Disruption of mstnb by CRISPR/Cas9 promotes muscle growth and affects muscle nutritional composition in Acrossocheilus fasciatus

Enhancing muscle growth is a key goal in aquaculture. Myostatin (MSTN), a conserved negative regulator of muscle development, is a prime target for genetic improvement. Here, CRISPR/Cas9 was used to disrupt mstnb in the freshwater fish Acrossocheilus fasciatus . High editing efficiency was observed in F 0 juveniles. At 27 months of age, mstnb -mosaic F 0 adults exhibited a pronounced double-muscling phenotype, with increases in body weight (22.07%), body width (18.13%), and body height (13.02%) compared to controls. In the F 1 progeny, mstnb mutant fish showed a 36.1% higher condition factor and a 29.2% larger muscle fiber cross-sectional area compared to controls, suggesting inheritance of the growth trait. Preliminary nutritional analysis indicated potential increases in total amino acid and essential amino acid contents in F 1 muscle, while fatty acid profiles appeared largely stable. Collectively, these findings suggest that mstnb disruption can promote muscle growth and may affect nutritional composition of muscle in A. fasciatus . This study supports mstnb as a promising target for genetic improvement and offers initial insights into the pleiotropic effects of MSTN signaling in fish.