CNS DEVELOPMENT AND MUTANT GENE ACTION

遗传和表观遗传机制使大脑发育成 高度有序的结构在很大程度上是未知的。这项提议的目标是 阐明神经发生中的一些早期有丝分裂后事件。那里 是几个神经性老鼠突变体，它们特别有缺陷 这一发展计划的各个方面。两个这样的基因突变体， Weaver(WV)和The Reeler(RL)提供了令人着迷的信息 关于神经发生迁移阶段的遗传控制。 这些突变会影响单细胞类型(WV小脑)的能力 颗粒细胞)或几乎所有类型的细胞(Rl)以迁移和稳定 恰如其分。实验性的小鼠嵌合体提供了一种直接的方法 确定突变基因作用的靶点(S)。正常的四个细胞胚胎 (Mus Caroli)和神经突变(Mus Musculus)小鼠将聚集在一起 形成由基因正常和突变组成的单个嵌合胚胎 细胞。将使用一种新的细胞标记系统来识别 嵌合脑，基因正常或突变的嵌合脑这种新的细胞标记， 这涉及到物种特异性cdna探针的原位杂交。 标记小鼠肌肉，但不标记卡罗利小鼠细胞，将允许小心照明 以及电子显微镜分析每个细胞的基因型与其 表型。基因型/表型比较将定义内在或 Wv和rl突变基因与所有细胞类型相关的外源性作用 在小脑里。这种类型的信息将提供更好的 对大脑正常发育和异常发育的理解 发生在更明显的(例如，先天性共济失调)和更隐蔽的情况下 (例如，智力低下)发育不全的程度。

The genetic and epigenetic mechanisms by which the brain develops into a highly ordered structure are largely unknown. The goal of this proposal is to elucidate some of the early postmitotic events in neurogenesis. There are several neurological mouse mutants which are defective in particular aspects of this developmental program. Two such genetic mutants, the weaver (wv) and the reeler (rl), hold forth fascinating information concerning the genetic control over the migratory phase of neurogenesis. These mutations affect the ability of a single cell type (the wv cerebellar granule cells) or virtually all cell types (rl) to migrate and stabilize appropriately. Experimental mouse chimeras provide a direct means to ascertain the target(s) of mutant gene action. Four cell embryos of normal (Mus caroli) and neurological mutant (Mus musculus) mice will be aggregated to form a single chimeric embryo composed of genetically normal and mutant cells. A new cell marking system will be used to identify each cell of the chimeric brain, as genotypically normal or mutant. This new cell marker, which involves the in situ hybridization of a species-specific cDNA probe to mark Mus musculus but not Mus caroli cells, will permit careful light and electron microscopic analyses of each cell's genotype compared to its phenotype. The genotype/phenotype comparisons will define the intrinsic or extrinsic nature of wv and rl mutant gene action relative to all cell types in the cerebellum. This type of information will provide a better understanding of normal brain development and how abnormal development occurs at both the more obvious (e.g., congenital ataxias) and more subtle (e.g., mental retardation) levels of dysgenesis.