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Agudo-Rios C, Sanchez-Rodriguez A, Idrovo IID, Laborda-Gomariz JÁ, Soler AJ, Teves ME, Roldan ERS. Sperm Chromatin Status and DNA Fragmentation in Mouse Species with Divergent Mating Systems. Int J Mol Sci 2023; 24:15954. [PMID: 37958937 PMCID: PMC10648696 DOI: 10.3390/ijms242115954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Revised: 10/30/2023] [Accepted: 10/31/2023] [Indexed: 11/15/2023] Open
Abstract
Sperm DNA integrity and chromatin status serve as pivotal indicators of sperm quality, given their intricate link to sperm function, embryo development, and overall fertility. Defects in chromatin compaction, which are often associated with compromised protamine content, can lead to damaged DNA strands. In this study, the chromatin status and possible correlation with DNA damage was assessed in males of three mouse species: Mus musculus, M. spretus, and M. spicilegus. We employed various staining methods, including aniline blue, methylene blue (Diff-Quik), toluidine blue, and chromomycin A3, to assess chromatin compaction in cauda epididymal sperm. Samples were also analyzed by the sperm chromatin structure assay (SCSA) to estimate DNA fragmentation (%tDFI, %HDS). Analyses were carried out on freshly collected sperm and cells incubated for 3 h in a HEPES-buffered modified Tyrode's medium simulating conditions of the female reproductive tract. Notably, the analysis of chromatin status yielded minimal abnormal values across all three species employing diverse methodologies. SCSA analyses revealed distinct variations in %tDFI between species. Following sperm incubation, the percentages of sperm stained with methylene blue exhibited differences among the species and were significantly correlated to the DNA fragmentation index. HDS demonstrated correlations with the percentages of sperm stained by aniline blue, methylene blue, and chromomycin A3. Overall, chromatin compaction was high across all species, with limited differences among them. The relationship between chromatin status and DNA integrity appeared to be related to levels of sperm competition among species.
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Affiliation(s)
- Clara Agudo-Rios
- Department of Biodiversity and Evolutionary Biology, Museo Nacional de Ciencias Naturales (CSIC), 28006 Madrid, Spain
| | - Ana Sanchez-Rodriguez
- Department of Biodiversity and Evolutionary Biology, Museo Nacional de Ciencias Naturales (CSIC), 28006 Madrid, Spain
| | - Ingrid I. D. Idrovo
- Department of Biodiversity and Evolutionary Biology, Museo Nacional de Ciencias Naturales (CSIC), 28006 Madrid, Spain
| | | | - Ana J. Soler
- SaBio IREC (CSIC-UCLM-JCCM), ETSIAM, Campus Universitario, 02071 Albacete, Spain
| | - Maria E. Teves
- Department of Obstetrics and Gynecology, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Eduardo R. S. Roldan
- Department of Biodiversity and Evolutionary Biology, Museo Nacional de Ciencias Naturales (CSIC), 28006 Madrid, Spain
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Ogle RA, Netherton J, Schneider E, Velkov T, Zhang H, Cole N, Hetherington L, Villaverde AISB, Baker MA. Nuclear heterogeneity is prevalent in high-quality fractionated human sperm cells typically used for assisted conception. Hum Reprod 2021; 36:2073-2082. [PMID: 34097020 DOI: 10.1093/humrep/deab134] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Revised: 04/07/2021] [Indexed: 11/14/2022] Open
Abstract
STUDY QUESTION What is the nuclear heterogeneity of high-density purified human spermatozoa typically used for IVF purposes. SUMMARY ANSWER The data show that while density gradient separation has improved the overall sperm population, there is still a large degree of nuclear heterogeneity within these cells. WHAT IS KNOWN ALREADY Chromomycin A3 (CMA3) is an important DNA binding fluorochrome for the assessment of male-factor fertility. It is typically used to predict IVF outcomes on entire sperm ejaculates with very high receiver operating characteristic. Here we used CMA3 to characterise typical populations of human spermatozoa that would be used for IVF purposes after density gradient separation. STUDY DESIGN, SIZE, DURATION We compared the intensity of CMA3 binding within high-dense sperm populations obtained from men. Binding heterogeneity was confirmed through fluorescence microscopy and FACS analysis independently. We also looked at CMA3 staining directly with head morphology in this sperm population. Finally, we looked at electron micrographs of nuclear heterogeneity (vacuoles, chromatin compaction) of spermatozoa following density gradient sorting of CMA3-stained cells. PARTICIPANTS/MATERIALS, SETTING, METHODS We used sperm donors who had fathered one or more children. Semen was collected after 2 days abstinence and purified over Percoll gradients. Only the high-quality spermatozoa, the same used for assisted conception, were then used. Cells were stained with CMA3 and sorted using FACS. Following this, electron micrographs were used to assess nuclear heterogeneity of CMA3-dependent sorted spermatozoa. MAIN RESULTS AND THE ROLE OF CHANCE CMA3 staining occurs within morphologically normal as well as abnormal spermatozoa. High-intensity CMA3-stained sperm possessed large vacuoles that were not seen in the low-CMA3 population. In addition, the high-CMA3 stained cells possess higher amounts of nuclear granulation. LIMITATIONS, REASONS FOR CAUTION The present study only describes the issues within the chromatin of these cells and does not suggest an alternate selection technique. WIDER IMPLICATIONS OF THE FINDINGS CMA3 is one of the better reported prognostic assays in predicting pregnancy outcomes, especially in cases where the male is at fault. However, it is clear that even in fractionated populations of human spermatozoa, there are sperm cells that are morphologically normal yet possess high levels of CMA3 staining and chromatin granulation. The implication of this is that the embryologist, whom selects on the basis of sperm morphology, may choose a cell with poor chromatin, which may lead to poor embryo outcomes. STUDY FUNDING/COMPETING INTEREST(S) The project was funded by the National Health and Medical Research council, APP1118943. The authors have no conflict of interest to declare. TRIAL REGISTRATION NUMBER N/A.
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Affiliation(s)
- R A Ogle
- Department of Biological Science, University of Newcastle, Callaghan, NSW, Australia
| | - J Netherton
- Department of Biological Science, University of Newcastle, Callaghan, NSW, Australia
| | - E Schneider
- Department of Pharmacology and Therapeutics, University of Melbourne, Parkville, VIC, Australia
| | - T Velkov
- Department of Pharmacology and Therapeutics, University of Melbourne, Parkville, VIC, Australia
| | - H Zhang
- Department of Pharmacology and Therapeutics, University of Melbourne, Parkville, VIC, Australia
| | - N Cole
- Department of Biological Science, University of Newcastle, Callaghan, NSW, Australia
| | - L Hetherington
- Department of Biological Science, University of Newcastle, Callaghan, NSW, Australia
| | | | - M A Baker
- Department of Biological Science, University of Newcastle, Callaghan, NSW, Australia
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Garcia-Segura S, Ribas-Maynou J, Lara-Cerrillo S, Garcia-Peiró A, Castel AB, Benet J, Oliver-Bonet M. Relationship of Seminal Oxidation-Reduction Potential with Sperm DNA Integrity and pH in Idiopathic Infertile Patients. Biology (Basel) 2020; 9:biology9090262. [PMID: 32882928 PMCID: PMC7564726 DOI: 10.3390/biology9090262] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 08/12/2020] [Accepted: 08/28/2020] [Indexed: 12/23/2022]
Abstract
Seminal oxidative stress (OS) is one of the most promising factors to describe the causes of idiopathic male infertility. Redox balance is essential in several biological processes related to fertility, so alterations such as high reactive oxygen species (ROS) levels or low antioxidant agent levels can compromise it. MiOXSYS has been developed to evaluate the seminal static oxidation-reduction potential (sORP) and it has been proposed as an effective diagnostic biomarker. However, its relationship with parameters like sperm DNA fragmentation (SDF), chromatin compaction status or seminal pH requires further analysis, making it the object of this study. Semen and sORP analysis were performed for all samples. A terminal deoxynucleotidyl transferase dUTP nick end labeling assay (TUNEL) and Comet assay were used to assess SDF and chromomycin a3 (CMA3) test to assess sperm chromatin compaction. Regarding sORP measures, it was found that alkaline pH has an effect on sample reproducibility. To our knowledge, this unexpected effect has not been previously described. A statistical analysis showed that sORP correlated negatively with CMA3 positive cells and sperm motility, but not with SDF. As redox dysregulation, which occurs mainly at the testicular and epididymal level, causes chromatin compaction problems and leaves DNA exposed to damage, an excess of ROS could be counterbalanced further by a seminal supply of antioxidant molecules, explaining the negative correlation with CMA3 positive cells but no correlation with SDF. Our results show that the study of idiopathic infertility would benefit from a combined approach comprising OS analysis, SDF and chromatin compaction analysis.
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Affiliation(s)
- Sergio Garcia-Segura
- Unit of Cell Biology and Medical Genetics, Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Av. Can Domenech s/n, Bellaterra, 08193 Catalunya, Spain;
- Correspondence: (S.G.-S.); (J.B.); (M.O.-B.)
| | - Jordi Ribas-Maynou
- Unit of Cell Biology and Medical Genetics, Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Av. Can Domenech s/n, Bellaterra, 08193 Catalunya, Spain;
| | - Sandra Lara-Cerrillo
- CIMAB, Barcelona Male Infertility Centre, C. Vallcorba 1-3, Sant Quirze del Vallès, 08192 Catalunya, Spain; (S.L.-C.); (A.G.-P.)
| | - Agustín Garcia-Peiró
- CIMAB, Barcelona Male Infertility Centre, C. Vallcorba 1-3, Sant Quirze del Vallès, 08192 Catalunya, Spain; (S.L.-C.); (A.G.-P.)
| | - Ana Belén Castel
- Instituto de Fertilidad, C. Calçat 6, 07011 Palma Mallorca, Spain;
| | - Jordi Benet
- Unit of Cell Biology and Medical Genetics, Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Av. Can Domenech s/n, Bellaterra, 08193 Catalunya, Spain;
- Correspondence: (S.G.-S.); (J.B.); (M.O.-B.)
| | - Maria Oliver-Bonet
- Unit of Cell Biology and Medical Genetics, Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Av. Can Domenech s/n, Bellaterra, 08193 Catalunya, Spain;
- Genosalut, Camí dels Reis 308, 07010 Palma Mallorca, Spain
- Correspondence: (S.G.-S.); (J.B.); (M.O.-B.)
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Abstract
Male factor infertility has been diagnosed as the cause of infertility in about 20% of infertile couples. Sperm analysis is the most common method for diagnosing infertility in a laboratory. However, approximately 15% of infertile men have a normal sperm analysis. Therefore, the result of a routine sperm analysis often cannot be a definitive diagnosis for male factor infertility. Also, approximately 8% of infertile men with normal sperm parameters have high levels of abnormal sperm DNA. This indicates the role of the integrity of sperm DNA in male infertility. Here, we review the current tests available to evaluate the sperm DNA integrity along with their benefits and limitations.
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Affiliation(s)
- Soheila Pourmasumi
- Non-Communicable Diseases Research Center, Rafsanjan University of Medical Sciences, Rafsanjan, Iran
| | - Alireza Nazari
- Non-Communicable Diseases Research Center, Rafsanjan University of Medical Sciences, Rafsanjan, Iran
| | | | - Parvin Sabeti
- Department of Anatomy, Faculty of Medicine, Kurdistan University of Medical Sciences, Sanandaj, Iran
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Chen YW, Satange R, Wu PC, Jhan CR, Chang CK, Chung KR, Waring MJ, Lin SW, Hsieh LC, Hou MH. Co II(Chromomycin)₂ Complex Induces a Conformational Change of CCG Repeats from i-Motif to Base-Extruded DNA Duplex. Int J Mol Sci 2018; 19:ijms19092796. [PMID: 30227633 PMCID: PMC6164834 DOI: 10.3390/ijms19092796] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 09/07/2018] [Indexed: 01/07/2023] Open
Abstract
We have reported the propensity of a DNA sequence containing CCG repeats to form a stable i-motif tetraplex structure in the absence of ligands. Here we show that an i-motif DNA sequence may transition to a base-extruded duplex structure with a GGCC tetranucleotide tract when bound to the (CoII)-mediated dimer of chromomycin A3, CoII(Chro)₂. Biophysical experiments reveal that CCG trinucleotide repeats provide favorable binding sites for CoII(Chro)₂. In addition, water hydration and divalent metal ion (CoII) interactions also play a crucial role in the stabilization of CCG trinucleotide repeats (TNRs). Our data furnish useful structural information for the design of novel therapeutic strategies to treat neurological diseases caused by repeat expansions.
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Affiliation(s)
- Yu-Wen Chen
- Institute of Biotechnology, National Chung-Hsing University, Taichung 402, Taiwan.
| | - Roshan Satange
- Institute of Genomics and Bioinformatics, National Chung-Hsing University, Taichung 402, Taiwan.
- Ph.D. Program in Medical Biotechnology, National Chung Hsing University, Taichung 402, Taiwan.
| | - Pei-Ching Wu
- Institute of Genomics and Bioinformatics, National Chung-Hsing University, Taichung 402, Taiwan.
| | - Cyong-Ru Jhan
- Department of Life Sciences, National Chung-Hsing University, Taichung 402, Taiwan.
| | - Chung-Ke Chang
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan.
| | - Kuang-Ren Chung
- Department of Plant Pathology, National Chung-Hsing University, Taichung 402, Taiwan.
| | - Michael J Waring
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK.
| | - Sheng-Wei Lin
- Institute of Biological Chemistry, Academia Sinica, Taipei 115, Taiwan.
| | - Li-Ching Hsieh
- Institute of Genomics and Bioinformatics, National Chung-Hsing University, Taichung 402, Taiwan.
- Advanced Plant Biotechnology Center, National Chung-Hsing University, Taichung 402, Taiwan.
| | - Ming-Hon Hou
- Institute of Biotechnology, National Chung-Hsing University, Taichung 402, Taiwan.
- Institute of Genomics and Bioinformatics, National Chung-Hsing University, Taichung 402, Taiwan.
- Ph.D. Program in Medical Biotechnology, National Chung Hsing University, Taichung 402, Taiwan.
- Department of Life Sciences, National Chung-Hsing University, Taichung 402, Taiwan.
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Ozkosem B, Feinstein SI, Fisher AB, O'Flaherty C. Absence of Peroxiredoxin 6 Amplifies the Effect of Oxidant Stress on Mobility and SCSA/CMA3 Defined Chromatin Quality and Impairs Fertilizing Ability of Mouse Spermatozoa. Biol Reprod 2016; 94:68. [PMID: 26792942 PMCID: PMC4829091 DOI: 10.1095/biolreprod.115.137646] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 01/15/2016] [Indexed: 12/22/2022] Open
Abstract
Oxidative stress, the imbalance between reactive oxygen species production and antioxidant defenses, is associated with male infertility. Peroxiredoxins (PRDXs) are antioxidant enzymes with a wide distribution in spermatozoa. PRDX6 is highly abundant and located in all subcellular compartments of the spermatozoon. Infertile men have lower levels of sperm PRDX6 associated with low sperm motility and high DNA damage. In order to better understand the role of PRDX6 in male reproduction, the aim of this study was to elucidate the impact of the lack of PRDX6 on male mouse fertility. Spermatozoa lacking PRDX6 showed significantly increased levels of cellular oxidative damage evidenced by high levels of lipid peroxidation, 8-hydroxy-deoxyguanosine (DNA oxidation), and protein oxidation (S-glutathionylation and carbonylation), lower sperm chromatin quality (high DNA fragmentation and low DNA compaction, due to low levels of protamination and a high percentage of free thiols), along with decreased sperm motility and impairment of capacitation as compared with wild-type (WT) spermatozoa. These manifestations of damage are exacerbated by tert-butyl hydroperoxide treatment in vivo. While WT males partially recovered the quality of their spermatozoa (in terms of motility and sperm DNA integrity), Prdx6(-/-) males showed higher levels of sperm damage (lower motility and chromatin integrity) 6 mo after the end of treatment. In conclusion, Prdx6(-/-) males are more vulnerable to oxidative stress than WT males, resulting in impairment of sperm quality and ability to fertilize the oocyte, compatible with the subfertility phenotype observed in these knockout mice.
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Affiliation(s)
- Burak Ozkosem
- Urology Research Laboratory, Research Institute of the McGill University Health Centre, McGill University, Montréal, Québec, Canada Department of Surgery (Urology Division), McGill University, Montréal, Québec, Canada
| | - Sheldon I Feinstein
- Institute for Environmental Medicine, Department of Physiology, University of Pennsylvania, Philadelphia, Pennsylvania Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Aron B Fisher
- Institute for Environmental Medicine, Department of Physiology, University of Pennsylvania, Philadelphia, Pennsylvania Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Cristian O'Flaherty
- Urology Research Laboratory, Research Institute of the McGill University Health Centre, McGill University, Montréal, Québec, Canada Department of Surgery (Urology Division), McGill University, Montréal, Québec, Canada Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada
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7
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Abstract
BACKGROUND Sperm DNA in human beings and most vertebrates is packed by protamines into highly compact form of chromatin. There are many staining methods to assess sperm chromatin. Three different methods of staining were used simultaneously in this study and the goal was to determine which of these sperm tests has a relation with fertilization rate in intracytoplasmic sperm injection (ICSI). MATERIALS AND METHODS Thirty couples who referred to Yamagata University Hospital (Yamagata, Japan) for ICSI were included in this study. The greater part of semen was prepared for ICSI. The remaining part was used for staining with aniline blue, acridine orange, and chromomycin A3 (CMA3). For evaluation of abnormal morphology and abnormality of head, Papanicolaou-stained smears were used. The analysis of data was done using Spearman coefficient of correlation and logistic regression model. Receiver operator characteristic (ROC) curve was used for discrimination of CMA3 staining power to identify ICSI rates. RESULTS Percentage of CMA3 positivity, unlike those of aniline blue and acridine orange, showed significant negative correlation with fertilization rate. Moreover, the percentage of CMA3 positivity showed a positive correlation with the percentage of abnormal morphology and abnormality of head. By dividing patients into CMA3 <48% and CMA3> 48% groups, the area under the curve was 0.646. CONCLUSIONS CMA3 staining (protamine deficiency) could be considered as a useful tool for evaluation of male fertility prior to infertility treatment.
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Fortes MRS, Satake N, Corbet DH, Corbet NJ, Burns BM, Moore SS, Boe-Hansen GB. Sperm protamine deficiency correlates with sperm DNA damage in Bos indicus bulls. Andrology 2014; 2:370-8. [PMID: 24634207 DOI: 10.1111/j.2047-2927.2014.00196.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 01/23/2014] [Accepted: 01/24/2014] [Indexed: 11/30/2022]
Abstract
The primary purpose of spermatozoa is to deliver the paternal DNA to the oocyte at fertilization. During the complex events of fertilization, if the spermatozoon penetrating the oocyte contains compromised or damaged sperm chromatin, the subsequent progression of embryogenesis and foetal development may be affected. Variation in sperm DNA damage and protamine content in ejaculated spermatozoa was reported in the cattle, with potential consequences to bull fertility. Protamines are sperm-specific nuclear proteins that are essential to packaging of the condensed paternal genome in spermatozoa. Sperm DNA damage is thought to be repaired during the process of protamination. This study investigates the potential correlation between sperm protamine content, sperm DNA damage and the subsequent relationships between sperm chromatin and commonly measured reproductive phenotypes. Bos indicus sperm samples (n = 133) were assessed by two flow cytometric methods: the sperm chromatin structure assay (SCSA) and an optimized sperm protamine deficiency assay (SPDA). To verify the SPDA assay for bovine sperm protamine content, samples collected from testis, caput and cauda epididymidis were analyzed. As expected, mature spermatozoa in the cauda epididymidis had higher protamine content when compared with sperm samples from testis and caput epididymidis (p < 0.01). The DNA fragmentation index (DFI), determined by SCSA, was positively correlated (r = 0.33 ± 0.08, p < 0.05) with the percentage of spermatozoa that showed low protamine content using SPDA. Also, DFI was negatively correlated (r = -0.21 ± 0.09, p < 0.05) with the percentage of spermatozoa with high protamine content. Larger scrotal circumference contributes to higher sperm protamine content and lower content of sperm DNA damage (p < 0.05). In conclusion, sperm protamine content and sperm DNA damage are closely associated. Protamine deficiency is likely to be one of the contributing factors to DNA instability and damage, which can affect bull fertility.
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Affiliation(s)
- M R S Fortes
- Queensland Alliance for Agriculture and Food Innovation, Centre for Animal Science, The University of Queensland, Saint Lucia, Qld, Australia
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Nabais C, Rampin M, Collares-Pereira MJ. Comparative cytogenetics of two endangered leuciscine fish, Squalius aradensis and S. torgalensis (Teleostei, Cyprinidae), from the Iberian Peninsula. Comp Cytogenet 2013; 7:33-42. [PMID: 24260688 PMCID: PMC3833748 DOI: 10.3897/compcytogen.v7i1.4672] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/12/2013] [Accepted: 02/14/2013] [Indexed: 06/02/2023]
Abstract
In this study, the description of the karyotypes of the endangered chubs Squalius aradensis (Coelho, Bogutskaya, Rodrigues and Collares-Pereira, 1998) and Squalius torgalensis (Coelho, Bogutskaya, Rodrigues and Collares-Pereira, 1998) is presented by means of conventional (Giemsa-staining, Chromomycin A3 (CMA3)-fluorescence, Silver-impregnation (Ag-NORs)) and molecular (fluorescence in situ hybridization (FISH) with 18S rDNA probe) protocols. These endemic sister-species have an allopatric but adjacent distribution in the most southwestern part of the Iberian Peninsula. Diploid chromosome number was invariably 2n = 50 and karyotypes of both species were grossly similar, composed of metacentric and submetacentric elements with a reduced number of acrocentric pairs. Sequential staining using FISH with an 18S rDNA probe, CMA3 and Ag-NORs treatments revealed consistent positive signals located at the end of the short arms of a submetacentric chromosome pair, likely homologous in both species. While providing useful cytogenetic comparative data against other members of the genus Squalius Bonaparte, 1837, the work aimed to draw attention towards the conservation of two narrow-range and highly confined fish species.
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Affiliation(s)
- Catarina Nabais
- Universidade de Lisboa, Faculdade de Ciências, Centro de Biologia Ambiental, Campo Grande, Lisboa, Portugal
| | - Massimiliano Rampin
- Universidade de Lisboa, Faculdade de Ciências, Centro de Biologia Ambiental, Campo Grande, Lisboa, Portugal
- Present address: University of South Bohemia in České Budějovice, Faculty of Fisheries and Protection of Waters, Research Institute of Fish Culture and Hydrobiology, Vodňany, Czech Republic
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