A successful strategy for comparative mapping with human ESTs: 65 new regional assignments in the pig

Large-scale sequencing of cDNAs from numerous tissues is currently being pe rformed within the framework of the Human Genome Project. These expressed s equence tags (ESTs) are then mapped on a radiation hybrid panel to produce a high-resolution map of human genes. In this report, we estimate the effic iency of mapping these ESTs in the pig. A total of 344 human ESTs from Gene thon were selected for amplification in other species by Zoo-PCR: 186 of th ese could be reproducibly amplified by use of pig DNA and the corresponding human primer pairs. One-hundred seven of these were tested on a porcine-ro dent somatic cell hybrid panel, permitting regional localizations of 65 EST s with agarose or single-strand conformation polymorphism analysis gels. Th e corresponding pig PCR products were sequenced: 60 ESTs matched significan tly with the expected human sequences. Fifty-one of these localizations in the pig are in agreement with the comparative mapping data between humans a nd pigs based on heterologous chromosome painting. Seven ESTs that were loc alized in an unexpected region may indicate new chromosomal correspondences . This work significantly increases the number of genes mapped on the pig g enome and demonstrates that this approach can be successfully applied to im prove the gene density of mammalian genomic maps in chromosomal regions of interest, such as those in which QTL, (Quantative Trait Loci) have been ide ntified.