sna18 mutants do not exhibit defects in nicotine sensitivity.
Ventral cells of sna18 mutants fail to constrict productively during gastrulation.
The class I da neurons of sna18 mutants show dorsal overextension of primary dendrites as well as a severe reduction in lateral branching.
Despite the loss of the caudal visceral mesoderm (CVM) stellate cells still remain though their numbers are strongly reduced.
Malpighian tubules arrest early in their morphogenesis in homozygous embryos. The tubules are similar to those of wild-type embryos just after evagination, but the tubules are typically spherical at stages 16 and 17 (when they are elongated in wild-type embryos). The tip cells are seldom apparent and may be absent. The tubules remain fairly small, apparently ceasing cell division soon after they bud. The hindgut is often normal in shape and length but are sometimes shorter than normal.
Very little ventral cell invagination is seen by mid to late germ band extension.
Patches of wild type cells injected into a twi, sna double mutant embryos undergo typical ventral shape changes, nuclear movements and apical constrictions, as long as they are in a region that would normally be occupied by prospective mesoderm.
The endodermal part of the anterior midgut primordium does not become specified. The stomodeum invaginates almost normally, but no cells attach to its posterior surface and the stomodeum stays epithelial for a long time.
Defective in gonad assembly when in double mutant combination with twi.
In spite of normal AMG and PMG invagination, neither anterior nor posterior midgut primordia shows any sign of extension towards each other, but remain as large mesenchymal cell masses immersed in yolk at the ends of the embryo. The cells of these primordia fail to arrange into an epithelium.
Homozygous embryos do not form a ventral furrow. Mesectodermal domain is expanded.
sna8 embryos also mutant for twi have a few extra neuroblasts around the midline.
Dorsalized embryos: all cuticle cells along the dorsoventral axis behave like dorsal cells of the wild type embryo. zen expression pattern refines at stage 5, dpp pattern does not refine at all, twi and sna are expressed during late stages of embryogenesis.
No changes in phenotype of tor13D embryos.
Ventral furrow fails to form.
The ventral epithelium becomes thinner, due to the mesodermal cells becoming shorter and more cuboidal, in sna18 mutant embryos at germ band extension. The epithelium then buckles, forming irregular folds. As the germ band elongates, the epithelium straightens out again and the folds disappear. Two deep folds form where the dorsal ectoderm and neuroectoderm meet. Very few morphogenetic changes occur in sna18 Df(2R)twi double mutant embryos, with small transient indentations in the centre of the ventral surface being seen only occasionally.
Homozygous females lay dorsalised eggs.
Homozygous embryos fail to form a ventral furrow. Cephalic furrow formation, invagination of the endoderm and germ band elongation do take place in these embryos. Embryos show varying defects in the segmental denticle belts.