In order to determine candidate genes involved in production traits, the mRNA levels of muscle tissue of extremely different pig breeds (genotypes) were studied using microarray tool. Casertana, an autochthonous breed characterized by slow growth and a massive accumulation of backfat, was compared to Large White and to crossbred (Duroc x Landrace x Large White) pigs. The differential expression of muscle genes was evaluated on 3 pigs for each genetic type using a microarray consisting of 10,665 oligos. Animals were of the same age and raised in the same environmental conditions. Muscle tissues were collected at 3, 6, 9, and 11 months and a total of 219 (157 genes in the two main clusters) genes showed differential expression between genetic types. Time series cluster analysis indicated that Casertana breed had a different pattern of gene expressions compared to the Large White and the crossbreed. For Casertana pigs, a first cluster showed 105 genes under expressed at 3 months of age and a second cluster indicated 52 genes over expressed at 3 months of age, in comparison to the other genetic types. As expected, some of the differentially expressed genes were in the category of "contractile fiber" and transcriptional factors involved in muscle development and differentiation.
