Meadows L A, Gell D, Broadie K, Gould A P, White R A
Department of Anatomy, University of Cambridge, UK.
J Cell Sci. 1994 Jan;107 ( Pt 1):321-8. doi: 10.1242/jcs.107.1.321.
The connectin gene of Drosophila has been identified as a candidate direct target of homeotic gene control and has also been implicated in the formation of specific neuromuscular connections. The gene product, connectin, is a member of the leucine-rich repeat protein family and we show that it is attached to the cell surface via a glycosylphosphatidylinositol linkage and that it can mediate homotypic cell-cell adhesion in vitro. The expression of connectin protein during Drosophila embryogenesis provides support for a role in adhesion in vivo. In the central nervous system, it is initially expressed on longitudinal glia and on a few identified neurons. These cells extend processes and connect up to form a continuous scaffold of connectin-expressing cells, presaging the development of axonal pathways. Later, connectin is expressed on specific axons as they track along the connectin scaffold. Glial expression then declines and connectin appears on axons that fasciculate with pre-existing connectin-positive bundles. Thus scaffold formation, axon pathfinding and fasciculation involve specific contacts between connectin-positive cells. The timing and pattern of connectin expression suggest that it may play an important role in mediating specific interactions through homotypic cell adhesion.
果蝇的连接蛋白基因已被确定为同源异型基因控制的候选直接靶点，并且也与特定神经肌肉连接的形成有关。该基因产物连接蛋白是富含亮氨酸重复蛋白家族的成员，我们发现它通过糖基磷脂酰肌醇连接附着在细胞表面，并且它能够在体外介导同型细胞间黏附。果蝇胚胎发育过程中连接蛋白的表达为其在体内黏附中的作用提供了支持。在中枢神经系统中，它最初在纵向神经胶质细胞和一些已确定的神经元上表达。这些细胞伸出突起并连接起来形成一个表达连接蛋白的细胞的连续支架，预示着轴突通路的发育。后来，连接蛋白在特定轴突沿着连接蛋白支架追踪时表达。然后神经胶质细胞的表达下降，连接蛋白出现在与预先存在的连接蛋白阳性束成束的轴突上。因此，支架形成、轴突寻路和成束涉及连接蛋白阳性细胞之间的特定接触。连接蛋白表达的时间和模式表明，它可能在通过同型细胞黏附介导特定相互作用中发挥重要作用。
