CELL-AUTONOMOUS ACTION OF ZEBRAFISH SPT-1 MUTATION IN SPECIFIC MESODERMAL PRECURSORS

IN zebrafish, as in Xenopus1 the well-orchestrated cell movements of gastrulation can be dissected into several components, including epiboly2, involution3,4, convergence and extension4. Embryos homozygous for the recessive lethal mutation spt-l(b104) or 'spadetail' have a complex set of defects in the trunk of the embryo that may arise secondarily after loss of one of these movements, convergence, from those precursors that would normally have given rise to trunk somitic mesoderm5 (Fig. 1). We have now tested this hypothesis by transplanting cells between wild-type and mutant embryos, to identify the cells that spt-1 affects directly. Our results show that the mutation autonomously affects only those mesodermal precursors located along the lateral margin of the early gastrula blastoderm6. Other mesodermal cells and all ectodermal precursors seem not to require function of the wild-type gene. Our findings reveal an unexpectedly delicate genetic control of vertebrate gastrulation. © 1990 Nature Publishing Group.