Examining how the novel S64F MAFA variant produces glucose intolerance or hypoglycemia in a sex-dependent manner

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PROJECT ABSTRACT As of 2018, 30.3 million Americans have been diagnosed with diabetes (10% of the U.S. population with a male sex bias). Its close associations with many chronic diseases, such as heart attacks, strokes, and cancers, make diabetes a leading risk factor for morbidity and mortality. In all forms of diabetes, the inability to maintain normal glucose levels results from progressive dysfunction and eventual loss of insulin-producing b-cells in the pancreas. With high rates of treatment failure on standard therapy, developing new therapeutic approaches to preserve or even enhance b-cell function is a priority. Furthermore, differences in metabolism between men and women during healthy aging and disease are appreciated but poorly understood. Pancreatic b-cells require several key factors to appropriately secrete insulin. One such factor is MafA, a transcription factor fundamental to mature b-cell function. The early loss of human MafA (MAFA) in b-cells in patients with type 2 diabetes highlights its importance to human b-cell health. In addition, a naturally occurring, genetic mutation in MAFA (S64F MAFA) was recently identified to predispose carriers to either familial, adult- onset diabetes or hypoglycemia (low blood glucose). Curiously, S64F MAFA-associated diabetes is much more prevalent in men while women tend to present with hypoglycemia. To better understand the sex- dependent effects of this variant, we generated a mouse model harboring this mutation. This model shows the expected sex-dependent effects seen in humans, suggesting similar mechanisms between mice and humans. Male S64F MAFA mice were hyperglycemic due to widespread, premature b-cell aging and senescence, while female S64F MAFA mice were hypoglycemic by a mechanism which is not yet clearly defined. However, our preliminary studies suggest that S64F MAFA creates different b-cell subtypes in females, one of which is hyperfunctional. Taken together, these results suggest that S64F MAFA can incur diverse b-cell responses to produce sex-dependent diseases: diabetes (b-cell hypofunction) and hypoglycemia (b-cell hyperfunction). This investigation will identify and compare the diverse molecular responses to S64F MAFA in male and female b-cells across mice and humans to understand the sex-dependent, b-cell responses unique to human b-cells. We will first use the penetrant, proof-of-principle S64F MAFA mouse model which mimics several aspects of human disease to identify the diverse b-cell populations by single cell transcriptomics. For example, diversity in premature aging signatures will be related to the dysfunction seen in senescent, male S64F MAFA b-cells. We will then investigate the molecular and functional responses to the S64F MAFA protein in genetically modified, male and female human b-cells using novel pseudoislet technology to identify targets unique to human b-cell function. In sum, our work will advance fundamental understanding of sex-dependent b-cell responses in humans. Mechanisms underlying a relative male vulnerability and female resistance to diabetes in this model can be harnessed to develop therapies tailored to the individual.