Identification of putative homology between horse microsatellite flanking sequences and cross-species ESTs, mRNAs and genomic sequences.

The study explores the similarities between horse microsatellite flanking sequences and human sequences. Using a BLAST search, a significant number of horse flanking sequences were found to match human sequences. This has led to the discovery of new potential areas of shared DNA between horses and humans.

Background of the Research

• Microsatellites are DNA sequences that contain a repeating sequence motif, and their flanking sequences are the DNA sequences that lie on either side of these repeat sections. The homology or similar structure between these sequences in different species could imply common evolution and genetic relations.
• In this research, the team used the flanking sequences of 1534 horse microsatellites to explore potential similarities with human sequences.

Methodology

• The researchers used a type of database search known as BLAST (Basic Local Alignment Search Tool) to compare horse microsatellite sequences to human sequences. BLAST searches look for regions of local similarity between sequences and can provide insight into homologies.
• 129 flanking sequences had significant matches with human sequences under certain criteria. These sequences were then subjected to a BLAT (BLAST-Like Alignment Tool) search of the University of California Santa Cruz human genome assembly. This was done to provide a reference point in the human genome.

Results and Implications

• The analysis found that 83 flanking sequences showed high similarity to sequences of known or putative human genes. Additionally, 46 sequences demonstrated high similarity to human intragenic regions, areas within a gene.
• Interestingly, 87 of the microsatellites showed conservation of the tandem repeat in addition to flanking regions. This suggests that these features are maintained in both horses and humans, indicative of shared genetic code.
• 41 of the microsatellites had been previously mapped in the horse and 37 of these were localized to the expected syntenic location, an area on a chromosome where the genes are in the same order as they are on a chromosome of another species. The remaining 4 represent new putative regions of human-horse synteny.
• The data from this research can be used to increase the density of markers on the human-horse comparative map. This simply indicates that this research has provided more reference points or ‘markers’ on the map that shows human and horse genetic similarities, thus improving our understanding of their genetic correlation.