ASSOCIATION OF AN UNUSUAL FORM OF A PAX7-LIKE GENE WITH INCREASED EFFICIENCY OF SKELETAL-MUSCLE REGENERATION

Efficiency of regeneration of mechanically injured skeletal muscle is more pronounced in SJL/J mice, as compared to other laboratory strains in which regenerative properties of skeletal muscle are uniformly poo r. Previously, we postulated that a small number of genes might differ between SJL/J and; other mouse strains, and would be responsible for this variation in the efficiency of skeletal muscle regeneration. The results of initial experiments demonstrated that SJL/J mice have a uni que form of the myogenic gene, Myo-D1, which partly influences efficie ncy of skeletal muscle repair, and that other genes were also involved . To identify other candidate genes, differences were sought within th e myogenic paired box/homeobox-containing gene Pax7 between SJL/J and other laboratory mouse strains. Southern blotting indicated that SJL/J , Quackenbush and DDO mice share a Pax7/TaqI RFLP which differs from a ll other laboratory strains tested. This RFLP is most likely due to se quence differences within the homeobox of a Pax7-like gene. In vivo st udies revealed that Quackenbush and DDO mice also share the same regen erative properties of mechanically damaged skeletal muscle as SJL/J mi ce. Since Quackenbush and DDO mice lack the SJL/J type of Myo-D1, and DDO belong to a different mouse sub-species, these studies suggest tha t structural alterations in the homeobox of a Pax7-like gene may be im plicated in the effectiveness of renewal of damaged skeletal muscle of the limb in the mature animal.