Organizer transplantation to the opposite, ventral side of the gastrula embryo induces the formation of a secondary axis, in which neighboring ventral cells adopt both a dorsal fate and undergo gastrulation movements 4. The vertebrate body plan is established during gastrulation through the activity of the primary embryonic organizer (Spemann organizer), a specialized group of cells located at the amphibian dorsal lip of the blastopore or homologous structures in other vertebrates (node in birds and mammals, embryonic shield in fish 3). How the spatial patterning is maintained and reinforced in the highly dynamic environment of the elongating and developing vertebrate embryo has yet to be defined. Molecular cues, which control and orient CE relative to the AP axis, have not been described in vertebrate embryos. Likewise, AP-patterning was shown to be directly linked to CE movements in explanted chordamesoderm of Xenopus embryos 2. In Drosophila it has been shown that positional AP information, encoded by Eve, Runt and localized Toll-receptor expression, is directly translated into germ band CE 1. CE is driven by intercalation of bipolar cells perpendicular to the previously established AP axis, necessitating a perfect coordination between spatial cues and cellular behavior. cell intercalation.ĭuring development, invertebrate and vertebrate embryos alike elongate and narrow their anterior-posterior (AP) axis by convergent extension (CE). In this model, Gsc provides a switch between cell migration and CE, i.e. We propose that in the organizer Gsc represses CE as well: Gsc-expressing prechordal cells, which leave the organizer first, migrate and do not undergo CE like the Gsc-negative notochordal cells, which subsequently emerge from the organizer. Our results assign a novel function to Gsc as an inhibitor of Wnt/PCP-mediated CE. Re-evaluation of endogenous Gsc functions in MO-mediated gene knockdown frog and knockout mouse embryos unearthed PCP/CE-related phenotypes as well, including cartilage defects in Xenopus and misalignment of inner ear hair cells in mouse. Dvl2 recruitment to the cell membrane was inhibited by Gsc in Xenopus animal cap assays and key Wnt/PCP factors ( RhoA, Vangl2, Prickle, Wnt11) rescued Gsc-mediated NTDs. Both phenotypes represent convergent extension (CE) defects, arising from impaired Wnt/planar cell polarity (PCP) signaling. Using conditional gain-of-function approaches in Xenopus and mouse to maintain Gsc expression in the organizer and along the axial midline, neural tube closure defects (NTDs) arose and dorsal extension was compromised. While functions have been assigned during later embryogenesis, the role of Gsc in the organizer has remained enigmatic. Goosecoid (Gsc) expression marks the primary embryonic organizer in vertebrates and beyond.

Blastopore closure high salt