Model Systems for PXE

描述（由申请人提供）：这是一个新的赠款申请的第二次修订，围绕弹性假黄瘤（PXE），一种常染色体隐性遗传疾病，其特征是在各种器官，包括皮肤，眼睛和心血管系统的结缔组织异位矿化，具有相当大的发病率和死亡率。目前已知PXE是由ABCC 6基因突变引起的，ABCC 6基因编码多药耐药相关蛋白6（MRP 6），MRP 6是一种推定的跨膜转运蛋白，主要在肝脏中表达，在肾脏近端小管中表达程度较低，在遭受PXE的组织中表达水平非常低。增加了这种疾病的复杂性的是，有相当大的家庭间和家庭内的异质性，诊断往往是延迟，由于迟发的表现，和一些环境和生活方式的变量似乎调节疾病的进展和最终的结果。目前尚不清楚外周组织中ABCC 6表达改变导致异常矿化的病理机制细节。具体而言，MRP 6及其生理配体的功能仍未公开。这个应用程序将利用在了解ABC转运蛋白和我们最近开发的模型系统来研究这种疾病的一般进展。该申请代表了三个主要研究小组之间的联盟，将解决以下具体目标：1）Abcc 6-/-小鼠作为PXE的表型模型; 2）人ABCC 6/MRP 6转运蛋白的表征和生理底物的搜索。具体目标1建议开发联体共生和血浆/候选蛋白补充，并对Abcc 6-/-小鼠进行广泛表征，作为PXE模型。具体目标2提出了最先进的技术，以通过全局和候选分子方法鉴定MRP 6的生理底物。然后将这些生理底物用于MRP 6的结构-功能研究。这些具体的目标测试的统一假设，即PXE是一种遗传性疾病的基因组/环境界面，与一个整体的目标，以确定导致表型表达的PXE的分子事件。该应用的可行性通过我们最近通过靶向切除Abcc 6基因开发的PXE小鼠模型得到证实，通过建立昆虫细胞转运系统，研究了MRP 6转运机制的细节以及PXE突变对MRP 6转运的影响，以期为研究导致异常矿化的病理机制提供新的思路在PXE及相关遗传性疾病中的应用，并展望了一般人群的共同特征，如年龄相关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提供机会，以改善甚至治愈这些目前难以治愈的疾病。 公共卫生敬畏。本研究项目围绕弹性假黄瘤（PXE），一种遗传性疾病的特点是异位矿化的结缔组织，具有相当大的发病率和死亡率。这些研究的总体目标是确定导致异常矿化的病理机制途径，并具有转化意义。这些结果有望提供新的方法来改善，也许治愈，PXE和其他相关的，目前难治性，矿化障碍。

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.