Characterization of Ste20-like kinase (SLK) expression in transgenic lines. (A) Total lysates from anterior hind leg muscles were immunoprecipitated with anti-hemagglutinin (HA) antibodies (12CA5). Subsequent probing for SLK showed expression of HA-tagged kinase in the 654 and 3405 transgenic lines. (B) Total lysates were immunoprecipitated for total SLK and used for in vitro kinase assays. Total SLK activity was markedly reduced in both transgenic lines. (C) Total tissue lysates from cardiac and hind leg muscles were surveyed for transgene expression using immunoprecipitation and anti-HA western blot. No expression was detected in the heart muscle of transgenic mice. (D) Monitoring wild-type to transgenic crosses showed that the higher-expressing 654 transgenic line produced fewer pups (absolute numbers) compared with the 3405 line. The proportion of transgenic animals was the same. (E) Monitoring of litter numbers over 4 to 6 months showed reduced breeding capacity in the 654 line.