Generation and propagation of high fecundity gene edited fine wool sheep by CRISPR/Cas9

CRISPR/Cas9 technology has been widely utilized to enhance productive performance, increase disease resistance and generate medical models in livestock. The FecB allele in sheep is a mutation in the BMPRIB gene, recognized as the first major gene responsible for the high fecundity trait in sheep, leading to an increased ovulation rate in ewe. In this study, we employed CRISPR/Cas9-mediated homologous-directed repair (HDR) to introduce a defined point mutation (c.746 A > G) using single-stranded oligonucleotides (ssODN) and the ligase IV inhibitor (SCR7) into the BMPRIB gene of fine wool sheep. A total of nine gene-edited sheep were produced, six of which carried the targeted point mutation, with a precise base substitution efficiency (A > G) of 31.6%. Based on the six targeted founders (F0), we expanded the BMPRIB-targeted population, which included F1 heterozygous (B+) and F2 homozygous(BB) or heterozygous offspring. The average litter size of F1 ewes carrying the B + allele reached 170%, comparable to that of heterozygous native Australian Booroola sheep. Gene-edited ewes with B + and BB genotype produced 0.62 and 0.42 more lambs, respectively, compared to wide-type ewes (p < 0.01). Our results also indicated that the parity signification, our data demonstrate that highly efficient introduction of the intended base mutation into the sheep genome can be achieved by combining the CRISPR/Cas9 system with ssODN and SCR7. The offspring of BMPR/B edited sheep with the defined mutation exhibited high fecundity performance. Compared to conventional sheep breeding strategies, genetic improvement through gene editing offered significant advantages without compromising the fine wool traits of Merino sheep, which are often affected by routine cross-breeding methods.