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.

Identification of a common haplotype in carriers of rob(1;29) in 32 Italian cattle breeds

Robertsonian translocation 1;29 (rob(1;29)), a widespread chromosomal anomaly affecting cattle fertility, appears to have originated from a common ancestor. This study utilizes routine SNP data to investigate the chromosomal region associated with rob(1;29) and confirm the presence of a shared haplotype among carriers in diverse Italian breeds. Three datasets were employed: Dataset 1 included 151 subjects from 5 beef cattle breeds genotyped with the GGP Bovine 33 k SNP chip; Dataset 2 encompassed 800 subjects from 32 Italian breeds genotyped with the Illumina 50 k SNP chip, sourced from the BOVITA dataset; Dataset 3 combined Dataset 2 with 21 karyologically tested subjects from breeds with a high carrier frequency, genotyped using the Affymetrix 65 K SNP chip. FST analysis pinpointed a distinctive genomic region on the first six Mb of BTA29, the centromeric region involved in the translocation. Haplotype comparisons within this non-recombining region revealed a common haplotype shared among all carriers, supporting the theory of a common ancestor. Principal component and haplotype analysis allowed clear differentiation of rob(1;29) homozygous and heterozygous carriers. Expanding to Dataset 2 revealed rob(1;29) carriers in unexpected breeds, all sharing the same ancestral haplotype. Notably, previously untested breeds, including Cinisara, exhibited a high carrier prevalence (nearly 50%), confirmed by karyological analysis. This study validates the presence of a shared haplotype among all identified rob(1;29) carriers, reinforcing the common ancestor theory as the origin of this translocation's spread throughout the cattle population. Furthermore, it underscores the potential of SNP data analysis as a rapid, accurate, and cost-effective tool for broad rob(1;29) screening, given the translocation's consistent nature across all analyzed breeds.

The Economic Burden of Chromosome Translocations and the Benefits of Enhanced Screening for Cattle Breeding

Simple Summary

The global cattle industry, dairy and beef, provides 81% of the world’s milk and 22% of its meat requirements. Milk production has more than doubled in the last 50 years, and there is increased focus on increasing production by more efficient, sustainable means. A key to this success is the bull, which, if sub-fertile, can have a severe impact on costs and the environment. The leading cause of bull infertility is so called “RTs”, where large parts of the genome are translocated to other parts where they would not normally reside. The purpose of this study was to provide a framework for calculating the financial impact that an RT can have, and therefore the benefits of a screening programme to not using such bulls for breeding. We recently developed a novel method of RT screening, which we think detects at least three times as many compared to the traditional method. We calculated that the economic benefit of proactively screening (and therefore not using) a bull with an RT could be GBP 7.2 million pounds (nearly USD 9 million) per bull over six years. Our expanding knowledge of the incidence of genetic abnormalities and their associated costs to production support the decision of the cattle industry to use screening approaches to guard against the use of bulls with RTs.

Abstract

The cattle breeding industry, through both of its derivatives (dairy and beef), provides 81% of milk and 22% of meat required globally. If a breeding bull is sub-fertile, this impacts herd conception and birth rates, and it is generally accepted that having a proactive genetic screening programme can prevent further losses. Chromosome translocations are the leading genetic cause of infertility in livestock and, in cattle, this extends beyond the classical 1:29 to other Robertsonian translocations (RobTs) and to reciprocal translocations (RECTs). The incidence of both (collectively termed RTs) varies between breeds and herds; however, we estimate that RECTs are, most likely, at least twice as common as RobTs. The purpose of this study was to develop an industry economic model to estimate the financial impact of an RT event at the herd level. If we assume a conservative incidence rate of 0.4% for Rob1:29 with each one impacting the conception rate by 5%, we calculate that actively screening for and removing a Rob1:29 bull could benefit an impacted herd by GBP 2.3 million (approx. USD 2.8 million) over six years. A recently updated screening protocol developed in our lab for all RTs, however (with a projected combined incidence of 1.2%, impacting conception rates by 10%), could benefit an impacted herd by GBP 7.2 million (nearly USD 9 million) for each RT found. For an industry worth USD 827.4 billion (dairy) and USD 467.7 billion (beef), expanding knowledge on incidence and further dissection of the potential costs (financial and environmental) from RTs is essential to prevent further losses.

The effect of the Robertsonian translocation 1/29 on the fertility of beef cattle reared under extensive conditions: a 30 years retrospective study

The Robertsonian translocation 1/29 (rob(1;29)) is the most worldwide widespread chromosomal abnormality in domestic animals. Previous studies have demonstrated its negative effect on fertility in dairy herds, but not in beef cattle extensively bred. In this study, we analyzed the effect of rob(1;29) in a Retinta cattle breed dataset gathered during the last 30 years. The data presented herein includes rob(1;29) analysis of 11,505 cows from 251 herds, pedigree information of 24,790 animals, and 67,457 calving records. Fertility was evaluated using estimated breeding values for the reproductive efficiency (Re), calculated as the percentage ratio between the number of calvings of an individual with the number expected in an optimal situation. Our results showed that cows carrying the heterozygote genotype showed a significant decrease in their Re (-5.10%, p<0.001). No decrease was detected in free rob(1;29) animals and homozygous carriers. In addition, the incidence of rob(1;29) in the breed fertility was decreased to very low values after 30 years of avoiding selection bulls carrier as stallions. The effect of rob(1;29) in cattle fertility is only significant when the prevalence of carrier individuals is high. Selecting against the disease only by the paternal side reduced the incidence to negligible values.

Analysis of the Robertsonian (1;29) fusion in Bovinae reveals a common mechanism: insights into its clinical occurrence and chromosomal evolution

The interest in Robertsonian fusion chromosomes (Rb fusions), sometimes referred to as Robertsonian translocations, derives from their impact on mammalian karyotype evolution, as well from their influence on fertility and disease. The formation of a Rb chromosome necessitates the occurrence of double strand breaks in the pericentromeric regions of two chromosomes in the satellite DNA (satDNA) sequences. Here, we report on the fine-scale molecular analysis of the centromeric satDNA families in the Rb(1;29) translocation of domestic cattle and six antelope species of the subfamily Bovinae. We do so from two perspectives: its occurrence as a chromosomal abnormality in cattle and, secondly, as a fixed evolutionarily rearrangement in spiral-horned antelope (Tragelaphini). By analysing the reorganization of satDNAs in the centromeric regions of translocated chromosomes, we show that Rb fusions are multistep, complex rearrangements which entail the precise elimination and reorganization of specific (peri)centromeric satDNA sequences. Importantly, these structural changes do not influence the centromeric activity of the satellite DNAs that provide segregation stability to the translocated chromosome. Our results suggest a common mechanism for Rb fusions in these bovids and, more widely, for mammals in general.

Sperm chromosome segregation of rob(4;16) and rob(4;16)inv(4) in the brown brocket deer (Mazama gouazoubira)

The genus Mazama stands out among the Neotropical deer due to their wide intra and interspecific karyotypic diversification, which is associated with an accentuated chromosomal fragility. There are reports of heterozygous Robertsonian translocation (RT) carriers in a free-range population of Mazama gouazoubira (brown brocket deer), as well as in captive animals of this and other species of the genus. To analyze possible negative impacts of heterozygous chromosome rearrangements on reproductive fitness of the carriers, we performed an analysis of sperm meiotic segregation in four brown brocket bucks, carriers of a rob(4;16), and compared the results with those of a normal buck. We established a reliable FISH and sperm-FISH protocol for the brown brocket deer using bovine (Bos taurus; diploid number, 2n = 60) whole chromosome painting (WCP) and BAC probes. Using BAC probes, we revealed the presence of a paracentric inversion (PAI) of the fused chromosome 4 in two of the four analyzed RT carriers. The mean frequency of normal/balanced sperm in the translocation carriers was significantly lower than in the normal buck (94.78% vs 98.40%). The mean value of total unbalanced spermatozoa was almost doubled in the RT/PAI carriers (6.68%) when compared to RT carriers (3.76%), but the difference was not statistically significant. This study demonstrated the efficiency of FISH with bovine WCP and BAC probes in the characterization of chromosome rearrangements and gametic segregation patterns in brown brocket deer. Our results indicate a low to moderate increase in the rates of unbalanced meiotic segregation products in brown brocket bucks heterozygous for RT and RT/PAIs.

Chromosomal Polymorphism and Speciation: The Case of the Genus Mazama (Cetartiodactyla; Cervidae)

Chromosomal polymorphism plays a major role in speciation processes in mammals with high rates of karyotypic evolution, as observed in the family Cervidae. One remarkable example is the genus Mazama that comprises wide inter- and intra-specific chromosomal variability. To evaluate the impact of chromosomal polymorphisms as reproductive barriers within the genus Mazama, inter-specific hybrids between Mazama gouazoubira and Mazama nemorivaga (MGO × MNE) and intra-specific hybrids between cytotypes of Mazama americana (MAM) differing by a tandem (TF) or centric fusion (Robertsonian translocations—RT) were evaluated. MGO × MNE hybrid fertility was evaluated by the seminal quality and testicular histology. MAM hybrids estimation of the meiotic segregation products was performed by sperm-FISH analysis. MGO × MNE hybrids analyses showed different degrees of fertility reduction, from severe subfertility to complete sterility. Regarding MAM, RT, and TF carriers showed a mean value for alternate segregation rate of 97.74%, and 67.23%, and adjacent segregation rate of 1.80%, and 29.07%, respectively. Our results suggested an efficient post-zygotic barrier represented by severe fertility reduction for MGO × MNE and MAM with heterozygous TF. Nevertheless, RT did not show a severe effect on the reproductive fitness in MAM. Our data support the validity of MGO and MNE as different species and reveals cryptic species within MAM.

Analysis of meiotic segregation by triple-color fish on both total and motile sperm fractions in a t(1p;18) river buffalo bull

Chromosomal aberrations are relatively frequent pathologies in both humans and animals. Among them, translocations present a specific meiotic segregation pattern able to give a higher percentage of unbalanced gametes that can induce fertility problems. In this study, the meiotic segregation patterns of 1p, 1q and 18 Bubalus bubalis chromosomes were analyzed in both total sperm fraction and motile sperm fraction of a t(1p;18) carrier and a control bulls by triple-color FISH analysis with a pool of specific BAC probes. The frequencies of each total sperm fraction products in the carrier resulting from alternate, adjacent I, adjacent II and 3:1 segregation were 39%, 20%, 1% and 38%, respectively. On the other hand, the frequencies of each motile sperm fraction products in the carrier resulting from alternate, adjacent I, adjacent II and 3:1 segregation were 93%, 5%, 0% and 2%, respectively. The frequencies of normal sperms in the carrier were 27% and 69% in total sperm fraction and motile sperm fraction, respectively. The frequencies detected in motile sperm fraction were also validated by comparison with bull’s progeny. To our knowledge, this is the first report on the meiotic segregation patterns in motile sperm fractions of B. bubalis bull carrying a chromosomal translocation. These data suggest that translocation has a very limited effect on aneuploidy in the gametes, and therefore, on the reproductive abilities of the bull.

A new Approach for Accurate Detection of Chromosome Rearrangements That Affect Fertility in Cattle

Simple Summary

Globally, cattle production has more than doubled since the 1960s, with widespread use of artificial insemination (AI) and an emphasis on a small pool of high-genetic-merit animals. Selecting AI bulls with optimal fertility is therefore vital, as impaired fertility reduces genetic gains and reduces production, resulting in heavy financial and environmental losses. Chromosome translocations, where large parts of the genome are inappropriately attached in abnormal patterns, are a common cause of reduced fertility; however, reciprocal translocations are significantly underreported due to the difficulties inherent in analysing cattle chromosomes. Based on our previous work, we have developed an approach for the unambiguous detection of abnormalities that affect fertility. We applied this method on the chromosomes of 39 bulls, detecting multiple abnormalities that affect fertility, including those that would be undetectable using traditional screening techniques. With UK dairy calving rates of only 50–60%, it is vital to reduce further fertility loss in order to maximise productivity. The approach developed here identifies abnormalities that DNA sequencing will not, and has the potential to lead to long-term gains, delivering meat and milk products in a more cost-effective and environmentally-responsible manner to a growing population.

Abstract

Globally, cattle production has more than doubled since the 1960s, with widespread use of artificial insemination (AI) and an emphasis on a small pool of high genetic merit animals. Selecting AI bulls with optimal fertility is, therefore, vital, as impaired fertility reduces genetic gains and production, resulting in heavy financial and environmental losses. Chromosome translocations, particularly the 1;29 Robertsonian translocation, are a common cause of reduced fertility; however, reciprocal translocations are significantly underreported due to the difficulties inherent in analysing cattle chromosomes. Based on our porcine work, we have developed an approach for the unambiguous detection of Robertsonian and reciprocal translocations, using a multiple-hybridization probe detection strategy. We applied this method on the chromosomes of 39 bulls, detecting heterozygous and homozygous 1;29 translocations and a 12;23 reciprocal translocation in a total of seven animals. Previously, karyotype analysis was the only method of diagnosing chromosomal rearrangements in cattle, and was time-consuming and error-prone. With calving rates of only 50–60%, it is vital to reduce further fertility loss in order to maximise productivity. The approach developed here identifies abnormalities that DNA sequencing will not, and has the potential to lead to long-term gains, delivering meat and milk products in a more cost-effective and environmentally-responsible manner to a growing population.

Chromosome Aberrations and Fertility Disorders in Domestic Animals

The association between chromosomal abnormalities and reduced fertility in domestic animals is well recorded and has been studied for decades. Chromosome aberrations directly affect meiosis, gametogenesis, and the viability of zygotes and embryos. In some instances, balanced structural rearrangements can be transmitted, causing fertility problems in subsequent generations. Here, we aim to give a comprehensive overview of the current status and future prospects of clinical cytogenetics of animal reproduction by focusing on the advances in molecular cytogenetics during the genomics era. We describe how advancing knowledge about animal genomes has improved our understanding of connections between gross structural or molecular chromosome variations and reproductive disorders. Further, we expand on a key area of reproduction genetics: cytogenetics of animal gametes and embryos. Finally, we describe how traditional cytogenetics is interfacing with advanced genomics approaches, such as array technologies and next-generation sequencing, and speculate about the future prospects.

Fatal Outcome in a Newborn Calf Associated with Partial Trisomy 25q and Partial Monosomy 11q, 60,XX,der(11)t(11;25)(q11;q14∼21)

A newborn calf of the Agerolese cattle breed underwent clinical cytogenetic investigation because of hyperflexion of the forelimbs, red eyes and the inability to stand. Anamnesis revealed that the mother, phenotypically normal, carried a chromosomal aberration. The newborn died after 2 weeks, and no remarkable alterations were found by the veterinarian on postmortem examination. The mother was a carrier of a reciprocal balanced translocation rcp(11;25)(q11,q14∼21) detected after a cytogenetic investigation in 2011; however, the analysis of the newborn revealed a different chromosomal aberration with partial trisomy of chromosome 25 and partial monosomy of chromosome 11. In fact, the results showed both chromosomes 25, one chromosome 11 and only one long derivative chromosome (der11). FISH analysis, performed using BAC clones, confirmed the chromosomes and their regions involved. Finally, both the localization of the breakpoints on band q11 (centromere) of chromosome 11 and band q14-21 of chromosome 25, and the complete loss of the der25 identified the aberration as an unbalanced translocation 60,XX,der(11)t(11;25)(q11;q14∼21). A comparison with human chromosomes was also performed to search for similarities and possible genes involved in order to study their effects, thus extending the knowledge of these aberrations by case reports.

Chromosomal polymorphism in mammals: an evolutionary perspective

Although chromosome rearrangements (CRs) are central to studies of genome evolution, our understanding of the evolutionary consequences of the early stages of karyotypic differentiation (i.e. polymorphism), especially the non-meiotic impacts, is surprisingly limited. We review the available data on chromosomal polymorphisms in mammals so as to identify taxa that hold promise for developing a more comprehensive understanding of chromosomal change. In doing so, we address several key questions: (i) to what extent are mammalian karyotypes polymorphic, and what types of rearrangements are principally involved? (ii) Are some mammalian lineages more prone to chromosomal polymorphism than others? More specifically, do (karyotypically) polymorphic mammalian species belong to lineages that are also characterized by past, extensive karyotype repatterning? (iii) How long can chromosomal polymorphisms persist in mammals? We discuss the evolutionary implications of these questions and propose several research avenues that may shed light on the role of chromosome change in the diversification of mammalian populations and species.

Genomic analysis of cattle rob(1;29)

Robertsonian translocation (rob) involving chromosomes 1 and 29 represents the most frequent chromosome abnormality observed in cattle breeds intended for meat production. The negative effects of this anomaly on fertility are widely demonstrated, and in many countries, screening programs are being carried out to eliminate carriers from reproduction. Although rob(1;29) was first observed in 1964, the genomic structure of this anomaly is partially unclear. In this work, we demonstrate that, during the fusion process, around 5.4 Mb of the pericentromeric region of BTA29 moves to the q arm, close to the centromere, of rob(1;29). We also clearly show that this fragment is inverted. We find that no deletion/duplication involving sequences reported in the BosTau6 genome assembly occurred during the fusion process which originates this translocation.

Reciprocal translocations in cattle: frequency estimation

Chromosomal anomalies, like Robertsonian and reciprocal translocations, represent a big problem in cattle breeding as their presence induces, in the carrier subjects, a well-documented fertility reduction. In cattle, reciprocal translocations (RCPs, a chromosome abnormality caused by an exchange of material between non-homologous chromosomes) are considered rare as to date only 19 reciprocal translocations have been described. In cattle, it is common knowledge that the Robertsonian translocations represent the most common cytogenetic anomalies, and this is probably due to the existence of the endemic 1;29 Robertsonian translocation. However, these considerations are based on data obtained using techniques that are unable to identify all reciprocal translocations, and thus, their frequency is clearly underestimated. The purpose of this work is to provide a first realistic estimate of the impact of RCPs in the cattle population studied, trying to eliminate the factors that have caused an underestimation of their frequency so far. We performed this work using a mathematical as well as a simulation approach and, as biological data, we considered the cytogenetic results obtained in the last 15 years. The results obtained show that only 16% of reciprocal translocations can be detected using simple Giemsa techniques, and consequently, they could be present in no <0.14% of cattle subjects, a frequency five times higher than that shown by de novo Robertsonian translocations. This data is useful to open a debate about the need to introduce a more efficient method to identify RCP in cattle.

The measurement of induced genetic change in mammalian germ cells

In vivo methods are described to detect clastogenic and aneugenic effects of chemical agents in male and female germ cells in vivo. The knowledge of stages of germ cell development and their duration for a given test animal is essential for these experiments. Commonly, mice or rats are employed. Structural chromosome aberrations can be analyzed microscopically in mitotic cell divisions of differentiating spermatogonia, zygotes, or early embryos as well as in first meiotic cell divisions of spermatocytes and oocytes. Numerical chromosome aberrations are scorable during second meiotic divisions of spermatocytes and oocytes. The micronucleus test is applicable to early round spermatids and to first cleavage embryos, and as in somatic cells, it assesses structural as well as numerical chromosome aberrations. In contrast to the somatic micronucleus assay, the timing of cell sampling determines whether the micronuclei scored in round spermatids were formed from structural or numerical aberrations, i.e. with short treatment-sampling intervals the micronuclei are formed by exposed meiotic divisions and represent induced non-disjunction. On the -contrary, after longer intervals of 12-14 days micronuclei are formed from induced unstable structural aberrations in differentiating spermatogonia or during the last round of DNA-synthesis in early spermatocytes. Furthermore, labelling with fluorescent DNA-probes can be used to confirm these theoretical expectations. The mouse sperm-FISH assay is totally based on scoring colour spots from individual chromosomes (e.g. X, Y, and 8) hybridized with specific DNA-probes. The most animal demanding assay described here is the dominant lethal test. It is commonly performed with treated male laboratory rodents and allows the determination of the most sensitive developmental stage of spermatogenesis to a particular chemical under test. Theoretically, unstable structural chromosome aberrations in sperm will lead to foetal deaths after fertilization at around the time of implantation in the uterus wall. These can be scored as deciduomata or early dead foetuses in the uterus wall of the females at mid-pregnancy. None of the tests described in this chapter provide data for a quantitative estimate of the genetic risk to progeny from exposed germ cells. The only tests on which such calculations can be based, the heritable translocation assay and the specific locus test, are so animal and time-consuming that they can no more be performed anywhere in the world and thus are not described here.

Extended cytogenetic maps of sheep chromosome 1 and their cattle and river buffalo homoeologues: comparison with the OAR1 RH map and human chromosomes 2, 3, 21 and 1q

Cytogenetic maps are useful tools for several applications, such as the physical anchoring of linkage and RH maps or genome sequence contigs to specific chromosome regions or the analysis of chromosome rearrangements. Recently, a detailed RH map was reported in OAR1. In the present study, we selected 38 markers equally distributed in this RH map for identification of ovine genomic DNA clones within the ovine BAC library CHORI-243 using the virtual sheep genome browser and performed FISH mapping for both comparison of OAR1 and homoeologous chromosomes BBU1q-BBU6 and BTA1-BTA3 and considerably extending the cytogenetic maps of the involved species-specific chromosomes. Comparison of the resulting maps with human-identified homology with HSA2q, HSA3, HSA21 and HSA1q reveals complex chromosome rearrangements differentiating human and bovid chromosomes. In addition, we identified 2 new small human segments from HSA2q and HSA3q conserved in the telomeric regions of OAR1p and homoeologous chromosome regions of BTA3 and BBU6, and OAR1q, respectively. Evaluation of the present OAR1 cytogenetic map and the OAR1 RH map supports previous RH assignments with 2 main exceptions. The 2 loci BMS4011 and CL638002 occupy inverted positions in these 2 maps.

Effects of 5-azacytidine on lymphocyte-metaphases of Creole cows carrying the rob(1;29)

The Robertsonian translocation rob(1;29) is the most important chromosomal abnormality in cattle. It has been demonstrated that carriers of this chromosomal alteration exhibit reduced fertility due to an early embryonic loss. In the present study we analyzed the effects of DNA methylation inhibitor 5-azacytidine (5-aza-C) on metaphase lymphocytes from Uruguayan Creole cows carrying the rob(1;29). The analysis was focused on the chromatin structure of rob(1;29) comparing it to active and inactive BTAX chromosomes. Lymphocyte cultures were treated with 5-aza-C (1 x 10(-3)M) for 2 h to analyze regions of chromatin decondensation. A comparative analysis of chromatin decondensation among rob(1;29), active BTAX and inactive BTAX showed significant differences (p=1.07 x 10(-7)). Post-hoc pair-wise comparisons using the Mann-Whitney U-test showed significant differences between rob(1;29) and active BTAX (p=1.97 x 10(-5)) and between the active BTAX and inactive BTAX (p=2.55 x 10(-7)). Nevertheless, rob(1;29) did not show significant differences when compared to inactive BTAX (p=0.078). Robertsonian translocation rob(1;29) showed a despiralization pattern similar to the inactive X chromosome. Pericentromeric despiralization in rob(1;29) and the inactive X chromosome was similar, with an average value and standard error of 0.75+/-0.11 and 0.75+/-0.083, respectively. A single condensed region was observed in the inactive X chromosome, whereas in rob(1;29) two regions of condensation, one proximal to the centromere and another proximal to the telomere were detected. Our results show that rob(1;29) and the inactive X chromosome present instability regions susceptible to 5-aza-C. Further studies will be needed to understand the nature and expression pattern of genes located in chromatin condensed regions of rob(1;29).

Short communication: Robertsonian translocations, chimerism, and aneuploidy in cattle

The aim of this study was to evaluate frequencies of Robertsonian translocations, aneuploidy, and chimerism in Holstein-Friesian, Czech Simmental, and different beef breeds in the Czech Republic from 1996 to 2007. A total of 2,425 animals were examined: 2,377 males, (991 Holstein-Friesians, 1,218 Czech Simmental sires, 168 sires of beef breeds) and 48 females. Translocation was found in 10 Czech Simmental sires, 2 Highland, 1 Charolais, and 3 Blonde d' Aquitaine sires, and in 13 females. Chimerism (XX/XY) was found in 9 Czech Simmental sires, and in 5 Holstein-Friesian sires; XXX trisomy was found in 2 heifers and XXY trisomy in 3 Charolais sires. We recommend that animals with such anomalies should be disqualified from siring stock bulls.

Phylogenomic study of spiral-horned antelope by cross-species chromosome painting

Chromosomal homologies have been established between cattle (Bos taurus, 2n = 60) and eight species of spiral-horned antelope, Tribe Tragelaphini: Nyala (Tragelaphus angasii, 2n = 55male/56female), Lesser kudu (T. imberbis, 2n = 38male,female), Bongo (T. eurycerus, 2n = 33male/34female), Bushbuck (T. scriptus, 2n = 33male/34female), Greater kudu (T. strepsiceros, 2n = 31male/32female), Sitatunga (T. spekei, 2n = 30male,female) Derby eland (Taurotragus derbianus 2n = 31male/32female) and Common eland (T. oryx 2n = 31male/32female). Chromosomes involved in centric fusions in these species were identified using a complete set of cattle painting probes generated by laser microdissection. Our data support the monophyly of Tragelaphini and a clade comprising T. scriptus, T. spekei, T. euryceros and the eland species T. oryx and T. derbianus, findings that are largely in agreement with sequence-based molecular phylogenies. In contrast, our study suggests that the arid adaptiveness of T. oryx and T. derbianus is recent. Finally, we have identified the presence of the rob(1;29) fusion as an evolutionary marker in most of the tragelaphid species investigated. This rearrangement is associated with reproductive impairment in cattle and raises questions whether subtle distinctions in breakpoint location or differential rescue during meiosis underpin the different outcomes detected among these lineages.

Chromosomal abnormalities, meiotic behavior and fertility in domestic animals

Since the advent of the surface microspreading technique for synaptonemal complex analysis, increasing interest in describing the synapsis patterns of chromosome abnormalities associated with fertility of domestic animals has been noticed during the past three decades. In spite of the number of scientific reports describing the occurrence of structural chromosome abnormalities, their meiotic behavior and gametic products, little is known in domestic animal species about the functional effects of such chromosome aberrations in the germ cell line of carriers. However, some interesting facts gained from recent and previous studies on the meiotic behavior of chromosome abnormalities of domestic animals permit us to discuss, in the frame of recent knowledge emerging from mouse and human investigations, the possible mechanism implicated in the well known association between meiotic disruption and chromosome pairing failure. New cytogenetic techniques, based on molecular and immunofluorescent analyses, are allowing a better description of meiotic processes, including gamete production. The present communication reviews the knowledge of the meiotic consequences of chromosome abnormalities in domestic animals.