Desmin-lacZ transgene, a marker of regenerating skeletal muscle

Transgenic C57 mice bearing a transgene of the desmin gene linked to the lacZ reporter gene which encoded for the enzyme beta-galactosidase were used. In the muscle cell, a blue nuclear product appearing in the presence of the X-gal substrate for the enzyme provided evidence of the expression of the desmin gene. However, no transgene expression was observed 2 weeks postnatal in skeletal muscles, even though endogenous desmin was present. In order to investigate the regulatory mechanisms of the desmin gene during regeneration, adult pectoralis fragments (without expression of the desmin transgene) from transgenic mice were implanted into the tibialis anterior of 4 day or 6 week old Swiss mice. Adult pectoralis transplants reexpressed the transgene from day 4 to 10 after implantation. In addition, lesions were performed in adult transgenic pectoralis and transgenic expression in injured muscles was observed 2 days later. This new transgenic mouse is a powerful tool for the study of the various steps of skeletal muscle regeneration.