In the vole, sex chromosomes did not synapse, but demonstrated CDK2 signals of varying intensity, similar to the rat X and Y chromosomes. to telomeric and interstitial regions of autosomes in all species WBP4 investigated (rat, vole, hamster, subterranean mole voles, and mole rats). In sex bivalents following synaptic specificity, the CDK2 signals were distributed in three different modes. In the XY bivalent in the rat and mole rat, we detected numerous CDK2 signals in asynaptic regions and a single CDK2 focus on synaptic segments, similar to the mouse sex chromosomes. In the mole voles, which have unique XX sex chromosomes in males, CDK2 signals were nevertheless distributed similarly to the rat XY sex chromosomes. In the vole, sex chromosomes did not synapse, but exhibited CDK2 signals of varying intensity, similar to the rat X and Y chromosomes. In female mole voles, the XX bivalent experienced CDK2 LB-100 pattern much like autosomes of all species. In the hamster, CDK2 signals were revealed in telomeric regions in the short synaptic segment of the sex bivalent. We found that CDK2 signals colocalize with SUN1 and MLH1 signals in meiotic chromosomes in rats and mole voles, similar to the mouse. The difference in CDK2 manifestation at the prophase I sex chromosomes can be considered an example of the quick chromosome development in mammals. (Muridae), with XX-XY and PAR, the common vole with XX, achiasmatic XY and no PAR; LB-100 the smaller mole rat (Spalacidae), with XX-XY and PAR; the gray dwarf hamster (Cricetidae), with XX-XY, PAR and equal-length heteromorphic chromosomes; and three species with isomorphic (homomorphic) sex chromosomes for both sexes: The northern mole vole (male XX with broad central asynaptic zone [25,26] and female XX with delayed synapsis LB-100 [27]). The primary focus was around the classical system XX-XY (rat) and the deviant XX-XX (the northern mole voles). 2. Results The major protein of SC, SYCP3, indicates the structure and behavior of axial/lateral elements in prophase I [28] and CREST marks the proteins of kinetochores [29]. We used single-, double-, and triple-round immunostaining to analyze the distribution of these proteins and kinase CDK2 in meiotic nuclei (Figures S2, S3 and combination 1 in Physique S4). In rats (Physique 1aCi and Physique 2aCf), during the zygotene stage, axial elements initiated telomeric or interstitial synapsis in autosomes (Physique 1a). Sex chromosomes were detected as univalents (Physique 1a,c). In the mid zygotene, CDK2 foci were localized in the telomeric sites of the axial elements (Physique 1aCc). In only a few partially synapsed SC bivalents, CDK2 was localized to interstitial sites. In the mid pachytene, 20 autosomal bivalents and a sex bivalent LB-100 were created. CDK2 localized to both telomeric sites and interstitial sites along SCs (Physique 1dCf and Physique 2b,d,f). A short (Physique 1d,f) or longer (Physique 2aCd) synaptic region between X and Y chromosomes was detected. For the first time, we detected that centromeric regions of sex chromosomes were not co-oriented: A centromere in X was inside the synaptic site, but in the Y the centromere was at the pretelomeric end of the asynaptic axis. This important and unusual feature of male meiosis in rats was previously unknown. In the sex bivalent, a strong CDK2 signal appeared in the telomeric sites, and weaker dot-like foci were seen along asynaptic parts of the X (15.8 0.6 foci) and Y (1.42 0.17) (Physique 1fCf and Physique 2b,d,f, Physique S5). In the.