Dataset Information

Identification of a Novel Missense Mutation of the PHEX Gene in a Large Chinese Family with X-Linked Hypophosphataemia.

ABSTRACT: X-linked hypophosphataemia (XLH) is an X-linked dominant rare disease that refers to the most common hereditary hypophosphatemia (HH) caused by mutations in the phosphate-regulating endopeptidase homolog X-linked gene (PHEX; OMIM: * 300550). However, mutations that have already been reported cannot account for all cases of XLH. Extensive genetic analysis can thus be helpful for arriving at the diagnosis of XLH. Herein, we identified a novel heterozygous mutation of PHEX (NM_000444.5: c.1768G > A) in a large Chinese family with XLH by whole-exome sequencing (WES). In addition, the negative effect of this mutation in PHEX was confirmed by both bioinformatics analysis and in vitro experimentation. The three-dimensional protein-model analysis predicted that this mutation might impair normal zinc binding. Immunofluorescence staining, qPCR, and western blotting analysis confirmed that the mutation we detected attenuated PHEX protein expression. The heterozygous mutation of PHEX (NM_000444.5: c.1768G > A) identified in this study by genetic and functional experiments constitutes a novel genetic cause of XLH, but further study will be required to expand its use in clinical and molecular diagnoses of XLH.

SUBMITTER: Yang Y

PROVIDER: S-EPMC8891598 | biostudies-literature | 2022

REPOSITORIES: biostudies-literature

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Identification of a Novel Missense Mutation of the PHEX Gene in a Large Chinese Family with X-Linked Hypophosphataemia.

Yang Yanting Y Wang Yuanda Y Shen Ying Y Liu Mohan M Dai Siyu S Wang Xiaodong X Liu Hongqian H

Frontiers in genetics 20220217

X-linked hypophosphataemia (XLH) is an X-linked dominant rare disease that refers to the most common hereditary hypophosphatemia (HH) caused by mutations in the phosphate-regulating endopeptidase homolog X-linked gene (PHEX; OMIM: * 300550). However, mutations that have already been reported cannot account for all cases of XLH. Extensive genetic analysis can thus be helpful for arriving at the diagnosis of XLH. Herein, we identified a novel heterozygous mutation of PHEX (NM_000444. ...[more]

PMID: 35251124

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Project description:BackgroundX-linked hypophosphatemic rickets (XLH) is a heterogeneous genetic phosphate wasting disorder that occupies the majority of inheritable hypophosphatemic rickets (HR). XLH is caused by loss-of-function mutations in the phosphate-regulating endopeptidase gene (PHEX) located on the X chromosome.MethodIn this study, we performed whole-exome sequencing (WES) on the proband to identify the causative gene. The mutations were analyzed by predictive online software, such as PolyPhen-2. Plasmids containing the wild-type (WT) and mutant cDNA of the candidate gene were transfected into HEK293, then, the expression, cellular localization, and glycosylation state of the candidate proteins were detected by western blot, immunostaining, and endoglycosidase H digestion. The expression and concentration of related factor were measured by RT-PCR and ELISA.ResultsWe identified a novel missense mutation c.2179T>C in the PHEX that results in the substitution of p.Phe727Leu (F727L). This mutation was predicted to be disease-causing by all four predictive online software. In vitro studies demonstrated that the F727L substitution hindered the intracellular trafficking of the mutant PHEX, with ~59% of mutant PHEX protein retained in the endoplasmic reticulum (ER) and only ~16% of the mutant protein localized on the cell surface. Endoglycosidase H digestion assay showed that the mutant F727L PHEX protein was not fully glycosylated. The concentration of intact FGF23 in hFOB1.19 cell culture medium collected from the mutant PHEX group was the highest (62.9 pg/ml) compared to the WT group (32.1 pg/ml) and control group (23.5 pg/ml).ConclusionOur results confirmed that the mutant PHEX protein was lowly glycosylated and retarded within the ER, the intact FGF23 level in cell culture media caused by the mutant PHEX protein was significantly elevated compared to that of the WT group, which may explain why the single base mutation in the PHEX led to XLH syndrome in this family.

Project description:BackgroundProximal symphalangism (SYM1) is a rare genetic bone disorder characterized by the fusion of proximal interphalangeal joints in the hands and feet. Genetic studies have identified two genes underlying SYM1 as the noggin (NOG) and the growth differentiation factor 5 (GDF5).Case reportIn the present report, a 43-year-old gravida at 11 weeks of gestation was referred for evaluation of abnormal fusions of the joints. In the initial diagnosis, physical examination was undertaken. However, traditional radiological examination was not applied due to the need to protect the fetus, making diagnosis results inefficient to determine the exact disease affecting the proband. To acquire alternative clinical evidences, we conducted radiological examinations on two other affected family members. The radiological examination revealed that they carried the symphalangism accompanied with tarsal coalition, a very rare manifestation of SYM1. A combination of whole exome sequencing (WES) and Sanger sequencing revealed a novel heterozygous missense mutation (c.163G > T; p.Asp55Tyr) in the NOG gene, which could be associated with the observed pathogenic SYM1 in the studied family. The p.Asp55Tyr mutation co-segregated with SYM1 through the affected and unaffected family members. In silico structural modeling of the p.Asp55Tyr mutation showed that it abolishes the interaction with the Arg167 residue and causes a change in the electrostatic potential profile of the type II binding site of the noggin protein.ConclusionOur findings indicate that the genetic test based on WES can be useful in diagnosing SYM1 patients, with particular advantages in preventing the fetus from contacting harmful X-ray through the traditional radiography. The novel pathogenic mutation identified would further expand our understanding of the mutation spectrum of NOG in association with SYM1 disease and provide a guidance on how to determine whether the fetus is affected by SYM1 through the prenatal diagnosis.

Dataset Information

Identification of a Novel Missense Mutation of the PHEX Gene in a Large Chinese Family with X-Linked Hypophosphataemia.

Publications

Identification of a Novel Missense Mutation of the <i>PHEX</i> Gene in a Large Chinese Family with X-Linked Hypophosphataemia.

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