Molecular Analysis of Mucolipidosis IV

IV型黏脂沉积症(MLLV)是一种以严重的神经系统和眼科异常为特征的发育障碍。被归类为溶酶体储存障碍，它是进行性的，通常出现在生命的第一年，伴有智力低下、角膜混浊和运动里程碑延迟。 大多数MLiV儿童在15个月时语言和运动功能发育停滞，最终由于视网膜退化而完全失明。考虑到这种疾病的不同临床谱系，很可能许多患者仍然没有得到诊断。MLiV是由MCOLN1基因突变引起的，MCOLN1基因是瞬时受体电位(Trp)阳离子通道基因家族的成员。 MCOLN1编码一种名为粘蛋白-1的蛋白质，和其他色氨酸基因一样，它有六个预测的跨膜结构域和一个通道孔。MCOLN1与映射到人类1号染色体上的两个同源基因MCOLN2和MCOLN3一起构成了TRPML亚家族。MCOLN1突变的鉴定是由色氨酸相关通道引起的神经系统疾病的第一个例子。 我们最近的研究表明，TRPML-1在伴侣蛋白介导的自噬和溶酶体胞吐中发挥作用，我们已经确定TRPML家族成员可以形成调节通道功能的异源多聚体。然而，最重要的是，我们最近建立了MLiV的准确表型小鼠模型。这个小鼠模型首次提供了一个研究TRPML 1神经元丢失的病理生理学的独特系统，以及一个测试潜在治疗方法的模型。有了这个小鼠模型，我们的目标是产生一个神经细胞模型，这将首次允许研究 神经细胞溶酶体功能与TRPML-1缺失 除了这个细胞培养系统，我们还将使用小鼠的原代神经元培养和组织来研究TRPML 1在自噬和线粒体功能中的作用。我们以前的研究表明，TRPML家族可以形成异多聚体，然而， 这些相互作用的生理相关性尚不清楚。因此，我们计划建立Mcoln2和Mcoln3的条件性基因敲除小鼠模型，以阐明它们在MLiV病理生理学中的作用。 从长远来看，这些研究将有助于从根本上了解正常的细胞运输和溶酶体功能，并最终希望MLiV患者能够获得有效的治疗，旨在消除这种毁灭性疾病中异常的细胞存储。

Mucolipidosis Type IV (MLlV) is a developmental disorder that is characterized by severe neurologic and ophthalmologic abnormalities. Classified as a lysosomal storage disorder, it is progressive and usually presents during the first year of life with mental retardation, corneal opacities, and delayed motor milestones. Most MLiV children are developmentally arrested at 15 months in language and motor function, and are eventually totally blind as the result of retinal degeneration. It is very likely that many patients remain undiagnosed given the heterogeneous clinical spectrum of the disorder. MLiV is caused by mutations in the MCOLN1 gene, which is a member of the transient receptor potential (TRP) cation channel gene family. MCOLN1 encodes a protein called mucolipin-1 that, like the other TRP genes, has six predicted transmembrane domains and a channel pore. MCOLN1, together with MCOLN2 and MCOLN3, two homologous genes that map to human chromosome 1, constitute the TRPML subfamily. The identification of mutations in MCOLN1 represents the first example of a neurological disease caused by a TRP-related channel. Our recent studies have shown that TRPML 1 plays a role in chaperone mediated autophagy and lysosomal exocytosis, and we have determined that the TRPML family members can form heteromultimers which modulate channel function. Most significantly, however, we have recently created accurate phenotypic mouse model of MLiV. This mouse model provides, for the first time, a unique system in which to study the pathophysiology of TRPML 1 loss in neurons, as well as a model in which to test potential therapies. Armed with this mouse model, we aim to generate a neuronal cell model that will for the first time permit studies of lysosomal function and TRPML 1 loss in neuronsl. In addition to this cell culture system, we will use primary neuronal cultures and tissues from the mice to investigate the role of TRPML 1 in autophagy and mitochondrial function. Our previous studies show that the TRPML family can form heteromultimers, however, the physiological relevance of these interactions is unknown. Therefore, we plan to create conditional knock-out mouse models for Mcoln2 and Mcoln3 to elucidate their role in MLiV pathophysiology. In the long-term these studies will contribute to the fundamental understanding of normal cellular trafficking and lysosomal function, and ultimately to the hope of MLiV patients for an effective treatment aimed at abolishing the abnormal cellular storage in this devastating disease.