Fis1 ablation in the male germline disrupts mitochondrial morphology and mitophagy, and arrests spermatid maturation

Male germline development involves choreographed changes to mitochondrial number, morphology, and organization. Mitochondrial reorganization during spermatogenesis was recently shown to require mitochondrial fusion and fission. Mitophagy, the autophagic degradation of mitochondria, is another mechanism for controlling mitochondrial number and physiology, but its role during spermatogenesis is largely unknown. During post-meiotic spermatid development, restructuring of the mitochondrial network results in packing of mitochondria into a tight array in the sperm midpiece to fuel motility. Here, we show that disruption of mouse Fis1 in the male germline results in early spermatid arrest that is associated with increased mitochondrial content. Mutant spermatids coalesce into multinucleated giant cells (GCs) that accumulate mitochondria of aberrant ultrastructure and numerous mitophagic and autophagic intermediates, suggesting a defect in mitophagy. We conclude that Fis1 regulates mitochondrial morphology and turnover to promote spermatid maturation.

Age Dependency of Spermatogenesis Efficiency in Cats

The purpose of this study is to study the efficiency of spermatogenesis in old and young cats in various seasons of the yearMaterial and methods. The material has been collected from 16 cats of different ages in winter and summer periods in Voronezh veterinary clinics while animals being sterilized. The testicles were fixed in Shtiva’s liquid and Buen’s liquid. The material was poured into paraffin and a series of paraffin sections 4–5 μm thick were prepared. Sections were stained with hematoxylin and eosin, iron hematoxylin, Heidengain azane, trichrome-PAS reaction and tetrachrome-PAS reaction. By means of a helical eyepiece-micrometer, the diameter of the testicles tubules and the epididymis (50 measurements for each animal) were measured. To determine the effectiveness of spermatogenesis at an increase in 900 times, the number of first-order spermatocytes in the zigotene and pachitene stage, early spermatid (50 canals for each animal) was estimated. The normality of the distribution was determined using the Kolmogorov–Smirnov test and the Lilliefors adjustment. The measurement results were processed using the nonparametric Mann–Whitney U-criteria. Changes at Р<0.05 were considered statistically significant.Results. The maximum diameter of the testicular tubules and the canal of the epididymis was found in animals at two years of age. These parameters in cats at the age of 8 years are reduced by 29.2%, and by17.0%, respectively. Comparing the number of dying cells in old and young animals, it can be noted that in cats at the age of 8 years the number of dying spermatids increases, while spermatogenesis efficiency decrease is statistically significant (by 19.1%).

Spermatoproteasome-deficient mice are proficient in meiotic DNA repair but defective in meiotic exit

Meiotic recombination generates crossovers which are essential to ensure genome haploidization. The ubiquitin proteasome system regulates meiotic recombination through its association to the synaptonemal complex, a ‘zipper’-like structure that holds homologs and provides the structural framework for meiotic recombination. Here we show that the testis-specific α4s subunit (PSMA8) of the spermatoproteasome is located at the synaptonemal complex and is essential for the assembly of its activator PA200. Accordingly, synapsis-deficient mice show delocalization of PSMA8 from the synaptonemal complex. Genetic analysis of Psma8-deficient mice shows normal meiotic DNA repair, crossing over formation and an increase of spermatocytes at metaphase I and metaphase II which either enter into apoptosis or slip to give rise to an early spermatid arrest and infertility. Thus, spermatoproteasome-dependent histone degradation is dispensable for meiotic recombination. We show that PSMA8 deficiency alters the proteostasis of several key meiotic players such as acetylated histones, SYCP3, SYCP1, CDK1 and TRIP13 which in turn leads to an aberrant meiotic exit and early spermatid arrest prior to the histone displacement process that take place subsequently.

Relationship between chromosome content and nuclear diameter in early spermatids of Drosophila melanogaster

SummaryWe have studied, using light microscopy, the relationship between chromosome content and nuclear diameter in early spermatids of males carrying different combinations of wild-type and compound chromosomes in Drosophila melanogaster. By using these genotypes we have been able to observe spermatid nuclei bearing various numbers of chromosomes ranging from only one sex chromosome and no major autosomes to almost twice the normal chromosome complement. We have found that variations in the chromosome content are accompanied by increasing the variance in early spermatid nuclear diameter; the more gametic classes produced, the higher the variance of nuclear diameters. These results indicate that measuring nuclear diameters in early spermatids represents a useful way to estimate the levels of meiotic non-disjunction and thereby to improve the characterization of lethal or male sterile mutants in which analysis of meiotic chrosome non-disjunction cannot be achieved by conventional genetic methods.

Pattern of nucleolar organizer region activity during male meiosis in Callicrania seoanei (Orthoptera) as analyzed by silver staining: evidences for a possible reactivation in the period between the two meiotic divisions

Silver staining of spermatocytes and early spermatid nuclei from the neo XY race of the Tettigonioid species Callicrania seoanei reveals an active nucleolar organizer region (NOR) located proximally in a medium-sized bivalent. Ag-positive material was present at the NOR in all stages of male meiosis. However, the results obtained indicate that transcriptional activity of ribosomal cistrons (rDNA) is not maintained throughout spermatogenesis, but that NOR reactivation might occur in the period between the two meiotic divisions in addition to the more general postmeiotical reactivation in the early spermatid nuclei. Key words: NOR activity, silver staining, male meiosis, Callicrania seoanei (Orthoptera).

The Genital System of Temnocephala. I. Ultrastructural Features of the Differentiating Spermatid of Temnocephala Novaezealandiae, Including Notes on a Possible Correlation Between Cellular Autophagy and Mitochondrial Function.

The early spermatid of I: novaezealandiae possesses two centrioles, between which lies a transient lamellar body. The centrioles form the basal bodies of two flagella of the '9+1' type, which remain free throughout spermatogenesis. Following cell elongation and organelle migration, the advanced spermatid is composed of a proximal cytoplasmic mass, a greatly attenuated nuclear region, an elongated mid-piece, an end piece, and the subterminally inserted flagella. There is no acrosome. Rows of glycogen granules occur in the spermatid shaft. Extrusion of nuclear components probably contributes to the modelling and compaction of the nucleus. The mitochondria of the cytoplasmic mass possess indentations filled with membrane whorls; it is proposed that the membrane accumulates in cellular autophagy. Mitochondria in the spermatid shaft are also indented; perhaps autophagic vesicles occupying the invaginations are related to glycogen metabolism. Modified membranes lining the indentations may be sites for the entry of lytic products into the mitochondria. Knowledge of the sperm morphology of Temnocephala assists in the determination of the taxonomic position of the genus.

CYTOGENETIC ANALYSIS OF HOMOZYGOUS SEGREGATION DISTORTER MALES OF DROSOPHILA MELANOGASTER

Certain homozygous SD males are nearly sterile. Sterility is not due to aneuploid gametes — no significant second chromosome nondisjunction was found in matings to attached-2 and mei-S332 females. Some fourth chromosome aneuploidy was observed here, and in the cytological work. Otherwise, cytology of the meiotic divisions was essentially normal. Early spermatid bundles are normal, sperm head counts approximating the normal 64. In the later, coiled bundle stage, one observes less than 30 heads, many of which are grossly abnormal: twisted, club-like, or globular. In double mating experiments, SD/SD sperm did not displace normal sperm introduced first. In the reverse experiment, sperm (or fluid) from SD/SD males markedly reduced capacity of the females to store and utilize sperm from normal males, as scored from progeny and by counts of stored sperm. No sperm were seen in the storage organs of females imseminated first by SD/SD males, then by normal males. Many females refuse such a second mating. Our observations are quantitatively different from those with heterozygous SD males, but qualitatively similar, supporting the view that the near sterility of homozygous SD males arises from a mechanism of sperm dysfunction like that in SD/+ males.

Mutagenicity of DDT in Mice, Drosophila melanogaster and Neurospora crassa

The pesticide DDT was examined for possible mutagenicity in mice, D. melanogaster and N. crassa. Through the use of the dominant-lethal assay it was found that acute oral doses of DDT (2 x 150 mg/kg body weight) in male mice induced dominant lethal mutations in early spermatid and spermato-cyte stages. Chronic oral doses of DDT (2 x 100 mg/kg body weight per week for 10 weeks) in male mice caused a persistent increase in the number of dominant lethal mutations. Histological sections showed that chronic treatment of mice with DDT caused changes in seminiferous tubule morphology and degeneration of B-type spermatogonia. Acute treatment of mice with DDT caused an increase in spermatocyte chromosome breakage, stickiness and precocious separation of the X and Y bivalent.