Extracellular matrix in synapse formation in the CNS

描述（由申请人提供）：层粘连蛋白是具有生物活性的分子，作为细胞粘附分子，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，分别是α、β和γ。已经确定了5条，3条和3条链。层粘连蛋白广泛表达于中枢神经系统；它们的受体也是如此。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（美罗辛蛋白）；- 2链在Walker-Warburg综合征中减少；和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基因的位置。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发生。我们鉴定了两种新的CNS层粘连蛋白，alpha4beta2gamma3和alpha5beta2gamma3（分别为LN 14和LN 15）；它们存在于感光细胞间基质和外丛状层基质中。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，这些链在杆状体发生前表达，并持续到成年期。其次，基因编码β 2链之一的消融导致畸变光感受器的产生；具体来说，光感受器外段长度减少，OPL中的光感受器末端被破坏。最后，ERG b波的振幅急剧减弱，表明从光感受器到二级细胞的传输因含β 2层粘连蛋白的损失而中断。我们假设ln14和ln15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，与光感受器终端相互作用。具体来说，我们假设光感受器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。我们建议测试这一假设的几个方面。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；界定ECM在此过程中的角色；并揭示了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.