Fig. 1. Analysis of mutant mice for the presence of K19. (A) Extracts of muscle were analyzed by RT-PCR for the presence of mRNA encoding K8 and K19. K19^–/– extracts contained mRNA encoding K8, at levels similar to controls, but lacked mRNA encoding K19. (B) K19 was immunoprecipitated from extracts of TA muscle from wild-type or K19^–/– mice, then immunoblotted with anti-K19 antibodies. Lanes show immunoblots of: K19, purified K19; +/+, immunoprecipitate from wild-type muscle; –/–, immunoprecipitate from K19^–/– muscle; IgG, immunoprecipitate from wild-type muscle probed with a non-immune control (MOPC). Equal loading and transfer was confirmed by Ponceau S staining (not shown). K19 was not detected in muscle of K19^–/– mice. (C) Immunoblots of desmin and K8 in extracts of TA muscle from wild-type (+/+) and K19^–/– mice. Desmin is slightly but significantly elevated in the K19^–/– TA muscle compared with wild type; K8 levels are unchanged.