Morphological changes and regulation mechanisms of oligodendrocyte migration and myelination

用谱系标记抗体O 4和O 1检测少突胶质前体细胞（OPCs）的迁移和增殖。(1)后脑（脑干和小脑）中的OPCs经历从脑干内侧、外侧部分和最后到小脑原基的逐渐分散。为了验证OPCs的迁移，将编码EGFP基因的质粒转染至E4或E5的后脑脑室细胞，并依次检查O 4阳性/EGFP阳性细胞的出现和分散。将质粒转染到内侧脑室层导致脑干和小脑中出现O 4阳性/EGFP阳性细胞。这一结果表明，OPCs出现在内侧脑干脑室层，至少有一部分OPCs可能从脑干迁移到小脑原基。(2)OPCs的增殖通过用溴脱氧尿苷（BrdU）和O 4或O 1双标记OPCs来检查。大约20%的O 4阳性心室细胞掺入BrdU，而40- 50%的O 4阳性细胞在这些区域出现后立即在实质中被标记。随着胚的发育，标记指数逐渐降低。最后，少于5%的成熟少突胶质细胞被BrdU标记。少突胶质细胞谱系细胞可能在它们离开心室层之后在实质中最活跃地产生它们的队列。(3)用细胞表面识别分子的中和抗体检测调节OPC迁移的分子。将分泌抗体的杂交瘤注射到E5鸡胚的第三脑室中，并在E8检查视神经中的O 4阳性细胞分布。当胚胎接受产生针对N-钙粘蛋白的抗体的杂交瘤注射时，与对照胚胎相比，O 4阳性细胞数量减少至50%。N-cadherin可能参与OPC在视神经内的迁移。

Migration and proliferation of oligodendrocyte precursor cells (OPCs) were examined with lineage marker antibodies O4 and O1.(1) OPCs in the metencephalon (brainstem and cerebellum) undergo gradual dispersal from the medial brainstem, the lateral part and finally to the cerebellar anlage. To verify the migration of OPCs, plasmid encoding EGFP gene was transfected to the metencephalon ventricular cells on E4 or E5, and appearance and dispersal of O4-positive/EGFP-positive cells were examined sequentially. Transfection of the plasmid to the medial ventricular layer resulted in appearance of O4-positive/EGFP-positive cells in the brainstem and also in the cerebellum. This result indicates that OPCs arise in the medial brainstem ventricular layer and that at least some fractions of OPCs may migrate to the cerebellar anlage from the brainstem.(2) Proliferation of OPCs was examined by double-labeling of OPCs with bromodeoxyuridine (BrdU) and with O4 or O1. Approximately 20 % of O4-positive ventricular cells incorporated BrdU, while 40-50 % of O4-positive cells was labeled in the parenchyma right after their appearance in these regions. Labeling indices gradually decreased as embryo developed. Finally, less than 5 % of mature oligodendrocytes were labeled with BrdU. Oligodendrocyte lineage cells may generate their cohorts most actively in the parenchyma just after they leave from the ventricular layer.(3) Molecules regulating the OPC migration were examined with neutralizing antibodies against cell surface recognition molecules. Hybridomas secreting antibody was injected into the third ventricle of the E5 chick embryo and O4-positive cell distribution in the optic nerve was examined at E8. When the embryos were received injection of the hybridoma generating the antibody against N-cadherin, O4-positive cell number decreased to 50 % as compared to the control embryos. N-cadherin may be involved in the OPC migration in the optic nerve.