Katanin microtubule-severing enzymes are key microtubule regulators. Previously, we showed the katanin regulatory B-subunit, KATNB1, is essential for male meiosis and spermiogenesis. While our data suggests the katanin enzymatic A-subunit KATNAL2 mediates KATNB1 function in spermiogenesis, the enzyme(s) mediating KATNB1 meiosis functions remain unclear. Herein, we sought to characterise the role of katanin A-subunits KATNA1 and KATNAL1 in male germ cells.
To study this, we used Stra8-Cre to generate Katna1 and Katnal1 germ cell-specific knockout (Katna1GCKO/GCKO and Katnal1GCKO/GCKO) models, in addition to a Katna1 and Katnal1 double GCKO (Katna1/al1GCKO/GCKO) model. While single GCKO of Katna1 revealed it is not essential for spermatogenesis, single Katnal1 deletion revealed germ cell-KATNAL1 is required for optimal male fertility. Katnal1GCKO/GCKO males were subfertile, exhibited a 42.3% reduction in daily sperm production and, due to spermiation failure, a more dramatic 73.7% reduction in epididymal sperm number. Of the sperm present, they were abnormal with reduced motility. Analysis of Katnal1GCKO/GCKO meiosis, revealed chromosome alignment, segregation, and cytokinesis defects, however most cells completed meiosis. During spermiogenesis, we found KATNAL1 regulates axoneme and head-to-tail coupling apparatus formation and manchette-dependent head shaping. More interestingly however, double Katna1 and Katnal1 GCKO resulted in complete male sterility and a phenotype much worse than in Katnal1GCKO/GCKO. Katna1/al1GCKO/GCKO daily sperm production and epididymal sperm count were reduced by 86.9% and 96.2%, due to catastrophic meiosis and spermiogenesis defects. Katna1/al1GCKO/GCKO spermatocytes frequently stalled and underwent apoptosis in metaphase and anaphase. Moreover, of the few spermatids produced, they exhibited abnormal vesicle trafficking during acrosome biogenesis, followed by global microtubule dysregulation, ultimately becoming pyknotic by step 13. This study establishes KATNA1 and KATNAL1 as collective mediators KATNB1 meiosis functions and reveals they function in a compensatory manner to regulate microtubule dynamics and bulk during multiple aspects of male germ cell development.