Study of Thirteen Causal Genes in Turkish Patients with Clinically Suspected Maturity-Onset Diabetes of the Young (MODY) using a Targeted Next-Generation Sequencing Panel

Abstract Background: Maturity-onset diabetes of the young (MODY), which is the most common cause of monogenic diabetes, has an autosomal dominant pattern of inheritance and exhibits marked clinical and genetic heterogeneity. The aim of the current study was to investigate molecular defects in patients with clinically suspected MODY using a next-generation sequencing (NGS)-based targeted gene panel. Candidate patients with clinical suspicion of MODY and their parents were included in the study. Molecular genetic analyses were performed on genomic DNA by using NGS. A panel of thirteen MODY-related genes involving ABCC8, BLK, CEL, GCK, HNF1A, HNF1B, HNF4A, INS, KCNJ11, KLF11, NEUROD1, PAX4, PDX1 was designed and subsequently implemented to screen 44 patients for genetic variants. Ten different pathogenic or likely pathogenic variants were identified in MODY-suspected patients, with a diagnostic rate of 22.7%. Eight variants of uncertain significance were also detected. Four novel pathogenic or likely pathogenic variants were detected in the genes GCK (c.1301G>T [p.Cys434Phe]), HNF1A (c.505_506delAA [p.Lys169AlafsTer18]), ABCC8 (c.3584C>T [p.Thr1195Ile]), and CEL (c.679-1G>A). Intriguingly, we were able to detect variants associated with rare forms of MODY in our study population. Our results suggest that in heterogenous diseases such as MODY, NGS analysis enables accurate identification of underlying molecular defects in a timely and cost-effective manner. Although MODY accounts for 1–2% of all diabetic cases, molecular genetic diagnosis of MODY is necessary for optimal long-term treatment and prognosis as well as for effective genetic counseling.