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Effects of rs3842753 on insulin expression in single beta cells. Wang, Su


Type 1 diabetes (T1D) is characterized by the autoimmune destruction of insulin-secreting beta-cells. Genetic variations upstream at the insulin (INS) locus contribute to ~10% of T1D heritable risk. Multiple studies showed an association between rs3842753 C/C genotype and T1D susceptibility. Three small studies reported an association between rs3842753 C allele and increased whole pancreas INS expression. To date, no large-scale studies have looked at the effect of those genetic variations on insulin expression at the single cell level. We aligned all available human pancreatic single cell RNA sequencing datasets using STAR and used Samtools mpileup to genotype rs3842753. Using Seurat, we integrated 2315 beta-cells from 13 A/A donors, 23 A/C heterozygous donors, and 35 C/C at-risk donors. The donors included persons with and without type 2 diabetes, but not T1D. We compared variance using Bartlett’s test or Fligner-Killeen test and means using Wilcox Rank Sum, Student-t, ANOVA, or Kruskal-Wallis tests. Per β-cell INS expression mean and variance were significantly higher in females compared with males. In male cells, INS expression appeared to be significantly lower in T2D compared to non-diabetic cells. Comparing across all cells, we found that rs3842753 A/C genotype had the highest INS expression followed by C/C genotype, lastly by A/A genotype. Donor level comparisons between genotypes were not statistically significant. Conversely, within A/C heterozygous β-cells, A allele specific INS expression was higher. This association was consistent at the donor level. Lastly, we examined whole pancreatic islets from a small subset of donors and found no relationship between insulin protein abundance and rs3842753 genotype. Our analysis suggests that in single β-cells, rs3842753 may affect INS variance and expression. The contribution of these differences to T1D risk remains unclear.

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