Screening Of DUOX2 Mutations In Children With Congenital Hypothyroidism

Objective: Congenital hypothyroidism（CH）is the most common neonatal metabolic disorder.Two main mechanisms known resulting in CH are thyroid gland dysgenesis and thyroid gland dyshormomogenesis which lead to the deficiencies of the enzymes relevant to the course of thyroid hormone synthesis,respectively.Studies have shown that most of CH patients with thyroid gland dyshormomogenesis have genetic factors.Although many candidate genes associated with CH have been found,there’s still a lack of large-scale CH patients gene screening.Defects in the human thyroid oxidase 2 gene（DUOX2）are reported to be the most important cause of CH due to thyroid dysgenesis.This study aims to analyze the mutation spectrum and the prevalence of DUOX2 gene in 86 CH children,and then analyzes the genotype-phenotype correlations of various DUOX2 gene variants.Methods: In this study,86 children diagnosed as CH by neonatal screening and 200 healthy children were selected.All exons and exon-introns of DUOX2 gene were sequenced by next-generation sequencing.At the same time,the suspected disease-causing gene variants were verified by one-generation sequencing.Then the function and effect of potential pathogenic variants were analyzed by means of computational biology.Meanwhile,the American College of Medical Genetics and Genomics and the Association for Molecular Pathology（ACMG/AMP）assessment guidelines were used for classification of diseases grades.The relationship between CH patients with different numbers of DUOX2 gene variants and the thyroid function test results were also analyzed.Results: The results showed that 20 different DUOX2 gene variants were found,including 10 non-synonymous variants,4 nonsense mutations,3 whole-code variants,and 3 frame-shift variants.Of these 20 variants,16 are known to be pathogenic or likely pathogenic,and 4 are suspected to be uncertain significance,and their frequencies in healthy controls less than 1%.The prevalence of DUOX2 variants in 86 CH children was 30.2%（26/86）,and three mutations（p.K530 X,p.L1343 F and p.R1110Q）had the highest prevalence in our study.Using protein homology modeling method,the analysis of its three-dimensional structure suggested that the mutations p.336₃37del and p.T1107 fs caused change of the protein.Conclusion: According to the next-generation sequencing of DUOX2 gene,30.2% of the 86 CH children had at least one suspected disease-causing gene variants and 20 suspected pathogenic gene variants were found.Variants of p.K530 X,p.L1343 F and p.R1110 Q had the highest prevalence in our study,which was consistent with the specificity of the DUOX2 gene variants in Asian populations with CH.Children with DUOX2 single allele heterozygous mutation or compound heterozygous mutation have different thyroid gland.