Gubb D
University of Cambridge, Department of Genetics, UK.
Dev Suppl. 1993:269-77.
The control of cellular polarity is one of the least understood aspects of development. Genes have been identified in Drosophila that affect the polarity of embryonic cells in all three axes, apical-basal, proximodistal and dorsoventral. Mutations that affect adult polarity are also known and mutant flies show several types of pattern alteration, including rotations and mirror-image duplications. Imaginal discs are much greater in size, however, than the embryo, and adult structures contain very large numbers of cells, many of which are not visibly differentiated with respect to their immediate neighbours. In regions where neighbouring cells are similar to each other, the imaginal polarity mutants alter the orientation of bristles and hairs, but do not change cellular fate. Other regions, such as the tarsal segments of the legs, the ommatidia of the eye and the bracketed bristle sockets on the tibia, behave as discrete fields. Within these fields, fine-scale mirror-image reversals and pattern duplications are observed, analogous to those caused by the embryonic segment polarity mutants. Thus, the polarised transmission of information can affect either orientation or fate depending on whether cells are differentiated from their immediate neighbours. Cellular polarity will be critically dependent on both the internal cytoskeletal architecture and the spatial organisation of signal transduction molecules within the cell membrane.
细胞极性的控制是发育过程中最不为人所理解的方面之一。在果蝇中已鉴定出影响胚胎细胞在顶-基、近-远和背-腹三个轴上极性的基因。影响成虫极性的突变也为人所知，突变果蝇表现出几种类型的模式改变，包括旋转和镜像重复。然而，成虫盘的尺寸比胚胎大得多，成虫结构包含大量细胞，其中许多细胞与其紧邻细胞相比并无明显分化。在相邻细胞彼此相似的区域，成虫极性突变体改变刚毛和毛发的方向，但不改变细胞命运。其他区域，如腿部的跗节、眼睛的小眼以及胫节上带括号的刚毛窝，表现为离散区域。在这些区域内，观察到精细尺度的镜像反转和模式重复，类似于胚胎节段极性突变体所引起的情况。因此，信息的极化传递可根据细胞与其紧邻细胞是否分化而影响方向或命运。细胞极性将严重依赖于细胞内的细胞骨架结构和细胞膜内信号转导分子的空间组织。
