Genetic Study of Pigment Granule Transport in the Mouse

小鼠色素颗粒运输的遗传学研究

• 批准号: 6559259
• 负责人: NANCY JENKINS COPELAND
• 金额: --
• 依托单位: DIVISION OF BASIC SCIENCES - NCI
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6559259
• 关键词: alleles; animal genetic material tag; biological transport; cerebellar Purkinje cell; developmental genetics; endoplasmic reticulum; gene mutation; granule; intracellular transport; isozymes; melanosomes; microtubules; molecular cloning; myosins; pigmentation; pigments; polymerase chain reaction; protein structure function; vesicle /vacuole; yeast two hybrid system

The dilute (d), ashen (ash), and leaden (ln) coat color mutations provide a unique model system for the study of vesicle transport in mammals. All three mutant loci encode genes that are required for the polarized transport of melanosomes, the specialized, pigment-containing organelles of melanocytes, to the neighboring keratinocytes and eventually into coat hairs. Furthermore, all three mutations are suppressed by a fourth mutation, dilute suppressor (dsu). Genetic studies suggest that d, ln, and ash function in the same or overlapping pathways and are supported by biochemical studies showing that d encodes an actin-based melanosome transport motor, MyoVA. We have also shown that ash encodes Rab27a, a small GTP-binding protein previously implicated in vesicle transport. In collaboration with John Hammer's laboratory, we demonstrated that Rab27a localizes to melanosomes and provided evidence suggesting that Rab27a serves as the MyoVA receptor on melanosomes. Subsequently, a number of investigators have confirmed our predictions and showed that Rab27a attachment to the melanosome is required for the recruitment of MyoVA into the transport complex. Myo5a and Rab27a are also mutated in human disease. Patients with a rare autosomal recessive disorder, Griscelli Syndrome, display hypopigmentation of the skin and hair. Some patients also display neurological impairment, which correlates with mutations in MYO5A; others show immune disorders in addition to the pigmentation alterations and this phenotype correlates with mutations in RAB27A. Very recently, we cloned the ln mutation based on its position on mouse chromosome 1. Interestingly, ln encodes a Rab effector that we have named melanophilin (Mlph). Ongoing work suggests that Mlph is a critical component of the melanosomal transport complex. Thus, as predicted by genetic studies, all three proteins appear to function as part of an integrated motor complex that is essential for vesicle transport in mammalian cells. Studies are also in progress to identify the product of dsu and to understand how the protein participates in directional vesicular transport.

稀（d），灰（ash），铅（ln）毛色突变提供了一个独特的模型系统，研究囊泡运输哺乳动物。所有三个突变基因座编码的基因是所需的极化运输黑素体，黑素细胞的专门的，含有色素的细胞器，到邻近的角质形成细胞，并最终进入被毛。此外，所有三种突变都被第四种突变抑制，稀释抑制基因（dsu）。遗传学研究表明，d，ln和ash在相同或重叠的途径中起作用，并得到生化研究的支持，表明d编码基于肌动蛋白的黑素体转运马达MyoVA。我们还表明，灰编码Rab 27 a，一个小的GTP结合蛋白，以前涉及囊泡运输。与John Hammer的实验室合作，我们证明Rab 27 a定位于黑素体，并提供证据表明Rab 27 a作为黑素体上的MyoVA受体。随后，一些研究人员证实了我们的预测，并表明Rab 27 a与黑素体的连接是MyoVA进入运输复合体所需的。Myo 5a和Rab 27 a在人类疾病中也发生突变。患有罕见的常染色体隐性遗传疾病Griscelli综合征的患者显示皮肤和毛发色素减退。一些患者还表现出神经功能障碍，这与MYO 5A突变相关;其他患者除了色素沉着改变外还表现出免疫疾病，这种表型与RAB 27 A突变相关。最近，我们根据ln在小鼠1号染色体上的位置克隆了ln突变。有趣的是，ln编码Rab效应子，我们将其命名为黑素蛋白（Mlph）。正在进行的工作表明，Mlph是黑素体运输复合物的关键组成部分。因此，正如遗传学研究所预测的那样，这三种蛋白质似乎都是哺乳动物细胞中囊泡运输所必需的综合马达复合物的一部分。研究也在进行中，以确定产品的dsu和了解如何蛋白质参与定向囊泡运输。