Identification of Novel Potential Type 2 Diabetes Genes Mediating β-Cell Loss and Hyperglycemia Using Positional Cloning

Abstract

Type 2 diabetes (T2D) is a complex metabolic disease regulated by an interaction of genetic predisposition and environmental factors. To understand the genetic contribution in the development of diabetes, mice varying in their disease susceptibility were crossed with the obese and diabetes-prone New Zealand obese (NZO) mouse. Subsequent whole-genome sequence scans revealed one major quantitative trait loci (QTL), Nidd/DBA on chromosome 4, linked to elevated blood glucose and reduced plasma insulin and low levels of pancreatic insulin. Phenotypical characterization of congenic mice carrying 13.6 Mbp of the critical fragment of DBA mice displayed severe hyperglycemia and impaired glucose clearance at week 10, decreased glucose response in week 13, and loss of β-cells and pancreatic insulin in week 16. To identify the responsible gene variant(s), further congenic mice were generated and phenotyped, which resulted in a fragment of 3.3 Mbp that was sufficient to induce hyperglycemia. By combining transcriptome analysis and haplotype mapping, the number of putative responsible variant(s) was narrowed from initial 284 to 18 genes, including gene models and non-coding RNAs. Consideration of haplotype blocks reduced the number of candidate genes to four ( Kti12 , Osbpl9 , Ttc39a , and Calr4 ) as potential T2D candidates as they display a differential expression in pancreatic islets and/or sequence variation. In conclusion, the integration of comparative analysis of multiple inbred populations such as haplotype mapping, transcriptomics, and sequence data substantially improved the mapping resolution of the diabetes QTL Nidd/DBA . Future studies are necessary to understand the exact role of the different candidates in β-cell function and their contribution in maintaining glycemic control.

Temporal metabolic and transcriptomic characteristics crossing islets and liver reveal dynamic pathophysiology in diet-induced diabetes

“…Regardless of whether basal hyperinsulinemia or insulin resistance is the primary driver of T2DM, it is widely accepted that the progressive deterioration of β-cell function/loss of functional β-cell mass is key to the onset of diabetes ( Saisho, 2015 ). In order to identify molecules and mechanisms associated with β-cells’ transition from adaption to failure, high-throughput “omics” technologies (particularly microarray-based transcriptomics and mass-spectrometry-based proteomics) were broadly used on islets from different T2DM animal models ( Aga et al., 2020 ; Hou et al., 2017 ; Kluth et al., 2014 ; Neelankal John et al., 2018 ; Roat et al., 2014 ) and diabetic human donors ( Mencucci et al, 2021 ). Longitudinal observations and temporal “omics” analyses across the full spectrum of disease have gradually established a comprehensive picture of diabetic progression ( Fadista et al., 2014 ; Hou et al., 2017 ; Solimena et al., 2018 ).…”

Novel loci for hyperglycemia identified by QTL mapping of longitudinal phenotypes and congenic analysis

“…A QTL on distal Chr1, Nob3 , has been identified in genome-wide scans of diabetic NZO with non-diabetic C57BL/6J 25 . On Chr4, some QTLs have been identified in NZO with SJL mice ( Nidd/SJL ) 26 , 27 , in NZO with several mouse lines 28 , and in NZO with DBA mice ( Nidd/DBA ) 29 . On Chr10, a QTL has been identified in SM/J and A/J recombinant inbred strains ( t2dm1sa ) 30 .…”

Comparative genomic analyses of multiple backcross mouse populations suggestSGCGas a novel potential obesity-modifier gene

“…Several researchers ( 18–24 ), including ourselves ( 11–13 , 25 , 26 ), have used the NZO strain in genome-wide linkage studies attempting to uncover the gene variants that may drive the high susceptibility for obesity and T2D. All these studies were successful in identifying novel genomic regions, designated quantitative trait loci (QTL), associated with T2D-related phenotypes.…”