Fig. 4

Quantitative analysis of slow muscle fiber numbers in uninjected, shh injected and dnPKA injected embryos from a cross of two smu+/- animals. S58- labeled slow muscle fibers in uninjected and injected embryos were counted blind, and fiber tallies binned in sets of 100 for clarity of presentation. Uninjected siblings of shh injected, dnPKA injected and rsmo injected embryos (Fig. 7) were pooled. shh injection (n=453) has no effect on the expected Mendelian proportion of mutant embryos; as in uninjected embryos (n=1219), approximately 25% had <100 fibers, and approximately 75% had >1000 fibers. Conversely, only 5% of the embryos injected with dnPKA exhibited <100 fibers (black bars, n=421). Numbers of dead and malformed embryos (in which we did not count fibers) for injected embryos and their siblings were very similar (shh injected: 58 of 511, siblings 34 of 607; dnPKA injected 10 of 431, siblings 29 of 651). Although we saw variation between clutches of uninjected embryos in the number of slow muscle fibers per embryo, among embryos with <1000 slow muscle fibers shh injection did not affect the number of fibers within clutches, whereas dnPKA injection consistently increased the mean number of slow muscle fibers. shh injected embryos had an average of 3.9±0.14 slow muscle fibers per fish (n=114), and their uninjected siblings had an average of 3.2±0.3 (n=154). This difference is not significant (t-test, P≤0.10). dnPKA injected embryos had an average of 259.0±25.6 slow muscle fibers per fish (n=71), while their uninjected siblings had an average of 8.3±0.6 (n=162). This difference is significant (t-test, P≤0.0005). Values are means ± s.e.m. Insets depict representative embryos for uninjected controls with 0-99 (a) and >1000 (b) fibers, shh injected embryos with 0-99 (c) and >1000 (d) fibers, and dnPKA injected embryos with 300-399 (e) and >1000 (f) fibers.