Pax7 is expressed in the capsules surrounding adult mouse neuromuscular spindles

The multigene Pax family of transcription factors plays an important role i n the development of the central nervous system as well as in organ morphog enesis. Expression of one of the members of the family, Pax7, has been desc ribed in embryonic muscle and in both embryonic and adult brain. We recentl y detected Pax7 transcripts in RNA isolated from adult mouse skeletal muscl e and brain and here use in situ hybridisation to localise the expression w ithin these tissues. Pax7 expression was observed in neural cells of the br ain and in cells of neural crest origin in the inner and outer capsules of neuromuscular spindles. The results suggest that Pax7 may be implicated in the formation and maintenance of neuromuscular contacts within the muscle s pindle throughout life.