A Myostatin ( MSTN −/− ) Knockout Buffalo Produced by CRISPR-Cas9 Mediated Genome Editing and Somatic Cell Nuclear Transfer

Abstract

CRISPR-Cas9 genome editing offers significant opportunities to improve livestock traits; however, its application in buffalo has been very limited, with no prior reports of live gene-edited animals. Here, we report the successful birth of a buffalo edited in the myostatin (MSTN) gene. To achieve this, five single-guide RNAs (sgRNAs) targeting the buffalo MSTN gene were designed and tested in skin-derived fibroblasts. Among these, sgRNA5 exhibited the highest editing efficiency, approaching ∼50%, as confirmed by T7 Endonuclease I assay, Tracking of Indels by Decomposition, and Inference of CRISPR Edits analyses. Single-cell cloning identified six edited fibroblast clonal populations, including one with a bi-allelic frameshift mutation predicted to severely truncate the MSTN protein. These bi-allelic clonal cells were subsequently used as nuclear donors to produce somatic cell nuclear transfer (SCNT) embryos, which were transferred into recipient buffaloes (n = 15). This effort established three pregnancies and resulted in the birth of one live MSTN knockout buffalo calf. Phenotypically, the calf displayed accelerated growth and increased muscle fiber number and size while maintaining normal meat composition. In conclusion, this study reports the world’s first gene-edited buffalo generated through CRISPR-Cas9-mediated genome editing combined with SCNT. These findings provide a proof-of-concept for genome editing in buffalo and demonstrate that MSTN disruption can effectively enhance muscle growth and meat production traits.