From zebrafish (Danio rerio) to mouse, the function of Nfix in skeletal muscle development is partially conserved during the evolution

The transcription factor Nfix regulates fetal-specific transcription in developing murine skeletal muscle, as previously demonstrated by our group. Zebrafish and murine muscle development is similar, however, zebrafish develops at a much faster rate. By 24 hours post fertilization (24 hpf), a functional myotome is formed with primary slow and fast fibers. At 48 hpf, secondary slow fibers differentiate in several body locations. These distinct primary and secondary myogenic waves in zebrafish are reminiscent of specific murine muscle developmental stages (embryonic and fetal). Knock-down of the Nfix ortholog in zebrafish (nfixa) alters fiber type development, similar to what has been observed previously in the mouse. In contrast, whereas Nfix mutant mice are motile, nfixa knock-down in zebrafish results in impaired motility with disruption of the sarcoplasmic reticulum. These results demonstrate a conserved role for Nfix and nfixa in governing secondary myogenesis, however nfixa plays a non-conserved role during myofiber maturation in the zebrafish.