Comparative mapping between humans and pigs: localization of 58 anchorage markers (TOASTs) by use of porcine somatic cell and radiation hybrid panels

To increase the number of Type I markers that are directly informative for comparative mapping, 58 anchorage markers, TOASTs (Traced Orthologous Ampli fied Sequence Tags), were mapped in pig. With specific consensus primers, 7 6 TOASTs were tested in pig: 50 were regionally localized in pig on a somat ic cell hybrid panel (SCHP), and 51 were mapped on the whole genome, INA/Un iversity of Minnesota porcine Radiation Hybrid panel (IMpRH). Comparison of marker positions on RH and cytogenetic maps indicated general concordance except for two chromosomal regions. For RH mapping, all markers, apart from one, were significantly linked (LOD > 4.8) to a marker of the first-genera tion radiation hybrid map. Localization of new markers on the initial map i s necessary for drawing a framework map as shown for Chromosome Sscr 14. Th e addition of four TOASTs has enabled us to propose an improved map, using a threshold likelihood ratio of 1000/1. At the whole-genome level, this wor k significantly increased (by 50%) the number of precisely mapped gents on the porcine RH map and confirmed that the IMpRH panel is a valuable tool fo r high-resolution gene mapping in pig. Porcine PCR products were sequenced and compared with human sequences to verify their identity. Most of the loc alizations made it possible to either confirm or refine the previous compar ative data between humans and pigs obtained through heterologous chromosoma l painting or gene mapping. Moreover, the use of TOASTs in mapping studies appears to be a complement to other strategies using CATS, human ESTs, or h eterologous FISH with BACs which had already been applied to improve the ge ne density of comparative genomic maps for mammals.