Model Systems for PXE

描述(由申请者提供)：第二次修订的新资助申请围绕着弹性假黄瘤(PXE)，这是一种常染色体隐性遗传病，其特征是各种器官中结缔组织的异位矿化，包括皮肤、眼睛和心血管系统，具有相当高的发病率和死亡率。目前已知PXE是由ABCC6基因突变引起的，该基因编码多药耐药相关蛋白6(MRP6)，这是一种假定的跨膜转运蛋白，主要在肝脏表达，在肾脏近端小管中表达较少，在PXE患者的组织中表达水平很低(如果有的话)。增加这种疾病的复杂性的是观察到有相当大的家庭间和家庭内的异质性，诊断往往由于症状的迟发而被推迟，以及一些环境和生活方式的变量似乎调节了疾病的进展和最终结果。从ABCC6表达改变到周围组织异常矿化的病理机制细节目前尚不清楚。具体地说，MRP6及其生理配体(S)的功能仍未披露。这一应用将利用在理解ABC转运蛋白方面取得的一般进展以及我们最近开发的模型系统来研究这种疾病。该申请代表了三个主要研究小组的联合，将致力于以下具体目标：1)将Abcc6-/-小鼠作为PXE的表型模型；2)表征人ABCC6/MRP6转运蛋白并寻找生理底物。具体目标1建议发展异种共生和血浆/候选蛋白补充，并广泛表征Abcc6-/-小鼠，作为PXE的模型。具体目标2提出了用全局和候选分子方法识别MRP6生理底物(S)的最新技术。这些生理底物将用于MRP6的结构和功能研究。这些特定的目标检验了统一的假设，即PXE是一种在基因组/环境界面上可遗传的疾病，总体目标是定义导致PXE表型表达的分子事件。我们最近通过靶向切割Abcc6基因建立了PXE小鼠模型，并建立了昆虫细胞运输系统来研究MRP6运输机制的细节以及PXE突变对其的影响，证明了这一应用的可行性。预计这项研究的结果将为PXE中导致异常矿化的病理机制和相关的遗传性疾病提供新的见解，并展望普通人群的共同特征，如老年性黄斑变性和动脉硬化。对这些途径的了解有望为开发新的药理学方法来改善甚至治愈这些目前难以治愈的疾病提供机会。 公共卫生评论。本研究项目围绕弹性假黄瘤(PXE)展开，这是一种以结缔组织异位矿化为特征的遗传性疾病，具有相当高的发病率和死亡率。这些研究的总体目标是确定导致异常矿化的病理机制路径，并具有翻译意义。这一结果有望为改善、甚至治愈PXE和其他相关的、目前难以治愈的矿化疾病提供新的方法。

DESCRIPTION (provided by applicant): This second revision of a new grant application revolves around pseudoxanthoma elasticum (PXE), an autosomal recessive disorder characterized by ectopic mineralization of connective tissues in a variety of organs, including the skin, the eyes, and the cardiovascular system, with considerable morbidity and mortality. PXE is now known to result from mutations in the ABCC6 gene which encodes the multi-drug resistance-associated protein 6 (MRP6), a putative transmembrane transporter, expressed primarily in the liver, to a lesser extent in proximal tubules of kidneys, and at very low levels, if at all, in tissues afflicted by PXE. Adding to the complexity of this disorder are the observations that there is considerable both inter- and intra-familial heterogeneity, the diagnosis is often delayed due to late onset of manifestations, and a number of environmental and life-style variables appear to modulate the progression and eventual outcome of the disease. The pathomechanistic details leading from altered ABCC6 expression to aberrant mineralization in peripheral tissues are currently unknown. Specifically, the function of MRP6 and its physiologic ligand(s) remain undisclosed. This application will take advantage of the general progress made in understanding the ABC transporters and of our recent development of model systems to study this disorder. The application represents a consortium between three major research groups that will address the following Specific Aims: 1) The Abcc6-/- Mice as a Phenotypic Model of PXE; 2) Characterization of Human ABCC6/MRP6 Transporter and Search for the Physiological Substrates. The Specific Aim 1 proposes development of parabiosis and plasma/candidate protein supplementation, with extensive characterization of Abcc6-/- mice, as models for PXE. The Specific Aim 2 proposes state-of-the-art technologies to identify physiologic substrate(s) for MRP6 with global and candidate molecule approaches. Such physiologic substrates will then be used for structure-function studies of MRP6. These specific aims test the unifying hypothesis that PXE is a heritable disorder at the genome/environment interface, with an overall goal to define the molecular events that lead to phenotypic expression of PXE. The feasibility of this application is attested by our recent development of a mouse model for PXE through targeted ablation of the Abcc6 gene, and by establishment of the insect cell transport system to study the details of the MRP6 transport mechanisms as well as the effects of PXE mutations on it. It is expected that the results of this study will provide novel insights into the pathomechanistic pathways leading to aberrant mineralization in PXE and related heritable disorders, with perspective to common traits in general population, such as age-associated macular degeneration and arteriosclerosis. Understanding of such pathways is expected to provide opportunities for development of novel pharmacologic approaches to ameliorate, and perhaps cure, these currently intractable conditions. PUBLIC HEALTH REVELANCE. This research project revolves around pseudoxanthoma elasticum (PXE), a heritable disorder characterized by ectopic mineralization of connective tissues, with considerable morbidity and mortality. The overall goal of these studies is to identify the pathomechanistic pathways leading to abnormal mineralization, with translational implications. The results are expected to provide novel approaches to ameliorate, and perhaps cure, PXE and other related, currently intractable, mineralization disorders.