Department of Cellular and Physiological Sciences, Life Sciences Institute, The University of British Columbia, Vancouver, British Columbia, Canada.
J Neurosci Res. 2010 Mar;88(4):837-49. doi: 10.1002/jnr.22258.
Several recent studies have shown that neuroligin 2 (NL2), a component of the cell adhesion neurexins-neuroligins complex, is localized postsynaptically at hippocampal and other inhibitory synapses throughout the brain. Other studies have shown that components of the dystroglycan complex are also localized at a subset of inhibitory synapses and are coexpressed with NL2 in brain. These data prompted us to undertake a comparative study between the localization of NL2 and the dystroglycan complex in the rodent retina. First, we determined that NL2 mRNA is expressed both in the inner and in the outer nuclear layers. Second, we found that NL2 is localized both in the inner and in the outer synaptic plexiform layers. In the latter, the horseshoe-shaped pattern of NL2 and its extensive colocalization with RIM2, a component of the presynaptic active zone at ribbon synapses, argue that NL2 is localized presynaptically at photoreceptor terminals. Third, comparison of NL2 and the dystroglycan complex distribution patterns reveals that, despite their coexpression in the outer plexiform layer, they are spatially segregated within distinct domains of the photoreceptor terminals, where NL2 is selectively associated with the active zone and the dystroglycan complex is distally distributed in the lateral regions. Finally, we report that the dystroglycan deficiency in the mdx(3cv) mouse does not alter NL2 localization in the outer plexiform layer. These data show that the NL2- and dystroglycan-containing complexes are differentially localized in the presynaptic photoreceptor terminals and suggest that they may serve distinct functions in retina.
几项最近的研究表明，神经黏附素 2（NL2）是细胞黏附素神经连接蛋白-神经黏附素复合物的一个组成部分，定位于大脑中海马和其他抑制性突触的突触后。其他研究表明， dystroglycan 复合物的成分也定位于抑制性突触的一部分，并与 NL2 在大脑中共同表达。这些数据促使我们对 NL2 和 dystroglycan 复合物在啮齿动物视网膜中的定位进行了比较研究。首先，我们确定 NL2 mRNA 在内核层和外核层中均有表达。其次，我们发现 NL2 既定位于内突触丛状层，也定位于外突触丛状层。在后一种情况下，NL2 的马蹄形模式及其与 RIM2（位于带状突触的突触前活性区的一个组成部分）的广泛共定位表明，NL2 定位于光感受器末梢的突触前。第三，比较 NL2 和 dystroglycan 复合物的分布模式表明，尽管它们在外丛状层中共表达，但它们在光感受器末梢的不同区域内空间分离，其中 NL2 选择性地与活性区相关，而 dystroglycan 复合物在侧区远部分布。最后，我们报告 mdx(3cv) 小鼠中的 dystroglycan 缺乏并不改变 NL2 在外侧丛状层中的定位。这些数据表明，NL2 和 dystroglycan 包含的复合物在光感受器末梢的突触前分别定位，并表明它们可能在视网膜中具有不同的功能。
