CRISPR/Cas9-mediated pou4f3 knockout induces defects in the development of the zebrafish inner ear

Objective:The zebrafish is an excellent model for studying gene function in auditory system development.Pou4f3 plays an important role in mouse hair cell formation.Here,we constructed apou4f3-knockoutTg(Brn3c:GFP)zebrafish to provide an efficient fluorescence-visualized model for studying the molecular mechanisms of ear development.Methods:Cas9/single guide RNAs targeting exon 2 ofpou4f3 were designed and injected into one-cell stage zebrafish embryos(G0 generation).The G0 generation were crossed withTg(Brn3c:GFP)zebrafish to obtainpou4f3-mutantTg(Brn3c:GFP)zebrafish.The targeting efficiency was detected by polymerase chain reaction amplification and Sanger sequencing.Zebrafish hair cells were observed by laser scanning confocal microscopyin vivo.The morphology of the otoliths and semicircular canals were analyzed.All animal experiments were approved by the Animal Care and Use Committee of Shandong Provincial Hospital,Cheeloo College of Medicine,Shandong University(approval No.2016-KY-040)on March 3,2016.Results:Thepou4f3-mutantTg(Brn3c:GFP)zebrafish line was successfully established.Fluorescence observation suggested that hair cell development was delayed inpou4f3-knockout zebrafish.Knockout ofpou4f3 also induced defects in the otoliths and semicircular canals and impaired ear function in zebrafish.Conclusion:A CRISPR/Cas9-mediatedpou4f3 mutantTg(Brn3c:GFP)zebrafish model was established for the first time to demonstrate the essential role ofpou4f3 in zebrafish ear development.Our study provides a highly efficient method for the establishment of a visualized model of gene knockout zebrafish and has the potential to allow high-throughput drug screening to explore therapeutics for related diseases.