Type 1 and Type 2 diabetes (TID and TIID) differ in etiology, but both have decreased functional pancreatic β‐cell mass. Genome‐wide association studies identified transcription factor 19 (Tcf19) as a potential causal gene for both TID and TIID. Tcf19 is expressed in both humans and rodents, most highly in the pancreatic islet and upregulated in mouse models of non‐diabetic obesity. We showed that TCF19 is necessary for β‐cell proliferation and survival in INS1 cells. Thus, we hypothesized that TCF19 regulates β‐cell mass developmentally and in adaptive response to stress. A germline whole‐body knockout (wbTcf19KO) of Tcf19 mouse model was generated. wbTcf19KO and control (C57BL6/N) mice were fed a chow diet. Lean wbTcf19KO are metabolically similar to controls other than significantly higher body weights. Markers of proliferation (Ki67) and β‐cell identity (Pdx1, Nkx6.1, Nkx2.2) were significantly decreased while markers of pro‐apoptosis (Chop) and DNA damage response (Bak, Gadd45a, Dtx3l) were significantly increased in islets from wbTcf19KO mice. DNA damage is significantly elevated in wbTcf19KO islets as measured by y‐H2AX Western blot. Islet size distribution is significantly altered in wbTcf19KO islets, skewed by many very small islets. wbTcf19KO and control male mice were challenged with high fat diet (HFD; 1‐week & 10‐week) feeding. These mice failed to appropriately upregulate proliferation markers (Ki67, CyclinD2) in islets after 1‐week of HFD. Glucose intolerance and elevated fasting glucose develop in these mice after 10‐weeks of HFD. Female mice, less susceptible to diet induced hyperglycemia, were stressed with long‐term high fat high sucrose diet (HFHS) feeding to induce insulin resistance. After 8‐weeks of HFHS feeding wbTcf19KO females became significantly more glucose intolerant than control HFHS fed female mice. Ongoing studies will examine the impact of Tcf19 knockout on β‐cell mass during pregnancy in these HFHS‐fed females. Overall, loss of Tcf19 reveals changes in proliferation and DNA damage, which may be critical in stress‐induced β‐cell mass regulation.
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