Raven Mary A, Stagg Stephanie B, Nassar Hadi, Reese Benjamin E
Neuroscience Research Institute and Department of Psychology, University of California at Santa Barbara, Santa Barbara, CA 93106-5060, USA.
Vis Neurosci. 2005 Sep-Oct;22(5):569-73. doi: 10.1017/S095252380522504X.
The present investigation has sought to determine whether the population of retinal horizontal cells undergoes an increase in the precision of its mosaic patterning during postnatal development, and if so, whether this increase is compatible with three different mechanistic accounts of retinal mosaic formation. Horizontal cells were labeled with antibodies to neurofilaments or calbindin at different developmental stages, and then visualized in retinal wholemounts. Multiple fields were sampled from each retina to determine horizontal cell density, while the X-Y coordinates of each cell in a field were determined. An estimate of total horizontal cell number was calculated for each retina, while the Voronoi domain regularity index and the packing factor were computed for each field. Two strains of mice showing a two-fold difference in the size of their horizontal cell population in maturity were sampled, C57BL/6J and A/J. Horizontal cell number in C57BL/6J was approximately twice that observed in A/J at all postnatal stages, with neither strain showing an effect of age on horizontal cell number. In both strains, however, the Voronoi domain regularity index and the packing factor were significantly lower at P-1 relative to later developmental stages. These results show that accounts of mosaic formation proposing the selective death of irregularly positioned cells, or the periodic occurrence of fate-determining events, are insufficient to establish the final patterning achieved by horizontal cells. Rather, they support the hypothesis that tangential dispersion enhances mosaic patterning during postnatal development.
本研究旨在确定视网膜水平细胞群体在出生后发育过程中其镶嵌模式的精度是否会提高，如果是，这种提高是否与视网膜镶嵌形成的三种不同机制解释相符。在不同发育阶段，用抗神经丝或钙结合蛋白的抗体标记水平细胞，然后在视网膜整装标本中进行可视化观察。从每个视网膜中采集多个视野以确定水平细胞密度，同时确定视野中每个细胞的X-Y坐标。计算每个视网膜的水平细胞总数估计值，同时计算每个视野的Voronoi域规则性指数和堆积因子。选取了成熟时水平细胞群体大小相差两倍的两种小鼠品系，即C57BL/6J和A/J。在所有出生后阶段，C57BL/6J的水平细胞数量约为A/J的两倍，两个品系均未显示年龄对水平细胞数量有影响。然而，在这两个品系中，相对于后期发育阶段，P-1时的Voronoi域规则性指数和堆积因子均显著较低。这些结果表明，提出不规则定位细胞选择性死亡或命运决定事件周期性发生的镶嵌形成解释，不足以确立水平细胞最终形成的模式。相反，它们支持这样一种假说，即切向扩散在出生后发育过程中增强了镶嵌模式。
