Identification of genetic variations responsible for differential muscle traits, in particular water binding capacity

Intramuscular fat content and water holding capacity are important traits in livestock as they influence meat quality, nutritive value of the muscle and animal health. As a model for livestock, inbred lines of the Berlin Muscle Mouse population, which had been long term-selected for high muscle mass, were used to identify genomic regions affecting intramuscular fat content and water holding capacity. The intramuscular fat content of the Musculus longissimus was on average 1.4 fold higher in BMMI806 than in BMMI816 mice. This was accompanied by a 1.5 fold lower water holding capacity of the Musculus quadriceps in BMMI816 mice. Linkage analyses with 332 G3-animals of reciprocal crosses between these two lines revealed quantitative trait loci for intramuscular fat content on chromosome 7 and for water holding capacity on chromosome 2. In addition, physiological and meat quality traits were examined in the two hypermuscular sub-lines BMMI806 and BMMI866. The BMMI866 line carries a myostatin mutation and was lean, while the BMMI806 line displays high intramuscular fat content and high body fat percentage. Linkage analyses with 308 G3-animals confirmed the influence of the myostatin mutation on hypermuscularity and reduced intramuscular fat content. The magnitudes of the effects were higher in males than in females and depended on the direction-of-cross. In addition to the strong effect of the myostatin mutation, another locus was identified for total fat mass on chromosome 16 at 94 Mb (86-94 Mb) with negative heterosis effects. In part, the identified loci coincide with syntenic regions in pigs, in which genetic effects for the same traits were found. Therefore, these muscle-weight-selected mouse lines and the produced intercross populations are valuable genetic resources to identify genes, which could also contribute to meat quality in other species.