Figure 1.

Sapje-like mutant offspring show muscle defects which can be assayed using birefringence. (A) Muscle degeneration in sapje-like mutants is clearly visible as small dark spots at 5 dpf using birefringence. These spots represent areas of muscle tearing. (B) The sapje-like birefringence is very similar to that seen for sapje, a known zebrafish dystrophin mutant. (C) Sapje and sapje-like fail to complement each other. Heterozygous sapje mutants (±) were crossed with heterozygous sapje-like mutants (±) and the offspring assayed at 4 dpf for defects in muscle using birefringence. From this cross, 25% of the offspring showed muscle lesions (top fish, right) suggesting that the two fish have mutations in the same gene. All panels are shown at approximately 10-fold magnification.