LAUSR

Abstract The gene mstn is a negative regulator of skeletal muscle growth and development in vertebrates, including teleosts. Common carp (Cyprinus carpio) is an economically important food fish, and an increase in its skeletal muscle mass, and improvement in growth without introducing exogenous DNA is highly desirable. In our study, sgRNA/Cas9 ribonucleoprotein (RNP) (62 ng/μL Cas9 and 186 ng/μL cc sgRNA2) was used to knockout (KO) the mstn gene of common carp, and subsequent hatchability, survivability, body deformity and growth performance of the mstn+/− F0 common carp was monitored till 90 days post-hatching (dph). Insertion-deletion (indel) mutation of 1–11 bp was observed in the first exon of the mstn gene of KO common carp, and approximately, 88–95% mutation was observed in the target protein-coding site of this gene. Off-target effects, including skeletal deformity, and other phenotypic abnormality were not observed in mstn+/− F0 common carp. Total body length, body weight, width of the body, and the body depth of mstn+/− F0 common carp were significantly (p