CYTOCHROME OXIDASE ASSEMBLY GENES IN HUMAN DISEASE

细胞色素c氧化酶（Cytochrome c oxidase， COX），或线粒体呼吸链复合体IV，是一种含铜和血红素的金属蛋白，由13个亚基组成，其中3个亚基由线粒体DNA （mtDNA）编码，10个亚基由核DNA （nDNA）编码。许多COX缺乏性疾病与mtdna编码的COX亚基的点突变有关，但关于孟德尔遗传COX缺乏性疾病的分子基础几乎一无所知，这些疾病表现出广泛不同的表型，包括普遍的和组织特异性的临床表现。特别是，尚未发现10个ndna编码的COX亚基中的任何一个发生突变。我们现在已经在三名新发现的以致命心脑肌病和COX缺乏症为特征的临床实体患者中发现了人类SC02基因的突变，该基因编码一种假定的铜转运蛋白，该蛋白是COX全蛋白组装所必需的。我们打算在以下四个方面跟进这一令人兴奋的发现：(1)我们将阐明两个已知的人类SCO基因（hSCO1和hSCO2）意想不到的复杂转录和蛋白质表达模式；(2)我们将在两种SCO功能受损的细胞模型中研究hSCO2缺乏症，即携带hSC02突变的患者细胞和携带SCO1/SCO2零突变的酵母细胞；(3)建立hSCO2缺失小鼠模型（敲除小鼠和敲入小鼠）；(4)我们将在我们和哥伦比亚大学的同事可以获得的大量候选患者组织中寻找hSCO1和hSCO2以及其他cox组装基因的突变。

Cytochrome c oxidase (COX), or complex IV of the mitochondrial respiratory chain, is a copper- and heme-containing metalloprotein composed of 13 subunits, 3 encoded by mitochondrial DNA (mtDNA) and 10 by nuclear DNA (nDNA). A number of COX-deficiency disorders are associated with point mutations in mtDNA-encoded COX subunits, but almost nothing is known regarding the molecular basis of mendelian-inherited COX deficiency disorders, which display widely varying phenotypes, including both generalized and tissue-specific clinical presentations. In particular, no mutation in any of the 10 nDNA-encoded COX subunits has yet been found. We have now identified mutations in the human SC02 gene, encoding a putative copper-transport protein that is required for the assembly of the COX holoprotein, in three patients with a newly-identified clinical entity characterized by fatal cardioencephalomyopathy and COX deficiency limited to clinically-affected tissues. We propose to follow up on this exciting finding in four areas: (1) we will clarify the unexpectedly complex patterns of transcription and protein expression of the two known human SCO genes (hSCO1 and hSCO2); (2) we will study hSCO2 deficiency in two cellular models in which SCO function is compromised, namely, in patient cells harboring hSC02 mutations and in yeast cells harboring SCO1/SCO2 null mutations; (3) we will create mouse models of hSCO2 deficiency (both knock-out and knock-in mice); and (4) we will search for mutations in hSCO1 and hSCO2, and in other COX-assembly genes as well, in a large series of candidate patient tissues available to us and our colleagues here at Columbia.