PAX7 INCLUDES 2 POLYMORPHIC HOMEOBOXES WHICH CONTAIN REARRANGEMENTS ASSOCIATED WITH DIFFERENCES IN THE ABILITY TO REGENERATE DAMAGED SKELETAL-MUSCLE IN ADULT MICE

Pax7 is a paired-type homeobox gene which has previously been shown to play an important role in skeletal muscle formation. It is expressed in skeletal muscle of the limbs during embryogenesis and in adulthood. The aims of this study were firstly to determine the degree of polymo rphism of Pax7 amongst inbred laboratory mice using Southern blotting and Pax7 regional specific sub-probes. Secondly, functional studies we re performed on mice with each of the different structural forms of Pa x7 to determine whether they were associated with differences in the a bility to regenerate damaged skeletal muscle. Four different allelic f orms of Pax7 have now been identified in laboratory mice indicating th at the previously reported DNA sequence of Pax7 is not applicable to a ll laboratory mice. Hybridisation patterns of TaqI digested DNA repres enting each of the different Pax7 alleles with the Pax7 specific sub-p robes suggested that in contrast to previous findings, Pax7 is associa ted with two highly polymorphic homeoboxes. The presence of two homeob oxes in BALB/c mice has been confirmed by DNA sequencing. Results of f unctional studies have also shown that the ability to regenerate damag ed skeletal muscle in adult mice is strongly associated with the prese nce of a 0.15-kb TaqI fragment derived from one of the homeoboxes. (C) 1998 Elsevier Science Ltd. All rights reserved.