Sequence analysis of trinucleotide repeat microsatellites from an enrichment library of the equine genome.

This research focuses on the construction of a genomic library of equines enriched with DNA fragments containing (CAG)n repeats, useful for linkage mapping and parentage testing. The study resulted in the identification of 66 different microsatellites, potentially beneficial for chromosome comparison between equines and humans.

Construction of Enriched Equine Genomic Library

• The researchers priority was tackling the limited number of known equine microsatellites, crucial for equine parentage testing and construction of a linkage map.
• To overcome this limitation, they built an equine genomic library, filled with DNA fragments containing (CAG)n repeats.

Enrichment Method Used

• The enrichment method implemented was a blend of several steps: hybridization-capture of repeat regions using biotin-tagged oligonucleotides, a nucleotide substrate-biased polymerase reaction, and subsequent PCR amplification.
• This method was chosen due to its efficiency in cloning trinucleotide microsatellites that are less common.

Result of the Enrichment Process

• The (CAG)n repeat microsatellites were obtained at a ratio of one per 3-4 clones, representing a 10(4)-fold enrichment. This denotes a considerably efficient method that requires less time and cost for cloning.

Microsatellites Identified

• The study succeeded in identifying 66 different microsatellites containing (CAG)n repeats. The number of complete simple CAG repeats in the clones varied between 4-33, showing an average repeat length of 8.8 units.
• These microsatellites can function as sequence-tagged site (STS) markers.

Potential Utility in Comparative Genomics

• Some clones containing (CAG)n repeats revealed homology to human (CAG)n-containing genes which have been previously located.
• This suggests that these clones could serve as valuable tools for contrasting chromosomes between humans and equines.