Case Report Repeated Early Embryonic Loss in a Thoroughbred Mare with a Chromosomal Translocation [64,XX,t(2;13)] Teri L. Lear PhD a, * , Terje Raudsepp PhD b , Judith M. Lundquist BS a , Stuart E. Brown DVM c a Department of Veterinary Science, Maxwell H. Gluck Equine Research Center, University of Kentucky, Lexington, KY b Department of Veterinary Integrated Biosciences, Texas A&M University, College Station, TX c Hagyard Equine Medical Institute, Lexington, KY article info Article history: Received 22 October 2013 Received in revised form 16 December 2013 Accepted 8 January 2014 Available online xxxx Keywords: Horse Equine Chromosome Translocation Fertility Reproduction abstract Peripheral blood samples from a 13-year-old Thoroughbred mare were submitted for chromosome analysis. The mare had a poor reproduction record only producing four live foals during her 10 years as a broodmare. She had remained barren or experienced early embryonic loss in the other 6 years. Chromosomal analysis revealed the mare carried a rare nonreciprocal translocation involving chromosomes 2 and 13 [64,XX,t(2;13)]. Fluorescence in situ hybridization with probes specific for horse chromosomes 2 and 13 were used to confirm the nonreciprocal translocation. Both conventional and molecular cytogenetic techniques are important for identifying and characterizing chromosomal abnormalities in horses with poor reproductive performance, particularly in mares experiencing repeated early embryonic loss. Ó 2014 Elsevier Inc. All rights reserved. 1. Introduction Horses with chromosome translocations will appear healthy and normal as long as the complement of genetic material is complete, called a balanced translocation. Chromosome translocations can disrupt normal meiosis and cause the production of unbalanced gametes. The percentage of unbalanced gametes depends on the location and size of the translocation. If the gametes are unbalanced, then repeated early embryonic loss (REEL) can occur resulting in infertility and/or subfertility. Depending on the size and nature of the translocation, some mares are able to have a reasonable number of offspring whereas, for un- known reasons, others may never produce a live foal. Previously, only six cases of autosomal translocations causing REEL have been reported for the horse [1–5]. All cases were described in Thoroughbreds, five mares and two stal- lions. In each case, the translocations were different (Equus caballus, ECA) (ECA1;3), (ECA1;30), (ECA1;16), (ECA16;22), (ECA4;13), (ECA5;16þmar), and (ECA1;21). Although some translocations shared a chromosome (ECA1 and ECA16), the chromosomal breakpoints appeared to be different. Here we report a 13-year-old Thoroughbred mare pre- sented for karyotyping because of REEL. Although the mare had produced four foals, breeding records indicated that she had been barren or aborted in 5 of 9 years and required mul- tiple breedings to conceive (Table 1). Numerous pregnancies had been lost during most breeding seasons, all but one loss occurring between 20–45 days of gestation. One pregnancy was lost at 245 days and the fetus was submitted for necropsy. None of her offspring was available for karyotyping; thus, their chromosomal status could not be determined. 2. Materials and Methods 2.1. Peripheral Blood Collection, Lymphocyte Culture, and Chromosome Banding Peripheral blood was collected in sodium heparin tubes by the veterinary staff and immediately sent to the Gluck * Corresponding author at: Teri L. Lear, PhD, Veterinary Science Department, Maxwell H. Gluck Equine Research Center, University of Kentucky, Lexington, KY 40546. E-mail address: equigene@uky.edu (T.L. Lear). Contents lists available at ScienceDirect Journal of Equine Veterinary Science journal homepage: www.j-evs.com 0737-0806/$ – see front matter Ó 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jevs.2014.01.007 Journal of Equine Veterinary Science xx (2014) 1–5