Comprehensive molecular analysis of Japanese patients with pediatric-onset MODY-type diabetes mellitus

Yorifuji T, Fujimaru R, Hosokawa Y, Tamagawa N, Shiozaki M, Aizu K, Jinno K, Maruo Y, Nagasaka H, Tajima T, Kobayashi K, Urakami T. Comprehensive molecular analysis of Japanese patients with pediatric‐onset MODY‐type diabetes mellitus. Background: In Asians, mutations in the known maturity‐onset diabetes of the young (MODY) genes have been identified in only <15% of patients. These results were obtained mostly through studies on adult patients. Objective: To investigate the molecular basis of Japanese patients with pediatric‐onset MODY‐type diabetes. Subjects: Eighty Japanese patients with pediatric‐onset MODY‐type diabetes. Methods: Mitochondrial 3243A>G mutation was first tested by the polymerase chain reaction restriction fragment length polymorphism analysis for maternally inherited families. Then, all coding exons and exon–intron boundaries of the HNF1A, HNF1B, GCK, and HNF4A genes were amplified from genomic DNA and directly sequenced. Multiplex ligation‐dependent probe amplification analysis was also performed to detect whole‐exon deletions. Results: After excluding one patient with a mitochondrial 3243A>G, mutations were identified in 38 (48.1%) patients; 18 had GCK mutations, 11 had HNF1A mutations, 3 had HNF4A mutations, and 6 had HNF1B mutations. In patients aged <8 yr, mutations were detected mostly in GCK at a higher frequency (63.6%). In patients >9 yr of age, mutations were identified less frequently (45.1%), with HNF1A mutations being the most frequent. A large fraction of mutation‐negative patients showed elevated homeostasis model assessment (HOMA) insulin‐resistance and normal HOMA‐β indices. Most of the HNF1B mutations were large deletions, and, interestingly, renal cysts were undetectable in two patients with whole‐gene deletion of HNF1B. Conclusion: In Japanese patients with pediatric‐onset MODY‐type diabetes, mutations in known genes were identified at a much higher frequency than previously reported for adult Asians. A fraction of mutation‐negative patients presented with insulin‐resistance and normal insulin‐secretory capacities resembling early‐onset type 2 diabetes.