Rhyu M S, Jan L Y, Jan Y N
Howard Hughes Medical Institute, University of California, San Francisco 94143-0724.
Cell. 1994 Feb 11;76(3):477-91. doi: 10.1016/0092-8674(94)90112-0.
The four cells of an external sense organ in the Drosophila peripheral nervous system, the neuron, its sheath cell, and two "outer support cells" that form the hair and socket, are derived from a common precursor, the sensory organ precursor (SOP), after two rounds of division. We determined by immunocytochemistry that numb is a membrane-associated protein which localizes asymmetrically to one-half of the predivisional SOP cell. Upon division, numb segregates differentially to one daughter. Loss of numb function causes the descendants of the SOP to differentiate inappropriately, producing four outer support cells and no neuron or sheath. Ectopic expression of numb during the time of SOP division results in a transformation that is opposite to the null mutant transformation. Thus, numb functions to determine the fates of the secondary precursors; the differential distribution of numb as the SOP divides generates an asymmetric division in which the daughter cells acquire distinct identities.
果蝇外周神经系统中一个外部感觉器官的四个细胞，即神经元、其鞘细胞以及形成刚毛和窝的两个“外部支持细胞”，是由一个共同的前体细胞——感觉器官前体细胞（SOP）经过两轮分裂产生的。我们通过免疫细胞化学方法确定，麻木蛋白是一种膜相关蛋白，它不对称地定位于分裂前SOP细胞的一半。在细胞分裂时，麻木蛋白差异地分离到一个子细胞中。麻木蛋白功能的丧失会导致SOP的后代细胞分化异常，产生四个外部支持细胞，而没有神经元或鞘细胞。在SOP分裂期间异位表达麻木蛋白会导致一种与无效突变体转变相反的转变。因此，麻木蛋白起到确定二级前体细胞命运的作用；SOP分裂时麻木蛋白的差异分布产生了一种不对称分裂，其中子细胞获得了不同的身份。
