CYLD and Infertility: Because male CKO mice are infertile [28], and Hdac6 is an X-linked gene [29], we selected female CKO mice (i.e., Cyld −/−, Hdac6 +/+) and male Hdac6 KO (HKO) mice (i.e., Cyld +/+, Hdac6 −/Y) for the production of first-generation heterozygous mice (Figure 1A).