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The Journal of Clinical Investigation Apr 2023Genetic defects of GNAS, the imprinted gene encoding the stimulatory G protein α-subunit, are responsible for multiple diseases. Abnormal GNAS imprinting causes...
Genetic defects of GNAS, the imprinted gene encoding the stimulatory G protein α-subunit, are responsible for multiple diseases. Abnormal GNAS imprinting causes pseudohypoparathyroidism type 1B (PHP1B), a prototype of mammalian end-organ hormone resistance. Hypomethylation at the maternally methylated GNAS A/B region is the only shared defect in patients with PHP1B. In autosomal dominant (AD) PHP1B kindreds, A/B hypomethylation is associated with maternal microdeletions at either the GNAS NESP55 differentially methylated region or the STX16 gene located approximately 170 kb upstream. Functional evidence is meager regarding the causality of these microdeletions. Moreover, the mechanisms linking A/B methylation and the putative imprinting control regions (ICRs) NESP-ICR and STX16-ICR remain unknown. Here, we generated a human embryonic stem cell model of AD-PHP1B by introducing ICR deletions using CRISPR/Cas9. With this model, we showed that the NESP-ICR is required for methylation and transcriptional silencing of A/B on the maternal allele. We also found that the SXT16-ICR is a long-range enhancer of NESP55 transcription, which originates from the maternal NESP-ICR. Furthermore, we demonstrated that the STX16-ICR is an embryonic stage-specific enhancer enabled by the direct binding of pluripotency factors. Our findings uncover an essential GNAS imprinting control mechanism and advance the molecular understanding of PHP1B pathogenesis.
Topics: Animals; Humans; Darbepoetin alfa; Chromogranins; Pseudohypoparathyroidism; GTP-Binding Protein alpha Subunits, Gs; DNA Methylation; Genomic Imprinting; Mammals
PubMed: 36853809
DOI: 10.1172/JCI167953 -
International Journal of Molecular... Feb 2023Heterotrimeric guanine nucleotide-binding proteins (G proteins) are among the most important cellular signaling components, especially G protein-coupled receptors...
Heterotrimeric guanine nucleotide-binding proteins (G proteins) are among the most important cellular signaling components, especially G protein-coupled receptors (GPCRs). G proteins comprise three subunits, Gα, Gβ, and Gγ. Gα is the key subunit, and its structural state regulates the active status of G proteins. Interaction of guanosine diphosphate (GDP) or guanosine triphosphate (GTP) with Gα switches G protein into basal or active states, respectively. Genetic alteration in Gα could be responsible for the development of various diseases due to its critical role in cell signaling. Specifically, loss-of-function mutations of Gαs are associated with parathyroid hormone-resistant syndrome such as inactivating parathyroid hormone/parathyroid hormone-related peptide (PTH/PTHrP) signaling disorders (iPPSDs), whereas gain-of-function mutations of Gαs are associated with McCune-Albright syndrome and tumor development. In the present study, we analyzed the structural and functional implications of natural variants of the Gαs subtype observed in iPPSDs. Although a few tested natural variants did not alter the structure and function of Gαs, others induced drastic conformational changes in Gαs, resulting in improper folding and aggregation of the proteins. Other natural variants induced only mild conformational changes but altered the GDP/GTP exchange kinetics. Therefore, the results shed light on the relationship between natural variants of Gα and iPPSDs.
Topics: Guanosine Diphosphate; Guanosine Triphosphate; Parathyroid Hormone; Signal Transduction; GTP-Binding Protein alpha Subunits, Gs; Humans; Pseudohypoparathyroidism; Protein Conformation
PubMed: 36835474
DOI: 10.3390/ijms24044064 -
Genes Jan 2023Pseudohypoparathyroidism (PHP) is a heterogeneous orphan disease characterized by multihormonal resistance and several phenotypic features. In some cases, PHP is caused...
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 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 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 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 (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.
Topics: Humans; GTP-Binding Protein alpha Subunits, Gs; Chromogranins; Pseudohypoparathyroidism; Mutation; Phenotype
PubMed: 36833251
DOI: 10.3390/genes14020324 -
American Journal of Medical Genetics.... May 2023
Topics: Humans; Pseudohypoparathyroidism; DNA Methylation; GTP-Binding Protein alpha Subunits, Gs; Chromogranins; Syntaxin 16
PubMed: 36807968
DOI: 10.1002/ajmg.a.63154 -
Proceedings of the National Academy of... Feb 2023Like other secreted peptides, nascent parathyroid hormone (PTH) is synthesized with a pre- and a pro-sequence (25 and 6 amino acids, respectively). These precursor...
Like other secreted peptides, nascent parathyroid hormone (PTH) is synthesized with a pre- and a pro-sequence (25 and 6 amino acids, respectively). These precursor segments are sequentially removed in parathyroid cells before packaging into secretory granules. Three patients from two unrelated families who presented during infancy with symptomatic hypocalcemia were found to have a homozygous serine (S) to proline (P) change affecting the first amino acid of the mature PTH. Unexpectedly, biological activity of synthetic [P1]PTH(1-34) was indistinguishable from that of unmodified [S1]PTH(1-34). However, in contrast to conditioned medium from COS-7 cells expressing prepro[S1]PTH(1-84), medium from cells expressing prepro[P1]PTH(1-84) failed to stimulate cAMP production despite similar PTH levels when measured by an intact assay that detects PTH(1-84) and large amino-terminally truncated fragments thereof. Analysis of the secreted, but inactive PTH variant led to the identification of pro[P1]PTH(-6 to +84). Synthetic pro[P1]PTH(-6 to +34) and pro[S1]PTH(-6 to +34) had much less bioactivity than the corresponding PTH(1-34) analogs. Unlike pro[S1]PTH(-6 to +34), pro[P1]PTH(-6 to +34) was resistant to cleavage by furin suggesting that the amino acid variant impairs preproPTH processing. Consistent with this conclusion, plasma of patients with the homozygous P1 mutation had elevated proPTH levels, as determined with an in-house assay specific for pro[P1]PTH(-6 to +84). In fact, a large fraction of PTH detected by the commercial intact assay represented the secreted pro[P1]PTH. In contrast, two commercial biointact assays that use antibodies directed against the first few amino acid residues of PTH(1-84) for capture or detection failed to detect pro[P1]PTH.
Topics: Humans; Hypocalcemia; Parathyroid Hormone; Mutation; Proline; Amino Acids
PubMed: 36795755
DOI: 10.1073/pnas.2208047120 -
Journal of Endocrinological... Jun 2023Parathyroid diseases are related to parathyroid hormone (PTH) dysregulation by parathyroid cells or alteration of PTH function. They include hyperparathyroidism (PTH... (Review)
Review
PURPOSE
Parathyroid diseases are related to parathyroid hormone (PTH) dysregulation by parathyroid cells or alteration of PTH function. They include hyperparathyroidism (PTH excess), hypoparathyroidism (PTH deficiency) and pseudohypoparathyroidism (PTH resistance). Little is known about correlation between parathyroid diseases and metabolic syndrome (MetS).
METHODS
An electronic-based search using PubMed was performed until October 2022 and articles were selected based on relevance of title, abstract, English language and publication in peer-reviewed journals.
RESULTS
Possible association between PTH alterations and the diverse manifestation of MetS have been proposed and it could be supposed that MetS may negatively influence parathyroid diseases. Available data show significant association for hyperparathyroidism and pseudohypoparathyroidism.
CONCLUSIONS
This review highlights the possible implications between MetS and parathyroid diseases. Given the increasing MetS global prevalence and the higher parathyroid diseases awareness and diagnosis, it may be interesting to further explore the possible role of alterations in parathyroid homeostasis in the development of MetS components with dedicated prospective studies.
Topics: Humans; Metabolic Syndrome; Prospective Studies; Parathyroid Diseases; Parathyroid Hormone; Hypoparathyroidism; Pseudohypoparathyroidism; Hyperparathyroidism
PubMed: 36773188
DOI: 10.1007/s40618-023-02018-2 -
Journal of Cutaneous Pathology Apr 2023
Topics: Humans; Pseudohypoparathyroidism; Bone Diseases, Metabolic; Skin Diseases, Genetic; Ossification, Heterotopic
PubMed: 36691934
DOI: 10.1111/cup.14397 -
Frontiers in Endocrinology 2022iPPSD2 (which includes PHP1A and PPHP/POH) is a rare inherited autosomal dominant endocrine disorder caused by inactivating pathogenic variants. A high percentage of...
OBJECTIVE
iPPSD2 (which includes PHP1A and PPHP/POH) is a rare inherited autosomal dominant endocrine disorder caused by inactivating pathogenic variants. A high percentage of cases has been suggested. In rare cases, parental mosaicism has been described, but its real frequency is unknown.
DESIGN
A retrospective study including a series of 95 genetically confirmed iPPSD2 probands.
METHODS
The frequency of cases was evaluated and the distribution of the type of variants was compared according to the type of inheritance. The putative involved allele was determined by reverse transcriptase PCR (RT-PCR) or allele specific oligonucleotide RT-PCR (ASO-RT-PCR). The possibility of mosaicism was studied by next-generation sequencing (NGS) on the corresponding parental DNA.
RESULTS
In 41 patients the variant was of origin and in 24 the origin could not be established. In both cases 66.67% of variants generated a truncated or absent protein whereas the rest of the variants were missense or in-frame deletion/duplication. Parental origin was studied in 45 of those patients and determined in 35. Curiously, the percentage of variants at the paternal allele was higher than when paternally inherited (31.1% vs 6.67%). NGS detected mosaicism in three independent families: one from paternal DNA (allelic ratio 10%) and two from maternal DNA (allelic ratio 10% and 2%).
CONCLUSION
pathogenic variants are frequent in iPPSD2 (around 45%). Parental mosaicism is infrequent (8.11%) but should be analyzed with NGS, taking into account its importance in genetic counselling.
Topics: Humans; Mosaicism; Parathyroid Hormone-Related Protein; Retrospective Studies; Mutation; Parents; DNA
PubMed: 36686455
DOI: 10.3389/fendo.2022.1055431 -
Molecular Genetics & Genomic Medicine May 2023Pseudohypoparathyroidism (PHP) is a series of diseases related to pathological changes and neurocognitive and endocrine abnormalities, mainly due to the GNAS mutation on...
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.
Topics: Female; Humans; GTP-Binding Protein alpha Subunits, Gs; DNA Methylation; Chromogranins; Pseudohypoparathyroidism; Sequence Deletion
PubMed: 36669868
DOI: 10.1002/mgg3.2144 -
PloS One 2023Albright hereditary osteodystrophy (AHO) is caused by heterozygous inactivating mutations in GNAS. Patients with maternally-inherited mutations develop...
BACKGROUND
Albright hereditary osteodystrophy (AHO) is caused by heterozygous inactivating mutations in GNAS. Patients with maternally-inherited mutations develop pseudohypoparathyroidism type 1A (PHP1A) with multi-hormone resistance and aberrant craniofacial and skeletal development among other abnormalities. Chiari malformation type 1 (CM1), a condition in which brain tissue extends into the spinal canal when the skull is too small, has been reported in isolated cases of PHP1A. It has been hypothesized to be associated with growth hormone (GH) deficiency. Given the adverse clinical sequelae that can occur if CM1 goes unrecognized, we investigated the previously undetermined prevalence of CM1, as well as any potential correlations with GH status, given the known increased prevalence of GH deficiency in PHP1A. We also investigated these metrics for low lying cerebellar tonsils (LLCT), defined as tonsillar descent less than 5 mm below the foramen magnum. In addition, we investigated possible correlations of CM1/LLCT with advanced hand/wrist bone ages and craniofacial abnormalities known to occur in PHP1A to determine whether premature chondrocyte differentiation and/or aberrant craniofacial development could be potential etiologies of CM1/LLCT through both human studies and investigations of our AHO mouse model.
METHODS
We examined patients with PHP1A in our clinic and noticed CM1 more frequently than expected. Therefore, we set out to determine the true prevalence of CM1 and LLCT in a cohort of 54 mutation-confirmed PHP1A participants who had clinically-indicated brain imaging. We examined potential correlations with GH status, clinical features, biological sex, genotype, and hand/wrist bone age determinations. In addition, we investigated the craniofacial development in our mouse model of AHO (Gnas E1+/-m) by histologic analyses, dynamic histomorphometry, and micro-computerized tomographic imaging (MCT) in order to determine potential etiologies of CM1/LLCT in PHP1A.
RESULTS
In our cohort of PHP1A, the prevalence of CM1 is 10.8%, which is at least 10-fold higher than in the general population. If LLCT is included, the prevalence increases to 21.7%. We found no correlation with GH status, biological sex, genotype, or hand/wrist bone age. Through investigations of our Gnas E1+/-m mice, the correlate to PHP1A, we identified a smaller cranial vault and increased cranial dome angle with evidence of hyperostosis due to increased osteogenesis. We also demonstrated that there was premature closure of the spheno-occipital synchondrosis (SOS), a cartilaginous structure essential to the development of the cranial base. These findings lead to craniofacial abnormalities and could contribute to CM1 and LLCT development in PHP1A.
CONCLUSION
The prevalence of CM1 is at least 10-fold higher in PHP1A compared to the general population and 20-fold higher when including LLCT. This is independent of the GH deficiency that is found in approximately two-thirds of patients with PHP1A. In light of potential serious consequences of CM1, clinicians should have a low threshold for brain imaging. Investigations of our AHO mouse model revealed aberrant cranial formation including a smaller cranium, increased cranial dome angle, hyperostosis, and premature SOS closure rates, providing a potential etiology for the increased prevalence of CM1 and LLCT in PHP1A.
Topics: Humans; Animals; Mice; Prevalence; Pseudohypoparathyroidism; GTP-Binding Protein alpha Subunits, Gs; Bone Development; Genotype; Arnold-Chiari Malformation; Chromogranins
PubMed: 36662765
DOI: 10.1371/journal.pone.0280463