神经细胞粘连分子L1胞外域段对小鼠原代培养神经元的影响及其脑特异性表达转基因小鼠的构建

神经细胞粘连分子L1是神经系统发育过程中介导细胞-细胞相互作用的重要分子。L1能启动轴突的延伸并与神经细胞迁移有关,在神经系统发育和维持方面起重要作用。L1基因突变会导致智力迟钝,痉挛性截瘫,脑积水和其他的发育异常。L1基因突变导致遗传性神经细胞疾病的分子机理目前还不清楚,本研究介绍L1转基因小鼠的构建。在小鼠神经细胞粘连分子L1细胞外区段(L1ECD)cDNA的末端上加一终止密码子后,置于神经系统特异性的pCAMKⅡ启动子之后,构建成L1ECD转基因DNA。为验证构建物的正确性,将其与真核细胞表达载体pCEP4连接并转染C6细胞,实现了L1ECD在C6细胞中的表达,并观察了L1ECD对体外培养的C6细胞和原代培养的神经元的效应。采用显微注射的方法将L1ECD转基因DNA导入小鼠受精卵,产出的仔鼠经尾组织基因组DNA Southern杂交分析和组织RNA Northern杂交分析,证明L1ECD转基因DNA已整合在转基因小鼠基因组内,并呈脑特异性表达。

EFFECT OF L1ECD ON MOUSE PRIMARILY CULTURED NEURONS AND CONSTRUCTION OF TRANSGENIC MICE SPECIFICALLY EXPRESSING LlECD IN BRAIN

Neural cell adhesion molecule L1 is an important molecule mediating cell-cell interactions during the development of nervous system. L1 can promote axonal outgrowth and is related with nerve cell migration, and therefore L1 plays an important role both in the development and main-taince of the nervous system. In humans, mutations in the L1 gene can lead to mental retardation, spastic paraplegia, hydrocephalus, and other developmental abnormalities. The molecular mechanisms of mutations in L1 gene to induce inherited neurological diseases are not clear. In present investigation, a transgenic DNA of mouse L1 extracellular domain (L1ECD) was constructed by adding a stop codon to the end of L1ECD cDNA and then putting it under the con-trol of CAMK II promoter, which is active specifically in the brain. To verify this construct, L1ECD cDNA was subcloned into an expression vector pCEP4 and then transfected the C6 cells. The expression of L1ECD cDNA in C6 cells was confirmed by Northern blotting and the effects of L1ECD on the growth rate and morphology of C6 cells in vitro as well as primarily cultured neurons were observed. The L1ECD constructs were microinjected into the fertilized zygotes of C57BL/6 mice. The transgenic mice thus produced were identified by Southern and Northern hybridization analysis. The results demonstrated that the L1ECD was integrated in the genome of transgenic mice and expressed specifically in the brain.