The relationship between mitochondrial DNA copy number and stallion sperm function.
Abstract: Mitochondrial DNA (mtDNA) copy number has been utilized as a measure of sperm quality in several species including mice, dogs, and humans, and has been suggested as a potential biomarker of fertility in stallion sperm. The results of the present study extend this recent discovery using sperm samples from American Quarter Horse stallions of varying age. By determining copy number of three mitochondrial genes, cytochrome b (CYTB), NADH dehydrogenase 1 (ND1) and NADH dehydrogenase 4 (ND4), instead of a single gene, we demonstrate an improved understanding of mtDNA fate in stallion sperm mitochondria following spermatogenesis. Sperm samples from 37 stallions ranging from 3 to 24 years old were collected at four breeding ranches in north and central Texas during the 2015 breeding season. Samples were analyzed for sperm motion characteristics, nuclear DNA denaturability and mtDNA copy number. Mitochondrial DNA content in individual sperm was determined by real-time qPCR and normalized with a single copy nuclear gene, Beta actin. Exploratory correlation analysis revealed that total motility was negatively correlated with CYTB copy number and sperm chromatin structure. Stallion age did not have a significant effect on copy number for any of the genes. Copy number differences existed between the three genes with CYTB having the greatest number of copies (20.6 ± 1.2 copies, range: 6.0 to 41.1) followed by ND4 (15.5 ± 0.8 copies, range: 6.7 to 27.8) and finally ND1 (12.0 ± 1.0 copies, range: 0.4 to 26.6) (P < 0.05). Varying copy number across mitochondrial genes is likely to be a result of mtDNA fragmentation and degradation since downregulation of sperm mtDNA occurs during spermatogenesis and may be important for normal sperm function. Beta regression analysis suggested that for every unit increase in mtDNA copy number of CYTB, there was a 4% decrease in the odds of sperm movement (P = 0.001). Influential analysis suggested that results are robust and not highly influenced by data from individual stallions despite the low number of stallions sampled with low sperm motility. Further genome sequencing is necessary to investigate if mutations or deletions are the underlying causes of inconsistent copy numbers across mitochondrial genes. In conclusion, we show, for the first time, that increased mtDNA copy number is associated with decreased total sperm motility in stallions. We therefore suggest that mtDNA copy number may be an indicator of defective spermatogenesis in stallions.
Copyright © 2017 Elsevier Inc. All rights reserved.
Publication Date: 2017-02-21 PubMed ID: 28407867DOI: 10.1016/j.theriogenology.2017.02.015Google Scholar: Lookup
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- Journal Article
Summary
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The research examines the relationship between the mitochondrial DNA copy number and the quality of stallion sperm, suggesting that a higher mtDNA copy number could indicate decreased sperm motility, and thus defective spermatogenesis, in stallions.
Research Focus
- The core focus of the research is to investigate whether the mitochondrial DNA (mtDNA) copy number could serve as a potential biomarker of fertility in stallions, and particularly American Quarter Horse stallions.
- The study takes into account the mitochondrial genes, cytochrome b (CYTB), NADH dehydrogenase 1 (ND1), and NADH dehydrogenase 4 (ND4) to provide a well-rounded understanding of mtDNA in stallion sperm cells after spermatogenesis, i.e., the process in which mature sperm cells are produced.
Methodology
- Sperm samples were collected from 37 stallions, aged between 3 and 24 years, from four breeding ranches in north and central Texas.
- These samples were then subjected to analysis for sperm motion traits, the extent of nuclear DNA denaturability, and the mtDNA copy number.
- The mtDNA content within each sperm was evaluated through real-time qPCR and then normalized using a single copy nuclear gene, Beta actin.
Key Findings
- The researchers found that total motility, an essential quality of sperm, was inversely correlated with the copy number of the CYTB gene and the structure of sperm chromatin.
- Age of the stallions had no significant impact on the gene copy number.
- Among the three mtDNA genes, CYTB had the most copies followed by ND4, with ND1 having the least.
- In every increment of the CYTB mtDNA copy number, there was a 4% reduction in the odds of sperm movement.
- The variations in the copy number across mitochondrial genes may be caused due to mtDNA fragmentation and degradation occurring during spermatogenesis, suggesting its importance for normal sperm function.
Conclusions and Future Directions
- The present study suggests that a higher mtDNA copy number may implicate decreased total sperm motility in stallions, hence indicating defective spermatogenesis.
- However, the researchers suggest that to fully clarify the reasons for varying copy numbers across mitochondrial genes, more extensive genome sequencing is required to determine if mutations or deletions are the root cause.
Cite This Article
APA
Darr CR, Moraes LE, Connon RE, Love CC, Teague S, Varner DD, Meyers SA.
(2017).
The relationship between mitochondrial DNA copy number and stallion sperm function.
Theriogenology, 94, 94-99.
https://doi.org/10.1016/j.theriogenology.2017.02.015 Publication
Researcher Affiliations
- Department of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California Davis, 1089 Veterinary Medicine Dr., Veterinary Medicine 3B, Davis, CA 95616, USA. Electronic address: crdarr@ucdavis.edu.
- Department of Animal Science, University of California Davis, One Shields Ave., Meyer Hall, Davis, CA 95616, USA. Electronic address: lemoraes@ucdavis.edu.
- Department of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California Davis, 1089 Veterinary Medicine Dr., Veterinary Medicine 3B, Davis, CA 95616, USA. Electronic address: reconnon@ucdavis.edu.
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, Texas A&M University and Biomedical Sciences, 4475 TAMU, College Station, TX 77843-4475, USA. Electronic address: clove@cvm.tamu.edu.
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, Texas A&M University and Biomedical Sciences, 4475 TAMU, College Station, TX 77843-4475, USA. Electronic address: steague@cvm.tamu.edu.
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, Texas A&M University and Biomedical Sciences, 4475 TAMU, College Station, TX 77843-4475, USA. Electronic address: dvarner@cvm.tamu.edu.
- Department of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California Davis, 1089 Veterinary Medicine Dr., Veterinary Medicine 3B, Davis, CA 95616, USA. Electronic address: smeyers@ucdavis.edu.
MeSH Terms
- Animals
- DNA Copy Number Variations
- DNA, Mitochondrial
- Horses / genetics
- Male
- Real-Time Polymerase Chain Reaction / veterinary
- Regression Analysis
- Semen Analysis / veterinary
- Sperm Motility / genetics
- Spermatozoa / physiology
Citations
This article has been cited 10 times.- Finelli R, Moreira BP, Alves MG, Agarwal A. Unraveling the Molecular Impact of Sperm DNA Damage on Human Reproduction. Adv Exp Med Biol 2022;1358:77-113.
- Shi WH, Ye MJ, Qin NX, Zhou ZY, Zhou XY, Xu NX, Chen SC, Li SY, Xu CM. Associations of Sperm mtDNA Copy Number, DNA Fragmentation Index, and Reactive Oxygen Species With Clinical Outcomes in ART Treatments. Front Endocrinol (Lausanne) 2022;13:849534.
- Knief U, Forstmeier W, Kempenaers B, Wolf JBW. A sex chromosome inversion is associated with copy number variation of mitochondrial DNA in zebra finch sperm. R Soc Open Sci 2021 Sep;8(9):211025.
- Madeja ZE, Podralska M, Nadel A, Pszczola M, Pawlak P, Rozwadowska N. Mitochondria Content and Activity Are Crucial Parameters for Bull Sperm Quality Evaluation. Antioxidants (Basel) 2021 Jul 27;10(8).
- Rosati AJ, Whitcomb BW, Brandon N, Buck Louis GM, Mumford SL, Schisterman EF, Pilsner JR. Sperm mitochondrial DNA biomarkers and couple fecundity. Hum Reprod 2020 Nov 1;35(11):2619-2625.
- Li L, Zhu Y, Chen T, Sun J, Luo J, Shu G, Wang S, Zhu X, Jiang Q, Zhang Y, Xi Q. MiR-125b-2 Knockout in Testis Is Associated with Targeting to the PAP Gene, Mitochondrial Copy Number, and Impaired Sperm Quality. Int J Mol Sci 2019 Jan 3;20(1).
- Sawant S, Paskavitz AL, Nowak K, Rosati AJ, Westling T, Bertolla RP, Whitcomb BW, Pilsner JR. A machine learning approach using semen parameters and sperm mitochondrial DNA copy number to predict couples' fecundity. F S Rep 2025 Sep;6(3):270-279.
- Hassanpour H, Javdani M, Changaniyan-Khorasgani Z, Rezazadeh E, Jalali R, Mojtahed M. Is castration leading to biological aging in dogs? Assessment of lipid peroxidation, inflammation, telomere length, mitochondrial DNA copy number, and expression of telomerase and age-related genes. BMC Vet Res 2024 Oct 24;20(1):485.
- Deng J, Huang Y, Liang J, Jiang Y, Chen T. Medaka (Oryzias latipes) Dmrt3a Is Involved in Male Fertility. Animals (Basel) 2024 Aug 19;14(16).
- Llavanera M, Mateo-Otero Y, Viñolas-Vergés E, Bonet S, Yeste M. Sperm function, mitochondrial activity and in vivo fertility are associated to their mitochondrial DNA content in pigs. J Anim Sci Biotechnol 2024 Feb 1;15(1):10.
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