Abnormal migration of the motor trigeminal, facial, and ambiguus nuclei neurons of the SRK rat

Reeler小鼠是一种常染色体隐性突变小鼠，以步态共济失调和震颤为特征。自从D’arcangelo等人（Nature 374: 719-723, 1995）发现了导致reelin突变的基因以来，这一领域取得了很大进展。reelin基因编码一种对神经元迁移至关重要的细胞外蛋白。在胚胎发生过程中，reelin在Cajal-Retzius细胞的大脑皮层和外颗粒细胞的小脑皮层中表达。虽然非层状结构如面核、下橄榄复合体和耳蜗背核在该突变体中也存在细胞结构紊乱，但只有少数研究明确了这些非层状结构的详细异常。在这篇综述中，我们集中讨论了reeler小鼠面部核的细胞结构异常。面神经核中的支运动神经元生于第四脑室底的脑室区，向腹侧移动，最终落在后脑腹侧面附近。面部运动神经元的产生、轴突形成和迁移的时间时间表在正常小鼠和reeler小鼠中是相似的，但在神经元迁移结束时，reeler表型变得可识别。虽然卷卷鼠面部细胞核细胞结构异常的原因，但卷卷鼠面部运动神经元的长时间迁移似乎比正常对照组更容易受到Reelin的影响。尽管存在细胞结构异常，逆行辣根过氧化物酶（HRP）研究证实，reeler小鼠面核内的肌位排列仍然保留，表明神经元迁移/重排和靶标识别是独立调节的。最近，其他种类的卷轴状突变体已经被发现（yotari，扰频者，SRK）。其中，yotari和scrambler小鼠是由mdab1突变引起的，mdab1是一种与果蝇基因失能（dab）相关的小鼠基因。十多年前，一种常染色体隐性大鼠突变，摇鼠川崎（SRK），被描述为表现出与reeler相同的表型，但负责这种大鼠突变的基因仍然未知。非常有趣的是，与正常人相比，yotari和SRK的面部细胞核在细胞结构上更加紊乱。为什么yotari在层状结构中表现出与reeler相同的表型，而在非层状结构（如面核）中却表现出不同的表型，原因尚不清楚，这表明mDab1和Reelin蛋白在非层状结构和层状结构之间以不同的方式作为信号分子。少

Reeler mouse is an autosomal recessive mutant mouse, and characterized by ataxic gait and tremor. Since reelin, the gene responsible for the reeler mutation is discovered by D'Arcangelo et al. (Nature 374 : 719-723, 1995), much progresses have occurred in this field. The reelin gene encodes an extracellular protein that is crucial for neuronal migration. During the embryogenesis, reelin is expressed in the cerebral cortex in Cajal-Retzius cells and in the cerebellar cortex in outer granule cells. Although non-laminated structures such as facial nucleus, inferior olivary complex, and dorsal cochlear nucleus are also cytoarchtectually deranged in this mutant, only a few studies have been done to clarify the detailed abnormalities in these non-laminated structures. In this review, we focused the cytoarchitectonic abnormality in the facial nucleus of the reeler mouse. The branchiomotor neurons in the facial nucleus are born in the ventricular zone of the floor of the fourth ventricle, migr … More ate ventrolaterally, and finally settle near by the ventral surface of the hindbrain. Time schedules for the generation, axon formation and migration of facial motoneurons are similar both in normal and reeler mouse, but the reeler phenotype becomes identifiable at the end of neuronal migration. Although the reason why the facial nucleus is cytoarchitecually abnormal in the reeler mouse, such a long migration of the facial motoneurons seems to be more susceptible to Reelin in the reeler mouse than in the normal control. In spite of cytoarcitectual abnormality, retrograde horseradish peroxidase (HRP) study confirmed that musculotopic arrangements within the facial nucleus of the reeler mouse are still preserved, suggesting neuronal migration/rearrangement and target recognition are independently regulated.More recently, other kinds of reeler-like mutants have been known (yotari, scrambler, SRK). Among these, yotari and scrambler mice arises from mutations in mdab1, a mouse gene related to the Drosophila gene disabled (dab). More than 10 years ago, an autosomal recessive rat mutant, shaking rat Kawasaki (SRK), has been described that exhibits a phenotype identical to reeler, but the gene responsible for this rat mutation has remained unknown. Very interestingly, the facial nucleus is cytoarchitectually more deranged in yotari and SRK compared to the normal counterparts. The reason why yotari exhibits a phenotype identical to reeler in the laminated structures but not in non-laminates structures such as the facial nucleus has remained obscure, suggesting mDab1 and Reelin proteins function as signaling molecules in a different way between non-laminated and laminated structures. Less