Identification of novel patterning genes in Drosophila development

信号分子Hedgehog (Hh), Decapentaplegic （Dpp）和Wingless （Wg）在果蝇中作为形态形成因子并组织翅膀模式。形成因子来自于离散的来源，并产生浓度梯度，从而在靶细胞中引发浓度依赖性反应。我们发现了两个新的果蝇突变体，分别是toutvelu的姐妹和兄弟，以及一个新的toutvelu等位基因。这些基因的预测产物属于EXT蛋白家族，具有或与生物合成硫酸肝素蛋白聚糖（HSPGs）所需的糖基转移酶活性密切相关。这些基因的突变降低了Hh、Dpp和Wg的蛋白和信号水平。Hh在EXT突变细胞前聚集，表明Hh需要HSPGs有效移动。我们提出HSPGs促进形态形成因子的扩散，从而产生浓度梯度。形态原在脊椎动物的发育过程中也起着重要的作用。我们研究了Wnt调控爪蟾早期胚胎发生的信号通路，Wnt是脊椎动物中Wg的同源物。尽管蛋白激酶C （PKC）与Wnt信号通路有关，但其分子作用尚不清楚。我们在爪蟾EST数据库中发现了新的PKCd编码基因。PKCd的功能缺失揭示了它在原肠形成过程中的收敛延伸是必不可少的。然后，我们研究了PKCd和Wnt通路之间的关系。PKCd易位到质膜响应卷曲信号。此外，PKCd的功能缺失抑制了disheveled的易位和c-Jun n -末端激酶（JNK）的激活。PKCd与disheveled形成复合物；phobol酯激活PKCd足以实现散乱转运和JNK激活。PKCd通过调节disheveled的定位和活性，在Wnt/JNK通路中发挥重要作用。

The signaling molecules Hedgehog (Hh), Decapentaplegic (Dpp) and Wingless (Wg) function as morphogens and organize wing patterning in Drosophila.Morphogens emanate from discrete sources and generate concentration gradients that elicit concentration-dependent responses in target cells. We identified two novel Drosophila mutants, sister of tout-velu and brother of tout-velu, and one new allele of tout-velu. The predicted products of these genes belong to an EXT family of proteins that have or are closely related to glycosyltransferase activities required for biosynthesis of heparan sulfate proteoglycans (HSPGs). Mutations in these genes reduced protein and signaling levels of Hh, Dpp and Wg. Hh accumulated in front of EXT mutant cells, suggesting that Hh requires HSPGs to move efficiently. We propose that HSPGs facilitate the spreading of morphogens that generates concentration gradients.Morphogens play an important role in vertebrate development as well. We have studied the signaling pathway by which Wnt, a vertebrate homologue of Wg, regulates early embryogenesis of Xenopus. Although protein kinase C (PKC) has been implicated in the Wnt signaling pathway, its molecular role is poorly understood. We identified novel genes encoding PKCd in Xenopus EST databases. Loss-of-function of PKCd revealed it is essential for convergent extension during gastrulation. Then, we examined relationship between PKCd and the Wnt pathway. PKCd is translocated to the plasma membrane in response to Frizzled signaling. In addition, loss-of-function of PKCd inhibited translocation of Dishevelled and activation of c-Jun N-terminal kinase (JNK) by Frizzled. Furthermore, PKCd forms a complex with Dishevelled ; and activation of PKCd by phorbol ester was sufficient for Dishevelled translocation and JNK activation. PKCd plays an essential role in Wnt/JNK pathway by regulating localization and activity of Dishevelled.