Male pseudohermaphroditism in a complex malformed calf born with an acardius amorphus cotwin-a case report.

BACKGROUND: Male pseudohermaphroditism is a developmental anomaly wherein animals are genetically and gonadally male, but their internal and/or external genitalia resemble those of females. In cattle, pseudohermaphroditism is often accompanied by multiple severe malformations. To the best of our knowledge, this is the first report of male pseudohermaphroditism in a complex malformed calf born with an acardius amorphous cotwin. CASE PRESENTATION: This report describes the case of a three-day-old, male anurous Japanese Black calf born with an acardius amorphous cotwin, complete absence of the tail, agenesis of the anus, separate scrota, and umbilical hernia. Transthoracic echocardiography and computed tomography revealed serious malformations in the skeletal system and the circulatory, digestive, urinary, and genital organs. Necropsy revealed rectal atresia, immature testes, epididymis, and penis, but no male accessory gonads. Histological analyses revealed vaginal- and uterine-like tissues adjacent to or fused to the rectum. Fluorescence in situ hybridization detected X and Y chromosomes, and some cells presented two X-probe signals in the same nucleus. CONCLUSIONS: In contrast to the male genitalia, the female genitalia derived from the Müllerian ducts were difficult to detect by necropsy in the presented case. Many similar cases may be overlooked in clinical practice.

First report of Perkinsus olseni infections in blood cockles Tegillarca granosa on the south coast of Korea.

The protozoan parasite Perkinsus olseni has become a focus of attention since it has been responsible for mass mortalities and economic losses in a wide range of bivalve hosts globally. The P. olseni host range along the south coast of Korea may extend beyond what was previously understood, and blood cockles in the Family Arcidae are also suggested to be potential hosts of P. olseni. In the present study, we applied histology and molecular techniques to identify Perkinsus sp. infections in the blood cockles Tegillarca granosa, which have been commercially exploited on the south coast of Korea for several decades. Histology and molecular techniques, including genus-specific immunofluorescence assay, species-specific fluorescence in situ hybridization, and phylogeny based on the ribosomal DNA internal transcribed spacer region revealed that T. granosa is infected by P. olseni, although the prevalence was low (0.5%). Histology revealed massive hemocyte infiltrations in the mantle, gill, and digestive gland connective tissues, indicating that the infection exerts negative impacts on the host cockles.

Genital mycobacteriosis caused by Mycobacterium marinum detected in two captive sharks by peptide nucleic acid-fluorescence in situ hybridization.

Mycobacterium marinum is a prevalent nontuberculous mycobacterium (NTM)-infecting teleosts. Conversely, little is known about mycobacteriosis in elasmobranchs, and M. marinum infection has never been reported from the subclass. This study investigated the histopathological characteristics and localization of this mycobacterium through molecular analysis of two captive sharks, a scalloped hammerhead Sphyrna lewini and a Japanese bullhead shark Heterodontus japonicus, exhibited in the same aquarium tank. We detected genital mycobacteriosis caused by M. marinum infection using molecular analyses, including polymerase chain reaction (PCR) and DNA sequencing targeting the 60 kDa heat-shock protein gene (hsp65), and peptide nucleic acid-fluorescence in situ hybridization (PNA-FISH) targeting the 16S rRNA gene. Both sharks showed granulomas in connective tissues of the gonads without central necrosis or surrounding fibrous capsules, which is unlike the typical mycobacterial granulomas seen in teleosts. This study reveals that elasmobranchs can be aquatic hosts of M. marinum. Because M. marinum is a representative waterborne NTM and a potential zoonotic agent, cautious and intensive research is needed to overcome a lack of data on the relationship between NTM and the aquatic environment in association with this subclass of Chondrichthyes.

DETERMINATION OF SPECIFIC ENTEROPATHOGEN PRESENCE IN CAPTIVE CHEETAHS (ACINONYX JUBATUS) FED VARIOUS DIETS USING FLUORESCENCE IN SITU HYBRIDIZATION.

Chronic enteropathies pose an important difficulty in the captive management of cheetahs (Acinonyx jubatus) because of suspected multifactorial pathogenesis and the complex nature of enteric microbiota dynamics. Enterobacteriaceae, Campylobacter spp., Clostridium perfringens, Helicobacter spp., and Salmonella spp. are enteropathogens of interest because of their zoonotic potential and suspected contribution to enteropathies. This study aimed to determine the presence of these enteropathogens of interest in fecal samples from cheetahs (N = 48) fed different diets from three different institutions and to investigate the associations between diet, fecal score, and specific enteropathogen presence. Fluorescence in situ hybridization (FISH) with rRNA-targeted oligonucleotide probes were used to visualize and quantify putative enteropathogens in each sample concurrent with selective culturing for Salmonella and Clostridium perfringens. From FISH counts, carcass-fed animals had greater numbers of Enterobacteriaceae compared with animals fed low-fat dog food, although this trend was not statistically significant (P = 0.088). Furthermore, no significant associations were found between fecal score and bacterial load. Abundance of Campylobacter spp., Clostridium perfringens, or Helicobacter spp. as measured by FISH were not correlated with diet or fecal score. On the basis of these data, in agreement with published literature, it is concluded that these microbes may be commensals in the cheetah gastrointestinal tract and do not appear to be a primary cause of abnormal fecal scores.

Development of a Multiplex Fluorescence in Situ Hybridization Assay to Identify Coinfections in Young-of-the-Year Smallmouth Bass.

Histopathological assessments of young-of-the-year (age-0) Smallmouth Bass Micropterus dolomieu in the Susquehanna River drainage identified a high prevalence of the myxozoan Myxobolus inornatus. This myxozoan infects the connective tissue of the muscle below the skin but is sometimes observed in the esophagus and buccal cavity. In some instances, shallow infections cause breaks in the skin, which could increase the chance of opportunistic bacterial infections. Several microbial pathogens, including Flavobacterium columnare, Aeromonas spp., and Largemouth Bass virus, have also been cultured from clinically diseased young of year. A multiplex fluorescence in situ hybridization (FISH) assay was developed to determine potential colocalization of M. inornatus, Flavobacterium spp., and Aeromonas spp. infections. With FISH, 75% of age-0 Smallmouth Bass exhibited M. inornatus infections, 10% had Aeromonas spp. infections, and 5% had Flavobacterium spp. infections, while 3% had coinfections with both bacterial species and M. inornatus. The results of the multiplex FISH assay revealed a low occurrence of coinfections of Flavobacterium spp. and/or Aeromonas spp. with M. inornatus in randomly sampled individuals.

HER2 Overexpression and Amplification in Feline Pulmonary Carcinoma.

HER2 is overexpressed, amplified, and mutated in a subset of human lung cancer. The aim of this study was to investigate HER2 protein overexpression and gene amplification in feline pulmonary carcinomas. Thirteen pulmonary carcinomas were selected and TTF-1 and HER2 expression was evaluated by immunohistochemistry. Fluorescence in situ hybridization (FISH) was performed with a HER2 probe and a BAC probe for the feline chromosome E1p1.12-p1.11 region. Twelve adenocarcinomas and 1 squamous cell carcinoma were diagnosed. TTF-1 was positive in 7 carcinomas (58%). HER2 was overexpressed in 2 (15%), equivocal in 5 (38%), and negative in 6 cases (46%). FISH analysis of HER2 was indeterminate in 2 cases. Three pulmonary carcinomas (27%) had HER2 amplification and 8 cases were not amplified (73%). The significant correlation between HER2 protein overexpression and gene amplification are promising preliminary data, but study of additional cases is needed to confirm HER2 as a target for possible innovative treatments.

Bacterial Biogeography of the Colon in Dogs With Chronic Inflammatory Enteropathy.

The intestinal microbiota is believed to play a role in the pathogenesis of inflammatory bowel disease in humans and chronic inflammatory enteropathy (CIE) in dogs. While most previous studies have described the gut microbiota using sequencing methods, it is fundamental to assess the spatial distribution of the bacteria for a better understanding of their relationship with the host. The microbiota in the colonic mucosa of 22 dogs with CIE and 11 control dogs was investigated using fluorescence in situ hybridization (FISH) with a universal eubacterial probe (EUB338) and specific probes for select bacterial groups. The number of total bacteria labeled with EUB338 probe was lower within the colonic crypts of dogs with CIE compared to controls. Helicobacter spp. and Akkermansia spp. were decreased on the colonic surface and in the crypts of dogs with CIE. Dogs with CIE had increased number of Escherichia coli/Shigella spp. on the colonic surface and within the crypts compared to control dogs. In conclusion, the bacterial microbiota in the colonic mucosa differed between dogs with and without CIE, with depletion of the crypt bacteria in dogs with CIE. The crypt bacterial species that was intimately associated with the host mucosa in control dogs was composed mainly of Helicobacter spp.

Technical note: Droplet digital PCR precisely and accurately quantifies sex skew in bovine semen.

Quantifying the relative population of sperm cells bearing the X or Y chromosome in a sexed-semen sample has historically been limited to methods that are either low throughput and sensitive to user subjectivity (e.g., fluorescence in situ hybridization), conterminous (using the same technology to generate and confirm the sex skew), or relatively insensitive (including quantitative PCR with a change detection threshold of 2×). Customers pay a premium for sexed semen and should have access to reliable sex skew data, generated by an accurate, precise test that is orthogonal to the method used to generate sexed semen. Droplet digital PCR (ddPCR) has the capacity to provide an accurate and precise sex skew quantitation by subdividing a pool of template DNA into nanoliter-scale droplets containing either 1 or 0 copies of template DNA. Then PCR amplification is conducted in the droplets, and the number of copies of the amplicon of interest can be counted as the number of fluorescence-positive droplets based on classic quantitative PCR fluorescent reporters. We have optimized and validated a multiplexed ddPCR assay that uses this copy counting method to quantify the sex skew (ratio of X or Y chromosomes) in frozen-thawed bovine sexed semen. The assay interrogates at least 1,000 cells per sample well, quantifying X and Y chromosome copy numbers along with an autosomal gene, GAPDH, used as an internal assay control to confirm total cells counted. The ddPCR sex skew assay achieved a 0.5-percentage-point variance for %X or %Y with a broad linear detection range, from 10 to 95% X, and provided reproducible skew values across a range of 9 to 27 ng of genomic DNA input. This approach overcomes some limitations of other sex skew assays by quantifying absolute X and Y chromosome copy numbers, thus providing a rigorous, independent assessment of sex-skewed semen.

A de novo reciprocal chromosomal translocation t(3;6)(p14;q26) in the black Lucano pig.

In the past two decades, several cytogenetic screening programmes identified different chromosome rearrangements in pig, most of which represented by reciprocal translocation (rcp). This chromosome abnormality does not involve the variation in the number of chromosomes, but only the rearrangement of genetic material, resulting in phenotypically normal carriers with fertility problems. During an occasional cytogenetic screening, a new reciprocal translocation was detected in the black Lucano pig native breed. We analysed 15 animals reared by a family-run piggery in Basilicata region (Southern Italy). After karyotyping, four pigs (two boars and two sows) revealed two unpaired chromosomes. Analysis of the RBA karyotype and the dual-colour FISH technique confirmed that these pigs showed the same reciprocal translocation involving the chromosomes SSC3 and SSC6. The precise location of breakpoints was identified by RBH-FISH t(3;6)(p14;q26), whereas the analysis of the pedigree showed a case of Mendelian inheritance within a family, after the de novo occurrence of the new rcp. Considering the consequences of the rcp on the fertility, this study points out the importance of the cytogenetic screening in the native breeds for the safeguard of the genetic biodiversity and the sustainability of the rural areas.

Karyotype Evolution and Distinct Evolutionary History of the W Chromosomes in Swallows (Aves, Passeriformes).

As in many other bird groups, data on karyotype organization and distribution of repetitive sequences are also lacking in species belonging to the family Hirundinidae. Thus, in the present study, we analyzed the karyotypes of 3 swallow species (Progne tapera, Progne chalybea, and Pygochelidon cyanoleuca) by Giemsa and AgNOR staining, C-banding, and FISH with 11 microsatellite sequences. The diploid chromosome number was 2n = 76 in all 3 species, and NORs were observed in 2 chromosome pairs each. The microsatellite distribution pattern was similar in both Progne species, whereas P. cyanoleuca presented a distinct organization. These repetitive DNA sequences were found in the centromeric, pericentromeric, and telomeric regions of the macrochromosomes, as well as in 2 interstitial blocks in the W chromosome. Most microchromosomes had mainly telomeric signals. The Z chromosome displayed 1 hybridization signal in P. tapera but none in the other species. In contrast, the W chromosome showed an accumulation of different microsatellite sequences. The swallow W chromosome is larger than that of most Passeriformes. The observed enlargement in chromosome size might be explained by these high amounts of repetitive sequences. In sum, our data highlight the significant role that microsatellite sequences may play in sex chromosome differentiation.

Insights into Emydid Turtle Cytogenetics: The European Pond Turtle as a Model Species.

Our knowledge of Testudines evolution is limited by the lack of modern cytogenetic data. Compared to other reptiles, there is little information even on chromosome banding, let alone molecular cytogenetic data. Here, we provide detailed information on the karyotype of the European pond turtle Emys orbicularis, a model Emydidae, employing both chromosome banding and molecular cytogenetics. We provide a high-resolution G-banded karyotype and a map of rDNA genes and telomeric sequences using fluorescence in situ hybridization. We test hypotheses of sex-determining mechanisms in Emys by comparative genomic hybridization to determine if Emys has a cryptic sex-specific region. Our results provide valuable data to guide future efforts on genome sequencing and anchoring in Emydidae and for understanding karyotype evolution in Testudines.

A dual colour FISH method for routine validation of sexed Bos taurus semen.

BACKGROUND: Usage of sexed semen that allows to choose the gender of the calves, is commonly practiced in livestock industry as a profitable breeding alternative, especially in dairy farming. The flow cytometric cell sorting is the only commercially available method for bovine sperm sexing. For validation of the sexing procedure several methods have been developed including sperm fluorescence in situ hybridisation techniques. Latter usually include the use of pre-labelled nucleotides for probe synthesis which is relatively expensive approach compared to combined application of aminoallyl-dUTP and chemical binding of fluorescent dyes. Here a sex determining dual colour bovine sperm fluorescence in situ hybridisation method is presented which is considered more cost-effective technique than the previously reported approaches. RESULTS: The reliability of sex chromosome identifying probes, designed in silico, was proven on bovine metaphase plate chromosomes and through comparison with a commercially available standard method. In the dual colour FISH experiments of unsexed and sexed bovine sperm samples the hybridisation efficiency was at least 98%, whereas the determined sex ratios were not statistically different from the expected. Very few cells carried both of the sex chromosome-specific signals (less than 0.2%). CONCLUSIONS: A protocol for a dual colour bovine sperm FISH method is provided which is cost-effective, simple and fast for sex determination of spermatozoa in bull semen samples.

Analysis of Meiotic Segregation Pattern and Interchromosomal Effects in a Bull Heterozygous for a 3/16 Robertsonian Translocation.

Robertsonian translocations are the most frequent chromosomal rearrangements detected in cattle. Here, we report on the detection of a new Robertsonian translocation between chromosomes BTA3 and BTA16. This rob(3;16) was dicentric, suggesting that its occurrence was recent. FISH analysis of decondensed sperm nuclei revealed a relatively low rate of unbalanced gametes produced by adjacent segregation (5.87%). In addition, and for the first time in bovines, a significant interchromosomal effect (ICE) was detected for 2 different autosomes: BTA17 (global disomy + nullisomy rate of 9%) and BTA20 (1.8%). These results suggest that ICE should be taken into consideration when assessing the putative effect of Robertsonian translocations on reproduction.

Sheep embryonic stem-like cells engrafted into sheep femoral condyle osteochondral defects: 4-year follow-up.

BACKGROUND: Articular cartilage lacks a regenerative response. Embryonic stem cells (ESCs) are a source of pluripotent cells for cartilage regeneration. Their use, however, is associated with a risk of teratoma development, which depends on multiple factors including the number of engrafted cells and their degree of histocompatibility with recipients, the immunosuppression of the host and the site of transplantation. Colonies of sheep embryonic stem-like (ES-like) cells from in vitro-produced embryos, positive for stage-specific embryonic antigens (SSEAs), alkaline phosphatase (ALP), Oct 4, Nanog, Sox 2 and Stat 3 gene expression, and forming embryoid bodies, were pooled in groups of two-three, embedded in fibrin glue and engrafted into osteochondral defects in the left medial femoral condyles of 3 allogeneic ewes (ES). Empty defects (ED) and defects filled with cell-free glue (G) in the condyles of the controlateral stifle joint served as controls. After euthanasia at 4 years post-engraftment, the regenerated tissue was evaluated by macroscopic, histological and immunohistochemical (collagen type II) examinations and fluorescent in situ hybridization (FISH) assay to prove the ES-like cells origin of the regenerated tissue. RESULTS: No teratoma occurred in any of the ES samples. No statistically significant macroscopic or histological differences were observed among the 3 treatment groups. FISH was positive in all the 3 ES samples. CONCLUSIONS: This in vivo preclinical study allowed a long-term evaluation of the occurrence of teratoma in non-immunosuppressed allogeneic adult sheep engrafted with allogeneic ES-like cells, supporting the safe and reliable application of ES cells in the clinic.

The cryptic Y-autosome translocation in the small Indian mongoose, Herpestes auropunctatus, revealed by molecular cytogenetic approaches.

In initial studies of the eutherian small Indian mongoose (Herpestes auropunctatus), the Y chromosome could not be identified in somatic cells. The male chromosome number is uniquely odd, 2n = 35, whereas that of females is 2n = 36. Previous reports indicated that this unique karyotype resulted from a translocation of the ancestral Y chromosome to an autosome. However, it has been difficult to identify the chromosomes that harbor the translocated Y chromosomal segment because it is an extremely small euchromatic region. Using a Southern blot analysis, we detected four conserved Y-linked genes, SRY, EIF2S3Y, KDM5D, and ZFY, in the male genome. We cloned homologues of these genes and determined their sequences, which showed high homology to genes in two carnivore species, cat and dog. To unambiguously identify the Y-bearing autosome, we performed immunostaining of pachytene spermatocytes using antibodies against SYCP3, γH2AX, and the centromere. We observed trivalent chromosomes, and the associations between the distal ends of the chromosomes were consistent with those of Y and X1 chromosomes. The centromere of the Y chromosome was located on the ancestral Y chromosomal segment. We mapped the complementary DNA (cDNA) clones of these genes to the male chromosomes using fluorescence in situ hybridization (FISH), and the linear localization of all genes was confirmed by two-colored FISH. These Y-linked genes were localized to the proximal region of the long arm of a single telomeric chromosome, and we successfully identified the chromosome harboring the ancestral Y chromosomal segment.

Gonadotropin characterization, localization and expression in the European hake (Merluccius merluccius).

In vertebrates, the regulation of gametogenesis is under the control of gonadotropins (Gth), follicle-stimulating hormone (Fsh) and luteinizing hormone (Lh). In fish, the physiological role of Gths is not fully understood, especially in species with asynchronous ovarian development. To elucidate the role of Gths in species with asynchronous ovary, we studied European hake (Merluccius merluccius) during the reproductive season. For this aim, we first cloned and sequenced both hormones. Then, we characterized their amino acid sequence and performed phylogenetic analyses to verify the relationship to their orthologues in other species. In addition, the quantification of gene expression during their natural reproductive season was analyzed in wild-caught female hake. Our results revealed that fshb peaked during the vitellogenic phase, remaining high until spawning. This is in contrast to the situation in species with synchronous ovary. lhb, on the other hand, peaked during maturation as it is also common in species with synchronous ovarian development. Finally, combining double-labeling fluorescent in situ hybridization (FISH) for Gth mRNAs with immunofluorescence for Lh protein, we evidenced the specific expression of fshb and lhb in different cells within the proximal pars distalis (PPD) of the pituitary. In addition to gonadotrope cells specific to expression of either fshb or lhb, some cells showed co-expression of both genes. This suggests either that gonadotropes with co-expression are not yet specified or they could have a plasticity that permits changes from one cell phenotype to another during certain life stages and in turn during different physiological states.

Differential chromosomal organization between Saguinus midas and Saguinus bicolor with accumulation of differences the repetitive sequence DNA.

Saguinus is the largest and most complex genus of the subfamily Callitrichinae, with 23 species distributed from the south of Central America to the north of South America with Saguinus midas having the largest geographical distribution while Saguinus bicolor has a very restricted one, affected by the population expansion in the state of Amazonas. Considering the phylogenetic proximity of the two species along with evidence on the existence of hybrids between them, as well as cytogenetic studies on Saguinus describing a conserved karyotypic macrostructure, we carried out a physical mapping of DNA repeated sequences in the mitotic chromosome of both species, since these sequences are less susceptible to evolutionary pressure and possibly perform an important function in speciation. Both species presented 2n = 46 chromosomes; in S. midas, chromosome Y is the smallest. Multiple ribosomal sites occur in both species, but chromosome pairs three and four may be regarded as markers that differ the species when subjected to G banding and distribution of retroelement LINE 1, suggesting that it may be cytogenetic marker in which it can contribute to identification of first generation hybrids in contact zone. Saguinus bicolor also presented differences in the LINE 1 distribution pattern for sexual chromosome X in individuals from different urban fragments, probably due to geographical isolation. In this context, cytogenetic analyses reveal a differential genomic organization pattern between species S. midas and S. bicolor, in addition to indicating that individuals from different urban fragments have been accumulating differences because of the isolation between them.

Clinical, microscopic and microbial characterization of exfoliative superficial pyoderma-associated epidermal collarettes in dogs.

BACKGROUND: The microscopic and microbial features of the spreading epidermal collarettes of canine exfoliative superficial pyodermas are poorly characterized. OBJECTIVES: To characterize the clinical, cytological, microbial and histopathological features of epidermal collarettes in five dogs. RESULTS: Cytology from the margins of collarettes identified neutrophils, extracellular and intracellular cocci within neutrophils but no acantholytic keratinocytes. Phenotypic and genotypic analyses identified all bacterial isolates from the centre and margin of five epidermal collarettes as Staphylococcus pseudintermedius. PCRs of collarette-associated Staphylococcus strains did not amplify genes encoding for the known exfoliative toxins expA and expB, whereas the predicted siet and speta amplification products were detected in all isolates. Microscopically, epidermal collarettes consisted of interfollicular, epidermal spongiotic pustules. Advancing edges of lesions consisted of peripheral intracorneal clefts in the deep stratum disjunctum above an intact stratum compactum; they contained lytic neutrophil debris, bacterial cocci and fluid, but no acantholytic keratinocytes. This intracorneal location of bacteria was confirmed using Gram stains and fluorescent in situ hybridization with eubacterial- and Staphylococcus-specific probes. The indirect immunofluorescence staining patterns of desmoglein-1, desmocollin-1, claudin-1, E-cadherin and corneodesmosin were discontinuous and patchy in areas of spongiotic pustules, whereas only that of corneodesmosin was weaker and patchy in advancing collarette edges. CONCLUSION: Epidermal collarettes represent unique clinical and histological lesions of exfoliative superficial pyodermas that are distinct from those of impetigo and superficial bacterial folliculitis. The characterization of possible causative staphylococcal exfoliatin proteases and the role of corneodesmosin in collarette pathogenesis deserve further investigation.

Helicobacter Species Identified in Captive Sooty Mangabeys (Cercocebus atys) with Metastatic Gastric Adenocarcinoma.

BACKGROUND: Of all human cancers, gastric carcinoma is the one of the leading causes of death. Helicobacter pylori is considered a major etiologic agent of this disease. Spontaneously occurring gastric carcinoma is a rare diagnosis in nonhuman primates. A 2011 case report documented a high incidence of gastric adenocarcinoma in a closed colony of captive sooty mangabeys (Cercebus atys). However, H. pylori infection was not detected in these animals. MATERIALS AND METHODS: In this study, using archived formalin-fixed, paraffin-embedded stomach sections of these animals alternative methodologies were used to identify H. pylori and other non-H. pylori Helicobacter species. In addition, two additional cases of sooty mangabeys with metastatic gastric carcinoma are characterized. RESULTS: Using fluorescent in situ hybridization, we identified gastric H. suis in 75% of archived and new gastric carcinoma cases. In the two newly reported cases, H. suis and a novel Helicobacter species were detected via PCR and sequence analysis of the 16S rRNA gene. H. pylori was not identified in any of the gastric carcinoma cases via FISH and/or PCR and sequence analysis of Helicobacter spp. in DNA from of available tissues. CONCLUSIONS: This report is the first to characterize Helicobacter species infection in spontaneous gastric carcinoma with metastatic potential in nonhuman primates.

A Non-Reciprocal Autosomal Translocation 64,XX, t(4;10)(q21;p15) in an Arabian Mare with Repeated Early Embryonic Loss.

Balanced autosomal translocations are a known cause for repeated early embryonic loss (REEL) in horses. In most cases, carriers of such translocations are phenotypically normal, but the chromosomal aberration negatively affects gametogenesis giving rise to both genetically balanced and unbalanced gametes. The latter, if involved in fertilization, result in REEL, whereas gametes with the balanced form of translocation will pass the defect into next generation. Therefore, in order to reduce the incidence of REEL, identification of translocation carriers is critical. Here, we report about a phenotypically normal 3-year-old Arabian mare that had repeated resorption of conceptuses prior to day 45 of gestation and was diagnosed with REEL. Conventional and molecular cytogenetic analyses revealed that the mare had normal chromosome number 64,XX but carried a non-mosaic and non-reciprocal autosomal translocation t(4;10)(q21;p15). This is a novel translocation described in horses with REEL and the first such report in Arabians. Previous cases of REEL due to autosomal translocations have exclusively involved Thoroughbreds. The findings underscore the importance of routine cytogenetic screening of breeding animals.