Establishment of an inducible knockout model for the chicken Z-chromosome-linked gene DMRT1.

Sex determination is a crucial process in animal development, regulated by complex genetic networks. In avian species, Doublesex and mab-3 related transcription factor 1 (DMRT1) plays a vital role in gonadal development and sex determination. To unravel the function of DMRT1 in chicken sex determination, establishing an inducible DMRT1 knockout model is essential. In this study, we constructed an inducible DMRT1 knockout system and verified its efficiency and effects on related genes and physiological indicators. To achieve precise genomic ablation, we screened multiple sgRNAs targeting the DMRT1 locus and integrated the optimal sequence into a doxycycline-responsive (Tet-on) CRISPR/Cas9 architecture. For in vitro experiments, vectors were delivered via cell transfection and induced with 20 µg mL-1 doxycycline (DOX), achieving an 80% knockout efficiency. Following the administration of polyethylenimine (PEI)-encapsulated plasmids into chicken embryos, we successfully implemented the inducible system in vivo. Quantitative analysis confirmed a mosaic knockout of DMRT1 with an observed efficiency reaching 45%. Following targeted disruption, we evaluated sex-related gene and protein expression alterations via qRT-PCR and Western blot (WB). Furthermore, ELISA was performed to measure testosterone levels in male embryonic gonads across multiple developmental stages (E4.5 to E18.5). qRT-PCR analysis showed that after induction, female-related genes (CYP19A1, FOXL2, ESR1) were significantly upregulated, and male-related genes (DMRT1, SOX9, AMH) were significantly downregulated. WB results revealed increased protein expression levels of CYP19A1 and FOXL2, and decreased protein expression of SOX9 post-induction. ELISA confirmed that testosterone levels in the gonads of induced male embryos were significantly reduced compared to normal and non-induced males. The study successfully established an inducible DMRT1 knockout system in chickens. This system effectively regulates the expression of sex-related genes and reduces testosterone levels in male embryos, providing theoretical and technical support for breeding novel sex-controlled breeding materials.