Targeted inactivation of the mouse epididymal beta-defensin 41 alters sperm flagellar beat pattern and zona pellucida binding

• Defb41iCre/+ knock-in mice can be used to make genetic modifications in the principal cells of proximal epididymis.
• Lack of Defb41 causes a defect in sperm motility.
• Lack of Defb41 causes sperm flagella primarily to bend in the pro-hook conformation in capacitated sperm.
• A change in flagellar binding pattern leads to a reduced straight line motility.

During epididymal maturation, sperm acquire the ability to swim progressively by interacting with proteins secreted by the epididymal epithelium. Beta-defensin proteins, expressed in the epididymis, continue to regulate sperm motility during capacitation and hyperactivation in the female reproductive tract. We characterized the mouse beta-defensin 41 (DEFB41), by generating a mouse model with iCre recombinase inserted into the first exon of the gene. The homozygous Defb41iCre/iCre knock-in mice lacked Defb41 expression and displayed iCre recombinase activity in the principal cells of the proximal epididymis. Heterozygous Defb41iCre/+ mice can be used to generate epididymis specific conditional knock-out mouse models. Homozygous Defb41iCre/iCre sperm displayed a defect in sperm motility with the flagella primarily bending in the pro-hook conformation while capacitated wild-type sperm more often displayed the anti-hook conformation. This led to a reduced straight line motility of Defb41iCre/iCre sperm and weaker binding to the oocyte. Thus, DEFB41 is required for proper sperm maturation.