Project description:Pitx2c, a homeodomain transcription factor, is classically known for its left-right patterning role. However, an early wave of pitx2 expression occurs at the onset of gastrulation in several species, indicating a possible earlier role that remains relatively unexplored. Here, we show that in zebrafish, maternal-zygotic (MZ) pitx2c mutants exhibit a shortened body axis indicative of convergence and extension (CE) defects. Live imaging reveals that MZpitx2c mutants display less persistent mesendodermal migration during later stages of gastrulation. Transplant experiments indicate that Pitx2c functions cell non-autonomously to regulate this cell behavior by modulating cell shape and protrusive activity. Using transcriptomic analyses and candidate gene approaches, we identify transcriptional changes in components of the chemokine-ECM-integrin dependent mesendodermal migration network. Together, our results define pathways downstream of Pitx2 that are required during early embryogenesis and reveal novel functions for Pitx2 as a regulator of morphogenesis.
Project description: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.