Gene and protein expression analysis of insulin-like growth factor-I and myostatin during development of Dicentrarchus labrax

This study reports the expression and cellular localization of insulin-like growth factor-I (IGF-I) and myostatin (MSTN) during the life cycle of sea bass (Dicentrarchus labrax) by RealTime PCR, in situ hybridization (ISH) and immunohistochemistry. RealTime PCR indicated that IGF-I mRNA increased significantly during the first week post-hatching (ph). In adults, the highest expression of IGF-I mRNA was observed in liver whereas MSTN mRNA was almost exclusively detected in muscle. ISH showed IGF-I mRNA expression in liver already at 8 days ph and, at 25 days ph, also in growing cartilage. MSTN mRNA increased significantly from day 25 and the expression of mRNA was higher in muscle and almost paltry in other organs/tissues. Interestingly, the lateral muscle showed a quantitative differential expression of IGF-I and MSTN mRNAs in red and white muscle, depending on the developmental stage examined. IGF-I immunoreactivity was detected at hatching in developing intestine, skeletal muscle, skin and yolk sac. At hatching, MSTN immunostaining was evident in skeletal muscle, skin and yolk sac. From the fourth day ph IGF-I and MSTN proteins were detected in liver and, subsequently, in kidney and heart muscle from day 10. These results suggest that IGF-I and MSTN are involved in the regulation of somatic growth in the sea bass.