Identification and evolution analysis of the fos gene family: highlighting the role of fosab in muscle growth of mandarin fish Siniperca chuatsi.

Fosab is a key transcription factor to regulate the proliferation cycle of satellite cells in mammalian skeletal muscle. To verify its regulatory function in mandarin fish (Siniperca chuatsi) satellite cells, a whole-genome identification and evolutionary analysis were conducted, and the regulation of fosab to satellite cells development was explored by both gene overexpressing and knocking down analysis. The results revealed that mandarin fish have 5 fos family members (fosaa, fosab, fosb, fosl1a, and fosl2), which are relatively lowly conserved (36.0 %-88.6 %) in amino acid among vertebrates. In teleosts, fosaa, fosab, and fosl1a were evolved through the third genome duplication event, accompanied with chromosomal rearrangements which resulted in co-localized fosaa and fosl2 on the same chromosome. Some synchronous evolution of conserved gene clusters, such as fosaa-jdp2a and mocs1-fosl2-babam2-rbks-mrpl33 were also abserved. In the tissue and developmental expression trends, fos members showed highly expression in gill, brain and liver (P < 0.05). In skeletal muscle, all members reached their highest expression levels on the 5th day post hatching (5 dph) (P < 0.05). The muscular injury model for mechanistic investigation showed that pax7, myod, and myf5 level significantly increased/decreased (P < 0.05) on the 4th days after injury. The number of pax7+ cells significantly increased (P < 0.05), with a significant upregulation of fosab expression (P < 0.05), indicating that the proliferation activity of satellite cells was highest at the 4th days after injury. Under this model, overexpressing or knocking down the level of fosab could significantly increase or decrease the number of pax7+ cells and the expression levels of cyclin genes like cyca, cycd, and cdk2, as well as myogenic marker genes such as myog and myf6 (P < 0.05). In conclusion, fosab could promote the growth of myoblasts by speeding up the satellite cell cycle in mandarin fish.