Higgins D, Waxman A, Banker G
Department of Pharmacology, State University of New York, Buffalo 14214.
Neuroscience. 1988 Feb;24(2):583-92. doi: 10.1016/0306-4522(88)90352-1.
We have examined the distribution of microtubule-associated protein 2 in embryonic rat sympathetic neurons grown under culture conditions that alter morphological development. Cultures were established in serum-free medium. After 8 days some were transferred to a serum-containing medium, which promotes dendritic development. Sister cultures were maintained in serum-free medium, which inhibits dendritic growth but permits normal axonal development. After growth for 2-6 weeks in serum-containing medium, sympathetic neurons were multipolar, with short, tapering dendrites and long, thin axons. Intense immunoreactivity for microtubule-associated protein 2 was observed in the somata and dendrites of all neurons, but there was little or no staining of the network of axonal processes that ran between cell somata. When the morphology of individual cells was assessed by injection of fluorescent dye before immunostaining, we found that staining for microtubule-associated protein 2 extended to the distal tips of the dendrites while the axon was essentially unstained, even in its proximal portion. Neurons from sister cultures that were not exposed to serum were usually unipolar, having only an axon. Under these conditions microtubule-associated protein 2 was also expressed, but its distribution was altered: intense immunostaining for microtubule-associated protein 2 was present in axons as well as somata. Staining in axons could sometimes be traced for several millimeters, but, since unstained segments of axons were also common, microtubule-associated protein 2 probably was not present throughout the entire axonal arborization. These results show that the expression of microtubule-associated protein 2 is not of itself sufficient to induce the formation of dendrites. Despite the association of microtubule-associated protein 2 with the axonal cytoskeleton, the light microscopic morphology of the axons was not obviously altered.
我们研究了在改变形态发育的培养条件下生长的胚胎大鼠交感神经元中微管相关蛋白2的分布。培养物在无血清培养基中建立。8天后，一些培养物被转移到含血清的培养基中，该培养基可促进树突发育。配对培养物则维持在无血清培养基中，该培养基抑制树突生长，但允许正常的轴突发育。在含血清的培养基中生长2至6周后，交感神经元呈多极，具有短而逐渐变细的树突和长而细的轴突。在所有神经元的胞体和树突中均观察到微管相关蛋白2的强烈免疫反应性，但在细胞胞体之间延伸的轴突网络几乎没有或没有染色。当在免疫染色前通过注射荧光染料评估单个细胞的形态时，我们发现微管相关蛋白2的染色延伸到树突的远端，而轴突即使在其近端部分也基本未染色。未暴露于血清的配对培养物中的神经元通常是单极的，只有一个轴突。在这些条件下，微管相关蛋白2也有表达，但其分布发生了改变：微管相关蛋白2的强烈免疫染色存在于轴突以及胞体中。轴突中的染色有时可以追踪到几毫米，但由于未染色的轴突段也很常见，微管相关蛋白2可能并不存在于整个轴突分支中。这些结果表明，微管相关蛋白2的表达本身不足以诱导树突的形成。尽管微管相关蛋白2与轴突细胞骨架有关，但轴突的光学显微镜形态并未明显改变。
