A procephalic territory in Drosophila exhibiting similarities and dissimilarities compared to the vertebrate midbrain/hindbrain boundary region.
A procephalic territory in Drosophila exhibiting similarities and dissimilarities compared to the vertebrate midbrain/hindbrain boundary region.
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与脊椎动物中脑/后脑边界区相比，果蝇中的近头领地表现出相似性和差异。
DOI：
10.1186/1749-8104-2-23
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发表时间：
2007-11-05
影响因子：
3.6
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在脊椎动物中，脑的原基通过Otx基因（前脑/前中脑）、Hox基因（后后脑）和基因Pax 2、Pax 5和Pax 8（中间区域）的表达而细分。后者包括中脑/后脑边界（MHB），它在大脑模式化过程中充当关键组织者。最近的研究表明，在果蝇的orthopathic组基因的表达在胚胎晚期的大脑，这表明果蝇中脑/tritocerebral边界区域和脊椎动物MHB之间的对应关系类似的三重模式。为了更深入地了解大脑区域的进化，特别是MHB，我研究了一个全面的阵列MHB特异性基因直系同源物在prephalic神经外胚层和单独识别的神经母细胞在胚胎早期阶段8-11，在大脑的节段组织是最清楚地显示。我发现，早期胚胎脑表现出前OTX/OTD域和后Hox 1/实验室域，但Pax 2/5/8同源基因不表达的神经外胚层和神经母细胞的干预领土。此外，Otx/otd和Gbx/unpg的表达结构域在前中脑内表现出小的共同界面。与脊椎动物相反，Fgf 8相关基因在otd/unpg界面后不表达。然而，在otd/unpg接口的其他MHB特异性基因（包括btd，wg，en）的早期表达，和背腹图案基因，非常类似的情况下，在脊椎动物MHB。总之，这些结果表明，存在一个祖先的领土内的原基的中脑和相邻的procerebrum，这可能是进化相当于该地区的脊椎动物MHB。然而，缺乏Pax 2/5/8和Fgf 8相关基因的表达，以及其他关键调节因子在otd/unpg界面的表达起始的显着差异，意味着对脊椎动物组织者活动至关重要的遗传相互作用在果蝇的早期胚胎脑中是不存在的。
In vertebrates, the primordium of the brain is subdivided by the expression of Otx genes (forebrain/anterior midbrain), Hox genes (posterior hindbrain), and the genes Pax2, Pax5 and Pax8 (intervening region). The latter includes the midbrain/hindbrain boundary (MHB), which acts as a key organizer during brain patterning. Recent studies in Drosophila revealed that orthologous sets of genes are expressed in a similar tripartite pattern in the late embryonic brain, which suggested correspondence between the Drosophila deutocerebral/tritocerebral boundary region and the vertebrate MHB. To gain more insight into the evolution of brain regions, and particularly the MHB, I examined the expression of a comprehensive array of MHB-specific gene orthologs in the procephalic neuroectoderm and in individually identified neuroblasts during early embryonic stages 8–11, at which the segmental organization of the brain is most clearly displayed. I show that the early embryonic brain exhibits an anterior Otx/otd domain and a posterior Hox1/lab domain, but that Pax2/5/8 orthologs are not expressed in the neuroectoderm and neuroblasts of the intervening territory. Furthermore, the expression domains of Otx/otd and Gbx/unpg exhibit a small common interface within the anterior deutocerebrum. In contrast to vertebrates, Fgf8-related genes are not expressed posterior to the otd/unpg interface. However, at the otd/unpg interface the early expression of other MHB-specific genes (including btd, wg, en), and of dorsoventral patterning genes, closely resembles the situation at the vertebrate MHB. Altogether, these results suggest the existence of an ancestral territory within the primordium of the deutocerebrum and adjacent protocerebrum, which might be the evolutionary equivalent of the region of the vertebrate MHB. However, lack of expression of Pax2/5/8 and Fgf8-related genes, and significant differences in the expression onset of other key regulators at the otd/unpg interface, imply that genetic interactions crucial for the vertebrate organizer activity are absent in the early embryonic brain of Drosophila.