SPADETAIL-DEPENDENT CELL COMPACTION OF THE DORSAL ZEBRAFISH BLASTULA

The dorsal marginal zone of the zebrafish blastula, equivalent to the amphibian Spemann organizer, is destined to become the tissues of the notochord and prechordal plate. Preceding gastrulation in the zebrafis h, we find that these future mesendodermal cells acquire a cohesive ce ll behavior characterized by flattening and maximization of intercellu lar contacts, somewhat resembling cell compaction in mouse blastocysts . This behavior may suppress cell intermingling. Surprisingly, this bl astula cell compaction requires normal function of spadetail, a gene k nown to be necessary for the dorsal convergent cell movement of paraxi al mesoderm later in the gastrula. We propose that spadetail-dependent cell compaction subtly controls the early mixing and dispersal of dor sal cells that coalesce into the prospective organizer region. This ea rly process may be necessary for the correct location of the boundary separating axial and paraxial cells. (C) 1998 Academic Press.