Effects of fasting and re-feeding on mstn and mstnb genes expressions in Cranoglanis bouderius

The myostatin (mstn) and myostatinb (mstnb) gene of Cranoglanis bouderius were cloned and sequenced and their expressions under nutritional restriction were characterized. The full cDNA sequences of mstn and mstnb were 1878 bp and 1928 bp, containing an open reading frame of 1170 bp and 1119 bp, which encoded 390 and 373 amino acids, respectively. The deduced mstn and mstnb sequence structures were similar to other members of TGF-beta superfamily, including the TGF beta pro-peptide, TGF beta domain, proteolytic processing site and nine conserved cysteines in the C-terminal. In addition, four mstn gene duplications were found in Cranoglanis bouderius. Sequence alignment and phylogenetic tree analyses indicated that the mstn gene and mstnb gene had a close relationship with Siluriformes fish, and the mstn and mstnb genes were roughly classified into two groups. RT-PCR analysis revealed that the mstn and mstnb were expressed in a variety of tissues in Cranoglanis bouderius although the mstn was highly expressed in skeletal muscle and the mstnb was mainly expressed in brain. We speculate that the mstn gene but not mstnb is likely to play a key role in managing muscle growth. A fasting-re-feeding experiment was used to evaluate the effects of starvation on mstn and mstnb expressions in juvenile Cranoglanis bouderius for 5 weeks. The result showed that the mstn and mstnb transcript levels varied among tissues. The mRNA expression levels of mstn in muscle, brain and liver gradually decreased during starvation and returned to the normal level after re-feeding. The mstnb mRNA levels in muscle, brain, liver, spleen, intestine and kidney increased during an early fast time but ultimately decreased with prolonged fasting time. The mstnb transcript levels in muscle, brain and liver increased significantly after re-feeding. In summary, the results supported that the mstn and mstnb may not be limited to control of muscle growth in fish but could also be involved in other biological functions.