Molecular Analysis of the A63 Gene That Is Essential for Drosophila Neurogenesis

果蝇的中枢神经系统由大量的神经元组成，这些神经元来源于神经干细胞和神经母细胞。它们产生一系列特定的神经节母细胞，每个母细胞一度分裂成一对神经元。神经元的身份似乎是由神经母细胞决定的，也由神经元出生的谱系决定的。虽然单个神经元正确获得其身份的分子过程尚不清楚，但已经表明，发育中的中枢神经系统中细胞命运的决定涉及到控制早期胚胎发生中节段结构建立的分割基因。我们通过增强子陷阱方法筛选了控制神经发生的基因突变，并确定了神经发生所需的prospero （pros）基因。pros功能的丧失导致神经形态学上的致命缺陷，中枢神经系统中分割基因fushitarazu （ftz）、even-跳过（eve）和engrailed （en）的表达模式异常，导致某些已鉴定的神经元轴突寻路错误。为了理解pros是如何起作用的，我们分离了pros基因。Pros编码含有同源结构域序列的核蛋白。在中枢神经系统的神经谱系中，pros蛋白在神经节母细胞中被特异性检测到，尽管它们的亲本神经母细胞已经开始表达显著水平的pros转录本，这表明pro表达有转录后控制。本研究结果提示，在神经元细胞分化过程中，神经节母细胞可能在其功能中起关键作用。

The Drosophila central nervous system comprises an enormous diversity of neurons that are originated from neuronal stem cells, neuroblasts. They generate a specific series of ganglion mother cells, each of which is once cleaved into a pair of neurons. Neuronal identity seems to be determined by neuroblasts from which, and by lineages through which neurons are born. While much is not known about the molecular process for individual neurons to correctly acquire their identity, it has been shown that cell fate determination in the developing central nervous system involves segmentation genes that are known to control the establishment of the segmental structure in early embryogenesis.We have screened for mutations in genes controlling neurogenesis by the enhancer trap method, and identified the prospero (pros) gene that is required for neurogenesis. Loss of pros function causes lethal defects in the neural morphology, and abnormal expression patterns of segmentation genes, fushitarazu (ftz), even-skipped (eve) and engrailed (en) in the central nervous system, resulting in wrong path finding of axons in some identified neurons. To understand how pros functions, we have isolated the pros gene. pros encodes a nuclear protein containing a homeodomain-like sequence. In neuronal lineages of the central nervous system, pros protein is specifically detected in ganglion mother cells, although their parental neuroblasts have begun expressing a significant level of pros transcripts, suggesting a post-transcriptional control of pros expression. Our results provoke that in neuronal cell differentiation ganglion mother cells might play a pivotal role associating with the pros function.