MOLECULAR GENETICS OF NEURAL SPECFICITY

拟议研究的长期目标是了解 神经特异性的分子基础 特定模式的 大脑不同区域的连通性与 具体的职能任务。 然而，人们对这些人如何做到这一点知之甚少。 网络已经建立。 神经元如何选择合适的突触 合伙人我们已经分离出一个基因，unc-4，它控制着 在线虫中，C.优雅 在缺乏功能性unc-4基因的突变体中， 通常，VA运动神经元的突触被来自VA运动神经元的输入所取代 VB运动神经元的突触前伙伴。 我们已经证明 unc-4编码在VA马达中表达的转录因子 因此，unc-4可能控制了 另一种基因产物，区分VA神经母细胞和VB神经母细胞， 姐妹细胞 那么问题就变成了，是什么基因使unc-4 规范？我们已经确定了一个候选基因，unc-37基因。 突变 使unc-37基因功能丧失导致Unc-4样表型（不能 备份）和定位到UNC-37位点的抑制突变恢复 unc-4变异体的正常运动 也许unc-37编码了一种细胞 在VA运动神经元中表达的介导输入的表面蛋白 来自一组突触前伴侣而不是另一组 unc37 基因将通过互补分离。 unc-37的DNA序列 基因将被确定为推断出的一级结构的 相应的蛋白质产物。unc-37蛋白的片段将被 在细菌中产生并用于制备特异性抗血清。 免疫学技术将被用来鉴定unc-37的模式 表情 将进行镶嵌分析，以识别 其中unc-37基因将被连续切片电子显微镜重建 显微镜检查以确定神经缺陷。 有了这种生化和 形态学数据，应该可以制定一个模型来解释 UNC-37作用的分子机制。 此外，预计 将从这些细胞中提取的核酸和免疫探针 这项工作可以用来鉴定同源基因和蛋白质， 在其他更复杂的神经系统中也有类似的功能。

The long term goal of the proposed research is to understand the molecular basis of neural specificity. Particular patterns of connectivity in different regions of the brain are correlated with specific functional tasks. Little is known, however, of how these networks are established. How do neurons choose appropriate synaptic partners? We have isolated a gene, unc-4 which controls the pattern of synaptic input to specific motor neurons in the nematode, C. elegans. In mutants lacking a functional unc-4 gene, input from interneurons which normally synapse with VA motor neurons is replaced with input from presynaptic partners appropriate to VB motor neurons. We have shown that unc-4 encodes a transcription factor that is expressed in the VA motor neurons but not in the VB's Thus, unc-4 may control the expression of another gene product that distinguishes the VA neuroblast from its VB sister cell. The question then becomes, What is the gene that unc-4 regulates? We have identified a candidate, the unc-37 gene. Mutations that disable unc-37 gene function cause an Unc-4-like phenotype (can't back up) and suppressor mutations that map to the unc-37 locus restore normal movement to an unc-4 mutant. Perhaps unc-37 encodes a cell surface protein that is expressed in VA motor neurons to mediate input from one set of presynaptic partners and not from another. The unc-37 gene will be isolated by complementation. The DNA sequence of the unc-37 gene will be determined to deduce the primary structure of the corresponding protein product. Fragments of the unc-37 protein will be produced in bacteria and used to prepare specific antisera. Immunological techniques will be used to identify the pattern of unc-37 expression. Mosaic analysis will be performed to identify the cells in which unc-37 gene will be reconstructed by serial section electron microscopy to define the neural defect. With this biochemical and morphological data, it should be possible to formulate a model to explain the molecular mechanism of unc-37 action. Furthermore, it is expected that the nucleic acid and immunological probes that will be derived from this work can be employed to identify homologous genes and proteins with similar functions in other more complex nervous systems.