KIF9 and Hydrocephalus: KIF9 belongs to the kinesin 9 family that contains another kinesin, KIF6.4 Northern blot analysis showed that Kif6 is expressed in mouse testis8; however, Kif6 mutant mice exhibited hydrocephalus leading to postnatal lethality,39 which makes it difficult to analyze KIF6 function in mature spermatozoa.