Alzheimer amyloid beta-protein precursor in sperm development.

We prepared antisera to both the N and C termini of amyloid beta-protein precursor (APP). Both antisera labeled 110 to 140 kd proteins from rat testis by immunoblotting. Northern blot analysis using oligonucleotide probes complementary to respective APPs showed that APPs expressed in rat testis contained Kunitz-type protease inhibitor domains. Immunocytochemically brain APP was localized in neurons and their processes. During sperm formation, APPs labeled by both antisera were localized only in acrosome and the growing tail of spermatids in the seminiferous tubules. This shows that APPs appear only in particular phases of spermatogenesis, that is, in the morphologic change phase from spermatid to mature sperm. Amyloid beta-protein precursors in testis may play a role in cellular differentiation or morphologic change.