Genotype-phenotype correlation in Taiwanese children with diazoxide-unresponsive congenital hyperinsulinism

Congenital hyperinsulinism (CHI) is a group of clinically and genetically heterogeneous disorders characterized by dysregulated insulin secretion. The aim of the study was to elucidate genetic etiologies of Taiwanese children with the most severe diazoxide-unresponsive CHI and analyze their genotype-phenotype correlations. We combined Sanger with whole exome sequencing (WES) to analyze CHI-related genes. The allele frequency of the most common variant was estimated by single-nucleotide polymorphism haplotype analysis. The functional effects of the ATP-sensitive potassium (K ) channel variants were assessed using patch clamp recording and Western blot. Nine of 13 (69%) patients with ten different pathogenic variants (7 in , 2 in and 1 in ) were identified by the combined sequencing. The variant p.T1042QfsX75 identified in three probands was located in a specific haplotype. Functional study revealed the human SUR1 (hSUR1)-L366F K channels failed to respond to intracellular MgADP and diazoxide while hSUR1-R797Q and hSUR1-R1393C K channels were defective in trafficking. One patient had a dominant mutation in the gene (p.I211F), and WES revealed mosaicism of this variant from another patient. Pathogenic variants in K channels are the most common underlying cause of diazoxide-unresponsive CHI in the Taiwanese cohort. The p.T1042QfsX75 variant in the gene is highly suggestive of a founder effect. The I211F mutation in the gene and three rare SUR1 variants associated with defective gating (p.L366F) or traffic (p.R797Q and p.R1393C) K channels are also associated with the diazoxide-unresponsive phenotype.