Fig. 3. INCENP distribution in early prophase I spermatocytes (INCENP, green; ACA serum, red; DAPI, blue). (A,B) Partial projection of 21 focal planes throughout an early prophase I spermatocyte. No INCENP signals are discerned; instead only ACA signals representing unpaired centromeres are seen. (C,D) Partial projection of 15 focal planes throughout an early prophase I spermatocyte. Some short and discontinuous INCENP threads (arrows) are observed in the nucleus. (E,F) Partial projection of three focal planes throughout a pachytene spermatocyte. Long INCENP threads (arrows) showing a heterogeneous thickness are detected in the nucleus. The sex body (XY) shows a faint INCENP labelling (arrowhead). (G) Projection of two focal planes of an INCENP-labelled thread at pachytene. The thread presents narrower regions (arrowheads) along its length. (H) Side view of the proximal end of an INCENP thread at pachytene. The single ACA signal, representing synapsed homologous centromeres, surrounds the end of the thread. (I,J) End-on view of the proximal end of an INCENP thread at pachytene. The spot representing the INCENP signal is lateral to the ACA signal. (K) Partial projection of three focal planes throughout the pachytene sex body that appears slightly labelled with INCENP. The unpaired sex centromeres (yellow arrowheads), and the INCENP-labelled pseudoautosomal region (arrow), are observed. (L-N) Two focal planes throughout a late pachytene spermatocyte. Chromocentres appear labelled (arrows), whereas INCENP labelling at nuclear threads is fainter. The sex body (XY) appears faintly labelled (white arrowhead in M). The centromeres of both sex chromosomes (yellow arrowheads in M) are separated. (A-F,L-N) Bar in N, 10 µm. (G,K) Bar in G, 5 µm. (H-J) Bar in H, 2 µm.