Molecular mechanism for zone-to-zone projection of axons

我们发现了一种新的细胞黏附分子OCAM。嗅觉细胞黏附分子在鼻上皮区2~4区表达，而在1区不表达。表达OCAM的嗅轴突选择性地投射到主嗅球的腹外侧区。这表明嗅轴突是一种“区对区的投射”。对表达OCAM、NeuroPilin-1或BIG-2的嗅神经轴突的追踪表明，在主嗅球内存在“细胞黏附分子图”和“气味感受器图”之间的精确对应。在副嗅觉系统中，顶区感觉神经元表达OCAM，而基底区感觉神经元不表达OCAM。表达OCAM的轴突选择性地投射到副嗅球(AOB)的吻区，提示犁鼻轴突的“带-带投射”。在胚胎和出生后早期，OCAM通过AOB尾侧区的二尖瓣/簇状细胞选择性表达。细胞黏附分子分析表明AOB中存在信息素受体图谱。在小脑皮层。在胚胎晚期和出生后早期小鼠中，OCAM有选择性表达。分布在矢状面旁带内的浦肯野细胞的一个子集。利用同源重组的方法，我们产生了缺失OCAM I基因的小鼠。我们现在正在分析OCAM缺陷小鼠的发育和维持，以研究OCAM在大脑区域间投射的形成和维持中所起的作用。

We found a novel cell adhesion molecule OCAM. OCAM was expressed by olfactory sensory neurons in zones 2-4 but not by those in zone 1 of the nasal epithelium. OCAM-expressing olfactory axons projected selectively to ventrolateral zones of the main olfactory bulb. This indicates a "zone-to-zone projection" of olfactory axons. Tracing of olfactory axons expressing OCAM, neuropilin-1, or BIG-2 indicated that there exists a Precise correspondence between "cell adhesion molecule map" and "odorant receptor map" in the main olfactory bulb. In the accessory olfactory system, OCAM was expressed by apical zone sensory neurons but not by basal zone sensory neurons in the vomeronasal sensory epithelium. OCAM-expressing axons projected selectively to the rostral zone of the accessory olfactory bulb (AOB), indicating the "zone-to-zone projection" of vomeronasal axons. In the embryonic and early postnatal mice, OCAM was expressed selectively by mitral/tufted cells in the caudal zone of the AOB. Analyses with cell adhesion molecules suggested the existence of "pheromone receptor map" in the AOB. In cerebellar cortex. of late embryonic and early postnatal mice, OCAM was expressed selectively. by a subset of Purkinje cells, which were distributed within parasagittal zones. Using the homologous recombination method, we generated mice that lack OCAM I gene. We are now analyzing the and maintenance of the OCAM-deficient mice to examine the role of OCAM in the formation and maintenance of the zone-to-zone projection in the brain.