Roxanna D. Hauck¹, Twan J.J. de Winter¹, Mandala Ajie¹, Sophie Kipper¹, Eelco J.P.

de Koning¹, Françoise Carlotti¹.

¹LUMC, Dept. of Internal Medicine

r.d.hauck@lumc.nl

Background: MODY1 is a monogenetic form of diabetes characterized by a mutation in the HNF4A gene, which encodes for the twelve isoforms of the transcription factor. In the pancreas, isoforms HNF4α1-3 and HNF4α7-9 are expressed during fetal development, while only the latter is found in adult tissue. Patients with MODY1 experience transient hyperinsulinemia at birth, but paradoxically develop hyperglycemia in early adulthood. To date, the exact role of HNF4α in the developmentand function of beta cells is unclear, partly due to the lack of models recapitulating the disease. We hypothesize that HNF4α is required for proper beta cell development and for beta cell function in adulthood.

Methods: In-house and publicly available single-cell RNA sequencing (scRNAseq) datasets of both adult primary human islets (n=19) and fetal human pancreatic tissue (n=10, 7-11 weeks post conception (wpc)) were analyzed for HNF4α (isoform) expression. Additionally, primary human fetal (n=3, 8-14 wpc) and healthy adult pancreatic tissue (n=6) were stained for HNF4α1-3 and HNF4α7-9 isoform expression. Results: ScRNA-seq data of primary human islets showed that HNF4α7-9 was predominantly expressed in alpha, PP, delta, acinar, and ductal cells in adult pancreatic tissue, while the expression in beta cells is much lower (beta vs alpha cells, p<0.001). HNF4α1-3 was not expressed. This finding was validated by immunohistochemistry, which did not show co-expression of HNF4α with C-peptide. In contrast, both fetal beta and alpha cells showed HNF4α expression, and no significant difference was found between fetal alpha vs. beta cells (p>0.59). Surprisingly, immunohistochemistry showed HNF4α7-9, but not HNF4α1-3 expression in fetal pancreatic tissue.

Discussion/Conclusion: This study demonstrates that HNF4α is differentially expressed between adult and fetal human pancreatic tissue at both mRNA and protein levels. These results suggest that HNF4α plays a role in beta cell development. It remains to be determined whether HNF4α influences beta cell development and function during childhood and in adulthood.