Developmental gene sets compiled from literature.

Given their capability to differentiate into each cell type of the human body, human pluripotent stem cells (hPSCs) provide a unique platform for developmental studies. In the current study, we employed this cell system to understand the role of pancreatic progenitor differentiation and proliferation factor (PPDPF), a protein that has been little explored so far. While the zebrafish orthologue exdpf is essential for exocrine pancreas specification, its importance for mammalian and human development has not been studied yet. We implemented a four times CRISPR/Cas9 nicking approach to knockout PPDPF in human embryonic stem cells (hESCs) and differentiated PPDPFKO/KO and PPDPFWT/WT cells towards the pancreatic lineage. In contrast to data obtained from zebrafish, a very modest effect of the knockout was observed in the development of pancreatic progenitors in vitro, not affecting lineage specification upon orthotopic transplantation in vivo. The modest effect is in line with the finding that genetic variants near PPDPF are associated with random glucose levels in humans, but not with type 2 diabetes risk, supporting that dysregulation of this gene may only result in minor alterations of glycaemic balance in humans. In addition, PPDPF is less organ- and cell type specifically expressed in higher vertebrates and its so far reported functions appear highly context-dependent.鉴于人类多能干细胞（human pluripotent stem cells, hPSCs）能够分化为人体各类细胞类型，其为发育生物学研究提供了独特的实验平台。本研究利用该细胞体系，探究此前鲜有研究的胰腺祖细胞分化与增殖因子（pancreatic progenitor differentiation and proliferation factor, PPDPF）的功能。尽管斑马鱼的直系同源基因exdpf对外分泌胰腺的特化至关重要，但该基因在哺乳动物及人类发育中的作用尚未得到研究。本研究采用四重CRISPR/Cas9切口法，在人类胚胎干细胞（human embryonic stem cells, hESCs）中敲除PPDPF，并分别诱导PPDPF敲除纯合（PPDPFKO/KO）与野生型纯合（PPDPFWT/WT）细胞向胰腺谱系分化。与斑马鱼中的研究结果不同，体外实验中PPDPF敲除对胰腺祖细胞的发育仅产生极轻微的影响，且在体内原位移植（orthotopic transplantation）实验中未影响细胞的谱系特化。该轻微效应与此前研究发现相符：PPDPF基因附近的遗传变异与人类的随机血糖水平相关，但与2型糖尿病（type 2 diabetes）患病风险无关，这支持该基因的表达失调仅会导致人类血糖稳态出现小幅紊乱。此外，PPDPF在高等脊椎动物中的表达组织特异性与细胞类型特异性均较弱，迄今已报道的其功能也高度依赖实验环境。