Molecular Analysis of Mucolipidosis IV

IV型粘脂沉积症（MLIV）是一种发育障碍，其特征是严重的神经系统和眼科异常。分类为溶酶体贮积症，它是进行性的，通常在出生后的第一年出现智力迟钝、角膜混浊和运动里程碑延迟。 大多数MLiV儿童在15个月时在语言和运动功能方面发育停滞，最终由于视网膜变性而完全失明。考虑到该疾病的异质性临床谱，很可能许多患者仍未确诊。MLiV是由MCOLN 1基因突变引起的，MCOLN 1基因是瞬时受体电位（TRP）阳离子通道基因家族的成员。 MCOLN 1编码一种称为粘脂蛋白-1的蛋白质，与其他TRP基因一样，具有六个预测的跨膜结构域和一个通道孔。MCOLN 1与MCOLN 2和MCOLN 3（两个定位于人类1号染色体的同源基因）一起构成TRPML亚家族。MCOLN 1突变的鉴定代表了由TRP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在分子伴侣介导的自噬和溶酶体胞吐中起作用，并且我们已经确定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，我们最近建立了精确的MLiV表型小鼠模型。这种小鼠模型首次提供了一种独特的系统，用于研究神经元中TRPML 1丢失的病理生理学，以及测试潜在疗法的模型。有了这个小鼠模型，我们的目标是生成一个神经元细胞模型，这将首次允许研究 神经元中的溶酶体功能和TRPML 1丢失。 除了这种细胞培养系统，我们将使用小鼠的原代神经元培养物和组织来研究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家族可以形成异源多聚体，然而， 这些相互作用的生理相关性是未知的。因此，我们计划建立Mcoln 2和Mcoln 3的条件性敲除小鼠模型，以阐明它们在MLiV病理生理学中的作用。 从长远来看，这些研究将有助于对正常细胞运输和溶酶体功能的基本理解，并最终为MLiV患者提供有效治疗的希望，旨在消除这种毁灭性疾病中的异常细胞储存。

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.