Genome-wide Rnai Screen In Pupal Intestinal Stem Cells And PIG Negatively Regulates Homeostasis Of Drosophila Midgut

In Drosophila,the digestive tract epithelium is the tissue with the fastest selfrenewal speed.The renewal and maintenance of the digestive tract epithelium depends on the division and differentiation of intestinal stem cells(ISC).Throughout the pupal stage of Drosophila,intestinal epithelial stem cells(p ISC)divide asymmetrically and symmetrically in sequence,and finally produce about 1200 p ISCs and 1200 enteroendocrine cells(EE).In order to understand the gene network that regulates the self-renewal of p ISC and the fate determination of EE cells during the development of intestinal epithelium at pupal stage,we designed a experiment of genome-wide RNAi screening.The screening has identified four types of phenotypes that gene knockdown affects p ISC survival,leads to excessive p ISC proliferation,changes in p ISC differentiation,and leads to pupal death.Through screening,we found that a total of 924 genes are involved in the regulation of p ISC maintenance and EE fate determination,and the gene regulation network was obtained by bioinformatics method after classification and induction.Among them,we focused on the study of PIG(Proliferation Increased Gene),which restricts the excessive proliferation of p ISC.Through CRISPR-Cas9-mediated molecular tag insertion in situ,we found that PIG is transiently expressed in ISC that is about to complete mitosis.This suggests that PIG is a gene related to the termination of division.Corresponding to this hypothesis,in addition to limiting the proliferation of p ISC,lack of PIG at the adult stage leads to a phenotype of over-proliferation of injury-induced intestinal stem cells.Over-expression of PIG accelerates the recovery of injury-induced mitotic ISC to the resting state.Further molecular genetic interaction experiments show that the proliferation restriction effect of PIG on ISC is negatively regulated by EGFR signaling pathway.