Genes “Unique” to Equids

In a previous study, two genes, UU1814 and UU18303, were found to be expressed in Equus caballus (horse) cerebellum and testis but were not represented in the genome sequences or annotation for any other species as reported in GENBANK.   These genes each appear to be comprised of three exons and, based on functional predictions, may be involved in signal transduction, membrane transport, cell communication or differentiation.  The purpose of this study was to determine whether these gene sequences are present in other species, especially relatives of the horse, such as hemiones, zebras, asses and potentially rhinos and tapirs.  Primers for all exons of both genes were designed based on the horse genomic sequence and tested using genomic DNA from diverse species.  Samples which tested negative for all three UU18303 exons include Bos taurus, Felis catus, Mus musculus and Oryctolagus cuniculus.  Samples which tested positive for all three UU18303 exons include horse, Equus asinus, Equus grevi, Equus zebra hartmannae, Equus quagga boehmi, Equus hemionus, Equus ferus przewalskii and hinny (E. caballus X E. asinus).   Test results for UU1814 were negative for Oryctolagus cuniculus, Bos taurus, Felis catus and Mus musculus samples.  Samples which tested positive for all three UU1814 exons included horse and Equus asinus.  Further testing of additional species, particularly members of the order Perissodactlya, will be carried out. Considering the source of these expressed genes, we hypothesize they may play a part in fertility or sexual behavior and possibly participated in the divergence of the order Perissodactyla.