Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106-9625, USA.
J Comp Neurol. 2010 Apr 15;518(8):1220-31. doi: 10.1002/cne.22270.
To determine the role of homotypic interactions between neighboring dopaminergic amacrine (DA) cells upon dendritic morphogenesis, the morphology of single cells was examined relative to the positioning of all neighboring homotypic cells. For each labeled cell, the dendritic field was reconstructed, its Voronoi domain was calculated, and the two were related. The dendritic fields of DA cells were observed to be large, sparse, and highly irregular. Dendrites readily overlapped those of neighboring cells, showing no evidence for dendritic tiling or inter-digitation consistent with homotypic repulsion or avoidance. Furthermore, a direct comparison of dendritic field area with the Voronoi domain area of the same cell showed no evidence for dendritic growth being constrained or biased by the local distribution of homotypic neighbors in wild-type retinas. A comparison of the processes of adjacent filled cells confirmed their immediate proximity to one another within the inner plexiform layer, indicating that they do not engage in mutual avoidance by coursing at different depths. Together, these results suggest that the morphogenesis of DA cells is independent of homotypic interactions. However, in the absence of the pro-apoptotic Bax gene, which yields a fourfold increase in DA cell number, a small but significant reduction in dendritic field size was obtained, although not so great as would be predicted by the increase in density. The present results are considered in light of recent studies on the role of cell adhesion molecules expressed by developing DA cells.
为了确定相邻多巴胺能无长突细胞（DA）之间的同质相互作用在树突形态发生中的作用，相对于所有相邻同型细胞的定位来检查单个细胞的形态。对于每个标记的细胞，重建其树突场，计算其 Voronoi 域，并将两者相关联。观察到 DA 细胞的树突场大、稀疏且高度不规则。树突很容易与相邻细胞的树突重叠，没有证据表明存在树突平铺或相互交织，这与同型排斥或回避一致。此外，直接比较树突场面积与同一细胞的 Voronoi 域面积，没有证据表明树突生长受到野生型视网膜中同型邻居的局部分布的限制或偏向。对相邻填充细胞的过程进行比较，证实了它们在神经内丛状层内彼此之间的紧邻关系，表明它们不会通过在不同深度上流动来相互回避。总之，这些结果表明 DA 细胞的形态发生不依赖于同质相互作用。然而，在缺乏促凋亡 Bax 基因的情况下，该基因使 DA 细胞数量增加了四倍，获得了树突场大小的微小但显著的减小，尽管减小幅度不及密度增加所预测的那么大。考虑到最近关于发育中的 DA 细胞表达的细胞粘附分子的作用的研究，对目前的结果进行了考虑。
