Mobility of Nuclear Components and Genome Functioning.

Cell nucleus is characterized by strong compartmentalization of structural components in its three-dimensional space. Certain genomic functions are accompanied by changes in the localization of chromatin loci and nuclear bodies. Here we review recent data on the mobility of nuclear components and the role of this mobility in genome functioning.

High-throughput analysis of TUNEL-stained sperm using image cytometry.

Sperm DNA integrity is an essential factor for successful fertilization and proper pregnancy progression. The terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) assay is commonly used for the estimation of the DNA fragmentation index. Analysis of TUNEL-stained sperm is often performed by flow cytometry, an approach that allows high-throughput analysis but in which any morphological information is lost. In this study, results of an automated image cytometry estimation of TUNEL-stained sperms were presented. The results of visual counting and automatic analysis were closely correlated, indicating that image cytometry is suitable for such analysis and may be applied in a clinical setting. © 2017 International Society for Advancement of Cytometry.

[Genetically Determined and Functional Human Sperm Motility Decrease].

Motility is the most important property of mammalian sperm required for fertilization. Axoneme and axoneme surrounding tail components are the morphological substrate of sperm motility. Quantitative research methods of human spermatozoa motility allowed the definition of the normative parameters for fertile men. Exogenous factors, and, rarely, genetic defects may cause a significant reduction in sperm motility. Axonemal anomalies (absence of external and/or internal dynein arms, central pair of microtubules absence) may be the cause of primary ciliary dyskinesia (PCD). PCD­a severe systemic disease of the reduction of sperm motility­is just one symptom. Dysplasia of the fibrous sheath (DFO) is also genetically determined sperm motility decrease. PCD and the DFO are multigene diseases that are inherited in an autosomal recessive manner. Modern molecular biological research methods are used to identify candidate genes. Assisted reproduction technologies (ART) allow men suffering from PCD and DFO to produce offspring. PCD and DFO symptoms appear in the homozygote. Children born after ART have the probability of being mutation carriers. We do not have complete information about etiological factor of genetically determined spermpathology. So we cannot assess the genetic risk degree. However, the possibility of mutations accumulation, which can be a risk factor for distant offspring, should be considered.

[Chromatin folding in human spermatozoa. I. Dynamics of chromatin remodelling in differentiating human spermatids].

Changes in chromatin structure at different stages of differentiation of human spermatids were studied. It was shown that, in nuclei of early spermatids, chromatin is loosely packed and its structural element is an 8-nm fiber. This "elementary" fiber is predominant at the initial stages of differentiation; in the course of maturation, it is replaced by globular elements approximately 60 nm in diameter. In intermediate spermatids, these globules start to condense into fibrillar aggregates and reduce their diameter to 30-40 nm. At all stages of spermatid maturation, except the final stages, these globules are convergence centers for elementary fibers. This remodelling process is vectored and directed from the apical (acrosomal) to the basal pole of the nucleus. In mature spermatids, the elementary 8-nm fibers are almost absent and the major components are 40-nm fibrillar aggregates. The nuclei of mature spermatids are structurally identical with the nuclei of spermatozoa with the so-called "immature chromatin," which are commonly found in a low proportion in sperm samples from healthy donors and may prevail over the normal cells in spermiogenetic disorders. The cause of this differentiation blockade remains unknown. Possibly, the formation of intermolecular bonds between protamines, which are required for the final stages of chromatin condensation, is blocked in a part of spermatids. The results of this study are discussed in comparison with the known models of nucleoprotamine chromatin organization in human spermatozoa.