PPDPF impacts pancreatic progenitor cell formation derived from human pluripotent stem cell

Given their capability to differentiate into every cell type of the adult human body, human embryonic stem cells (hESCs) provide a unique platform for developmental studies and regenerative medicine. The generation of pancreatic progenitor (PP) cells from pluripotent stem cells follows the sequential induction of virtually pure definitive endoderm (DE), foregut endoderm (GTE) and pancreatic endoderm (PE). We have recently reported the generation of a novel three-dimensional pancreatic organoid culture system that generates functional acinar-/ductal-like structures from pluripotent stem cells (Hohwieler et al, GUT, 2016). In the current study we implemented this culture system to understand the role of pancreatic progenitor differentiation and proliferation factor (PPDPF), a signalling molecule, whose orthologue Exdpf is involved in pancreatic differentiation in the zebrafish. CrisprCas9 technologies were used to ablate PPDPF in human embryonic stem cells, while a transient mRNA transfection approach allowed us timed over expression to study the role of both loss and gain of PPDPF function during pancreatic differentiation. First, a limited role of PPDPF was observed until the PE stage, while PP formation was strongly diminished as shown by immunostaining and FACS analysis. Next, RNA-sequencing of entire transcriptomes was performed followed by gene mining and gene set enrichment analysis to further substantiate our findings of altered capacity to form pancreatic progenitors. Finally, we were seeking for the mechanism of PPDPF, a small signalling peptide, harbouring several protein-protein interaction domains. To do so, we performed mass spectrometry using tagged PPDPF in Hek293 but also Panc1 cells. Indeed, we found a set of candidates e.g. the cancer-testis protein MAGED2 to impact the role of PPDPF during pancreatic development. Thus, we report a novel signalling molecule playing a critical role during human pancreas development based on a pluripotent stem cell differentiation platform.