| Carp (Cyprinus carpio) is one of the most widely cultured freshwater fish species in the world. Currently, carp breeding occupies a considerable proportion of natural freshwater fishery and fish farming industry worldwide. It is also important in the freshwater fishery in China. Therefore, the study on carp, especially on its production traits, and breeding for agricultural production are of great significance.Myocyte enhancer factor2(MEF2) is the member of the MADS box-containing proteins. Being capable of binding DNA, it plays an important role in regulating gene transcription during myoblast differentiation in the development of cardiac muscle, skeletal muscle and smooth muscle. MEF2can also regulate myogenesis through direct or indirect control of microRNAs. MicroRNAs (miRNAs) are a class of small, single-stranded RNA of18-25nucleotides in length, which function as regulators of post-transcriptional gene expression. miRNAs that are highly expressed in myocardium and skeletal muscles are called MyomiRs Previous studies have found that miR-1, miR-24, miR-27b, miR-133, miR-181a, miR-206, miR-208, miR-221/222, miR-486, and miR-499are all MyomiRs that play important roles in growth and maintaining of vertebrate muscle.As carp is not widely used in experimental study, there was little sequence information available for the family members of carp MEF2in Genbank. By comparing the data, we finally found that like in other vertebrates such as mice, the MEF2family in carp is also composed of four members:mef2a, mef2b, mef2c and mef2d. mef2c is consisted by two different genes, mef2ca and mef2cb. To study the roles of the MEF2family during the early development of carp, we detect via in situ hybridization the expression of each MEF2family member in carp embryo at different times (6h,12h,24h and48h), and found that all members of the MEF2family were expressed in the carp embryos. mef2ca and mef2d were only expressed in muscle tissues, mef2b was only expressed in the nervous system, while mef2a and mef2cb were expressed in both muscle and nerve tissues. The expression pattern of MEF2in different tissues of adult carp were similar to that during carp embryonic development, suggesting that mef2a, mef2b and mef2cb might have effect on early neural development, whereas mef2a, mef2ca, mef2cb and mef2d might have effect on early muscle development.Moreover, we conducted phenotype analysis, real-time quantitative PCR detection, and SPSS analysis to study the difference in the expression levels of five MyomiRs (miR-1, miR-21, miR-23a, miR-133, and miR-206) among German mirror carp, Heilongjiang carp and Hebao red carp, and the correlation between differential expression of myomiRs and morphological traits of the three carp species. The results demonstrated that weight, height and width of the three carp species were correlated with the expression levels of several MyomiRs. A significantly negative correlation were observed between body height/body length and the expression levels of miR-21and miR-23a. Body width/body length was positively correlated with the expression level of miR-1, but negatively correlated with the expression levels of miR-21and miR-23a. Suttle/body weight was in positive correlation with the expression level of miR-206. These results demonstrated that MyomiRs, such as miR-206, can be used as molecular markers of productive traits in common carp breeding.This study detected for the first time in carp embryos the expression of MEF2family genes important for muscle development, and associated the expression of MyomiRs with the production traits of carp. Our results will be helpful for better understanding the molecular mechanism of carp development in the future, and will provide a scientific basis for improving fish breed and production. |
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