Differentially expressed genes between human T2D beta cells and normal beta cells, determined from three separate single-cell studies with a combined 19 T2D donors and 33 non-diabetic donors138, included TAF1, PTPRD, NOXA1, MED13, AFF1, and MEST. These genes were also differentially expressed in our datasets between insectivorous big brown bat and Jamaican fruit bat beta cells (Fig. 5C). The gene discussed is MEST; the disease is type 2 diabetes mellitus.