Creatine Transport Across the Blood Brain Barrier

描述(申请人提供)：最近，我们描述了一例6岁男孩的严重表达和认知障碍，他在大脑中有独特的肌酸(Cr)缺乏，经质子磁共振波谱(MRS)诊断。进一步分析，我们发现他在X线铬转运蛋白基因(CT1；SLC6A8)上有一个无义突变，导致了一个截短的(无功能的)铬转运蛋白的表达。自那项研究以来，辛辛那提又发现了四个带有X连锁铬转运蛋白基因突变的家庭，世界各地有近30个家庭。这些患者都有智力低下、严重的语言表达障碍和轻度癫痫。尽管人们对大脑中的肌酸、肌酸激酶和磷酸肌酸系统的了解越来越多，但在脑肌酸转运蛋白缺乏的情况下，还没有标准化的方法来改善大脑功能。显然，我们需要的是一种合适的这种疾病的动物模型，这样就可以开发和测试让肌酸穿过血脑屏障的方法。在这个项目中，我们将开发一种铬转运蛋白基因敲除小鼠模型，这样就可以测试新的治疗范例、药物和其他疗法的疗效。对于这个研究项目，我们建议检验以下假设：1)小鼠敲除这种铬运输缺陷可以模拟人类疾病，2)可以给出治疗策略来使这些小鼠的大脑功能正常化。这种小鼠基因敲除将模拟我们已经发现的肌酸转运蛋白缺陷，即大脑将缺乏通过血脑屏障运输肌酸的能力。为了解决假设1，我们将产生一个铬转运蛋白基因敲除小鼠。这些小鼠的大脑中的铬水平将被测定，我们将描述在铬转运蛋白基因敲除小鼠中观察到的功能和生化变化。拥有一个与人类疾病密切相关的动物模型，将使人们能够充分测试和开发旨在使肌酸通过血脑屏障并改善大脑功能的疗法。为了解决假设2，铬转运蛋白基因敲除小鼠和对照组小鼠将接受铬制剂治疗，这些制剂可能能够将肌酸输送到血脑屏障，并改善小鼠的大脑新陈代谢和认知功能。假设2的目标是开发通过使肌酸进入大脑来改善大脑能量代谢的方法和药物。

DESCRIPTION (provided by applicant): Recently, we described severe expressive and cognitive delays in a 6-year-old boy, who has a unique creatine (Cr) deficiency in the brain, which was diagnosed by proton magnetic resonance spectroscopy (MRS). Upon further analysis, we found that he has a nonsense mutation in the X-lined Cr transporter gene (CT1;SLC6A8), which resulted in the expression of a truncated (non-functional) Cr transporter protein. Since that study, four additional families have been recognized in Cincinnati with mutations in the X-linked Cr transporter gene and nearly 30 families worldwide. These patients all have mental retardation, severe expressive language disorder and mild epilepsy. Despite a growing body of knowledge about the Cr, Cr kinase and phosphocreatine system in the brain, there is no standardized method for improving brain function when the brain creatine transporter is deficient. What is clearly needed is a suitable animal model of this disease such that methods to get creatine across the blood brain barrier can be developed and tested. In this project we will develop a Cr transporter knockout mouse model, such that the efficacy of new treatment paradigms, drugs, and other therapies can be tested. For this research project, we propose to test the following hypotheses: 1) a mouse knockout of this Cr transport defect can model the human disease, and 2) that therapeutic strategies can be given to normalize brain function in these mice. This mouse knockout will model the Cr transporter defect we have discovered in that the brain will lack the ability to transport creatine across the blood brain barrier. To address Hypothesis 1, we will generate a Cr transporter knockout mouse. Cr levels will be determined in the brains of these mice and we will characterize the functional, and biochemical changes observed in Cr transporter knockout mice. Having an animal model that closely mirrors the human disease will enable adequate testing and development of therapies designed at getting creatine across the blood brain barrier and improving brain function. To address Hypothesis 2, the Cr transporter knockout mice and control mice will be treated with Cr formulations that may be capable of transporting creatine across the blood brain barrier and improve brain metabolism and cognitive function of the mice. The goal for Hypothesis 2 is to develop methods and drugs to improve brain energy metabolism by getting creatine into the brain.