The development of new biomarkers for human male infertility is crucial to improve the diagnosis and the prognosis of this disease. Recently, seminal microbiota was shown to be related to sperm quality parameters, suggesting an effect in human fertility and postulating it as a biomarker candidate. However, its relationship to sperm DNA integrity has not been studied yet. The aim of the present study is to characterize the seminal microbiota of a western Mediterranean population and to evaluate its relationship to sperm chromatin integrity parameters, and oxidative stress. For that purpose, 14 samples from sperm donors and 42 samples from infertile idiopathic patients were obtained and were analyzed to assess the composition of the microbiota through full-length 16S rRNA gene sequencing (Illumina MiSeq platform). Microbial diversity and relative abundances were compared to classic sperm quality parameters (macroscopic semen parameters, motility, morphology and concentration), chromatin integrity (global DNA damage, double-stranded DNA breaks and DNA protamination status) and oxidative stress levels (oxidation-reduction potential). The seminal microbiota observed of these samples belonged to the phyla Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes. The most abundant genera were Finegoldia, Peptoniphilus, Anaerococcus, Campylobacter, Streptococcus, Staphylococcus, Moraxella, Prevotella, Ezakiella, Corynebacterium and Lactobacillus. To our knowledge, this is the first detection of Ezakiella genus in seminal samples. Two clusters of microbial profiles were built based on a clustering analysis, and specific genera were found with different frequencies in relation to seminal quality defects. The abundances of several bacteria negatively correlate with the sperm global DNA fragmentation, most notably Moraxella, Brevundimonas and Flavobacterium. The latter two were also associated with higher sperm motility and Brevundimonas additionally with lower oxidative-reduction potential. Actinomycetaceae, Ralstonia and Paenibacillus correlated with reduced chromatin protamination status and increased double-stranded DNA fragmentation. These effects on DNA integrity coincide in many cases with the metabolism or enzymatic activities of these genera. Significant differences between fertile and infertile men were found in the relative presence of the Propionibacteriaceae family and the Cutibacterium, Rhodopseudomonas and Oligotropha genera, which supports its possible involvement in male fertility. Our findings sustain the hypothesis that the seminal microbiome has an effect on male fertility.

A sperm chromosome analysis of 24 men with normal or balanced karyotypes was carried out to study the frequency of sperm chromosome aneuploidy. A total of 3,446 human sperm complements (36–315 per donor) was analyzed after in vitro penetration of hamster eggs. Two sets of donors were studied at two different centers in the United States (center 1) and Spain (center 2). The frequencies of hyperhaploidy and hypohaploidy in control donors were similar between center 1 (1.9% vs. 7.7%) and center 2 (1.8% vs. 10.3%). In carrier donors there were no significant differences between the two centers in the frequency of hyperhaploidy (0.8 % vs. 1.9 %), but that of hypohaploidy was significantly higher in center 2 (11.0%) than in center 1 (4.6%). A significant excess of hypohaploid complements, as compared to hyperhaploid complements, was found in both centers in both control and carrier donors. The sex ratio was similar in both centers and did not differ significantly from a 1:1 sex ratio. The larger chromosomes in the complement (1, 2, 3, 4, 5, 7, and 10) presented a significantly lower frequency of hypohaploidy, while some of the smaller chromosomes (13, 19, and 21) showed a higher frequency of hypohaploidy than expected. Chromosome 21 and the sex chromosomes showed an increase in the percentage of hyperhaploidy, as compared to other chromosomes, that was close to statistical significance (P = 0.08). Our results reflect a preferential loss of small chromosomes during slide preparation and suggest that chromosome 21 and the sex chromosomes could be more frequently involved in aneuploidy.

The most common structural rearrangements of the Y chromosome result in the production of dicentrics. In this work, we analyze an abnormal Y chromosome, detected as a mosaic in an azoospermic male ascertained for infertility. FISH with seven different DNA probes specific for Y chromosome sequences (Y alpha-satellite, Y alpha-satellite III, non-alpha-satellite centromeric Y, SRY gene, subtelomeric Yp, subtelomeric Yq, and PNA-tel) and CGH analysis were performed. FISH results showed that the abnormal Y chromosome was a dicentric Yq isochromosome and that the breakpoint was distally in band Yp11.32. Lymphocyte chromosomes showed a mosaicism with 46,X,idicY(qter-->p11.32::p11.32-->qter) (51.7%), 46,XY (45.6%), and other cell lines (2.7%). In oral interphase cells, the mosaicism was 46,XidicY (62.8%), 46,XY (25.7%), 45,X (6.6%), and others (4.9%). The possible origin of this dicentric Yq isochromosome is discussed. Finally, we compare differences in mosaicism and phenotype among three reported cases with the breakpoint at Yp11.32

Translocation carriers have an increased risk of reproductive failure or affected offspring, because of the production of unbalanced gametes by meiotic segregation or the possible presence of interchromosomal effects (ICE). We therefore performed an analysis of meiotic segregation using the human-hamster IVF technique, and an aneuploidy assay for chromosomes 6, 18, 21, X and Y, using dual and triple-colour fluorescence in-situ hybridization, in two translocation carriers, t(1;13)(q41;q22) and t(3;19)(p21;p13.3). Sperm chromosome complements were analysed by whole chromosome painting. The frequencies observed for alternate, adjacent I, adjacent II and 3:1 segregations were, for t(1;13), 41.6, 41.6, 14.5 and 2.3% respectively, and for t(3;19), the frequencies were 39.1, 35.9, 21.8 and 3.2% respectively. More than 20,000 sperm per subject were analysed in the aneuploidy assay. Disomy 21 was found to be higher than other autosome disomies. Evidence for a possible ICE was found only in t(3;19). This study has shown that unbalanced sperm are more frequent than aneuploid sperm in the total sperm population. However, data in the literature suggest that the importance of each aberrant population seems to be more significant for embryo viability than would be expected from the increases in the percentages of abnormal sperm.

Using the human sperm–hamster oocyte fusion technique and whole chromosome painting, we studied sperm chromosome segregation in a male heterozygous for a complex chromosome rearrangement, 46,XY,–2,+der(2)t(2;11)(q13; q23),–11,+der(11)t(11;22)(q23;q11.2),–22,+der(22)t(2;22)(q13; q11.2). A total of 208 sperm complements were analyzed. The frequency of sperm carrying a normal or a balanced complement was 13.5% (9.62% and 3.85%, respectively). The frequency of unbalanced sperm was 86.5% (64.9% from 3:3 segregation, including 30 different types; 20.7% from 4:2 segregation, including 21 different types; and 0.96% from 5:1 segregation, including 2 different types). The sex ratio, determined in 134 sperm complements, did not differ from the expected 1:1 ratio. The results obtained in this study are compatible with the formation, during the synaptic process, of a complex hexavalent figure involving chromosomes 2, 11, and 22. The behavior and segregation of this complex figure would explain the high frequency (86.5%) of unbalanced complements observed in this carrier.