SHORT COM M UNICATION Structure of the Human Gene (COX6A2) for the Heart/Muscle Isoform of Cytochrome c Oxidase Subunit VIa and Its Chromosomal Location in Humans, Mice, and Cattle Nancy J. Bachman,* Penny K. Riggs,² Nazema Siddiqui,* Gregory J. Makris,* James E. Womack,² and Margaret I. Lomax* ,1 * Department of Anatomy and Cell Biology, University of Michigan, Ann Arbor, Michigan 48109; and ² Department of Veterinary Pathobiology and Center for Animal Genetics, Institute of Biosciences and Technology, Texas A&M University, College Station, Texas 77843 Received July 11, 1996; accepted February 14, 1997 zyme are encoded in different genomes. Subunits I – III We have mapped the gene for the heart/muscle iso- are encoded in mitochondrial DNA (3) and perform the form of cytochrome c oxidase (COX) subunit VIa in catalytic functions of the enzyme (30). The remaining three mammalian species and isolated the human 10 subunits encoded in nuclear DNA are thought to COX6AH gene (HGMW-approved symbol COX6A2). The modulate cytochrome oxidase activity in response to bovine gene was mapped by somatic cell hybrid map- different physiological signals or metabolic environ- ping panels to bovine chromosome BTA 25 with ments (reviewed in 8). Amino acid sequencing (12, 35) 94–95% concordance. The mouse gene (Cox6ah) was revealed two forms of COX subunit VIa: a ubiquitous mapped using an interspecific backcross panel from form (COX VIa-L) and a heart/muscle form (COX VIa- the cross (C57BL/6J 1 Mus spretus)F 1 1 Mus spretus H). The gene for the heart isoform (COX6AH) 2 is ex- probed with the mouse COX VIa-H cDNA. Cox6ah was pressed only in striated muscle, e.g., heart and skeletal located on distal chromosome 7, between D7Mit8 and muscle, whereas the gene for the liver form (COX6AL) D7Mit13. From the regions of known gene conserva- is expressed in all tissues, albeit at low levels in con- tion among these three species, we predicted that hu- tractile muscle (5, 6, 8, 16, 19, 26, 28, 29). To under- man COX6AH would be located on chromosome 16p. stand signals regulating tissue-specific expression of We hybridized a human 1 rodent mapping panel of COX nuclear genes, we have begun to isolate and map somatic cell hybrids with the human cDNA to confirm genes for COX VIa-H (28) and VIII-H (17). In this pa- this assignment. These data taken together indicated per, we use comparative mapping approaches to map that the human COX6AH gene is located on the short the bovine COX6AH gene to BTA chromosome (Chr) arm of chromosome 16 and facilitated the isolation of 25 and the mouse Cox6ah gene to distal Chr 7. These the human gene from a chromosome 16-enriched li- data predicted that the human COX6AH gene would brary. The human COX6AH gene spans about 1 kb and contains three exons and two small introns. The se- be on human chromosome 16. We confirmed this as- quences of the proximal 5 flanking regions of COX6AH signment by screening a human 1 rodent mapping genes are highly conserved between human, bovine, panel with the human cDNA and isolated and se- and rodent.  1997 Academic Press quenced the human COX6AH gene from a chromosome 16-enriched genomic library. An approach similar to that used to map the bovine Cytochrome c oxidase (COX; EC 1.9.3.1), the termi- COX8H gene to BTA Chr 29, syntenic group U7 (27; nal enzyme complex of the mitochondrial electron Popescu et al., unpublished), was used to map the transport chain (10), catalyzes the transfer of electrons bovine COX6AH gene. Test blots containing HindIII from reduced cytochrome c to molecular oxygen and digests of bovine, mouse (LMTK 0 ), and hamster translocates protons across the mitochondrial inner (CHO) cell line DNAs were hybridized with radiola- membrane (2). The 13 subunits of the mammalian en- beled bovine COX6AH cDNA (28) under stringent hy- bridization and wash conditions. A single 8-kb Hin- dIII fragment observed previously (28) was detected Sequence data from this article have been deposited with the Gen- under these hybridization conditions (data not Bank Data Library under Accession No. U66875. 1 To whom correspondence should be addressed at the Department shown). Bovine 1 rodent somatic cell panels were of Anatomy and Cell Biology, University of Michigan Medical School, 5724 Medical Sciences II, Box 0616, Ann Arbor, MI 48109-0616. 2 The HGMW-approved symbol for the gene described in this paper Telephone: (313) 647-1893. Fax: (313) 763-1166. E-mail: mlomax@ umich.edu. is COX6A2. 146 GENOMICS 42, 146–151 (1997) ARTICLE NO. GE974687 0888-7543/97 $25.00 Copyright  1997 by Academic Press All rights of reproduction in any form reserved.