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Identification of a novel compound heterozygous IDUA mutation underlies Mucopolysaccharidoses type I in a Chinese pedigree.

ABSTRACT: BACKGROUND:Mucopolysaccharidosis type I (MPS I) is a rare autosomal storage disorder resulting from the defective alpha-L-iduronidase (encoded by IDUA) enzyme activity and accumulation of glycosaminoglycans (GAGs) in lysosomes. So far, more than 100 IDUA causative mutations have been identified leading to three MPS I phenotypic subtypes: Hurler syndrome (severe form), Hurler/Scheie syndrome (intermediate form), and Scheie syndrome (mild form). METHODS:Whole-exome sequencing (WES) was performed to identify the underlying genetic mutations. To verify the identified variations, Sanger sequencing was performed for all available family members following PCR amplification. The impact on IDUA protein was analyzed by sequential analysis and homology modeling. RESULTS:A novel IDUA heterozygous single base insertion (c.1815dupT, p.V606Cfs51* ) and a known missence mutation (c.T1037G, p.L346R) were detected in our patient diagnosed as congenital heart disease with heart valve abnormalities. The novel frameshift mutation results in a complete loss of 48 amino acids in the Ig-like domain and causes the formation of a putative protein product which might affect the IDUA enzyme activity. CONCLUSIONS:A novel compound heterozygous IDUA mutation (c.1815dupT, p.V606Cfs51* ) was found in a Chinese MPS I family. The identification of the mutation facilitated accurate genetic counseling and precise medical intervention for MPS I in China.

SUBMITTER: Zhou YA

PROVIDER: S-EPMC6978265 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Project description:Objective: To explore the molecular pathogenesis of a family with hereditary factor Ⅴ (FⅤ) deficiency. Methods: All the exons, flanking sequences, 5' and 3' untranslated regions of the F5 of the proband, and the corresponding mutation sites of the family members were analyzed via direct DNA sequencing. The CAT measurement was used to detect the amount of thrombin produced. The ClustalX software was used to analyze the conservation of mutation sites. The online bioinformatics software, Mutation Taster, PolyPhen-2, PROVEAN, LRT, and SIFT were applied to predict the effects of mutation sites on protein function. The Swiss-PdbViewer software was used to analyze the changes in the protein model and intermolecular force before and after amino acid variation. Results: The proband had a heterozygous missense mutation c.1258G>T (p.Gly392Cys) in exon 8 of the F5, and a heterozygous deletion mutation c.4797delG (p.Glu1572Lys fsX19) in exon 14, which results in a frameshift and produces a truncated protein. Her grandfather and father had p.Gly392Cys heterozygous variation, whereas her maternal grandmother, mother, little aunt, and cousin all had p.Glu1572LysfsX19 heterozygous variation. The ratio of proband's thrombin generation delay to peak time was significantly increased. Conservation analysis results showed that p.Gly392 was located in a conserved region among the 10 homologous species. Five online bioinformatics software predicted that p.Gly392Cys was pathogenic, and Mutation Taster also predicted p.Glu1572Lys fsX19 as a pathogenic variant. Protein model analysis showed that the replacement of Gly392 by Cys392 can lead to the extension of the original hydrogen bond and the formation of a new steric hindrance, which affected the stability of the protein structure. Conclusion: The c.1258G>T heterozygous missense mutation in exon 8 and the c.4797delG heterozygous deletion mutation in exon 14 of the F5 may be responsible for the decrease of FⅤ levels in this family.

Project description:Usher syndrome refers to a group of genetically and clinically heterogeneous autosomal recessive diseases with retinitis pigmentosa (RP) and hearing deficiencies. The association between Usher syndrome?causative genes and resultant Usher syndrome phenotypes in patients are highly variable. In the present study, a Chinese family with Usher syndrome was recruited, and targeted next?generation sequencing, Sanger sequencing and segregation analysis were performed. The expression profiles and functional effects of the pathogenic variants of USH2A identified were analyzed. Novel nonsense compound heterozygous variants, c.T449G (p.L150*) and c.T10695A (p.Y3565*), were identified in the USH2A gene, which showed co?segregation with the disease phenotype causing Usher syndrome type IIA in the recruited Chinese pedigree. The p.L150* variant was predicted to produce a truncated protein which lacked almost all the functional domains of USH2A, whereas the p.Y3565* variant is located in one of the fibronectin type 3 domains, resulting in the loss of several fibronectin type 3 domains at the C?terminus of USH2A by producing the truncated protein. It was shown that Ush2a mRNA expression levels were higher in the retina compared with those in the eye tissues (lens, sclera and cornea), uterus, ovary, breast, testis, spleen, kidney, liver, intestine, brain, skeletal muscle and blood. Additionally, the protein structure was shown to be highly conserved by comparing Homo sapiens USH2A to eight other species. To the best of our knowledge, the present study is the first to identify two novel pathogenic variants, c.T449G (p.L150*) and c.T10695A (p.Y3565*), in the USH2A gene in a patient with Usher syndrome type IIA, thereby expanding the known spectrums of USH2A causative mutations. The present discovery may assist in understanding the molecular pathogenesis underlying the development of RP and Usher syndrome type IIA, and in the development of diagnostic, therapeutic and genetic counseling strategies in patients with Usher syndrome type IIA disease.

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Identification of a novel compound heterozygous IDUA mutation underlies Mucopolysaccharidoses type I in a Chinese pedigree.

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