Doctoral Researcher University of Helsinki, Uusimaa, Finland
Abstract: Human pancreatic development is an intricately coordinated process that generates a gland composed of the endocrine and exocrine cells. Mutations in genes regulating this process result in developmental abnormalities, such as pancreatic agenesis. Our recent work identified loss-of-function mutations in the primate-specific gene ZNF808, leading to pancreatic agenesis, which manifests as neonatal diabetes and exocrine pancreatic insufficiency. ZNF808 belongs to the KRAB zinc finger family and is known to bind MER11 transposable elements and repress their gene regulatory activity. However, the precise mechanism by which ZNF808 regulates human pancreatic development remains unclear. To investigate the mechanism of ZNF808, we generated ZNF808 knockout (KO) in the H1 human embryonic stem cell (hESC) line and differentiated them alongside control H1 hESCs using a stem cell derived islet differentiation model optimized in our lab. Bulk RNAseq analysis revealed an aberrant activation of the hepatic lineage markers and a downregulation in the pancreatic lineage markers at the posterior foregut stage of differentiation. To further understand the regulatory networks disrupted by the lack of ZNF808 we conducted single cell RNAseq and single nuclear ATACseq from day 0 (stem cell stage) until posterior foregut stage. Our preliminary analysis of the single cell genomics data identified an upregulation of BMP-pathway signaling driven by the derepression of MER11 transposable elements, thereby resulting in increased differentiation into the hepatic lineage. This was accompanied by a downregulation of TGFβ-pathway signaling, disrupting the balance necessary for proper human pancreatic lineage specification. This work identifies a novel mechanism regulating human pancreas specification and highlights the need to study primate-specific regulatory processes controlling development. Additionally, the use of stem cell derived islet differentiation model has shown great potential for disease modelling purposes but also for use as cell therapy in diabetes treatment.
