Abstract
Mammalian spermatogonial stem cells reside on the basement membrane of the seminiferous tubules. The mechanisms responsible for maintenance of spermatogonia at the basement membrane are unclear. Since acetylated alpha-tubulin (Ac-alpha-Tu) is a component of long-lived, stable microtubules and deacetylation of alpha-tubulin enhances cell motility, we hypothesized that acetylation of alpha-tubulin might be associated with positioning of spermatogonia at the basement membrane. The expression pattern of Ac-alpha-Tu at different stages of testis development was characterized by immunohistochemistry for Ac-alpha-Tu and spermatogonia-specific proteins (PGP 9.5, DAZL). In immature pig testes, Ac-alpha-Tu was present exclusively in gonocytes at 1 week of age, and in a subset of spermatogonia at 10 weeks of age. At this age, spermatogonia are migrating toward the tubule periphery and Ac-alpha-Tu appeared polarized toward the basement membrane. In adult pig testes, Ac-alpha-Tu was detected in few single or paired spermatogonia at the basement membrane as well as in spermatids and spermatozoa. Only undifferentiated (DAZL-), proliferating (determined by BrdU incorporation) spermatogonia expressed high levels of Ac-alpha-Tu. Comparison with the expression pattern of beta-tubulin and tyrosinated alpha-tubulin confirmed that only Ac-alpha-Tu is specific to germ cells. The unique pattern of Ac-alpha-Tu in undifferentiated germ cells during postnatal development suggests that posttranslational modifications of microtubules may play an important role in recruiting and anchoring spermatogonia at the basement membrane. Mol. Reprod. Dev. 77: 348-352, 2010. (c) 2009 Wiley-Liss, Inc.
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