cDNA encoding sequences for myostatin and FGF6 in sea bass (Dicentrarchus labrax, L.) and the effect of fasting and refeeding on their abundance levels.

Fish have the ability to compensate for set-backs in growth as a result of fasting. When food levels
are restored, growth in these fish can increase over and above normal rates. This phenomenon, known
as “compensatory growth”, has been studied with respect to enhancing food conversion efficiency.
However, the mechanisms by which food intake activates an increase in somatic growth, and especially
in muscle growth, are not well understood. In this study,we report first on the isolation of two complete
cDNAs sequences encoding sea bass (Dicentrarchus labrax) myostatin and fibroblast growth factor 6
(FGF6), which have been shown to be major genetic determinants of skeletal muscle growth. The open
reading frames of myostatin (376 amino acids) and FGF6 (209 amino acids) showed 97–63% and
87–62% sequence identity with other vertebrate myostatins and FGF6s, respectively. We also report
on the expression profile of myostatin and FGF6 in sea bass skeletal muscle in response to different
feeding regimens, as quantified by real-time RT-PCR. Nutritional status significantly influenced the
myostatin expression levels in muscle, inducing an up-regulation during fasting and a down-regulation
during the recovery from fasting, whereas the muscular FGF6 mRNA levels were not significantly
affected by the feeding status of the animals. These findings suggest that myostatin has an inhibitory role in muscle growth in response to different feeding regimens, whereas FGF6 is not involved in the
muscle compensatory growth induced by refeeding.