GPI transamidase complex is required for primordial germ cell migration and development in zebrafish

Proteins without transmembrane domains could be anchored to the cell surface for regulating various biological processes when covalently linked to glycosylphosphatidylinositol (GPI) molecules by the GPI transamidase (GPIT) complex. However, it remains poorly understood whether and how the GPIT complex affects primordial germ cell (PGC) development. In this study, we report the important roles of GPI transamidase in PGC migration and development in zebrafish embryos. Mutation of pigu or pigk, both encoding essential GPIT complex subunits, resulted in defective PGC migration with ectopically located PGCs and reduction of PGC counts. Notably, a detailed analysis of filopodia in PGCs reveals the attenuated polarity of filopodia distribution along the migration direction in mutant embryos. PGC transplantation and PGC-specific rescue experiments demonstrate that both PGC and somatic cell-expressed Pigu are required for PGC migration. Furthermore, expression levels of PGC-specific genes are decreased in pigu mutant PGCs with the derepression of somatic cell genes. Hence, we propose that the GPIT complex plays a critical role during PGC migration and development. To reveal molecular mechanisms underlying GPI transamidase-mediated PGC migration regulation, we performed RNA-seq of PGCs in wild type and pigu-/- embryos at the shield and bud stages. We manually picked GFP-positive PGCs after cell dissociation of embryos at the shield and bud stages. Then, after genotyping of rest somatic cells, PGCs with the same genotypes were pooled together and lysed for Smart-seq of two biological replicates.