Application of arm-specific painting probes of horse X chromosome for karyotype analysis in an infertile Hutsul mare with 64,XX/65,XX+Xp karyotype: case report

Cytogenetic Diagnosis of a British Shorthair Tomcat with a 37, X/38, XY/39, XY+der(Y) Karyotype

In this study, the determination of three different cell lines in a two-year-old British shorthair tomcat, using fluorescence in situ hybridisation (FISH), is described. The FISH technique was instrumental in the identification of this chromosomal aberration, which had not been previously described in cats. The mosaic karyotype with three cell lines (37, X; 38, XY; and 39, XY+der(Y)), detected using X-, Yand autosomal B1-whole chromosome painting probes, were all visible in the metaphase and interphase nuclei. The ratios of the three cell lines were 3.6%, 85.6% and 10.8%, respectively. In addition, at the time of this examination, the cat had a temperamental disposition that had persisted beyond castration.

Horse Clinical Cytogenetics: Recurrent Themes and Novel Findings

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.

Detection of sex chromosome aneuploidy in equine spermatozoa using fluorescence in situ hybridization

The aim of our study was to diagnose aneuploidy in equine spermatozoa by multicolour fluorescence in situ hybridization (FISH) technique using specific molecular probes for equine sex chromosomes and autosome pair four (EGFR probe) labeled by different fluorochromes. These were applied on decondensed spermatozoa of four stallions. In total, more than 8800 sperm cells were examined. The total frequency of aberrant cells was 0.496%: aneuploidy of XX (0.135%), YY (0.023%), XY (0.102%), diploidy (0.057%), lack of sex chromosome (0.18%). In one stallion the ratio of normal X- and Y-bearing cells was different from the expected 1:1 ratio (p = 0.0002), in all three other stallions this ratio was close to 1:1. The present study demonstrated that the FISH technique is a powerful method to identify sex chromosome aberrations in equine spermatozoa and allows for the determination of the ratio between X-Y-spermatozoa.

[Progress on horse genome project]

There is unique genetic information belonging to various kinds of living beings. Understanding of the formation process of organisms and a variety of vital movement is associated with the achievements of genome study. As horse has a notable health condition and great record of the genealogy in the world, thus it becomes a valuable model animal for studying life science. Despite of a late start, the map of the horse genome has undergone unprecedented expansion during the last few years. The current progresses of the horse genome, including genetic map, physical map, comparative genomic map, and functional genomics, were reviewed in this paper. The maps are currently used worldwide to discover genes associated with various traits of significance in horse including general health, disease resistance, reproduction, fertility, athletic performance, phenotypic characteristics like coat color, etc. The results are believed to provide new ideas and approaches for prevention, diagnostics, and therapeutic for horses, and also better foundation of breed selection and equine genetic breeding.

Identification of chromosome abnormalities in the horse using a panel of chromosome-specific painting probes generated by microdissection

Fluorescent in situ hybridisation (FISH) using a panel of molecular probes for all chromosome pairs obtained by chromosome microdissection of the domestic horse ( Equus caballus ) was used to diagnose karyotype abnormalities in 35 horses (32 mares, 2 stallions and 1 intersex), which were selected for the study due to infertility (23 horses), reduced fertility (10 horses) and developmental anomalies (2 horses). The use of the FISH technique with probes for each horse chromosome pair enabled the diagnosis of many different chromosome aberrations in this population. Among the horses analysed, 21 animals had normal karyotype - 64,XX (19 mares) and 64,XY (2 stallions). Fourteen animals, constituting 40% of the population studied, showed the following chromosome abnormalities: 63,X (1 mare); 63,X/64,XX (6 mares); 63,X/64,XX/65,XXX (3 mares); 63,X/65,XXX (1 mare); 64,XX/65,XX+Xp (1 mare); 63,X/64,XX/65,XX+Xq (1 mare), and 63,X/64,XX/65,XX+delY (1 intersex). When only the mares studied because of complete infertility were taken into consideration, this proportion exceeded 56%. Due to the increased frequency of the above-mentioned aberrations in the mosaic form of two or more lines, it was necessary to analyse a large number (100-300) of metaphase spreads. The use of specific molecular probes obtained by chromosome microdissection made these diagnoses much easier.

The horse genome derby: racing from map to whole genome sequence

The map of the horse genome has undergone unprecedented expansion during the past six years. Beginning from a modest collection of approximately 300 mapped markers scattered on the 31 pairs of autosomes and the X chromosome in 2001, today the horse genome is among the best-mapped in domestic animals. Presently, high-resolution linearly ordered gene maps are available for all autosomes as well as the X and the Y chromosome. The approximately 4350 mapped markers distributed over the approximately 2.68 Gbp long equine genome provide on average 1 marker every 620 kb. Among the most remarkable developments in equine genome analysis is the availability of the assembled sequence (EquCab2) of the female horse genome and the generation approximately 1.5 million single nucleotide polymorphisms (SNPs) from diverse breeds. This has triggered the creation of new tools and resources like the 60K SNP-chip and whole genome expression microarrays that hold promise to study the equine genome and transcriptome in ways not previously envisaged. As a result of these developments it is anticipated that, during coming years, the genetics underlying important monogenic traits will be analyzed with improved accuracy and speed. Of larger interest will be the prospects of dissecting the genetic component of various complex/multigenic traits that are of vital significance for equine health and welfare. The number of investigations recently initiated to study a multitude of such traits hold promise for improved diagnostics, prevention and therapeutic approaches for horses.

Cytogenetic screening of livestock populations in Europe: an overview

Clinical animal cytogenetics development began in the 1960's, almost at the same time as human cytogenetics. However, the development of the two disciplines has been very different during the last four decades. Clinical animal cytogenetics reached its 'Golden Age' at the end of the 1980's. The majority of the laboratories, as well as the main screening programs in farm animal species, presented in this review, were implemented during that period, under the guidance of some historical leaders, the first of whom was Ingemar Gustavsson. Over the past 40 years, hundreds of scientific publications reporting original chromosomal abnormalities generally associated with clinical disorders (mainly fertility impairment) have been published. Since the 1980's, the number of scientists involved in clinical animal cytogenetics has drastically decreased for different reasons and the activities in that field are now concentrated in only a few laboratories (10 to 15, mainly in Europe), some of which have become highly specialized. Currently between 8,000 and 10,000 chromosomal analyses are carried out each year worldwide, mainly in cattle, pigs, and horses. About half of these analyses are performed in one French laboratory. Accurate estimates of the prevalence of chromosomal abnormalities in some populations are now available. For instance, one phenotypically normal pig in 200 controlled in France carries a structural chromosomal rearrangement. The frequency of the widespread 1;29 Robertsonian translocation in cattle has greatly decreased in most countries, but remains rather high in certain breeds (up to 20-25% in large beef cattle populations, even higher in some local breeds). The continuation, and in some instances the development of the chromosomal screening programs in farm animal populations allowed the implementation of new and original scientific projects, aimed at exploring some basic questions in the fields of chromosome and/or cell biology, thanks to easier access to interesting biological materials (germ cells, gametes, embryos ...).