Background: Diabetes mellitus (DM) is a group of metabolic disorders in the body, accompanied with increasing blood sugar levels. Diabetes is classified into three groups: Type 1 DM (T1DM), Type 2 DM (T2DM), and monogenic diabetes. Maturity-onset diabetes of the young (MODY) is a monogenic diabetes that is frequently mistaken for T1D or T2D. The aim of this study was to diagnose MODY and its subtype frequency in a diabetic population in Iran. Materials and Methods: In this study among ten diabetic families that were highly suspected to MODY by nongenetic biomarkers and without any pathogenic mutation in GCK and HNF1A genes, two patients from two unrelated families were examined via whole-exome sequencing (WES) in order to detect the causative gene of diabetes. Co-segregation analysis of the identified variant was performed using Sanger sequencing. Results: In this study, no pathogenic variant was found in GCK and HNF1A genes (MODY2 and MODY3), while these two types of MODY were introduced as the most frequent in other studies. By using WES, a pathogenic variant (p.I488T) was found in one of the patients in CEL gene causing MODY8 that its frequency is very rare in other studied populations. A high-risk variant associated with diabetes was found in another patient. Conclusion: WES was applied in this study to reveal the cause of MODY in 1 family. This pathogenic mutation was previously reported as a disease causing mutation.

Background:Maturity-onset diabetes of the young (MODY) is a clinically and genetically heterogeneous group of diabetes characterized by noninsulin-dependent, autosomal-dominant disorder with strong familial history, early age of onset, and pancreatic beta-cell dysfunction. Mutations in at least 14 different genes are responsible for various MODY subtypes. Heterozygous mutations in the hepatocyte nuclear factor 1 alpha (HNF1A) gene are responsible for the MODY3 subtype, which is a common subtype of MODY in different studied populations. To date, more than 450 different variants of this gene have been reported as disease causing for MODY3. This study was carried out to evaluate HNF1A mutations in Iranian diabetic families fulfilling MODY criteria.Materials and Methods:Polymerase chain reaction and Sanger sequencing were performed. All the ten exons of the HNF1A gene were sequenced in ten families, followed by cosegregation analysis and in silico evaluation. Computational protein modeling was accomplished for the identified mutation.Results:MODY3 was confirmed in two large families by detecting a mutation (p.G253E) in coding regions of HNF1A. Compound heterozygous state for two common variants in HNF1A (p.I27 L and p.S487N) was detected in affected members of 5 families, and in one family, a rare benign variant in the coding sequence for Kozak sequence was detected. Two new nonpathogenic variants were found in noncoding regions of HNF1A.Conclusion:It seems that HNF1A mutations are a common cause of MODY in Iranian diabetic patients. Identified common variants in heterozygous state can cause diabetes Type II in earlier ages. The role of rare variant rs3455720 is unknown, and more investigation is needed to uncover the function of this variant.

This is the first report of the genetic diagnosis of NDNC in Iran. We also report a novel pathogenic variant. The study of the FZD6 gene is recommended as the first step in the diagnostic routing of the autosomal recessive NDNC patients with enlarged nails.