Required for motile ciliogenesis and flagellar genesis by mediating the maturation of the glycolytic enzyme ENO4. Specifically expressed in tissues with motile cilia and flagella, such as brain ependyma, lung, testis, and oviduct but not in whole brain, liver,kidney, spleen, and eyeball. Detected as early as postnatal day 15 (P15), and then continually increased during the first 45 days. Male mice exhibit severe defects in spermatogenesis, leading to infertility and varying degrees of hydrocephalus. The epididymal ependymal cilia frequently show disorganized axonemes, reducing motility. Mutant testis shown lack of fully developed flagella in the lumen of the seminiferous tubules; the mutant spermatids elongate but do not maintain the axoneme, leading to severe destruction of the flagella. In contrast, the ultrastructures of motile cilia in the tracheal epithelia are intact. The deficient mice do not display laterality defects, polydactyly, polycystic kidney, or other notable abdominal organ abnormalities indicating that the nodal and primary cilia were unaffected. Named Hoatz according to the Hydrocephalus and Oligo-Astheno-Terato-Zoospermia phenotype of Hoatz knockout mice. Belongs to the HOATZ family.