Pcgf1 regulates early neural tube development through histone methylation in zebrafish

Objective: Early neural tube development in the embryo includes neural induction and self-renewal of neural stem cells (NSCs). The abnormal of neural tube development could lead to neural tube defects. The research on the mechanism of neural induction is the key to reveal the pathogenesis of the abnormal of neural tube. Though studies have confirmed a genetic component, the responsible mechanisms for the abnormal of neural tube are still largely unknown. Polycomb repressive complex 1 (PRC1) plays an important role in regulating early embryonic development, and has been sub-classified into six major complexes based on the presence of a Pcgf subunit. Pcgf1, as one of six Pcgf paralogs, is an important requirement in early embryonic brain development. Here, we intended to investigate the role and mechanism of Pcgf1 in early neural tube development of zebrafish embryos. Material and methods: Morpholino (MO) antisense oligonucleotides were used to construct a Pcgf1 loss-of function zebrafish model. We analyzed the phenotype of zebrafish embryos and the expression of related genes in the process of neural induction by in situ hybridization, immunolabelling and RNA-sEq. The regulation of histone modifications on gene was detected by western blot and chromatin immunoprecipitation. Results: In this study, we found that zebrafish embryos exhibited small head and reduced or even absence of telencephalon after inhibiting the expression of Pcgf1. Moreover, the neural induction process of zebrafish embryos was abnormal, and the subsequent NSCs self-renewal was inhibited under the inhibition of Pcgf1. RNA-seq and gene ontology (GO) analysis identified that the differentially expressed genes were enriched in many functional categories which related to the development phenotype. Finally, our results showed that Pcgf1 regulated the trimethylation of histone H3K27 in the Ngn1 and Otx2 promoter regions, and the levels of H3K4me3 at the promoters of Pou5f3 and Nanog. Conclusion: Together, our data for the first time demonstrate that Pcgf1 plays an essential role in early neural induction phase through histone methylation in neural tube development. Our findings reveal a critical context-specific function for Pcgf1 in directing PRC1 to control cell fate.