Confocal micrographs of SPNR staining in hop/hop testes show that, as in wild type, SPNR forms as a caplike structure around the caudal end of the nucleus in step 9 spermatids, entirely coincident with tubulin staining (arrowhead, Fig. 3L). SPNR staining continued to overlap with tubulin staining as the spermatids formed long, abnormal manchette microtubules (arrowhead, Fig. 3I). An apparent overabundance of SPNR was found in degenerating elongating spermatids, filling the cytoplasm of these cells (arrow, hop panel, Fig. 1 and Fig. 3, G and J).
Double im-munostaining of these degenerating cells with both SPNR and tubulin antibodies showed that these cells also had diffuse tubulin staining that was sometimes punctuated by brightly staining regions where SPNR staining was also concentrated (arrow, Fig. 3L). These areas of intense staining may be microtubule structures that have not completely disassembled. Thus it appears that manchettes form properly in these cells but undergo an abnormal proliferation that is followed by premature depolymerization as the spermatids degenerate.