Abundance of myostatin gene transcripts and their correlation with muscle hypertrophy during the development of barramundi, Lates calcarifer.

Myostatin (MSTN) is a pivotal protein that regulates vertebrate muscle growth and development. Teleost fish possess two MSTN paralogs (MSTN-1 and MSTN-2) whose respective physiological functions are still largely unclear. To clarify the role of each of these paralogs the transcript abundance of Mstn-1 and Mstn-2 was quantified during embryonic and larval development of the teleosts, barramundi, Lates calcarifer. Histological analyses of developing muscle fibers were also obtained to correlate Mstn paralog expression with muscle hypertrophy as larvae undergo metamorphosis. Mstn-1 and Mstn-2 transcripts were detected as early as immediately postfertilization of eggs, with the level of expression observed to increase during embryonic development and reach a peak near hatching. Mstn-2 expression was thousands-fold higher than that observed for Mstn-1. Close to metamorphosis, the expression of Mstn-1 was non-significantly, although positively associated, with muscle hypertrophy (r=0.384, p=0.064), while that of Mstn-2 showed a highly significant negative correlation (r=-0.691, p<0.0001) suggesting that this paralog may be responsible for muscle hypertrophy that occurs post-metamorphosis. Altogether, findings from this study support the hypothesis that Mstn paralogs are differentially regulated during various phases of fish development and that they may have evolved different functions in fish, particularly that related to muscle hypertrophy. Crown