Isolation of microsatellite markers in animals

Microsatellites, or simple sequences, consist of tandemly repeated units of DNA, each between one and ten base-pairs in length, such as (TG)n or (AAT)n. Because of their high variability and rapid evolution, microsatellites are becoming increasingly important in gene mapping and population studies. For the isolation of microsatellites, standard genomic libraries need to yield at least 5000 recombinants, since the proportion of recombinants containing microsatellites usually varies between only 0.5 and 2%. Conventional methods for isolating microsatellites rely on screening of vast numbers of recombinants to locate those few containing microsatellites. More recently, several laboratories have described methods for 'enriching' for specific microsatellite repeats. These enrichment methods increase the number of recombinant colonies with microsatellites 10-100-fold, greatly reducing the screening time and facilitating the identification of potentially hundreds of microsatellite loci in a short time period. In this study, we describe an enrichment method that has been independently developed in a number of different animal and plant laboratories. This method is generally robust and has proved successful in creating microsatellite enriched libraries in our laboratory in species ranging from antelopes to Komodo dragons.