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Abstract. A comparative map of human chromosome 12 (HSA 12) and pig chromosome 5 (SSC 5) was constructed using ten pig expressed sequence tags (ESTs). These ESTs were isolated from primary granulosa cell cultures by differential display (EST bI Ob), or from a granulosa cDNA library (VIIIE1, DRIM, N*9, RIIID2 and RVIC1) or from a small intestine cDNA library (ATPSB, ITGB7, MYH9, and STAT2). Also used were two Traced Orthologous Amplified Sequence Tags (TOASTs) (LALBA, TRA1), one microsatellite-associated gene (IGF1) and finally five human YACs selected for their cytogenetic position, with a view to increasing the number of informative markers for the comparison. Large-insert clones were obtained by screening a pig bacterial artificial chromosome
(BAC) library with specific primers for each EST and TOAST and for IGF 1. These BACs were used as probes for fluorescent in situ hybridisation (FISH) both on porcine and human metaphases. In addition, the human YACs were FISH mapped on pig chromosomes. This allowed us to refine and, in some cases, to correct the previous mapping obtained with a somatic cell hybrid panel. While these data confirm chromosome painting results showing that the distal part of SSC Sp arm is conserved on HSA 22, while the rest of the chromosome corresponds to HSA 12, they also demonstrate gene-order differences between human and pig. In addition, it was also possible to determine the position of the synteny breakpoint.
Knowledge of the genome of domestic species has been growing rapidly for the past ten years. Concerning the pig, more than 1,500 microsatellites spanning the whole genome, have been developed thus allowing the creation of a genetic map (Rohrer et al., 1996). Of these, 115 have been used to analyse a family resulting from a cross between Meishan and Large White pig breeds and highly significant quantitative trait loci (QTLs) have been found on several chromosomes, including chromosome 5 on the distal part of the q arm (Bidanel personal communication). In order to identify the genes responsible for these traits, a candidate gene strategy could be used. However its processing would require thorough knowledge of comparative maps between pig and a gene-rich species like the human species, in order to allow the choice of a candidate gene for a porcine QTL...