Molecular components of the clock system identified in fast skeletal muscle of Atlantic cod and myogenic genes with daily rhythmic expression.

<p>The peripheral clock components in Atlantic cod fast skeletal muscle that have been identified in this study are shown inside the green circle, which represents a muscle fiber. They comprise members of the transcriptional activator arm (in red: <i>arntl1, arntl2, clock</i> and <i>npas2</i>), transcriptional repressor arm (in blue: c<i>ry1a, cry1b, cry-dash, cry2, cry3, per1, per2a, per2b</i> and <i>tim</i>) and the stabilizing loop (in yellow: <i>nr1d1, nr1d2a</i> and <i>nr1d2b</i>). Clock genes with a colored background displayed a daily rhythmic expression in fast skeletal muscle. The daily rhythmicity of <i>myf5</i>, a gene for myogenic lineage specification, and <i>mbnl1</i>, a gene for terminal muscle differentiation, suggests a possible circadian clock control of myogenesis in Atlantic cod. The grey box indicates that the mechanism underlying this regulatory process remains to be identified.