Identification of gene mutations associated with Type 1 Diabetes by Next Generation Sequencing in Inflicted Palestinian Families رسالة ماجستير

Abstract

Diabetes Mellitus is a group of metabolic disorders that are characterized by the presence of hyperglycemia secondary to insulin resistance or deficiency. It is considered a major health problem worldwide. It is classified into several subgroups including Type 1 diabetes mellitus, type 2 diabetes mellitus, gestational diabetes, and monogenic diabetes such as maturity-onset diabetes of the young (MODY). T1DM results due to a combination between genetics, epigenetics, and environmental factors. Several genes have been associated with T1DM including HLA, INS, CTLA4, and PTPN22. However, none of them is based on linkage analysis because it’s rare to find families with several diabetic individuals. Two Palestinian families having several affected members with variations in the mode of inheritance were identified and selected for this study. We aimed to clearly identify the causative gene(s) responsible for T1DM development in these families, in order to improve the understanding of the molecular genetics of the disease. One inflicted member from each family was selected for Whole-exome sequencing. Data were mapped to the reference human genome and the resulting VCF file containing many thousands of variants was filtered. The variants with the highest phenotype correlation score (four variants in each family) were checked by Sanger sequencing in all the family members. The confirmed variants were in-silico analyzed by bioinformatics tools. In family I, variants in INS, KCNJ11, HNF1A, and IGF1R genes were identified and tested. Only the IGF1R p.V579F variant follows autosomal dominant inheritance was confirmed and segregated in the family. In family II, variants in ABCC8, NEUROD1, RYR1, and CTRC genes were identified and checked. NEUROD1 p.P197H variant which follows autosomal recessive inheritance was positively confirmed and vii segregated. In conclusion, IGF1R p.V579F and NEURID1 p.P197H variants were associated with T1DM development in the two inflicted families in our study. Further analysis and functional assays should be done to fully confirm these findings and unravel their specific role in the disease development. This data will be valuable in the screening and diagnosis of patients in addition to the potential significance of these genes to serve as therapeutic targets.