Generation of Knock‐In Syrian Hamsters via Zygote Microinjection Using <scp>CRISPR</scp> /Cas9 Genome Editing

Syrian hamsters (Mesocricetus auratus) have long served as valuable model organisms in diverse research fields such as oncology, immunology, and physiology owing to their unique biological and pathological characteristics. Although embryo manipulation techniques such as embryo collection, pronuclear microinjection, and embryo transfer have been established, gene knock-in (KI) hamsters have not yet been reported. Here, we report the successful generation of gene KI Syrian hamsters by microinjecting CRISPR/Cas9 components and plasmid DNA into pronuclear-stage zygotes. Targeted insertion of a DNA cassette up to 8 kb was achieved at the ROSA26 orthologous locus and other genomic sites. Importantly, we confirmed functional expression of a reporter cassette inserted at the ROSA26 site, providing evidence of transcriptional activity at this locus in Syrian hamsters. Furthermore, we demonstrated that frozen-thawed KI embryos could give rise to live offspring using a simplified freezing and thawing protocol originally developed for mice and rats. These results confirm the feasibility and applicability of advanced genome editing technologies in Syrian hamsters. These technological advancements enable the development of versatile KI models for applications such as gene expression monitoring and conditional mutagenesis, thereby expanding the utility of Syrian hamsters as model organisms, comparable to mice and rats.