The relevance of this inter-islet heterogeneity to both normal insulin secretion and type 1 diabetes pathogenesis, is difficult to study given the challenges of interrogating the function of multiple islets while preserving their spatial interrelationships simultaneously within the intact pancreas but may be achievable in pancreatic slice preparations, at least over relatively short ranges (a few mm). This evidence concerns the gene INS and type 1 diabetes mellitus.