Cytogenetics of Domestic Animals: Clinical, Molecular and Evolutionary Aspects

A special issue of Animals (ISSN 2076-2615). This special issue belongs to the section "Veterinary Clinical Studies".

Deadline for manuscript submissions: closed (30 November 2022) | Viewed by 52741

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Special Issue Editors

National Research Council (CNR) of Italy, Institute of Animal Production System in Mediterranean Environment (ISPAAM), Piazzale Enrico Fermi 1, 80055 –Portici (NA), Italy
Interests: animal cytogenetics; gene mapping by FISH; standard karyotypes; genetic improvement of livestock
Special Issues, Collections and Topics in MDPI journals
Department of Agricultural and Environmental Sciences, Milano University, 20131 Milano, Italy
Interests: clinical cytogenetics; molecular cytogenetics; bio-informatics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

After the discovery of 1;29 Robertsonian translocation in the Swedish red cattle occurred more than 50 years ago and the demonstration of its deleterious effects on fertility, the cytogenetics applied to domestic animals was largely applied by several scientific laboratories in all the world. The main interest of the scientists has been focused to the following sectors: (a) clinical cytogenetics (study of the relationships between chromosome abnormalities and fertility), (b) evolutionary cytogenetics (study of chromosome banding homologies and gene order between related and unrelated species); (c) molecular cytogenetics (use of molecular markers –generally BAC-clones- and the FISH-technique (i) to extend the genetic physical maps,(ii) to better characterize chromosome abnormalities and (iii) to better study the chromosome evolution of species); (d) environmental cytogenetics (use of several chromosome or molecular test to establish possible damages to the DNA derived by exposure to alleged mutagens present in the environment).

In this Special issue, both paper-review, original contributions and short communications will be published to both sum up the knowledge and update the most important questions and problems related to the domestic animal cytogenetics, giving particular attention to the clinical cytogenetics which is particularly under the screen of both breeders and scientists for the animal breeding improvement.


Dr. Leopoldo Iannuzzi
Dr. Pietro Parma
Guest Editors

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Keywords

  • animal cytogenetics
  • chromosome abnormality
  • animal fertility
  • genetic improvement
  • molecular cytogenetics
  • chromosome evolution

Published Papers (13 papers)

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Research

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11 pages, 2740 KiB  
Article
Supernumerary Marker Chromosome Identified in Asian Elephant (Elephas maximus)
by Halina Cernohorska, Svatava Kubickova, Petra Musilova, Miluse Vozdova, Roman Vodicka and Jiri Rubes
Animals 2023, 13(4), 701; https://0-doi-org.brum.beds.ac.uk/10.3390/ani13040701 - 17 Feb 2023
Viewed by 1839
Abstract
We identified a small, supernumerary marker chromosome (sSMC) in two phenotypically normal Asian elephants (Elephas maximus): a female (2n = 57,XX,+mar) and her male offspring (2n = 57,XY,+mar). sSMCs are defined as structurally abnormal chromosomes that cannot be identified by conventional [...] Read more.
We identified a small, supernumerary marker chromosome (sSMC) in two phenotypically normal Asian elephants (Elephas maximus): a female (2n = 57,XX,+mar) and her male offspring (2n = 57,XY,+mar). sSMCs are defined as structurally abnormal chromosomes that cannot be identified by conventional banding analysis since they are usually small and often lack distinct banding patterns. Although current molecular techniques can reveal their origin, the mechanism of their formation is not yet fully understood. We determined the origin of the marker using a suite of conventional and molecular cytogenetic approaches that included (a) G- and C-banding, (b) AgNOR staining, (c) preparation of a DNA clone using laser microdissection of the marker chromosome, (d) FISH with commercially available human painting and telomeric probes, and (e) FISH with centromeric DNA derived from the centromeric regions of a marker-free Asian elephant. Moreover, we present new information on the location and number of NORs in Asian and savanna elephants. We show that the metacentric marker was composed of heterochromatin with NORs at the terminal ends, originating most likely from the heterochromatic region of chromosome 27. In this context, we discuss the possible mechanism of marker formation. We also discuss the similarities between sSMCs and B chromosomes and whether the marker chromosome presented here could evolve into a B chromosome in the future. Full article
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9 pages, 1104 KiB  
Article
Prevalence of Sex-Related Chromosomal Abnormalities in a Large Cohort of Spanish Purebred Horses
by Sebastián Demyda-Peyrás, Nora Laseca, Gabriel Anaya, Barbara Kij-Mitka, Antonio Molina, Ayelén Karlau and Mercedes Valera
Animals 2023, 13(3), 539; https://0-doi-org.brum.beds.ac.uk/10.3390/ani13030539 - 03 Feb 2023
Cited by 1 | Viewed by 3843
Abstract
Chromosomal abnormalities are largely associated with fertility impairments in the domestic horse. To date, over 600 cases of individuals carrying abnormal chromosome complements have been reported, making the domestic horse the species with the highest prevalence. However, studies analyzing the prevalence of chromosomal [...] Read more.
Chromosomal abnormalities are largely associated with fertility impairments in the domestic horse. To date, over 600 cases of individuals carrying abnormal chromosome complements have been reported, making the domestic horse the species with the highest prevalence. However, studies analyzing the prevalence of chromosomal diseases in whole populations are scarce. We, therefore, employed a two-step molecular tool to screen and diagnose chromosomal abnormalities in a large population of 25,237 Pura Raza Español horses. Individuals were first screened using short tandem repeats parentage testing results and phenotypic evaluations. Those animals showing results suggesting chromosomal abnormalities were re-tested using a single nucleotide polymorphism (SNP)-based diagnostic methodology to accurately determine the chromosomal complements. Thirteen individuals showed a positive screening, all of which were diagnosed as chromosomally abnormal, including five 64,XY mares with sex development disorders (DSD) and four cases of blood chimerism (two male/female and two female/female cases). In addition, we detected one Turner and one Klinefelter syndrome and two individuals carrying complex karyotypes. The overall prevalence in the entire population was ~0.05%, with the prevalence of 64,XY DSD and blood chimerism ~0.02% and ~0.016%, respectively. However, the overall results should be taken with caution since the individuals carrying Turner syndrome (in full (63,X) or mosaic (mos 63,X/64,XX) forms) cannot be detected due to limitations in the methodology employed. Finally, the lack of agreement between populational studies performed using karyotyping or molecular methods is discussed. To our knowledge, this is the largest populational study performed evaluating the prevalence of the most common chromosomal abnormalities in the domestic horse. Full article
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12 pages, 3558 KiB  
Article
XX/XY Chimerism in Internal Genitalia of a Virilized Heifer
by Izabela Szczerbal, Joanna Nowacka-Woszuk, Monika Stachowiak, Anna Lukomska, Kacper Konieczny, Natalia Tarnogrodzka, Jakub Wozniak and Marek Switonski
Animals 2022, 12(21), 2932; https://0-doi-org.brum.beds.ac.uk/10.3390/ani12212932 - 26 Oct 2022
Cited by 3 | Viewed by 4418
Abstract
Five DSD heifers underwent genetic analysis in the present study. We cytogenetically analyzed in vitro cultured leukocytes and searched for SRY, AMELX/AMELY and ZFX/ZFY genes in leukocytes and hair follicles, finding that four of the studied heifers were [...] Read more.
Five DSD heifers underwent genetic analysis in the present study. We cytogenetically analyzed in vitro cultured leukocytes and searched for SRY, AMELX/AMELY and ZFX/ZFY genes in leukocytes and hair follicles, finding that four of the studied heifers were freemartins (XX/XY leukocyte chimerism). The fifth case had an underdeveloped vulva localized ventrally and cranially to the mammary gland, a normal female sex chromosome complement (60,XX) in the leukocytes, and a lack of Y-chromosome-derived genes in the leukocytes and hair follicles. Postmortem anatomical examination of this heifer revealed the presence of normal ovaries with follicles, uterus, and oviducts, but molecular detection of the SRY, ZFX, ZFY,AMELX, and AMELY genes in these organs indicated the presence of a cell line carrying the Y chromosome. Further analysis of twelve microsatellite markers revealed the presence of additional variants at six loci in DNA samples derived from the reproductive organs; XX/XY chimerism was thus suspected in these samples. On the basis of the detection of AMELY (Y-linked) versus AMELX (X-linked) and SOX9 (autosomal) versus AMELY genes by droplet digital PCR (ddPCR), the Y/X and Y/autosome ratios were evaluated; they indicated the presence of XX and XY cell lines in the reproductive tissues. Our study showed that XX/XY chimerism can be present in the internal reproductive organs of the virilized heifers with a normal female set of sex chromosomes (60,XX) and a lack of Y-chromosome-derived genes in the leukocytes. The etiology of this phenomenon remains unknown. Full article
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8 pages, 646 KiB  
Article
Comparative Fluorescence In Situ Hybridization (FISH) Mapping of Twenty-Three Endogenous Jaagsiekte Sheep Retrovirus (enJSRVs) in Sheep (Ovis aries) and River Buffalo (Bubalus bubalis) Chromosomes
by Angela Perucatti, Alessandra Iannuzzi, Alessia Armezzani, Massimo Palmarini and Leopoldo Iannuzzi
Animals 2022, 12(20), 2834; https://0-doi-org.brum.beds.ac.uk/10.3390/ani12202834 - 19 Oct 2022
Cited by 1 | Viewed by 1553
Abstract
Endogenous retroviruses (ERVs) are the remnants of ancient infections of host germline cells, thus representing key tools to study host and viral evolution. Homologous ERV sequences often map at the same genomic locus of different species, indicating that retroviral integration occurred in the [...] Read more.
Endogenous retroviruses (ERVs) are the remnants of ancient infections of host germline cells, thus representing key tools to study host and viral evolution. Homologous ERV sequences often map at the same genomic locus of different species, indicating that retroviral integration occurred in the genomes of the common ancestors of those species. The genome of domestic sheep (Ovis aries) harbors at least twenty-seven copies of ERVs related to the exogenous and pathogenic Jaagsiekte sheep retrovirus (JSRVs), thus referred to as enJSRVs. Some of these loci are unequally distributed between breeds and individuals of the host species due to polymorphic insertions, thereby representing invaluable tools to trace the evolutionary dynamics of virus populations within their hosts. In this study, we extend the cytogenetic physical maps of sheep and river buffalo by performing fluorescent in situ hybridization (FISH) mapping of twenty-three genetically characterized enJSRVs. Additionally, we report the first comparative FISH mapping of enJSRVs in domestic sheep (2n = 54) and river buffalo (Bubalus bubalis, 2n = 50). Finally, we demonstrate that enJSRV loci are conserved in the homologous chromosomes and chromosome bands of both species. Altogether, our results support the hypothesis that enJSRVs were present in the genomes of both species before they differentiated within the Bovidae family. Full article
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10 pages, 578 KiB  
Article
Chromosome Instability in Pony of Esperia Breed Naturally Infected by Intestinal Strongylidae
by Emanuele D’Anza, Francesco Buono, Sara Albarella, Elisa Castaldo, Mariagiulia Pugliano, Alessandra Iannuzzi, Ilaria Cascone, Edoardo Battista, Vincenzo Peretti and Francesca Ciotola
Animals 2022, 12(20), 2817; https://0-doi-org.brum.beds.ac.uk/10.3390/ani12202817 - 18 Oct 2022
Viewed by 1076
Abstract
The Pony of Esperia is an Italian autochthonous horse breed reared in the wild on the Aurunci and Ausoni Mountains. Currently, it is considered an endangered breed, as its population consists of 1623 animals. It is therefore essential to identify all aspects that [...] Read more.
The Pony of Esperia is an Italian autochthonous horse breed reared in the wild on the Aurunci and Ausoni Mountains. Currently, it is considered an endangered breed, as its population consists of 1623 animals. It is therefore essential to identify all aspects that can improve the management and economy of its breeding, favoring its diffusion. In this paper, the effects of intestinal strongyle infection on the chromosome stability of peripheral blood lymphocytes (PBLs) was evaluated through aneuploidy and chromosome aberration (gap, chromatid and chromosome breaks, and the number of abnormal cells) test. Statistical difference in the mean values of aneuploidy, cells with chromosome abnormalities, and chromosome and chromatid breaks were observed between ponies with high fecal egg counts (eggs per gram > 930) and those with undetectable intestinal strongylosis. The causes of this phenomenon and possible repercussions on the management of Pony of Esperia are discussed in the paper. Full article
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16 pages, 1993 KiB  
Article
Anchoring the CerEla1.0 Genome Assembly to Red Deer (Cervus elaphus) and Cattle (Bos taurus) Chromosomes and Specification of Evolutionary Chromosome Rearrangements in Cervidae
by Miluse Vozdova, Svatava Kubickova, Halina Cernohorska, Jan Fröhlich and Jiri Rubes
Animals 2021, 11(9), 2614; https://0-doi-org.brum.beds.ac.uk/10.3390/ani11092614 - 06 Sep 2021
Cited by 1 | Viewed by 2005
Abstract
The family Cervidae groups a range of species with an increasing economic significance. Their karyotypes share 35 evolutionary conserved chromosomal segments with cattle (Bos taurus). Recent publication of the annotated red deer (Cervus elaphus) whole genome assembly (CerEla1.0) has [...] Read more.
The family Cervidae groups a range of species with an increasing economic significance. Their karyotypes share 35 evolutionary conserved chromosomal segments with cattle (Bos taurus). Recent publication of the annotated red deer (Cervus elaphus) whole genome assembly (CerEla1.0) has provided a basis for advanced genetic studies. In this study, we compared the red deer CerEla1.0 and bovine ARS-UCD1.2 genome assembly and used fluorescence in situ hybridization with bovine BAC probes to verify the homology between bovine and deer chromosomes, determined the centromere-telomere orientation of the CerEla1.0 C-scaffolds and specified positions of the cervid evolutionary chromosome breakpoints. In addition, we revealed several incongruences between the current deer and bovine genome assemblies that were shown to be caused by errors in the CerEla1.0 assembly. Finally, we verified the centromere-to-centromere orientation of evolutionarily fused chromosomes in seven additional deer species, giving a support to previous studies on their chromosome evolution. Full article
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14 pages, 4365 KiB  
Article
Karyotype Evolution and Genomic Organization of Repetitive DNAs in the Saffron Finch, Sicalis flaveola (Passeriformes, Aves)
by Rafael Kretschmer, Benilson Silva Rodrigues, Suziane Alves Barcellos, Alice Lemos Costa, Marcelo de Bello Cioffi, Analía del Valle Garnero, Ricardo José Gunski, Edivaldo Herculano Corrêa de Oliveira and Darren K. Griffin
Animals 2021, 11(5), 1456; https://0-doi-org.brum.beds.ac.uk/10.3390/ani11051456 - 19 May 2021
Cited by 11 | Viewed by 4085
Abstract
The Saffron finch (Sicalis flaveola), a semi-domestic species, is tolerant of human proximity and nesting in roof spaces. Considering the importance of cytogenomic approaches in revealing different aspects of genomic organization and evolution, we provide detailed cytogenetic data for S. [...] Read more.
The Saffron finch (Sicalis flaveola), a semi-domestic species, is tolerant of human proximity and nesting in roof spaces. Considering the importance of cytogenomic approaches in revealing different aspects of genomic organization and evolution, we provide detailed cytogenetic data for S. flaveola, including the standard Giemsa karyotype, C- and G-banding, repetitive DNA mapping, and bacterial artificial chromosome (BAC) FISH. We also compared our results with the sister groups, Passeriformes and Psittaciformes, bringing new insights into the chromosome and genome evolution of birds. The results revealed contrasting rates of intrachromosomal changes, highlighting the role of SSR (simple short repetition probes) accumulation in the karyotype reorganization. The SSRs showed scattered hybridization, but brighter signals were observed in the microchromosomes and the short arms of Z chromosome in S. flaveola. BACs probes showed conservation of ancestral syntenies of macrochromosomes (except GGA1), as well as the tested microchromosomes. The comparison of our results with previous studies indicates that the great biological diversity observed in Passeriformes was not likely accompanied by interchromosomal changes. In addition, although repetitive sequences often act as hotspots of genome rearrangements, Passeriformes species showed a higher number of signals when compared with the sister group Psittaciformes, indicating that these sequences were not involved in the extensive karyotype reorganization seen in the latter. Full article
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Review

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34 pages, 3994 KiB  
Review
Molecular Cytogenetics in Domestic Bovids: A Review
by Alessandra Iannuzzi, Leopoldo Iannuzzi and Pietro Parma
Animals 2023, 13(5), 944; https://0-doi-org.brum.beds.ac.uk/10.3390/ani13050944 - 06 Mar 2023
Cited by 3 | Viewed by 1800
Abstract
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 [...] Read more.
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. Full article
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22 pages, 720 KiB  
Review
Classical, Molecular, and Genomic Cytogenetics of the Pig, a Clinical Perspective
by Brendan Donaldson, Daniel A. F. Villagomez and W. Allan King
Animals 2021, 11(5), 1257; https://0-doi-org.brum.beds.ac.uk/10.3390/ani11051257 - 27 Apr 2021
Cited by 6 | Viewed by 2927
Abstract
The chromosomes of the domestic pig (Sus scrofa domesticus) are known to be prone to reciprocal chromosome translocations and other balanced chromosome rearrangements with concomitant fertility impairment of carriers. In response to the remarkable prevalence of chromosome rearrangements in swine herds, [...] Read more.
The chromosomes of the domestic pig (Sus scrofa domesticus) are known to be prone to reciprocal chromosome translocations and other balanced chromosome rearrangements with concomitant fertility impairment of carriers. In response to the remarkable prevalence of chromosome rearrangements in swine herds, clinical cytogenetics laboratories have been established in several countries in order to screen young boars for chromosome rearrangements prior to service. At present, clinical cytogenetics laboratories typically apply classical cytogenetics techniques such as giemsa-trypsin (GTG)-banding to produce high-quality karyotypes and reveal large-scale chromosome ectopic exchanges. Further refinements to clinical cytogenetics practices have led to the implementation of molecular cytogenetics techniques such as fluorescent in-situ hybridization (FISH), allowing for rearrangements to be visualized and breakpoints refined using fluorescently labelled painting probes. The next-generation of clinical cytogenetics include the implementation of DNA microarrays, and next-generation sequencing (NGS) technologies such as DNA sequencing to better explore tentative genome architecture changes. The implementation of these cytogenomics techniques allow the genomes of rearrangement carriers to be deciphered at the highest resolution, allowing rearrangements to be detected; breakpoints to be delineated; and, most importantly, potential gene implications of those chromosome rearrangements to be interrogated. Clinical cytogenetics has become an integral tool in the livestock industry, identifying rearrangements and allowing breeders to make informed breeding decisions. Full article
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15 pages, 4528 KiB  
Review
Clinical Cytogenetics of the Dog: A Review
by Izabela Szczerbal and Marek Switonski
Animals 2021, 11(4), 947; https://0-doi-org.brum.beds.ac.uk/10.3390/ani11040947 - 27 Mar 2021
Cited by 12 | Viewed by 15418
Abstract
The dog is an important companion animal and has been recognized as a model in biomedical research. Its karyotype is characterized by a high chromosome number (2n = 78) and by the presence of one-arm autosomes, which are mostly small in size. This [...] Read more.
The dog is an important companion animal and has been recognized as a model in biomedical research. Its karyotype is characterized by a high chromosome number (2n = 78) and by the presence of one-arm autosomes, which are mostly small in size. This makes the dog a difficult subject for cytogenetic studies. However, there are some chromosome abnormalities that can be easily identified, such as sex chromosome aneuploidies, XX/XY leukocyte chimerism, and centric fusions (Robertsonian translocations). Fluorescence in situ hybridization (FISH) with the use of whole-chromosome painting or locus-specific probes has improved our ability to identify and characterize chromosomal abnormalities, including reciprocal translocations. The evaluation of sex chromosome complement is an important diagnostic step in dogs with disorders of sex development (DSD). In such cases, FISH can detect the copy number variants (CNVs) associated with the DSD phenotype. Since cancers are frequently diagnosed in dogs, cytogenetic evaluation of tumors has also been undertaken and specific chromosome mutations for some cancers have been reported. However, the study of meiotic, gamete, and embryo chromosomes is not very advanced. Knowledge of canine genome organization and new molecular tools, such as aCGH (array comparative genome hybridization), SNP (single nucleotide polymorphism) microarray, and ddPCR (droplet digital PCR) allow the identification of chromosomal rearrangements. It is anticipated that the comprehensive use of chromosome banding, FISH, and molecular techniques will substantially improve the diagnosis of chromosome abnormalities in dogs. Full article
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26 pages, 831 KiB  
Review
Horse Clinical Cytogenetics: Recurrent Themes and Novel Findings
by Monika Bugno-Poniewierska and Terje Raudsepp
Animals 2021, 11(3), 831; https://0-doi-org.brum.beds.ac.uk/10.3390/ani11030831 - 16 Mar 2021
Cited by 16 | Viewed by 5105
Abstract
Clinical cytogenetic studies in horses have been ongoing for over half a century and clearly demonstrate that chromosomal disorders are among the most common non-infectious causes of decreased fertility, infertility, and congenital defects. Large-scale cytogenetic surveys show that almost 30% of horses with [...] Read more.
Clinical cytogenetic studies in horses have been ongoing for over half a century and clearly demonstrate that chromosomal disorders are among the most common non-infectious causes of decreased fertility, infertility, and congenital defects. Large-scale cytogenetic surveys show that almost 30% of horses with reproductive or developmental problems have chromosome aberrations, whereas abnormal karyotypes are found in only 2–5% of the general population. Among the many chromosome abnormalities reported in the horse, most are unique or rare. However, all surveys agree that there are two recurrent conditions: X-monosomy and SRY-negative XY male-to-female sex reversal, making up approximately 35% and 11% of all chromosome abnormalities, respectively. The two are signature conditions for the horse and rare or absent in other domestic species. The progress in equine genomics and the development of molecular tools, have qualitatively improved clinical cytogenetics today, allowing for refined characterization of aberrations and understanding the underlying molecular mechanisms. While cutting-edge genomics tools promise further improvements in chromosome analysis, they will not entirely replace traditional cytogenetics, which still is the most straightforward, cost-effective, and fastest approach for the initial evaluation of potential breeding animals and horses with reproductive or developmental disorders. Full article
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27 pages, 2316 KiB  
Review
Chromosome Abnormalities and Fertility in Domestic Bovids: A Review
by Alessandra Iannuzzi, Pietro Parma and Leopoldo Iannuzzi
Animals 2021, 11(3), 802; https://0-doi-org.brum.beds.ac.uk/10.3390/ani11030802 - 12 Mar 2021
Cited by 22 | Viewed by 4254
Abstract
After discovering the Robertsonian translocation rob(1;29) in Swedish red cattle and demonstrating its harmful effect on fertility, the cytogenetics applied to domestic animals have been widely expanded in many laboratories in order to find relationships between chromosome abnormalities and their phenotypic effects on [...] Read more.
After discovering the Robertsonian translocation rob(1;29) in Swedish red cattle and demonstrating its harmful effect on fertility, the cytogenetics applied to domestic animals have been widely expanded in many laboratories in order to find relationships between chromosome abnormalities and their phenotypic effects on animal production. Numerical abnormalities involving autosomes have been rarely reported, as they present abnormal animal phenotypes quickly eliminated by breeders. In contrast, numerical sex chromosome abnormalities and structural chromosome anomalies have been more frequently detected in domestic bovids because they are often not phenotypically visible to breeders. For this reason, these chromosome abnormalities, without a cytogenetic control, escape selection, with subsequent harmful effects on fertility, especially in female carriers. Chromosome abnormalities can also be easily spread through the offspring, especially when using artificial insemination. The advent of chromosome banding and FISH-mapping techniques with specific molecular markers (or chromosome-painting probes) has led to the development of powerful tools for cytogeneticists in their daily work. With these tools, they can identify the chromosomes involved in abnormalities, even when the banding pattern resolution is low (as has been the case in many published papers, especially in the past). Indeed, clinical cytogenetics remains an essential step in the genetic improvement of livestock. Full article
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Other

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11 pages, 1109 KiB  
Case Report
The Second Case of Non-Mosaic Trisomy of Chromosome 26 with Homologous Fusion 26q;26q in the Horse
by Sharmila Ghosh, Josefina Kjöllerström, Laurie Metcalfe, Stephen Reed, Rytis Juras and Terje Raudsepp
Animals 2022, 12(7), 803; https://0-doi-org.brum.beds.ac.uk/10.3390/ani12070803 - 22 Mar 2022
Cited by 1 | Viewed by 2097
Abstract
We present cytogenetic and genotyping analysis of a Thoroughbred foal with congenital neurologic disorders and its phenotypically normal dam. We show that the foal has non-mosaic trisomy for chromosome 26 (ECA26) but normal 2n = 64 diploid number because two copies of ECA26 [...] Read more.
We present cytogenetic and genotyping analysis of a Thoroughbred foal with congenital neurologic disorders and its phenotypically normal dam. We show that the foal has non-mosaic trisomy for chromosome 26 (ECA26) but normal 2n = 64 diploid number because two copies of ECA26 form a metacentric derivative chromosome der(26q;26q). The dam has normal 64,XX karyotype indicating that der(26q;26q) in the foal originates from errors in parental meiosis or post-fertilization events. Genotyping ECA26 microsatellites in the foal and its dam suggests that trisomy ECA26 is likely of maternal origin and that der(26q;26q) resulted from Robertsonian fusion. We demonstrate that conventional and molecular cytogenetic approaches can accurately identify aneuploidy with a derivative chromosome but determining the mechanism and parental origin of the rearrangement requires genotyping with chromosome-specific polymorphic markers. Most curiously, this is the second case of trisomy ECA26 with der(26q;26q) in the horse, whereas all other equine autosomal trisomies are ‘traditional’ with three separate chromosomes. We discuss possible ECA26 instability as a contributing factor for the aberration and likely ECA26-specific genetic effects on the clinical phenotype. Finally, because ECA26 shares evolutionary homology with human chromosome 21, which trisomy causes Down syndrome, cytogenetic, molecular, and phenotypic similarities between trisomies ECA26 and HSA21 are discussed. Full article
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