CDNA Cloning Of Grass Carp Myostatin (MSTN) And Its Expression In Muscle Tissue In Response To Dexamethasone

Myostatin(MSTN) is a member of TGF-βsurper family,however,it has relatively low homology with other members of TGF-βsurper family,so myostatin also is named of Gdf-8(growth differentiation factor-8).Myostatin is a negative regulator of development,it supress the development and growth of muscle.In mammal,myostatin abundantly and widely distributed in muscle,however,it almost can supress in each tissues of fish,such as muscle,eyes,gills,brain, spleen,ovary,liver,intestine.Mammal and fish have different distribution and suspression,which suggests that in fish myostatin may affect development of other tissues for a example,nerve.In this study,the cDNA encoding myostatin(MSTN) was cloned from the skeletal muscle of grass carp by RT-PCR method and analyzed by bioinformatics.At the same time,its potential amino acid sequence was deduced and the corresponding protein structure was predicted and analysed. Meanwhile,the change of expression from muscle tissue of grass carp in the different concentrations (0μg/kg·d,60μg/kg·d,600μg/kg·d,1200μg/kg·d) of injecting grass carp with dexamethasone and in the 1d,5d,10d after injected with dexamethasone(600μg/kg·d),and the results provided the dexamethasone affect expression of myostatin,which provided the scientific approach for advancing fish output.1.The result showed that the cDNA of grass carp myostatin is 1764nt,which includes an open reading frame of 1128nt coding for a protein of 375 amino acids.Analysis of phylogenetic tree showed that Cyprinidae fishes myostatin proteins are highly homologous.Sequence alignment revealed that the MSTN precursor of grass carp shared high homology of more than 94%with that of pimephales promelas.The precursor sequence alignment of grass carp with other fish species demonstrated moderate degree of homology(78.1～82.3%).Relatively low degree of homology was shown in precursor sequence alignment of grass carp with birds and mammals.Phylogenetic analysis indicated that MSTN sequence homology among vertebrate species correlated primarily to their relationship.Analyzing grass carp MSTN primary structure,secondary structure,domain,tertiary structure,we could consider grass carp MSTN primary structure was base to conformation. 2.Through injected grass carp with dexamethasone in the different concentrations(0μg/kg·d,60μg/ kg·d,600μg/kg·d,1200μg/kg·d),the result showed the expession of grass carp MSTN mRNA (0μg/kg·d,60μg/kg·d,600μg/kg·d,1200μg/kg·d) was 0.247605,0.247723,0.330207,0.477166. There were significant differences(P＜0.05)of grass carp MSTN mRNA between group 60μg/kg·d and group 600μg/kg·d,group 600μg/kg·d and 1200μg/kg·d.in the 1d,5d,10d after injected with dexamethasone(600μg/kg·d),the levels of myostatin mRNA in group(1d,5d,10d) was 0.54074,0.65098,0.95023.There was a significant differences(P＜0.05) of grass carp MSTN mRNA between group in 5d and 10d.Taken together,these results further supported that dexamethasone infected the MSTN mRNA level.