Organization of dog myosin heavy chain gene clusters

Myosin heavy chain (MHCs) are actin-based motor proteins that play a key role in determining muscle contraction speed. MHC genes superfamily present a highly conserved gene clusters organization in genome of mammals. In this work we used computer–based programs to identify and characterize MHCs sequences in dog genome. The dog MHC sequences were assembled by NCBI Dog Genome Resources web site. BLAST searches suggest that the genes of dog encoding isoforms expressed in skeletal muscles (embryonic, 2A, 2X, 2B, perinatal and extraocular) have been located in a cluster on chromosomes 5; the two “cardiac” genes, coding for MHC-β (slow) and MHC-α (cardiac), are arranged tandemly on chromosomes 8; moreover, the gene for masticatory isoform (2M MHC) has been located on chromosomes 6. Dog MHC isoforms show high similarity of aminoacid sequence with orthologous isoforms in other species (94% for 2B MHC, 96% for 2X and between 96%-98% for 2A MHC). Multiple alignments on predicted protein sequences were used to create a phylogenetic tree. The neighbour-joining tree confirmed the position of the dog orthologous isoforms within each specific MHC group.