Fig. 4. INCENP expression in diplotene and diakinesis spermatocytes (INCENP, green; ACA serum, red; DAPI, blue). (A-C) Two partial projections from the same diplotene spermatocyte. INCENP labels the chromocentres, which appear very bright (arrowheads in B,C), the sex body (XY), which is fainter, and the short and faint nuclear threads (arrows). The unsynapsed sex centromeres (yellow arrowheads) are observed in the sex body. (D,E) Side view of the insertion of the proximal ends of two INCENP threads into the nuclear envelope in an early diplotene spermatocyte. The centromeric heterochromatin of these two threads appears joined as a single bright chromocentre. (F,G) End-on view of the insertion of five autosomal centromeric regions into the nuclear envelope in an early diplotene spermatocyte. Note that the INCENP-labelled heterochromatic regions are larger than the ACA signals representing synapsed homologous centromeres. (H,I) Partial projection of four focal planes throughout a late diplotene spermatocyte. No INCENP threads are observed. INCENP labels intensely the chromocentres, and dimly the sex body (XY) where the centromeres (yellow arrowheads) are indicated. (J,K) Partial projection of three focal planes throughout a diakinesis spermatocyte. INCENP signals partially colocalize with ACA ones. Inserts show a high magnification of two centromeres. (A-C,H-K) Bar in K, 10 µm. (D-G) Bar in G, 5 µm.

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