Evaluation of bovine sperm telomere length and association with semen quality

Resveratrol intake by males increased the mitochondrial DNA copy number and telomere length of blastocysts derived from aged mice

The present study examined whether male resveratrol intake affected mitochondrial DNA copy number (mt-cn) and telomere length (TL) in blastocysts fathered by young and aged male mice. C57BL/6N male mice supplied with water or water containing 0.1 mM resveratrol were used for embryo production at 14-23 and 48-58 weeks of age. Two-cell-stage embryos were collected from the oviducts of superovulated female mice (8-15 weeks old) and cultured for 3 days until the blastocyst stage. Mt-cn and TL levels were measured by real-time polymerase chain reaction. Resveratrol intake did not affect body weight or water consumption. Resveratrol intake increased the expression levels of SIRT1 in the liver, the antioxidative ability of serum, and extended TL in the heart, whereas there was no significant difference in mt-cn in the heart or TL in sperm. The rate of blastocyst development was significantly lower in aged male mice than in younger mice, and resveratrol intake increased the total number of blastocysts derived from both young and aged males. Resveratrol intake did not affect mt-cn or TL in blastomeres of blastocyst-stage embryos derived from young mice, but significantly increased both mt-cn and TL in blastomeres of blastocysts derived from aged fathers. In conclusion, resveratrol intake increased mt-cn and TL levels in blastocysts derived from aged male mice.

A genomic biomarker for the rapid identification of the rob(1;29) translocation in beef cattle breeds

Robertsonian translocations, specifically rob(1;29) translocation, have reportedly been the most prevalent chromosomal abnormalities in cattle, affecting various breeds and leading to a decrease in fertility and reproductive value. Currently, the identification of rob(1;29) carriers relies on cytogenetic analysis that has limitations in terms of accessibility, cost, and sample requirements. To address these limitations, a novel genomic biomarker was developed in this study for the rapid and precise identification of rob(1;29) carriers. Using q-PCR, a specific copy number variation associated with translocation was targeted, which effectively distinguished between wild-type, homozygous and heterozygous carriers. Crucially, the biomarker can be applied to DNA extracted from various biological matrices, such as semen, embryos, oocytes, milk, saliva, coat, and muscle, and it is compatible with fresh, refrigerated, or frozen samples. Furthermore, this approach offers significant reductions in cost compared to those associated with traditional cytogenetic analysis and provides results within a short turnaround time. The successful development of this genomic biomarker has considerable potential for widespread adoption in screening programs. It facilitates timely identification and management of rob(1;29) carriers while mitigating economic losses and preserving genetic integrity in bovine populations.

Telomere Dynamics in Livestock

Telomeres are repeated sequences of nucleotides at the end of chromosomes. They deteriorate across mitotic divisions of a cell. In Homo sapiens this process of lifetime reduction has been shown to correspond with aspects of organismal aging and exposure to stress or other insults. The early impetus to characterize telomere dynamics in livestock related to the concern that aged donor DNA would result in earlier cell senescence and overall aging in cloned animals. Telomere length investigations in dairy cows included breed effects, estimates of additive genetic control (heritability 0.12 to 0.46), and effects of external stressors on telomere degradation across animal life. Evaluation of telomeres with respect to aging has also been conducted in pigs and horses, and there are fewer reports of telomere biology in beef cattle, sheep, and goats. There were minimal associations of telomere length with animal productivity measures. Most, but not all, work in livestock has documented an inverse relationship between peripheral blood cell telomere length and age; that is, a longer telomere length was associated with younger age. Because livestock longevity affects productivity and profitability, the role of tissue-specific telomere attrition in aging may present alternative improvement strategies for genetic improvement while also providing translational biomedical knowledge.

A Multibreed Genome-Wide Association Study for Cattle Leukocyte Telomere Length

Telomeres are terminal DNA regions of chromosomes that prevent chromosomal fusion and degradation during cell division. In cattle, leukocyte telomere length (LTL) is associated with longevity, productive lifespan, and disease susceptibility. However, the genetic basis of LTL in this species is less studied than in humans. In this study, we utilized the whole-genome resequencing data of 239 animals from 17 cattle breeds for computational leukocyte telomere length estimation and subsequent genome-wide association study of LTL. As a result, we identified 42 significant SNPs, of which eight were found in seven genes (EXOC6B, PTPRD, RPS6KC1, NSL1, AGBL1, ENSBTAG00000052188, and GPC1) when using covariates for two major breed groups (Turano-Mongolian and European). Association analysis with covariates for breed effect detected 63 SNPs, including 13 in five genes (EXOC6B, PTPRD, RPS6KC1, ENSBTAG00000040318, and NELL1). The PTPRD gene, demonstrating the top signal in analysis with breed effect, was previously associated with leukocyte telomere length in cattle and likely is involved in the mechanism of alternative lengthening of telomeres. The single nucleotide variants found could be tested for marker-assisted selection to improve telomere-length-associated traits.

Molecular Cytogenetics in Domestic Bovids: A Review

The discovery of the Robertsonian translocation (rob) involving cattle chromosomes 1 and 29 and the demonstration of its deleterious effects on fertility focused the interest of many scientific groups on using chromosome banding techniques to reveal chromosome abnormalities and verify their effects on fertility in domestic animals. At the same time, comparative banding studies among various species of domestic or wild animals were found useful for delineating chromosome evolution among species. The advent of molecular cytogenetics, particularly the use of fluorescence in situ hybridization (FISH), has allowed a deeper investigation of the chromosomes of domestic animals through: (a) the physical mapping of specific DNA sequences on chromosome regions; (b) the use of specific chromosome markers for the identification of the chromosomes or chromosome regions involved in chromosome abnormalities, especially when poor banding patterns are produced; (c) better anchoring of radiation hybrid and genetic maps to specific chromosome regions; (d) better comparisons of related and unrelated species by comparative FISH mapping and/or Zoo-FISH techniques; (e) the study of meiotic segregation, especially by sperm-FISH, in some chromosome abnormalities; (f) better demonstration of conserved or lost DNA sequences in chromosome abnormalities; (g) the use of informatic and genomic reconstructions, in addition to CGH arrays, to predict conserved or lost chromosome regions in related species; and (h) the study of some chromosome abnormalities and genomic stability using PCR applications. This review summarizes the most important applications of molecular cytogenetics in domestic bovids, with an emphasis on FISH mapping applications.

Characterization of telomere length in Agerolese cattle breed, correlating blood and milk samples

Studies into telomere length in cattle are relatively recent and have focused mainly on the Holstein Friesian cattle breed, making it arduous to evaluate the correlation with ageing due to the early age of culling in this breed. Telomere length provides information about the productive lifespan and the quality of farm management, complying with the ‘One Health’ approach. This study evaluated telomere length in Agerolese cattle, an autochthonous dairy breed characterized by a long productive lifespan (13 years). Multiplex quantitative PCR estimated telomere length in DNA extracted from blood and milk matrices. Interestingly, the results showed longer telomeres in Agerolese (compared to the Holstein Friesian cattle control group), with a negative correlation between telomere length and increasing age and a synchronous trend between blood and milk samples, with a positive correlation between them.

Telomere Length in Pig Sperm Is Related to In Vitro Embryo Development Outcomes

Simple Summary

Understanding how gamete chromatin influences fertilization is highly important not only to improve animal production, but also to develop new biomarkers helping in the selection of those animals with higher fertility potential. In this regard, sperm telomere length has been pointed out as a putative biomarker in human infertility, but no studies have been conducted into its influence in pig fertility. Here, we determined that sperm telomere length is independent from the conventional sperm quality parameters and, through the production of in vitro embryos, we showed that it is indicative of the percentage of morulae and blastocysts, thus becoming useful to be used as biomarker in this species.

Abstract

Telomere length has attracted much interest as a topic of study in human reproduction; furthermore, the link between sperm telomere length and fertility outcomes has been investigated in other species. This biomarker, however, has not been much explored in other animals, such as pigs, and whether it is related to sperm quality and fertility outcomes remains unknown. The present work aimed to determine the absolute value of telomere length in pig sperm, as well as its relationship to sperm quality parameters and embryo development. Telomere length was determined through quantitative fluorescence in situ hybridization (qFISH) in 23 pig sperm samples and data were correlated to quality parameters (motility, morphology, and viability) and in vitro fertilization outcomes. We found that the mean telomere length in pig sperm was 22.1 ± 3.6 kb, which is longer than that previously described in humans. Whilst telomere length was not observed to be correlated to sperm quality variables (p > 0.05), a significant correlation between telomere length and the percentage of morulae 6 days after in vitro fertilization was observed (r_s = 0.559; 95% C.I. = (−0.007 to 0.854); p = 0.047). Interestingly, this correlation was not found when percentages of early blastocysts/blastocysts (r_s = 0.410; 95% C.I. = (−0.200 to 0.791); p = 0.164) and of hatching/hatched blastocysts (r_s = 0.356; 95% C.I. = (− 0.260 to 0.766); p = 0.233) were considered. Through the separation of the samples into two groups by the median value, statistically significant differences between samples with shorter telomeres than the median and samples with longer telomeres than the median were found regarding development to morula (11.5 ± 3.6 vs. 21.8 ± 6.9, respectively) and to early blastocyst/blastocysts (7.6 ± 1.4 vs. 17.9 ± 12.2, respectively) (p < 0.05). In the light of these results, sperm telomere length may be a useful biomarker for embryo development in pigs, as sperm with longer telomeres lead to higher rates of morulae and blastocysts.

Insights into the Role of Telomeres in Human Embryological Parameters. Opinions Regarding IVF

Telomeres promote genome integrity by protecting chromosome ends from the activation of the DNA damage response and protecting chromosomes from the loss of coding sequences due to the end replication problem. Telomere length (TL) is progressively shortened as age progresses, thus resulting in cellular senescence. Therefore, TL is in strong adverse linear correlation with aging. Mounting evidence supports the notion that telomeres and male/female infertility are in a close relationship, posing the biology of telomeres as a hot topic in the era of human-assisted reproduction. Specifically, the length of sperm telomeres is gradually increasing as men get older, while the telomere length of the oocytes seems not to follow similar patterns with that of sperm. Nonetheless, the telomere length of the embryos during the cleavage stages seems to have a paternal origin, but the telomere length can be further extended by telomerase activity during the blastocyst stage. The latter has been proposed as a new molecular biomarker with strong predictive value regarding male infertility. As far as the role of telomeres in assisted reproduction, the data is limited but the length of telomeres in both gametes seems to be affected mainly by the cause of infertility rather than the assisted reproductive therapy (ART) procedure itself. The present review aims to shed more light into the role of telomeres in human embryological parameters, including gametes and embryos and also presents opinions regarding the association between telomeres and in vitro fertilization (IVF).

Sperm Nuclei Analysis and Nuclear Organization of a Fertile Boar-Pig Hybrid by 2D FISH on Both Total and Motile Sperm Fractions

A wide range of mammalian hybrids has recently been found by chance or through population-screening programs, but studies about their fertilizing capacity remain scarce and incomplete. Most of them are assumed to be sterile due to meiotic arrest caused by the failure of chromosome pairings. In this study, we evaluated both sperm meiotic segregation, by 2D fluorescent in situ hybridization (FISH) analysis, and sperm quality (Sperm Chromatin Structure Assay) by flow cytometer in a fertile boar-pig hybrid (2n = 37,XY) originating from a Nero Siciliano pig breed (Sus scrofa domesticus) and a wild boar (Sus scrofa ferus). Spermatozoa were also separated by a dual-layer (75-60%) discontinuous Percoll gradient, resulting in two fractions with a significantly better overall quality in the motile sperm fraction. These data were confirmed by FISH analysis also, where the frequencies of spermatozoa with a regular chromosome composition were 27% in total sperm fraction and 64% in motile sperm fraction. We also evaluated the nuclear architecture in all counted spermatozoa, showing a chromatin distribution changing when chromosome abnormalities occur. Our results demonstrate that the chromosome pairing has a minimal effect on the sperm segregation and semen quality of a boar-pig hybrid, making it fertile and harmful for the conservation of autochthonous pig breeds.