CYTOCHROME OXIDASE ASSEMBLY GENES IN HUMAN DISEASE

细胞色素c氧化酶（考克斯），或线粒体呼吸链复合物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缺陷性疾病与mtDNA编码的考克斯亚基的点突变有关，但关于孟德尔遗传的考克斯缺陷性疾病的分子基础几乎一无所知，其表现出广泛不同的表型，包括全身性和组织特异性临床表现。 特别是，在任何10个nDNA编码的考克斯亚单位尚未发现突变。我们现在已经确定了突变的人SC 02基因，编码一个假定的铜转运蛋白，这是需要的组装的考克斯holoprotein，在3例新确定的临床实体的特点是致命的心脑肌病和考克斯缺乏症局限于临床受影响的组织。我们建议在四个方面对这一令人兴奋的发现进行后续研究：（1）我们将阐明两个已知的人类SCO基因的转录和蛋白表达的出乎意料的复杂模式（2）我们将在两种SCO功能受损的细胞模型中研究hSCO 2缺陷，即在携带hSC 02突变的患者细胞和携带SCO 1/SCO 2无效突变的酵母细胞中;（3）我们将建立hSCO 2缺陷的小鼠模型（包括敲除和敲入小鼠）;（4）我们将在我们和哥伦比亚的同事可获得的大量候选患者组织中寻找hSCO 1和hSCO 2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.