Association analysis of proopiomelanocortin (POMC) haplotypes in type 1 diabetes in a UK population

Coxsackievirus B infection invokes unique cell-type specific responses in primary human pancreatic islets

Coxsackievirus B (CVB) infection has long been considered an environmental factor precipitating Type 1 diabetes (T1D), an autoimmune disease marked by loss of insulin-producing β cells within pancreatic islets. Previous studies have shown CVB infection negatively impacts islet function and viability but do not report on how virus infection individually affects the multiple cell types present in human primary islets. Therefore, we hypothesized that the various islet cell populations have unique transcriptional responses to CVB infection. Here, we performed single-cell RNA sequencing on human cadaveric islets treated with either CVB or poly(I:C), a viral mimic, for 24 and 48 hours. Our global analysis reveals CVB differentially induces dynamic transcriptional changes associated with multiple cell processes and functions over time whereas poly(I:C) promotes an immune response that progressively increases with treatment duration. At the single-cell resolution, we find CVB infects all islet cell types at similar rates yet induces unique cell-type specific transcriptional responses with β, α, and ductal cells having the strongest response. Sequencing and functional data suggest that CVB negatively impacts mitochondrial respiration and morphology in distinct ways in β and α cells, while also promoting the generation of reactive oxygen species. We also observe an increase in the expression of the long-noncoding RNA MIR7-3HG in β cells with high viral titers and reveal its knockdown reduces gene expression of viral proteins as well as apoptosis in stem cell-derived islets. Together, these findings demonstrate a cell-specific transcriptional, temporal, and functional response to CVB infection and provide new insights into the relationship between CVB infection and T1D.

Hyperandrogenism in POMCa-deficient zebrafish enhances somatic growth without increasing adiposity

The endocrine regulatory roles of the hypothalamic-pituitary-adrenocortical axis on anxiety-like behavior and metabolic status have been found throughout animal taxa. However, the precise effects of the balancing adrenal corticosteroid biosynthesis under the influence of adrenocorticotrophic hormone (ACTH), a pro-opiomelanocortin (POMC)-derived peptide, on animal energy expenditure and somatic growth remain unknown. POMC has also been identified as one of the candidate loci for polycystic ovary syndrome, which features hyperandrogenism and some prevalence of obesity in patients. Here we show that zebrafish lacking functional POMCa exhibit similar phenotypes of stress response and body weight gain but not obesity as observed in mammalian models. In contrast with the impaired anorexigenic signaling cascade of melanocyte-stimulating hormones and leptin, which are responsible for their obesity-prone weight gain observed in various pomc mutant mammals, analyses with our pomca mutant series indicate that ACTH is the key regulator for the phenotype with enhanced somatic growth without obesity in pomca-deficient zebrafish. Hypocortisolism associated with hyperandrogenism has been observed in the pomca-deficient zebrafish, with enhanced activation of mammalian target of rapamycin complex 1; reutilization of amino acids and fatty acid β-oxidation are observed in the muscle tissue of the pomca-deficient fish. After reducing hyperandrogenism by crossing our pomca mutant fish with a cyp17a1-deficient background, the phenotype of enhanced somatic growth in pomca-deficient fish was no longer observed. Thus, our work also demonstrated that the role of POMCa in stress response seems to be conserved in vertebrates, whereas its effect on adipostasis is unique to teleosts.

Genes involved in type 1 diabetes: an update

Type 1 Diabetes (T1D) is a chronic multifactorial disease with a strong genetic component, which, through interactions with specific environmental factors, triggers disease onset. T1D typically manifests in early to mid childhood through the autoimmune destruction of pancreatic β cells resulting in a lack of insulin production. Historically, prior to genome-wide association studies (GWAS), six loci in the genome were fully established to be associated with T1D. With the advent of high-throughput single nucleotide polymorphism (SNP) genotyping array technologies, enabling investigators to perform high-density GWAS, many additional T1D susceptibility genes have been discovered. Indeed, recent meta-analyses of multiple datasets from independent investigators have brought the tally of well-validated T1D disease genes to almost 60. In this mini-review, we address recent advances in the genetics of T1D and provide an update on the latest susceptibility loci added to the list of genes involved in the pathogenesis of T1D.