EXPRESSED SEQUENCE TAGS FOR THE HORSE

Australian Equine Blood Typing Research Laboratory, University of Queensland, St Lucia, Australia. 4072

Two equine Radiation Hybrid (RH) panels have recently been constructed and are currently being characterised. A good source of information for designing species-specific Sequence Tagged Sites (STS) for screening RH panels is through sequencing cDNA clones. These Expressed Sequence Tags (ESTs) have been used extensively as tools for gene mapping in other species and databases of thousands of single-pass sequences have been established. Currently for the horse there are only approximately 350 reports of mRNA and 170 microsatellite sequences in Genbank, and there is no EST database or repository of cDNA libraries. Therefore, to increase the number of STS of Type I markers in the horse, we have sequenced randomly chosen clones from a cDNA library of a 60-day old foetus, and designed 50 pairs of primers for screening RH panels. Of 648 clones sequenced, 317 (49%) showed homology to known sequences in Genbank, 270 (42%) represented either novel transcripts or matched sequence with unknown identity in the database, and 21 (3%), 21 (3%), 11 (1.7%) were repetitive, ribosomal and mitochondrial sequences respectively. A number of sequences occurred at high frequency, including albumin (30), alpha-fetoprotein (13), elongation factor 1-alpha (10), tubulin (8), actin (alpha, beta or gamma) (5), and collagen 1A2 (4). This information adds significantly to the current equine database and represents the first determined effort to obtain EST data in the horse for future gene mapping studies.