Unraveling the Intricacies of the Seminal Microbiome and Its Impact on Human Fertility.

Although the microbial communities from seminal fluid were an unexplored field some decades ago, their characteristics and potential roles are gradually coming to light. Therefore, a complex and specific microbiome population with commensal niches and fluctuating species has started to be revealed. In fact, certain clusters of bacteria have been associated with fertility and health, while the outgrowth of several species is potentially correlated with infertility indicators.

The courtship choreography of homologous chromosomes: timing and mechanisms of DSB-independent pairing.

Meiosis involves deep changes in the spatial organisation and interactions of chromosomes enabling the two primary functions of this process: increasing genetic diversity and reducing ploidy level. These two functions are ensured by crucial events such as homologous chromosomal pairing, synapsis, recombination and segregation. In most sexually reproducing eukaryotes, homologous chromosome pairing depends on a set of mechanisms, some of them associated with the repair of DNA double-strand breaks (DSBs) induced at the onset of prophase I, and others that operate before DSBs formation.

Time to match; when do homologous chromosomes become closer?

In most eukaryotes, pairing of homologous chromosomes is an essential feature of meiosis that ensures homologous recombination and segregation. However, when the pairing process begins, it is still under investigation. Contrasting data exists in Mus musculus, since both leptotene DSB-dependent and preleptotene DSB-independent mechanisms have been described.

Chromosomal positioning in spermatogenic cells is influenced by chromosomal factors associated with gene activity, bouquet formation and meiotic sex chromosome inactivation.

Chromosome territoriality is not random along the cell cycle and it is mainly governed by intrinsic chromosome factors and gene expression patterns. Conversely, very few studies have explored the factors that determine chromosome territoriality and its influencing factors during meiosis. In this study, we analysed chromosome positioning in murine spermatogenic cells using three-dimensionally fluorescence in situ hybridization-based methodology, which allows the analysis of the entire karyotype.

The impact of chromosomal fusions on 3D genome folding and recombination in the germ line.

The spatial folding of chromosomes inside the nucleus has regulatory effects on gene expression, yet the impact of genome reshuffling on this organization remains unclear. Here, we take advantage of chromosome conformation capture in combination with single-nucleotide polymorphism (SNP) genotyping and analysis of crossover events to study how the higher-order chromatin organization and recombination landscapes are affected by chromosomal fusions in the mammalian germ line. We demonstrate that chromosomal fusions alter the nuclear architecture during meiosis, including an increased rate of heterologous interactions in primary spermatocytes, and alterations in both chromosome synapsis and axis length.

The RNA content of human sperm reflects prior events in spermatogenesis and potential post-fertilization effects.

Transcriptome analyses using high-throughput methodologies allow a deeper understanding of biological functions in different cell types/tissues. The present study provides an RNA-seq profiling of human sperm mRNAs and lncRNAs (messenger and long non-coding RNAs) in a well-characterized population of fertile individuals. Sperm RNA was extracted from twelve ejaculate samples under strict quality controls.

Sperm microRNA pairs: new perspectives in the search for male fertility biomarkers.

Objective: To identify candidates of fertility biomarkers among pairs of human sperm microRNAs.

Design: Expression data of 736 sperm microRNAs from fertile and infertile individuals characterized in previous published studies by means of TaqMan quantitative polymerase chain reaction (PCR) were reexamined. A set of microRNA pairs with the best biomarker potential were selected and validated by means of quantitative real-time (qRT) PCR in an independent cohort.

The use of fluorescence in situ hybridization analysis on sperm: indications to perform and assisted reproduction technology outcomes.

Purpose: To determine the consequences of an altered sperm fluorescence in situ hybridization (FISH) result for ART outcomes and the indications for a sperm FISH analysis.

Methods: Data from 439 infertile men were collected. Bivariate analyses were performed to determine the association of men's age, seminal alterations, and sperm FISH indication, with the incidence of X, Y, 13, 18, and 21 sperm chromosomal abnormalities.

Chromosome positioning and male infertility: it comes with the territory.

The production of functional spermatozoa through spermatogenesis requires a spatially and temporally highly regulated gene expression pattern, which in case of alterations, leads to male infertility. Changes of gene expression by chromosome anomalies, gene variants, and epigenetic alterations have been described as the main genetic causes of male infertility. Recent molecular and cytogenetic approaches have revealed that higher order chromosome positioning is essential for basic genome functions, including gene expression.

Altered bivalent positioning in metaphase I human spermatocytes from Robertsonian translocation carriers.

Purpose: The study aims to determine whether there is an altered bivalent positioning in metaphase I human spermatocytes from Robertsonian translocation carriers.

Methods: Metaphase I human spermatocytes from three 45,XY,der(13;14)(q10;q10) individuals and a 45,XY,der(14;15)(q10;q10) individual were analyzed. Proximity relationships of bivalents were established by analyzing meiotic preparations combining Leishman staining and multiplex-FISH procedures.

Apoptosis mediated by phosphatidylserine externalization in the elimination of aneuploid germ cells during human spermatogenesis.

It has been described that aneuploidies trigger cell cycle checkpoints leading to apoptosis. The aim of this study was to assess the relationship between the presence of chromosomal abnormalities and apoptosis in germ cells and in Sertoli cells. Fourteen diagnostic testicular biopsies from infertile patients were processed following a sequential methodology, which included enzymatic disaggregation, apoptotic staining, cell sorting, cell fixation, and fluorescent in situ hybridization analysis.

Meiotic abnormalities in metaphase I human spermatocytes from infertile males: frequencies, chromosomes involved, and the relationships with polymorphic karyotype and seminal parameters.

The aim of this study was to look in depth at the relationship between meiotic anomalies and male infertility, such as the determination of the chromosomes involved or the correlation with patient features. For this purpose, a total of 31 testicular tissue samples from individuals consulting for fertility problems were analyzed. Metaphase I cells were evaluated using a sequential methodology combining Leishman stained procedures and multiplex fluorescence in situ hybridization protocols.

Chromosome size, morphology, and gene density determine bivalent positioning in metaphase I human spermatocytes.

Objective: To determine whether there is a preferential bivalent distribution pattern in metaphase I human spermatocytes and to analyze whether this positioning is influenced by chiasmata count, chromosome size, gene density, acrocentric morphology, and heterochromatic blocks.

Design: Proximity frequencies of bivalents were evaluated with the analysis of meiotic preparations combining sequentially standard techniques and multiplex fluorescence in situ hybridization.

Setting: University.

A sequential methodology that allows apoptotic cell sorting and FISH analysis in human testicular cells.

The objective of this study was to develop a methodology that permits the detection and separation of apoptotic cells in human testicular tissue and their subsequent cytogenetic analysis by fluorescence in situ hybridization (FISH). The sequential methodology consisted of five steps: 1) enzymatic disaggregation of testicular tissue, 2) specific staining of apoptotic cells, 3) cell sorting by flow cytometry, 4) cell fixation, and 5) FISH. Enzymatic disaggregation yielded cell counts that ranged from 1.

Acrocentric bivalents positioned preferentially nearby to the XY pair in metaphase I human spermatocytes.

Objective: To analyze whether the preferential proximity between acrocentric bivalents and the XY pair described at pachytene was maintained in metaphase I human spermatocytes.

Design: Proximity frequencies of autosomic bivalents to the sex bivalent were evaluated with the analysis of meiotic preparations combining sequentially standard techniques and multiplex fluorescence in situ hybridization.

Setting: Assisted reproduction centers.

Hidden mosaicism in patients with Klinefelter's syndrome: implications for genetic reproductive counselling.

Background: Most individuals with Klinefelter's syndrome (KS) are azoospermic but residual foci of spermatogenesis have been observed in some patients. However, no consistent predictive factors for testicular sperm extraction success have been established and mosaicism could be a factor to investigate. In this study, we have assessed the degree of mosaicism in somatic and germinal tissues in KS, the meiotic competence of 47,XXY germ cells and the aneuploidy rate of post-reductional cells.

Fluorescence in situ hybridization (FISH) protocol in human sperm.

Aneuploidies are the most frequent chromosomal abnormalities in humans. Most of these abnormalities result from meiotic errors during the gametogenic process in the parents. In human males, these errors can lead to the production of spermatozoa with numerical chromosome abnormalities which represent an increased risk of transmitting these anomalies to the offspring.

Role of sperm fluorescent in situ hybridization studies in infertile patients: indications, study approach, and clinical relevance.

Objective: To determine the group of infertile patients that would benefit from sperm fluorescent in situ hybridization (FISH) analysis, the number of chromosomes to be analyzed, and the diagnostic interpretation of the results obtained.

Design: A retrospective study of sperm FISH analyses.

Setting: Universitat Autònoma de Barcelona.

FISH on sperm: spot-counting to stop counting? Not yet.

Objective: To evaluate the reliability and applicability of the spot-counting system (Cytovision Spot AX workstation) which offers an alternative to the tedious manual analysis of sperm fluorescence in situ hybridization (FISH).

Design: Manual and automatic analyses were performed and compared.

Setting: Universitat Autònoma de Barcelona.

Meiotic abnormalities in infertile males.

Meiotic anomalies, as reviewed here, are synaptic chromosome abnormalities, limited to germ cells that cannot be detected through the study of the karyotype. Although the importance of synaptic errors has been underestimated for many years, their presence is related to many cases of human male infertility. Synaptic anomalies can be studied by immunostaining of synaptonemal complexes (SCs), but in this case their frequency is probably underestimated due to the phenomenon of synaptic adjustment.

FISH studies of chromosome abnormalities in germ cells and its relevance in reproductive counseling.

Chromosome abnormalities are one of the major causes of human infertility. In infertile males, abnormal karyotypes are more frequent than in the general population. Furthermore, meiotic disorders affecting the germ cell-line have been observed in men with normal somatic karyotypes consulting for infertility.

Identification of meiotic anomalies with multiplex fluorescence in situ hybridization: Preliminary results.

Objective: To characterize meiotic anomalies in infertile men by multiplex fluorescence in situ hybridization (M-FISH) and to determine whether synaptic problems affect specific bivalents or whether anomalies are random.

Design: Analysis of meiotic preparations with standard techniques and M-FISH.

Setting: Assisted reproduction centers and Universitat Autònoma de Barcelona.