Structural and functional genomics to elucidate the genetic background of microstructural and biophysical muscle properties in the pig.

Linkage analyses enable identifying genomic regions that exhibit quantitative trait loci (QTL) without prior hypothesis on the physiology of a trait. Function-oriented expression analyses are a complementary approach to derive hypothesis on the genetic background of phenotypic variation. Muscle fibre types and size affect body composition and meat quality traits. The number and proportion of muscle fibres are to a large extent determined during the prenatal development. Consequently, QTL for muscle fibre, meat quality and carcass traits were detected in a porcine experimental population based on Duroc and Berlin Miniature Pig. Regions with either significant QTL for muscle fibre traits or significant QTL for meat quality and muscularity or both were detected on SSC1, 2, 3, 4, 5, 13, 14, 15 and 16. Here, effects on the complex traits of muscularity and meat quality might be the result of genetic variation primarily affecting fibre type distribution traits. To complement the QTL study expression profiling of prenatal muscle tissue of Duroc and Pietrain was conducted that revealed a list of functional candidate genes for meat quality and carcass traits of various physiological networks. Assignments of these genes to QTL regions highlight them as positional functional candidates. Exemplarily, five genes were analysed further and shown to be associated with meat quality and carcass traits. Further, the relative MYH isotype transcript abundance was found to be associated with muscularity. Relative MYH isotype transcript abundance is proposed as a new phenotype to unravel the genetic background of variation in traits related to muscle and meat properties.