families. Bone Rep 2022; 17:101637. [PMID: 36407415 PMCID: PMC9668531 DOI: 10.1016/j.bonr.2022.101637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 11/03/2022] [Accepted: 11/09/2022] [Indexed: 11/11/2022] Open
Abstract
Pseudohypoparathyroidism 1A (PHP1A) and pseudopseudohypoparathyroidism (PPHP) are caused by loss-of-function variants of GNAS, which encodes Gsα. We present two unrelated Japanese families with PHP1A and PPHP harboring unreported pathogenic variants of GNAS (c.1141delG, p.Asp381Thrfs*23 and c.1117delC, p.Arg373Alafs*31). These variants introduce abnormal amino acids in the β6 strand/α5 helix of Gsα, which interact with G protein coupling receptor (GPCR). We conclude that these variants alter the association of Gsα with GPCR and cause PHP1A or PPHP. Reports of GNAS variants causing extra amino acid sequences are limited. Two cases with extended Gsα mutants showed clinical characteristics of PHP1A/PPHP. No change was found in the affinity between mutant Gsα and GDP using I-TASSER. I-TASSER and AlphaFold2 suggested the Gsα mutants caused dysfunction with GPCR. Prediction by I-TASSER and AlphaFold2 are useful in determination of pathogenicity.
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Affiliation(s)
- Yasuhisa Ohata
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan
| | - Haruna Kakimoto
- Department of Pediatrics, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
| | - Yuko Seki
- Department of Pediatrics, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
| | - Yasuki Ishihara
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan
- The first Department of Oral and Maxillofacial Surgery, Osaka University Graduate School of Dentistry, Suita, Japan
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Japan
| | - Yukako Nakano
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan
| | - Kenichi Yamamoto
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan
- Department of Statistical Genetics, Osaka University Graduate School of Medicine, Suita, Japan
| | - Shinji Takeyari
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan
| | - Makoto Fujiwara
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan
- The first Department of Oral and Maxillofacial Surgery, Osaka University Graduate School of Dentistry, Suita, Japan
| | - Taichi Kitaoka
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan
| | - Satoshi Takakuwa
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan
- Department of Pediatrics, Hyogo Prefectural Nishinomiya Hospital, Japan
| | - Takuo Kubota
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan
| | - Keiichi Ozono
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan
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Newey PJ, Hannan FM, Wilson A, Thakker RV. Genetics of monogenic disorders of calcium and bone metabolism. Clin Endocrinol (Oxf) 2022; 97:483-501. [PMID: 34935164 PMCID: PMC7614875 DOI: 10.1111/cen.14644] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/24/2021] [Accepted: 11/07/2021] [Indexed: 12/19/2022]
Abstract
Disorders of calcium homeostasis are the most frequent metabolic bone and mineral disease encountered by endocrinologists. These disorders usually manifest as primary hyperparathyroidism (PHPT) or hypoparathyroidism (HP), which have a monogenic aetiology in 5%-10% of cases, and may occur as an isolated endocrinopathy, or as part of a complex syndrome. The recognition and diagnosis of these disorders is important to facilitate the most appropriate management of the patient, with regard to both the calcium-related phenotype and any associated clinical features, and also to allow the identification of other family members who may be at risk of disease. Genetic testing forms an important tool in the investigation of PHPT and HP patients and is usually reserved for those deemed to be an increased risk of a monogenic disorder. However, identifying those suitable for testing requires a thorough clinical evaluation of the patient, as well as an understanding of the diversity of relevant phenotypes and their genetic basis. This review aims to provide an overview of the genetic basis of monogenic metabolic bone and mineral disorders, primarily focusing on those associated with abnormal calcium homeostasis, and aims to provide a practical guide to the implementation of genetic testing in the clinic.
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Affiliation(s)
- Paul J Newey
- Division of Molecular and Clinical Medicine, Ninewells Hospital & Medical School, University of Dundee, Scotland, UK
| | - Fadil M Hannan
- Nuffield Department of Women's and Reproductive Health, University of Oxford, Oxford, UK
| | - Abbie Wilson
- Division of Molecular and Clinical Medicine, Ninewells Hospital & Medical School, University of Dundee, Scotland, UK
| | - Rajesh V Thakker
- Academic Endocrine Unit, Oxford Centre for Diabetes, Endocrinology & Metabolism (OCDEM), Churchill Hospital, University of Oxford, Oxford, UK
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Kottler ML. Pseudo-hypoparathyroïdie et ses variants. Med Sci (Paris) 2022; 38:655-662. [DOI: 10.1051/medsci/2022103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Les pseudohypoparathyroïdies (PHP) sont des maladies rares, caractérisées par une résistance à l’action rénale de la parathormone. Le défaut génétique est localisé au locus GNAS, qui code la sous-unité alpha stimulatrice des protéines G (Gαs). Ce locus est le siège de régulations complexes, épissage alternatif et empreinte parentale éteigant de façon tissu-spécifique l’expression de l’allèle paternel. Des mutations hétérozygotes perte de fonction, des épimutations responsables d’une perte d’expression sont associées à un large spectre pathologique : PHP1A, PHP1B, ossification hétérotopique, ostéodystophie, obésité, retard de croissance in utero, etc., dont les mécanismes restent encore incomplètement connus.
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Zhang J, Guan M, Zhao S, Wu S, Weng L, Sheng W. A patient with pseudohypoparathyroidism type 1A previously misdiagnosed as hereditary multiple exostosis: A case report. Exp Ther Med 2022; 24:597. [PMID: 35949342 PMCID: PMC9353500 DOI: 10.3892/etm.2022.11534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 06/14/2022] [Indexed: 11/11/2022] Open
Abstract
Pseudohypoparathyroidism type 1A (PHP1A), a rare hereditary disorder, is featured by end-organ resistance to parathyroid hormone and Albright's hereditary osteodystrophy. Heterozygous mutation of guanine nucleotide-binding protein α stimulating (GNAS) gene causes the half decreased bioactivity of the Gsα protein levels. Due to the diverse early clinical manifestations of PHP1A, a diagnosis of PHP1A is often easily overlooked and misdiagnosis or missed diagnosis is common. The present study described a girl who was initially diagnosed with hereditary multiple exostoses, but was afterwards confirmed with PHP1A. Moreover, genetic analysis indicated a new mutation (c2277deIC) of the gene.
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Affiliation(s)
- Jie Zhang
- Department of Pediatrics, Hangzhou Children's Hospital, Hangzhou, Zhejiang 310014, P.R. China
| | - Ming Guan
- Department of Otolaryngology, Affiliated Hangzhou First People's Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang 310006, P.R. China
| | - Shiyong Zhao
- Department of Pediatrics, Hangzhou Children's Hospital, Hangzhou, Zhejiang 310014, P.R. China
| | - Suling Wu
- Department of Pediatrics, Hangzhou Children's Hospital, Hangzhou, Zhejiang 310014, P.R. China
| | - Lingwei Weng
- Department of Pediatrics, Hangzhou Children's Hospital, Hangzhou, Zhejiang 310014, P.R. China
| | - Wenbin Sheng
- Department of Pediatrics, Hangzhou Children's Hospital, Hangzhou, Zhejiang 310014, P.R. China
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Milioto A, Reyes M, Hanna P, Kiuchi Z, Turan S, Zeve D, Agarwal C, Grigelioniene G, Chen A, Mericq V, Frangos M, Ten S, Mantovani G, Salusky IB, Tebben P, Jüppner H. Lack of GNAS Remethylation During Oogenesis May Be a Cause of Sporadic Pseudohypoparathyroidism Type Ib. J Clin Endocrinol Metab 2022; 107:e1610-e1619. [PMID: 34791361 PMCID: PMC8947795 DOI: 10.1210/clinem/dgab830] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Indexed: 12/11/2022]
Abstract
CONTEXT Pseudohypoparathyroidism type Ib (PHP1B) is characterized by hypocalcemia and hyperphosphatemia due to parathyroid hormone resistance in the proximal renal tubules. Maternal pathogenic STX16/GNAS variants leading to maternal epigenetic GNAS changes impair expression of the stimulatory G protein alpha-subunit (Gsα) thereby causing autosomal dominant PHP1B. In contrast, genetic defects responsible for sporadic PHP1B (sporPHP1B) remain mostly unknown. OBJECTIVE Determine whether PHP1B encountered after in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) causes GNAS remethylation defects similar to those in sporPHP1B. DESIGN Retrospective analysis. RESULTS Nine among 36 sporPHP1B patients investigated since 2000, all with loss of methylation (LOM) at the 3 maternal GNAS differentially methylated regions (DMRs) and gain of methylation at the paternal NESP DMR, had been conceived through IVF or ICSI. Besides abnormal GNAS methylation, IVF/ICSI PHP1B cases revealed no additional imprinting defects. Three of these PHP1B patients have dizygotic twins, and 4 have IVF/ICSI-conceived siblings, all with normal GNAS methylation; 2 unaffected younger siblings were conceived naturally. CONCLUSION Sporadic and IVF/ICSI-conceived PHP1B patients revealed indistinguishable epigenetic changes at all 4 GNAS DMRs, thus suggesting a similar underlying disease mechanism. Given that remethylation at the 3 maternal DMRs occurs during oogenesis, male factors are unlikely to cause LOM postfertilization. Instead, at least some of the sporPHP1B variants could be caused by a defect or defects in an oocyte-expressed gene that is required for fertility and for re-establishing maternal GNAS methylation imprints. It remains uncertain, however, whether the lack of GNAS remethylation alone and the resulting reduction in Gsα expression is sufficient to impair oocyte maturation.
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Affiliation(s)
- Angelo Milioto
- Endocrine Unit, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Monica Reyes
- Endocrine Unit, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Patrick Hanna
- Endocrine Unit, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Zentaro Kiuchi
- Endocrine Unit, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Serap Turan
- Department of Pediatric Endocrinology, Marmara University School of Medicine, Istanbul, Turkey
| | - Daniel Zeve
- Division of Endocrinology, Boston Children’s Hospital, Boston, MA, USA
| | | | - Giedre Grigelioniene
- Department of Molecular Medicine and Surgery, Karolinska Institutet, and Department of Clinical Genetics, Karolinska University Hospital Stockholm, Stockholm, Sweden
| | - Ang Chen
- Any Chen, Arizona Kidney Disease and Hypertension Center, Flagstaff, AZ, USA
| | - Veronica Mericq
- Institute of Maternal and Child Research (IDIMI), University of Chile, Santiago, Chile
| | | | - Svetlana Ten
- Consultant of Pediatric Endocrinology, Richmond University Medical Center, Staten Island, NY, USA
| | - Giovanna Mantovani
- Endocrinology Unit, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan, Italy
- Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
| | - Isidro B Salusky
- Division of Nephrology, Department of Pediatrics, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, CA, USA
| | - Peter Tebben
- Department of Internal Medicine and Pediatrics, Division of Endocrinology and Metabolism, Mayo Clinic, Rochester, MN, USA
| | - Harald Jüppner
- Endocrine Unit, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
- Pediatric Nephrology Unit, Department of Pediatrics, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
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Apetrei A, Molin A, Gruchy N, Godin M, Bracquemart C, Resbeut A, Rey G, Nadeau G, Richard N. 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. Bone Rep 2021; 14:101073. [PMID: 33997150 PMCID: PMC8100090 DOI: 10.1016/j.bonr.2021.101073] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 04/17/2021] [Accepted: 04/20/2021] [Indexed: 12/31/2022] Open
Abstract
INTRODUCTION Pseudohypoparathyroidism 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 PRESENTATION We 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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Affiliation(s)
- Andreea Apetrei
- Normandy University, UNICAEN, Caen University Hospital, Department of Genetics, Reference Center of Rare Diseases of Calcium and Phosphorus Metabolism, EA 7450 BioTARGen, Caen, France
| | - Arnaud Molin
- Normandy University, UNICAEN, Caen University Hospital, Department of Genetics, Reference Center of Rare Diseases of Calcium and Phosphorus Metabolism, EA 7450 BioTARGen, Caen, France
| | - Nicolas Gruchy
- Normandy University, UNICAEN, Caen University Hospital, Department of Genetics, Reference Center of Rare Diseases of Calcium and Phosphorus Metabolism, EA 7450 BioTARGen, Caen, France
| | - Manon Godin
- Normandy University, UNICAEN, Caen University Hospital, Department of Genetics, Reference Center of Rare Diseases of Calcium and Phosphorus Metabolism, EA 7450 BioTARGen, Caen, France
| | - Claire Bracquemart
- Normandy University, UNICAEN, Caen University Hospital, Department of Genetics, Reference Center of Rare Diseases of Calcium and Phosphorus Metabolism, EA 7450 BioTARGen, Caen, France
| | - Antoine Resbeut
- Normandy University, UNICAEN, Caen University Hospital, Department of Genetics, Reference Center of Rare Diseases of Calcium and Phosphorus Metabolism, EA 7450 BioTARGen, Caen, France
| | - Gaëlle Rey
- Metropole Savoie Hospital Center, Genetics Department, Chambéry, France
| | - Gwenaël Nadeau
- Metropole Savoie Hospital Center, Genetics Department, Chambéry, France
| | - Nicolas Richard
- Normandy University, UNICAEN, Caen University Hospital, Department of Genetics, Reference Center of Rare Diseases of Calcium and Phosphorus Metabolism, EA 7450 BioTARGen, Caen, France
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Abstract
Pseudohypoparathyroidism (PHP) and pseudopseudohypoparathyroidism (PPHP) are caused by mutations and/or epigenetic changes at the complex GNAS locus on chromosome 20q13.3 that undergoes parent-specific methylation changes at several differentially methylated regions (DMRs). GNAS encodes the alpha-subunit of the stimulatory G protein (Gsα) and several splice variants thereof. PHP type Ia (PHP1A) is caused by heterozygous inactivating mutations involving the maternal exons 1-13. Heterozygosity of these maternal GNAS mutations cause PTH-resistant hypocalcemia and hyperphosphatemia because paternal Gsα expression is suppressed in certain organs thus leading to little or no Gsα protein in the proximal renal tubules and other tissues. Besides biochemical abnormalities, PHP1A patients show developmental abnormalities, referred to as Albright's hereditary osteodystrophy (AHO). Some, but not all of these AHO features are encountered also in patients affected by PPHP, who carry paternal Gsα-specific mutations and typically show no laboratory abnormalities. Autosomal dominant PHP type Ib (AD-PHP1B) is caused by heterozygous maternal deletions within GNAS or STX16, which are associated with loss of methylation at the A/B DMR alone or at all maternally methylated GNAS exons. Loss of methylation of exon A/B and the resulting biallelic expression of A/B transcript reduces Gsα expression thus leading to hormonal resistance. Epigenetic changes at all differentially methylated GNAS regions are also observed in sporadic PHP1B, which is the most frequent PHP1B variant. However, this disease variant remains unresolved at the molecular level, except for rare cases with paternal uniparental isodisomy or heterodisomy of chromosome 20q (patUPD20q).
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Affiliation(s)
- Harald Jüppner
- Endocrine Unit, Department of Medicine and Pediatric Nephrology Unit, Department of Pediatrics, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
- Correspondence: Harald Jüppner, MD, Endocrine Unit, Thier 10, 50 Blossom Street, Massachusetts General Hospital, Boston, MA 02114, USA.
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Kiuchi Z, Reyes M, Jüppner H. Preferential Maternal Transmission of STX16-GNAS Mutations Responsible for Autosomal Dominant Pseudohypoparathyroidism Type Ib (PHP1B): Another Example of Transmission Ratio Distortion. J Bone Miner Res 2021; 36:696-703. [PMID: 33247854 DOI: 10.1002/jbmr.4221] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Revised: 11/11/2020] [Accepted: 11/19/2020] [Indexed: 01/13/2023]
Abstract
Preferential transmission of a genetic mutation to the next generation, referred to as transmission ratio distortion (TRD), is well established for several dominant disorders, but underlying mechanisms remain undefined. Recently, TRD was reported for patients affected by pseudohypoparathyroidism type Ia or pseudopseudohypoparathyroidism. To determine whether TRD is observed also for autosomal dominant pseudohypoparathyroidism type Ib (AD-PHP1B), we analyzed kindreds with the frequent 3-kb STX16 deletion or other STX16/GNAS mutations. If inherited from a female, these genetic defects lead to loss-of-methylation at exon A/B alone or at all three differentially methylated regions (DMR), resulting in parathyroid hormone (PTH)-resistant hypocalcemia and hyperphosphatemia and possibly resistance to other hormones. In total, we investigated 212 children born to 80 females who are unaffected carriers of a STX16/GNAS mutation (n = 47) or affected by PHP1B (n = 33). Of these offspring, 134 (63.2%) had inherited the genetic defect (p = .00012). TRD was indistinguishable for mothers with a STX16/GNAS mutation on their paternal (unaffected carriers) or maternal allele (affected). The mechanisms favoring transmission of the mutant allele remain undefined but are likely to include abnormalities in oocyte maturation. Search for mutations in available descendants of males revealed marginally significant evidence for TRD (p = .038), but these analyses are less reliable because many more offspring of males than females with a STX16/GNAS mutation were lost to follow-up (31 of 98 versus 6 of 218). This difference in follow-up is probably related to the fact that inheritance of a mutation from a male does not have clinical implications, whereas inheritance from an affected or unaffected female results in PHP1B. Lastly, affected PHP1B females had fewer descendants than unaffected carriers, but it remains unclear whether abnormal oocyte development or impaired actions of reproductive hormones are responsible. Our findings highlight previously not recognized aspects of AD-PHP1B that are likely to have implications for genetic testing and counseling. © 2020 American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Zentaro Kiuchi
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Monica Reyes
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Harald Jüppner
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA.,Pediatric Nephrology Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
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