Defb19 regulates the migration of germ cell and is involved in male fertility

β-defensins are small antimicrobial peptides that play essential roles in male fertility. Although several members of the β-defensin family are preferentially expressed in the testis, their involvement in spermatogenesis remains elusive. In this study, we have characterized the expression and function of Defb19 in mouse testis. Our results showed that Defb19 is expressed in both Sertoli cells and germ cells. Overexpression of Defb19 in the 15P-1 Sertoli cell line decreases the expression of cell junction molecules and promotes the matrix adhesion and migration of Sertoli cells. Recombinant DEFB19 and conditioned medium of Defb19-overexpressed 15P-1 cells promote the migration of GC2-spd spermatocyte cell line. Knockout of Defb19 in mouse by CRISPR/Cas9 resulted in male subfertility with testicular and epididymal atrophy. A marked increase in apoptosis and a significant decrease in the sperm count were observed in the KO mice. Together, our study has uncovered an important role of Defb19 in male fertility by regulating the migration of both the Sertoli cells and the germ cells. Our study has shed new light on the functions of β-defensins in the testis. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13578-022-00924-1.