LOCALIZATION OF THE ALPHA-7 INTEGRIN GENE (ITGA7) ON HUMAN-CHROMOSOME12Q13 - CLUSTERING OF INTEGRIN AND HOX GENES IMPLIES PARALLEL EVOLUTION OF THESE GENE FAMILIES

Expression of the alpha 7 integrin gene (ITGA7) is developmentally reg ulated during the formation of skeletal muscle. Increased levels of ex pression and production of isoforms containing different cytoplasmic a nd extracellular domains accompany myogenesis. To determine whether a single or multiple alpha 7 genes underlie the structural diversity in this alpha chain that accompanies development, we have examined the ra t and human genomes by Southern blotting and in situ hybridization, Ou r results demonstrate that there is only one alpha 7 gene in both the rat and the human genomes. In the human, ITGA7 is present on chromosom e 12q13. Phylogenetic analysis of the integrin alpha chain sequences s uggests that the early integrin genes evolved in two pathways to form the I-integrins and the non I-integrins. The I-integrin alpha chains c ontain an additional sequence of approximately 180 amino acids and aro se as a result of an early insertion into the non-I-gene. The I-chain subfamily further evolved by duplications within the same chromosome, The non-I-integrin alpha chain genes are localized in clusters on chro mosomes 2, 12, and 17, and this closely coincides with the localizatio n of the human homeobox gene clusters. Non-I-integrin alpha chain gene s appear to have evolved in parallel and in proximity to the Hox clust ers, Thus, the Hox genes that underlie the design of body structure an d the Integrin genes that underlie informed cell-cell and cell-matrix interactions appear to have evolved in parallel and coordinate fashion s. (C) 1995 Academic Press, Inc.