GENETIC-REGULATION OF SLOWLY PROGRESSING MILD MUSCLE ATROPHY IN FAST-TWITCH MUSCLES OF BUF MNA RATS/

BUF/Mna strain rats spontaneously develop slowly progressing mild-mode rate muscle atrophy of extensor digitorum longus, tibialis, and extrao cular muscles, which consist mainly of fast-twitch type fibers, at nea rly 100% incidence. They have lighter extensor digitorum longus muscle s than soleus muscles, when alive for more than 6 weeks. Genetic segre gation of the development of the muscle atrophy was studied by crossin g the BUF/Mna strain with three other strains, ACI/NMs, WKY/NCrj, and BDIX, which were free of muscle atrophy. Two autosomal dominant suscep tible genes, Mas-1 and Mas-2, determine the development of the muscle atrophy in these combinations of crosses. (C) 1997 John Wiley & Sons, Inc.