Linkage mapping and comparative analysis of bovine expressed sequence tags (ESTs)

Bovine expressed sequence tags (ESTs) containing microsatellites are suitable markers for both linkage and comparative maps. We isolated clones from a bovine fetal thigh skeletal muscle cDNA library that were positive for a (CA)(10) probe. Thirty individual clones were isolated and characterised by sequencing. Sequences from the 5' and 3' ends of a clone were considered as separate ESTs until a contiguous sequence was identified. A total of 47 ESTs were sequenced from the 5' and/or 3' ends and full sequence was obtained for the 30 clones. BLAST nucleotide analysis identified significant homology to known mammalian coding regions for 31 of the bovine ESTs, 30 of which also matched human ESTs or sequence-tagged sites (STS). The remaining 16 bovine ESTs represented novel transcripts. Microsatellites were isolated in 27 of the ESTs, 11 of which were developed into markers and placed on the MARC bovine linkage map. Human cytogenetic map positions were available for 20 of the 30 human EST orthologs, and a putative bovine map position for 17 of the sequences could be inferred using comparative mapping data. These results demonstrated that mapping bovine ESTs containing microsatellites is a plausible strategy to increase the density of gene markers on the bovine linkage and comparative maps.