Fig. 4. The SM unc-45 gene is strongly expressed in the contractile heart during embryogenesis. In situ hybridization was done on whole mouse embryos using gene-specific anti-sense and sense control probes. (A) SM UNC-45 mRNA was detected in the functional heart, as shown here at 8.75 days. (B) Comparison with an 8.5 day embryo labeled with the sense control demonstrates that the SM UNC-45 mRNA was not expressed in other tissues above background level.