Fig. 5. Double immunolabelling of INCENP and SCP3 in either squashed (A-O,R,S) or spread (P,Q) prophase I spermatocytes (INCENP, green; SCP3, red; regions of colocalization, yellow). (A-C) Single focal plane of a zygotene spermatocyte. Some short INCENP threads colocalize with SCP3 threads where homologous chromosomes have synapsed. (D-F) Partial projection of two focal planes throughout a pachytene spermatocyte. The long INCENP threads colocalize with SCP3-labelled synaptonemal complexes (SCs). (G-L) Selected pachytene SC fragments where the two lateral elements (LEs) (arrowheads) are clearly individualised. The INCENP threads, presenting narrow regions along their lengths (arrows in G), are located in between the LEs. (M-O) End of a pachytene SC showing that the INCENP thread also appears in between LEs (white arrowheads). (P,Q) Selected sex bivalent from a spread of an early pachytene spermatocyte. INCENP only labels the pseudoautosomal region. The unsynapsed sex axial elements (X,Y) are indicated. (R,S) Selected diplotene bivalent. A short INCENP thread (arrows) colocalizes with the region where LEs are still synapsed. Chromocentres show a bright INCENP labelling. (A-F) Bar in C, 5 µm. (G-O) Bar in I, 0.7 µm. (P,Q) Bar in Q, 2 µm. (R-S) Bar in S, 3.3 µm.

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