The role of RPTPzeta in models of Congenital Muscular Dystrophies

描述（由申请人提供）：参与蛋白质O-甘露糖基化的酶的突变产生一组以先天性肌营养不良（CMD）、II型无脑畸形和眼畸形为特征的毁灭性疾病。先前使用动物模型的研究已经证明，α-肌营养不良聚糖的低糖基化对这些疾病的发病机制有重要贡献。然而，越来越多的证据表明，O-甘露糖基化的其他底物可能有助于在动物模型和CMD患者中发现的特定脑异常。不幸的是，以前的研究未能确定O-甘露糖基化的其他神经底物，有助于这些脑病理。使用CMD的糖基转移酶POMGnT 1被敲除的动物模型，我们确定RPTP？作为脑中O-甘露糖基化的另一种重要底物。受体酪氨酸磷酸酶zeta/beta是一种主要在中枢神经系统中发现的受体磷酸酶，在神经发育的关键阶段高度表达。蛋白质的膜结合受体和分泌变体都在脑中表达，并且是许多发育重要的粘附分子、生长因子和细胞外基质蛋白的高亲和力配体。我们推测，低糖基化的RPTP 6由于破坏O-甘露糖基化改变的相互作用的RPTP？与这些关键的配体，并有助于异常的大脑发育。与这一假设相一致，我们发现，皮质神经元的发展在培养的细胞从POMGnT 1敲除是异常的，当他们被铺板在一个子集的已知RPTP？配体。在这个建议中，我们调查的假设，低糖RPTP？在O-甘露糖基糖基化突变动物中改变其配体结合特性，从而导致异常的细胞相互作用和异常的脑发育。本研究的主要目的是：1）确定RPTP的糖基化是否发生改变？调节其配体结合特性。2)以确定是否破坏RPTP的糖基化？改变细胞发育。和3）为了确定1-肌营养不良蛋白聚糖独立的神经异常的CMD动物模型，并确定这些异常是否是由于改变RPTP？磷酸聚糖糖基化。为了探索这些问题，我们将利用各种遗传小鼠模型系统，我们将破坏O-甘露糖基糖基化，α-dystrglycan表达或RPTP？表情研究将在体外和体内进行，以确定如何O-甘露聚糖调节RPTP？功能，以及这是否有助于在CMD动物模型中发现的大脑异常。这些研究将确定是否RPTP？是一个重要的贡献者CMD发病机制，并将提供重要的见解，在这些疾病的神经表型的病理机制。 公共卫生相关性：蛋白质糖基化改变是先天性肌营养不良症的一个众所周知的原因。然而，这些疾病中糖基化改变的所有蛋白质靶点都是未知的。在这个提案中，我们调查RPTP？作为先天性肌营养不良症中糖基化破坏的重要新靶点，在这些疾病的动物模型中研究其作用。

DESCRIPTION (provided by applicant): Mutations in enzymes involved in protein O-mannosyl glycosylation produce a group of devastating diseases characterized by congenital muscular dystrophy (CMD), type II lissencephaly, and eye abnormalities. Previous studies using animal models have demonstrated that hypoglycosylation of a-dystroglycan critically contributes to the pathogenesis of these disorders. A growing body of evidence, however, suggests that other substrates for O-mannosyl glycosylation likely contribute to particular brain abnormalities found both in animal models and in patients with CMDs. Unfortunately, previous studies have failed to identify the additional neural substrates of O-mannosylation that contribute to these brain pathologies. Using an animal model of CMD in which the glycosyltransferase POMGnT1 is knocked out we identified RPTP? as another important substrate for O-mannosyl glycosylation in the brain. Receptor tyrosine phosphatase zeta/beta is a receptor phosphatase that is found predominately in the central nervous system and is highly expressed during key stages of neural development. Both membrane-bound receptor and secreted variants of the protein are expressed in the brain and are high affinity ligands for a number of developmentally important adhesion molecules, growth factors and extracellular matrix proteins. We hypothesize that the hypoglycosylation of RPTP6 due to disrupted O-mannosylation alters the interactions of RPTP? with these key ligands and contributes to abnormal brain development. Consistent with this hypothesis we found that cortical neuron development in cultured cells from POMGnT1 knockouts is abnormal when they are plated on a subset of known RPTP? ligands. In this proposal we investigate the hypothesis that the hypoglycosylaton of RPTP? in O-mannosyl glycosylation mutant animals alters its ligand-binding characteristics thereby leading to aberrant cellular interactions and abnormal brain development. The proposal is focused on the following 3 specific aims: 1) To determine whether altered glycosylation of RPTP? modulates its ligand binding characteristics. 2) To determine whether disrupted glycosylation of RPTP? alter cell development. And 3) To identify the 1-dystroglycan-independent neural abnormalities in animal models of CMDs and to determine if these abnormalities are due to altered RPTP?/phosphacan glycosylation. To explore these questions, we will utilize a variety of genetic mouse model systems in which we will disrupt O-mannosyl glycosylation, a-dystrglycan expression or RPTP?expression. Studies will be conducted both in vitro and in vivo to determine how O-mannosyl glycans modulate RPTP? function and if this contributes to brain abnormalities found in animal models of CMDs. These studies will determine if RPTP? is an important contributor to CMD pathogenesis and will provide important insights into the pathomechanisms of the neural phenotypes in these disorders. PUBLIC HEALTH RELEVANCE: Altered protein glycosylation is a well-known cause of congenital muscular dystrophies. However, all the protein targets of altered glycosylation in these disorders are not known. In this proposal we investigate RPTP? as an important new target of the disrupted glycosylation in congenital muscular dystrophies in investigate its role in animals models of these disorders.