Mutations of maturity-onset diabetes of the young (MODY) genes in Thais with early-onset type 2 diabetes mellitus

Objective  Six known genes responsible for maturity-onset diabetes of the young (MODY) were analysed to evaluate the prevalence of their mutations in Thai patients with MODY and early-onset type 2 diabetes.
Patients and methods  Fifty-one unrelated probands with early-onset type 2 diabetes, 21 of them fitted into classic MODY criteria, were analysed for nucleotide variations in promoters, exons, and exon–intron boundaries of six known MODY genes, including HNF-4α , GCK , HNF-1α , IPF-1 , HNF-1β , and NeuroD1/β2 , by the polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) method followed by direct DNA sequencing. Missense mutations or mutations located in regulatory region, which were absent in 130 chromosomes of non-diabetic controls, were classified as potentially pathogenic mutations.
Results  We found that mutations of the six known MODY genes account for a small proportion of classic MODY (19%) and early-onset type 2 diabetes (10%) in Thais. Five of these mutations are novel including GCK R327H, HNF-1α P475L, HNF-1α G554fsX556, NeuroD1 –1972 G > A and NeuroD1 A322N. Mutations of IPF-1 and HNF-1β were not identified in the studied probands.
Conclusions  Mutations of the six known MODY genes may not be a major cause of MODY and early-onset type 2 diabetes in Thais. Therefore, unidentified genes await discovery in a majority of Thai patients with MODY and early-onset type 2 diabetes.