GSE135276
RNA-seq-based identification of StAR upregulation by islet amyloid formation
Aggregation of islet amyloid polypeptide (IAPP) into islet amyloid results in ß-cell toxicity in human type 2 diabetes. To determine the effect of islet amyloid formation on gene expression, we performed RNA-seq analysis using cultured islets from either wild-type mice (mIAPP), which are not amyloid prone, or mice that express human IAPP (hIAPP), which develop amyloid. Comparing mIAPP and hIAPP islets, 5025 genes were differentially regulated (2439 upregulated and 2586 downregulated). When considering gene sets (reactomes), 248 and 52 pathways were up- and downregulated, respectively. Of the top 100 genes upregulated under two conditions of amyloid formation, seven were common. Of these seven genes, only steroidogenic acute regulatory protein AQ2 (Star) demonstrated no effect of glucose per se to modify its expression. We confirmed this differential gene expression using quantitative reverse transcription polymerase chain reaction and also demonstrated the presence of StAR protein in islets containing amyloid. Furthermore, Star is a part of reactomes representing metabolism, metabolism of lipids, metabolism of steroid hormones, metabolism of steroids and pregnenolone biosynthesis. Thus, examining gene expression that is differentially regulated by islet amyloid has the ability to identify new molecules involved in islet physiology and pathology applicable to type 2 diabetes. Overall design: Here we applied RNA-seq to study the effect of high glucose and IAPP aggregation on the transcriptome. Aggregation was stimulated by transgenic replacement of the mouse IAPP gene sequence with the corresponding human IAPP sequence, as per Hiddinga et al (2011 DOI:10.1111/j.2040-1124.2011.00166.x).  To do this we profiled four sample groups with n=8 biological replicates: (1) wild type mouse islets cultured in 11.1 mmol/L glucose. (2) wild type mouse islets cultured in 16.7 mmol/L glucose. (3) transgenic hIAPP mouse islets cultured in 11.1 mmol/L glucose. (4) transgenic hIAPP mouse islets cultured in 16.7 mmol/L glucose