Genetic architecture of numbers of fast and slow muscle fibres in the mouse soleus muscle

Abstract

This report analyses the genetic architecture underlying a muscle fibre characteristic. We have counted numbers of fast and slow muscle fibres in the soleus muscle of male mice from different inbred strains and crosses between them (diallel cross). Broad heritabilities of 20 per cent and 73 per cent were found for the number of slow fibres and the number of fast fibres, respectively. Additive genetic variation was present for both phenotypes. Directional dominance was found for number of fast fibres only. This suggests that, in evolutionary history, stabilising selection has operated for intermediate numbers of slow muscle fibres and directional selection for high numbers of fast fibres.