KATNB1 is a master regulator of multiple katanin enzymes in male meiosis and haploid germ cell development.

Katanin microtubule severing enzymes are critical executers of microtubule regulation. Here, we have created an allelic loss-of-function series of katanin regulatory B-subunit KATNB1 in mice. We reveal KATNB1 is the master regulator of all katanin enzymatic A-subunits during mammalian spermatogenesis, wherein it is required to maintain katanin A-subunit abundance. Our data shows complete loss of KATNB1 from germ cells is incompatible with sperm production, and we reveal multiple new spermatogenesis functions for KATNB1, including critical roles in male meiosis, in acrosome formation, in sperm tail assembly, in regulating both the Sertoli and germ cell cytoskeletons during sperm nuclear remodelling and in maintaining seminiferous epithelium integrity. Collectively, our findings reveal that katanins are able to differentially regulate almost all key microtubule-based structures during mammalian male germ cell development, through the complexing of one master controller, KATNB1, with a 'toolbox' of neofunctionalized katanin A-subunits.