Factors that may regulate assembly of the mammalian sperm tail deduced from a mouse t complex mutation.

A unique pattern of aberrant sperm development occurs in laboratory mice (Mus domesticus) that have been made homozygous for an allele of an autosomal gene, Hst-6s, derived from another mouse species, Mus spretus. During the abnormal spermiogenic process of these sterile animals, the sperm tail fails to assemble normally, although a bud develops at the site of the centriole in early spermatids. The bud enlarges during sperm development and eventually contains elements of a mature sperm tail. Tubulin assembles primarily into single microtubules rather than doublets. These singlets form a circular array that is not oriented relative to the centriole. While dense fibers form in association with the singlet microtubules, the fibrous sheath components accumulate in a single irregular mass. These observations suggest that microtubule doublets are required for the organization of an axoneme. In addition, while dense fibers can form normally in association with singlet microtubules, the fibrous sheath requires the axoneme as a substrate for normal organization.