Genome functioning in hybrids faces inconsistency. This mismatch is manifested clearly in meiosis during chromosome synapsis and recombination. Species with chromosomal variability can be a model for exploring genomic battles with high visibility due to the use of advanced immunocytochemical methods. We studied synaptonemal complexes (SC) and prophase I processes in 44-chromosome intraspecific (Ellobius tancrei × E. tancrei) and interspecific (Ellobius talpinus × E. tancrei) hybrid mole voles heterozygous for 10 Robertsonian translocations. The same pachytene failures were found for both types of hybrids. In the intraspecific hybrid, the chains were visible in the pachytene stage, then 10 closed SC trivalents formed in the late pachytene and diplotene stage. In the interspecific hybrid, as a rule, SC trivalents composed the SC chains and rarely could form closed configurations. Metacentrics involved with SC trivalents had stretched centromeres in interspecific hybrids. Linkage between neighboring SC trivalents was maintained by stretched centromeric regions of acrocentrics. This centromeric plasticity in structure and dynamics of SC trivalents was found for the first time. We assume that stretched centromeres were a marker of altered nuclear architecture in heterozygotes due to differences in the ancestral chromosomal territories of the parental species. Restructuring of the intranuclear organization and meiotic disturbances can contribute to the sterility of interspecific hybrids, and lead to the reproductive isolation of studied species.

Introduction. Metabolic syndrome (MS) can cause impaired spermatogenesis and a decrease in sperm counts. However, the details of the effect of MS on developing spermatogenic cells remain unclear. Difficulties in solving this problem, the inconsistency of published clinical data, indicate the advisability of using experimental models to solve this urgent problem of andrology and reproductology.The study objective is to describe to investigate the specifics of the course of meiotic prophase I and the activity of the processes of phagocytosis and autophagy in Sertoli cells of rats with experimentally induced MS and in the course of therapeutic and prophylactic procedures during the development of experimental MS.Materials and methods. The animals were divided into three groups, each of which included four sexually mature male rats: 1st group – males fed a standard diet; 2nd group – males receiving a diet high in fat and fructose for 60 days; 3rd group – males with MS receiving sulphate mineral waters therapy, low-intensity ultrahigh frequency electromagnetic radiation therapy. Testicular cells were examined using light and transmission electron microscopy. For the first time in animals with MS, an immunocytochemical study of the peculiarities of chromosome synapsis in prophase I of meiosis was carried out on the basis of analysis of spread synaptonemal complexes of meiotic chromosomes and immunocytochemical analysis of Sertoli cells and spermatogenic cells in squashed preparations of seminiferous tubules. The parametric Student’s t-test and the nonparametric Mann–Whitney U-test were used for statistical data processing.Results. As a result of a histological study of the structure of the seminiferous tubules of animals of three groups, a statistically significant decrease in the indices of the spermatogenesis index in 2nd and 3rd groups compared to the control was revealed. Immunomorphologically, in the spread nuclei of primary spermatocytes of rats of the 2nd and 3rd groups, violations of the architectonics of nuclei, the formation of synaptonemal complexes fragments and circular synaptonemal complexes, numerous atypical inclusions were found. Signs of pachytene arrest were found in 40–50 % of spermatocyte nuclei. In the study of squashed cells preparations of the seminiferous tubules of rats of the 2nd and 3rd groups, signs of phagocytosed synaptonemal complexes were found in the cytoplasm of Sertoli cells, which were confirmed using antibodies to the SCP3 protein. Thus, evidence for the phagocytosis of degenerating primary spermatocytes by Sertoli cells has been obtained. In Sertoli cells, spermatocytes and spermatids, many autophagosomes are found, using LC3B protein marker. The presence of autophagosomes in Sertoli cells and spermatogenic cells in animals of these two groups was also confirmed by electron microscopy. In male rats of the 2nd group, significant disturbances in the structure of the pachytene nuclei were revealed. In the cytoplasm of Sertoli cells and spermatids of rats of the 2nd group, lipid droplets, numerous phagolysosomes containing cell detritus were revealed. Structural damage and phagocytosis of mitochondria were found in Sertoli cells and spermatocytes. Аutophagy in Sertoli cells were most distinctive in animals of the 3rd group.Conclusion. In male rats with experimental MS, significant disturbances in the structure of the nuclei of meiotic cells, a high content of primary spermatocytes with signs of pachytene arrest were revealed. The results obtained are in good agreement with the data of other authors, who revealed a decrease in the number of spermatozoa in the epididymis of rats and mice when modeling MS. It is assumed that the activation of autophagy is an important factor in supporting the viability of Sertoli cells and supporting the viability of germ cells in stressful situations, including MS. Apparently, autophagy is an adaptive mechanism that removes the remnants of apoptotic spermatogenic cells that are selected as a result of MS development.

Цель исследования-выявить взаимосвязь аномалий мейоза и изменений ультраструктуры базальной мембраны (БМ) семенных канальцев у пациентов при выраженном нарушении сперматогенеза-азооспермии или тяжелой форме олигозооспермии.

Genome functioning in hybrids faces inconsistency. This mismatch is manifested clearly in meiosis during chromosome synapsis and recombination. Species with chromosomal variability can be a model for exploring genomic battles with high visibility due to the use of advanced immunocytochemical methods. We studied synaptonemal complexes (SC) and prophase I processes in 44-chromosome intraspecific (Ellobius tancrei × E. tancrei) and interspecific (Ellobius talpinus × E. tancrei) hybrid mole voles heterozygous for 10 Robertsonian translocations. The same pachytene failures were found for both types of hybrids. In the intraspecific hybrid, the chains were visible in the pachytene stage, then 10 closed SC trivalents formed in the late pachytene and diplotene stage. In the interspecific hybrid, as a rule, SC trivalents composed the SC chains and rarely could form closed configurations. Metacentrics involved with SC trivalents had stretched centromeres in interspecific hybrids. Linkage between neighboring SC trivalents was maintained by stretched centromeric regions of acrocentrics. This centromeric plasticity in structure and dynamics of SC trivalents was found for the first time. We assume that stretched centromeres were a marker of altered nuclear architecture in heterozygotes due to differences in the ancestral chromosomal territories of the parental species. Restructuring of the intranuclear organization and meiotic disturbances can contribute to the sterility of interspecific hybrids, and lead to the reproductive isolation of studied species.Author summaryMeiosis is essential for sexual reproduction to produce haploid gametes. Prophase I represents a crucial meiotic stage because key processes such as chromosomal pairing, synapsis and desynapsis, recombination, and transcriptional silencing occur at this time. Alterations in each of these processes can activate meiotic checkpoints and lead to the elimination of meiocytes. Here we have shown that two groups of experimental hybrids, intraspecific and interspecific—which were heterozygous for 10 identical Robertsonian translocations—had pachytene irregularities and reduced recombination. However, intraspecific and interspecific hybrids exhibited different patterns of synaptonemal complex (SC) trivalent behavior. In the former, open SC trivalents comprised SC chains due to heterosynapsis of short arms of acrocentrics in early and mid-pachytene and were then able to form 2–4 and even 7 and 10 closed SC trivalents in the late pachytene and diplotene stages. In the second mole voles, SC trivalents had stretched centromeres of the metacentrics, and chains of SC trivalents were formed due to stretched centromeres of acrocentrics. Such compounds could not lead to the formation of separate closed SC trivalents. The distant ancestral points of chromosome attachment with a nuclear envelope in the heterozygous nuclei probably lead to stretching of SC trivalents and their centromeric regions, which can be regarded as an indicator of the reorganization of the intranuclear chromatin landscape. These abnormalities, which were revealed in in prophase I, contribute to a decrease the fertility of intraspecific mole voles and promote the sterility of interspecific mole voles.