Extracellular matrix in synapse formation in the CNS

描述(申请人提供)：层粘连蛋白是生物活性分子，起细胞黏附分子的作用，调节发育的各个方面，并用于稳定复杂的解剖结构。它们是大的细胞外基质分子，由三个亚单位链组成，分别为α、β和伽马。已经确定了五条α链、三条贝塔链和三条伽马链。层粘连蛋白广泛表达于中枢神经系统，其受体也是如此。神经系统的一些疾病与层粘连蛋白基因有关：一些先天性肌营养不良症涉及α2链(Merosin)；Walker-Warburg综合征的Beta2链减少；以及一组复杂的中枢神经系统发育障碍(肌肉-脑-眼疾病；视网膜色素变性伴耳聋(RP21伴耳聋)；Walker-Warburg综合征)映射到Gamma3基因的位点。一些层粘连蛋白相关基因的遗传中断也会导致人类疾病和动物模型的畸形发育。我们已经鉴定了两个新的CNS层粘连蛋白，α4β2Gamma3和α5beta2Gamma3(分别为LN14和LN15)，它们分别存在于光感受器间基质和外丛状层(OPL)的基质中。这些层粘连蛋白似乎在光感受器的形态发生中起着重要作用。首先，这些链在杆状突起发生之前表达，并持续到成年期。其次，去除编码Beta2链之一的基因会导致产生变形的光感受器；具体地说，光感受器外段的长度减少，OPL中的光感受器终末被破坏。最后，ERG b波的幅度急剧降低，这表明从光感受器到二级细胞的传输被含有Beta2的层粘连蛋白的丢失所干扰。我们假设LN 14和LN 15是突触组装和稳定的关键介质。此外，我们假设LN14和15形成独特的底物，光感受器终端与之相互作用。具体地说，我们假设光感受器突触的分子组装和结构取决于这些层粘连蛋白和它们的受体之间的相互作用。我们建议对这一假设的几个方面进行检验。我们将问两个具体的问题：1)OPL中层粘连蛋白复合体的功能组成是什么？2)层粘连蛋白复合体的破坏如何改变OPL的功能组织？通过这些研究，我们将：深入了解视网膜外部突触组装的分子机制；确定细胞外基质在这一过程中的作用；并阐明人类一系列遗传疾病的基础。

DESCRIPTION (provided by applicant): Laminins are biologically active molecules that function as cell adhesion molecules, regulate various aspects of development, and serve to stabilize complex anatomical structures. They are large extracellular matrix molecules which are composed of three subunit chains, designated alpha, beta and gamma. Five alpha, three beta and three gamma chains have been identified. Laminins are widely expressed in the CNS; as are their receptors. Several disorders of the nervous system are linked to laminin genes: some congenital muscular dystrophies involve the alpha2 chain (merosin); the beta2 chain is reduced in Walker-Warburg syndrome; and a complex group of CNS developmental disorders (muscle-brain-eye disease; retinitis pigmentosa with deafness (RP21 with deafness); Walker-Warburg syndrome) maps to the site of the gamma3 gene. Genetic disruptions in some laminin-related genes also result in human disease and in dysmorphogenesis in animal models. We have identified two novel CNS laminins, alpha4beta2gamma3 and alpha5beta2gamma3 (LN 14 & LN 15, respectively); these are found in the interphotoreceptor matrix and in the matrix of the outer plexiform layer (OPL). These laminins appear to play important roles in the morphogenesis of photoreceptors. First, these chains are expressed prior to the onset of rod genesis and persist into adulthood. Second, ablation of the gene encoding one of the beta2 chains results in the production of dysmorphic photoreceptors; specifically, photoreceptor outer segments are reduced in length and the photoreceptor terminals in the OPL are disrupted. Finally the amplitude of the ERG b-wave is drastically diminished suggesting that transmission from photoreceptors to second order cells is disrupted by loss of beta2-containing laminins. We hypothesize that LN 14 and 15 are critical mediators of synapse assembly and stabilization. Furthermore, we hypothesize that LN14 and 15 form unique substrates with which photoreceptor terminals interact. Specifically, we hypothesize that the molecular assembly and structure of the photoreceptor synapse is dependent on the interactions between these laminins and their receptors. We propose to test several aspects of this hypothesis. We will ask two specific questions: 1) What is the functional composition of the laminin complex in the OPL? 2) How does disruption of the laminin complex alter the functional organization of the OPL? With these studies, we will: gain insight into the molecular mechanisms of synaptic assembly in the outer retina; define the role of the ECM in this process; and shed light on the basis of a series of genetic disorders in humans.