Extracellular matrix in synapse formation in the CNS

描述（由申请人提供）：层粘连蛋白是生物活性分子，其作为细胞粘附分子发挥作用，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，由三个亚基链组成，命名为α、β和γ。已鉴定出5条α链、3条β链和3条γ链。层粘连蛋白在CNS中广泛表达;其受体也是如此。一些神经系统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α 2链（merosin）;沃克-沃伯格综合征中β 2链减少;一组复杂的中枢神经系统发育障碍（肌-脑-眼疾病;视网膜色素变性伴耳聋（RP21伴耳聋）;沃克-沃伯格综合征）映射到γ 3基因的位点。一些层粘连蛋白相关基因的遗传破坏也会导致人类疾病和动物模型中的畸形。我们已经鉴定了两种新的CNS层粘连蛋白，α 4 β 2 γ 3和α 5 β 2 γ 3（分别为LN 14和LN 15）;这些层粘连蛋白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重要作用。首先，这些链在杆发生之前表达，并持续到成年期。第二，编码β 2链之一的基因的消融导致畸形光感受器的产生;具体地说，光感受器外节长度减少，OPL中的光感受器末端被破坏。最后，ERG b波的振幅急剧减小，表明从光感受器到二级细胞的传输被含β 2层粘连蛋白的损失破坏。我们假设LN14和15是突触组装和稳定的关键介质。此外，我们假设，LN 14和15形成独特的基板与感光末梢相互作用。具体来说，我们假设感光突触的分子组装和结构依赖于这些层粘连蛋白和它们的受体之间的相互作用。我们建议测试这个假设的几个方面。我们将提出两个具体问题：1）OPL中层粘连蛋白复合物的功能组成是什么？2)层粘连蛋白复合物的破坏如何改变OPL的功能组织？通过这些研究，我们将：深入了解外视网膜突触组装的分子机制;定义ECM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.