CYTOCHROME OXIDASE ASSEMBLY GENES IN HUMAN DISEASE

细胞色素c氧化酶(COX)，或线粒体呼吸链的复合体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个由线粒体DNA(MtDNA)编码，10个由核DNA(NDNA)编码。许多COX缺乏症与线粒体DNA编码的COX亚基的点突变有关，但关于孟德尔遗传性COX缺乏症的分子基础几乎一无所知，表现出广泛不同的表型，包括全身性和组织特异性的临床表现。特别是，尚未在10个nDNA编码的COX亚基中发现任何突变。我们现在已经在三名新发现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运输蛋白，该蛋白是组装COX全蛋白所必需的，其特征是致命性心脑肌病和COX缺陷仅限于临床上受影响的组织。我们建议在四个方面跟进这一令人兴奋的发现：(1)我们将澄清两个已知的人类SCO基因(hSCO1和hSCO2)出人意料的复杂转录和蛋白质表达模式；(2)我们将在两个SCO功能受损的细胞模型中研究hSCO2缺乏，即在携带hSC02突变的患者细胞中和在携带SCO1/SCO2零突变的酵母细胞中；(3)我们将建立hSCO2缺乏的小鼠模型(包括敲除和敲入小鼠)；以及(4)我们将在我们和我们在哥伦比亚大学的同事可用的一大系列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.