Broadus J, Doe C Q
Howard Hughes Medical Institute, Department of Cell and Structural Biology, University of Illinois, Urbana 61801, USA.
Development. 1995 Dec;121(12):3989-96. doi: 10.1242/dev.121.12.3989.
In the Drosophila CNS, early neuroblast formation and fate are controlled by the pair-rule class of segmentation genes. The distantly related Schistocerca (grasshopper) embryo has a similar arrangement of neuroblasts, despite lack of known pair-rule gene function. Does divergent pair-rule gene function lead to different neuroblast identities, or can different patterning mechanisms produce homologous neuroblasts? We use four molecular markers to compare Drosophila and Schistocerca neuroblast identity: seven-up, prospero, engrailed, and fushi-tarazu/Dax. In both insects some early-forming neuroblasts share key features of neuroblast identity (position, time of formation, and temporally accurate gene expression); thus, different patterning mechanisms can generate similar neuroblast fates. In contrast, several later-forming neuroblasts show species-specific differences in position and/or gene expression; these neuroblast identities seem to have diverged, suggesting that evolution of the insect central nervous system can occur through changes in embryonic neuroblast identity.
在果蝇的中枢神经系统中，早期神经母细胞的形成和命运受成对规则类别的分节基因控制。尽管缺乏已知的成对规则基因功能，但亲缘关系较远的飞蝗胚胎却有着类似的神经母细胞排列方式。成对规则基因功能的差异会导致不同的神经母细胞特性吗？还是不同的模式形成机制能够产生同源的神经母细胞呢？我们使用四种分子标记来比较果蝇和飞蝗的神经母细胞特性：七上蛋白、prospero、engrailed以及fushi-tarazu/Dax。在这两种昆虫中，一些早期形成的神经母细胞具有神经母细胞特性的关键特征（位置、形成时间以及时间上精确的基因表达）；因此，不同的模式形成机制能够产生相似的神经母细胞命运。相比之下，一些后期形成的神经母细胞在位置和/或基因表达上表现出物种特异性差异；这些神经母细胞特性似乎已经发生了分化，这表明昆虫中枢神经系统的进化可能通过胚胎神经母细胞特性的改变而发生。
