Gfi1-P2A-GFP-CreERT2 Mouse Line:A New Tool For Hair Cell Specific Deletion

Inner ear specific Cre mouse lines are very useful and important tools for targeted gene deletion study.However,most of the inner ear Cre mouse lines available now are only tissue-specific,few of them are inducible and time-specific.Spatio-temporally specific Cre mouse line is pivotal for conditional genetic study,especially in late embryonic stages and in adult.Growth factor independence 1(Gfi1)is an essential transcription factor specifically expressed in the hair cells of mouse inner ear and is appropriate to be a good carrier gene for inducible Cre.We successfully generated the Gfil-P2A-GFP-Cre-ER(Gfi1-GCE)mouse line,which has been verified as a new inducible inner ear hair cells specific-gene deletion tool.Cre is induced to delete the target genes in inner ear hair cells soon after the injection of Tamoxifen in Gfi1-GCE mice.The Cre recombination efficiency is highly related with the injection time and dosage of Tamoxifen and could be as high as nearly 100%in both developing and mature hair cells under dosage as 5mg(lmg/d x5days).The Cre recombination efficiency seemed different between inner hair cells and outer hair cells in adult mice under relatively low dosages of Tamoxifen(1mg/d x1 day,lmg/d x3days).In addition,unlike other knock-in gene tools,the functions of carrier gene Gfil are maintained very well.No obvious morphologic or functional defects of mouse inner ear hair cells were observed in Gfi1GCE/GCE homozygotes.In sum,the inducible Gfil-GCE mouse line we generated is highly efficient and could be a good spatio-temporally specific gene deletion tool for inner ear hair cell study.