Figure 5.

CDK2 localization in meiotic chromosomes of males and females of distinct rodent species. In all species, CDK2 (white) localized in the telomeric and interstitial sites of autosomes (A). Blue arrowheads point to telomeric CDK2 localization in sex bivalents (XY). Schemes of sex chromosome synapsis, centromeric regions, and CDK2 dots are shown in the left bottom insets (a–e). (a) Pachytene oocyte of the mole vole E. tancrei. An incomplete synapsis occurred in the central part of the sex (XX) bivalent (white star). There were different CDK2 signals: Strong ones in the telomeric and interstitial sites, and weak signals in the synapsed parts of the sex bivalent (pink arrow). (b) Pachytene spermatocytes of the mole vole E. alaicus. CDK2 signals were detected in the telomeric and interstitial sites for all bivalents. A weak CDK2-cloud was visualized around the asynaptic area of XX. (c) In the pachytene spermatocyte of the vole M. arvalis X and Y were asynaptic (without synapsis between them). The X chromosome showed numerous CDK2 foci (not intense here). The Y chromosome showed CDK2 foci in telomeric sites only. (d) In the pachytene spermatocyte of the mole rat N. leucodon numerous CDK signals appeared in the asynaptic part of the X chromosome. Y had telomeric CDK2 foci only. (e) Pachytene spermatocytes of the hamster C. migratorius. Autosomes had the same regularities: Telomeric and one or two interstitial sites were CDK2-positive. Rare CDK2-dots were identified in asynaptic regions of XY. (f) In the late pachytene hamster spermatocyte, asynaptic X- and Y-axes had diffused SYCP3. Scale bar (a–e) = 5 µm.