BackgroundMaturity-onset of the young (MODY) is a clinically heterogeneous form of diabetes characterized by an autosomal-dominant mode of inheritance, an onset before the age of 25 years, and a primary defect in the pancreatic beta-cell function. Approximately 30% of MODY families remain genetically unexplained (MODY-X). Here, we aimed to use whole-exome sequencing (WES) in a four-generation MODY-X family to identify a new susceptibility gene for MODY.MethodologyWES (Agilent-SureSelect capture/Illumina-GAIIx sequencing) was performed in three affected and one non-affected relatives in the MODY-X family. We then performed a high-throughput multiplex genotyping (Illumina-GoldenGate assay) of the putative causal mutations in the whole family and in 406 controls. A linkage analysis was also carried out.Principal FindingsBy focusing on variants of interest (i.e. gains of stop codon, frameshift, non-synonymous and splice-site variants not reported in dbSNP130) present in the three affected relatives and not present in the control, we found 69 mutations. However, as WES was not uniform between samples, a total of 324 mutations had to be assessed in the whole family and in controls. Only one mutation (p.Glu227Lys in KCNJ11) co-segregated with diabetes in the family (with a LOD-score of 3.68). No KCNJ11 mutation was found in 25 other MODY-X unrelated subjects.Conclusions/SignificanceBeyond neonatal diabetes mellitus (NDM), KCNJ11 is also a MODY gene (‘MODY13’), confirming the wide spectrum of diabetes related phenotypes due to mutations in NDM genes (i.e. KCNJ11, ABCC8 and INS). Therefore, the molecular diagnosis of MODY should include KCNJ11 as affected carriers can be ideally treated with oral sulfonylureas.

Objective: Single gene mutations leading to severe obesity have so far been identified in 3-5% cases in European populations. However, prevalence of these pathogenic mutations has not systematically been examined in specific consanguineous populations. Here we describe the incidence of obesity-associated mutations through a step-wise sequence analysis, in a cohort of 73 Pakistani children with severe obesity from consanguineous families. Methods: Initially, all subjects were screened for mutations in coding regions of leptin (LEP) and melanocortin 4 receptor (MC4R) genes by direct sequencing. Subjects negative for mutation in these genes were screened using microdroplet PCR enrichment and NGS. Genomic structural variation was assessed by genotyping. Serum leptin, insulin, and cortisol were determined by ELISA. Results: Among 73 children with severe obesity (BMI SDS > 3.0), we identified 22 probands and 5 relatives, carrying 10 different loss-of-function homozygous mutations in LEP, leptin receptor (LEPR), and MC4R genes, including 4 novel variants. Hypercortisolemia was significantly emphasized in LEP mutation carriers. Conclusions: The prevalence of pathogenic mutations in genes known to directly influence leptinmelanocortin signaling is 30% in our cohort. The results of this study emphasize the desirability of undertaking systematic and in-depth genetic analysis of cases with severe obesity in specific consanguineous populations.