Reichert Heinrich
Institute of Zoology, Biocenter/Pharmacenter, University of Basel, Switzerland.
Int J Dev Biol. 2002 Jan;46(1):81-7.
A wealth of comparative embryological studies on the expression and function of homeotic genes and cephalic gap genes indicates that both gene groups are important for establishing and specifying the anteroposterior body axis during embryogenesis in bilaterian animals. Recently, studies of this kind have been extended to embryonic brain development in two genetic model systems, Drosophila and mouse. These studies demonstrate striking similarities in the pattern of expression and mode of action of these developmental control genes during embryonic patterning of the brain in both species. Thus, in both insect and mammalian species, members of the homeotic gene complex are involved in patterning the posterior brain anlage, where they control regionalized neuronal identity, and members of the cephalic gap genes, notably the otd/Otx gene family, are involved in patterning the anterior brain anlage where they control regionalized neurogenesis and neuronal identity. Furthermore, striking cross-phylum rescue experiments show that insect and mammalian members of the orthodenticle gene family can functionally replace each other in embryonic brain and CNS patterning. Comparable cross-phylum rescue experiments have now also been carried out for the empty spiracles cephalic gap gene family. Taken together, these experiments suggest that the genetic mechanisms involved in embryonic brain development are conserved and indicative of a common evolutionary origin of the insect and vertebrate brain. For a more extensive and quantitative investigation of the molecular conservation of developmental mechanisms for brain patterning, functional genomic experiments are now underway in Drosophila. These experiments exploit the advent of sequenced genome information and the technology for large scale transcript imaging, with the goal of identifying the entire set of downstream genes which is under the control of these regulatory genes in embryonic brain development.
大量关于同源异型基因和头部间隙基因表达与功能的比较胚胎学研究表明，这两类基因对于两侧对称动物胚胎发育过程中前后体轴的建立和特化都很重要。最近，这类研究已扩展到果蝇和小鼠这两个遗传模型系统中的胚胎脑发育。这些研究表明，在这两个物种的胚胎脑模式形成过程中，这些发育控制基因的表达模式和作用方式存在显著相似性。因此，在昆虫和哺乳动物物种中，同源异型基因复合体的成员都参与后脑原基的模式形成，在那里它们控制区域化的神经元身份；而头部间隙基因的成员，特别是otd/Otx基因家族，参与前脑原基的模式形成，在那里它们控制区域化的神经发生和神经元身份。此外，引人注目的跨门拯救实验表明，正齿突基因家族的昆虫和哺乳动物成员在胚胎脑和中枢神经系统模式形成中可以在功能上相互替代。现在也已经对空气门头部间隙基因家族进行了类似的跨门拯救实验。综合来看，这些实验表明，参与胚胎脑发育的遗传机制是保守的，这表明昆虫和脊椎动物的脑具有共同的进化起源。为了更广泛和定量地研究脑模式形成发育机制的分子保守性，目前正在果蝇中进行功能基因组实验。这些实验利用了已测序的基因组信息和大规模转录成像技术的出现，目标是确定在胚胎脑发育中受这些调控基因控制的全套下游基因。
