Effective RNA-silencing strategy of Lv-MSTN/GDF11 gene and its effects on the growth in shrimp, Litopenaeus vannamei.

Myostatin (MSTN), also known as GDF8, is a member of the transforming growth factor-β (TGF-β) superfamily and plays an important role in muscle growth, development, and differentiation. Recently, Lv-MSTN/GDF11, the primitive isoform of MSTN and GDF11, was identified from the shrimp Litopenaeus vannamei. The major production site for Lv-MSTN/GDF11 is in the heart, not the tail muscle, which differs from MSTNs in mammals. Among the three injected RNAs, long dsRNA was the most effective for Lv-MSTN/GDF11 knockdown and transcripts of Lv-MSTN/GDF11 decreased in both the heart (88.85%) and skeletal muscles (43.36%) 72h after injection of 10pmol of long dsRNA. We also found that higher doses of dsRNA did not lead to greater decreases in Lv-MSTN/GDF11 transcripts for amounts between 1pmol and 100pmol. Injection of Lv-MSTN/GDF11 dsRNA did not affect the upregulation of the skeletal actin gene (Lv-ACTINSK) in the tail muscle, but the expression of cytoplasmic and cardiac actins were upregulated in both the heart and tail muscle. Over the course of 8weeks of dsRNA injection, considerably higher mortality (~71%) was seen in the dsRNA-injected group compared to the control group (40%). Surviving shrimp in the dsRNA injected group had a lower growth rate due to the adverse effects of Lv-MSTN/GDF11 knockdown. Lv-MSTN/GDF11 appears to be involved in muscular or neuronal development, but not in doubling muscle fibers, as is the case with mammalian MSTN.