Rittenhouse K R, Berg C A
University of Washington, Department of Genetics, Seattle 98195-7360, USA.
Development. 1995 Sep;121(9):3023-33. doi: 10.1242/dev.121.9.3023.
Subcellular localization of gene products and cell migration are both critical for pattern formation during development. The bullwinkle gene is required in Drosophila for disparate aspects of these processes. In females mutant at the bullwinkle locus, the follicle cells that synthesize the dorsal eggshell filaments do not migrate properly, creating short, broad structures. Mosaic analyses demonstrate that wild-type BULLWINKLE function is required in the germ line for these migrations. Since the mRNA for gurken, the putative ligand that signals dorsal follicle cell fate, is correctly localized in bullwinkle mutants, we conclude that our bullwinkle alleles do not affect the dorsoventral polarity of the oocyte and thus must be affecting the follicle cell migrations in some other way. In addition, the embryos that develop from bullwinkle mothers are bicaudal. A KINESIN:beta-GALACTOSIDASE fusion protein is correctly localized to the posterior pole of bullwinkle oocytes during stage 9. Thus, the microtubule structure of the oocyte and general transport along it do not appear to be disrupted prior to cytoplasmic streaming. Unlike other bicaudal mutants, oskar mRNA is localized correctly to the posterior pole of the oocyte at stage 10. By early embryogenesis, however, some oskar mRNA is mislocalized to the anterior pole. Consistent with the mislocalization of oskar mRNA, a fraction of the VASA protein and nanos mRNA are also mislocalized to the anterior pole of bullwinkle embryos. Mislocalization of nanos mRNA to the anterior is dependent on functional VASA protein. Although the mirror-image segmentation defects appear to result from the action of the posterior group genes, germ cells are not formed at the anterior pole. The bicaudal phenotype is also germ-line dependent for bullwinkle. We suspect that BULLWINKLE interacts with the cytoskeleton and extracellular matrix and is necessary for gene product localization and cell migration during oogenesis after stage 10a.
基因产物的亚细胞定位和细胞迁移对于发育过程中的模式形成都至关重要。在果蝇中，海牛基因对于这些过程的不同方面是必需的。在海牛基因座处发生突变的雌性果蝇中，合成背侧卵壳丝的卵泡细胞不能正常迁移，从而形成短而宽的结构。镶嵌分析表明，这些迁移在生殖系中需要野生型海牛基因的功能。由于gurken（一种指示背侧卵泡细胞命运的假定配体）的mRNA在海牛突变体中定位正确，我们得出结论，我们的海牛等位基因不会影响卵母细胞的背腹极性，因此必定以某种其他方式影响卵泡细胞的迁移。此外，由海牛基因的母体发育而来的胚胎是双尾的。在第9阶段，一种驱动蛋白：β-半乳糖苷酶融合蛋白正确地定位于海牛卵母细胞的后极。因此，在细胞质流动之前，卵母细胞的微管结构及其上的一般运输似乎并未受到破坏。与其他双尾突变体不同，在第10阶段，oskar mRNA正确地定位于卵母细胞的后极。然而，到早期胚胎发生时，一些oskar mRNA会错误地定位于前极。与oskar mRNA的错误定位一致，一部分VASA蛋白和nanos mRNA也错误地定位于海牛胚胎的前极。nanos mRNA向前极的错误定位依赖于功能性VASA蛋白。尽管镜像分割缺陷似乎是由后组基因的作用导致的，但在前极并未形成生殖细胞。海牛基因的双尾表型也依赖于生殖系。我们怀疑海牛基因与细胞骨架和细胞外基质相互作用，并且对于10a阶段之后的卵子发生过程中的基因产物定位和细胞迁移是必需的。
