Abstract

The main driving force for gene mapping in farm animals is to understand the underlying genetics of traits, such as growth, reproduction, disease resistance and production. This study has been focused on physical mapping of important trait loci in the pig. The different physical mapping techniques are powerful to construct restriction maps, reveal syntenic groups of genes and to determine the chromosomal location of genes and markers. The aim has also been to expand the number of genes mapped in the pig and to compare the results with available human data. The major histocompability complex (Mhc), has a key role in the immune system. A fibre-FISH (fluorescence in situ hybridization) analysis was performed using clones from the Mhc class I11 region in pig. The objective was to fine map the region and to estimate the size of a region using three different approaches, and compare the results with available pulsed field gel electrophoresis (PFGE) data. The results showed that all three methods can be useful and they were in fairly good agreement with the PFGE data. The RN gene has a major effect on muscle glycogen content. The mutant RN allele is dominant and result in a lower technological yield of cooked ham and reduced meat quality. A FISH analysis of six YAC clones containing five microsatellites from the RN region were ordered and assigned to the distal half of band q25 on pig chromosome 15. The results provided a more precise localization of the RN gene which facilitated the subsequent positional cloning of this gene. Chromosome 13 (SSC13) harbours the K88acHabR locus, which encodes a receptor that allows the adherence of enterotoxic E.coli bacteria. This makes newborn piglets more susceptible to lethal diharrea. SSC 13 also contain QTLs (quantitative trait locus) affecting carcass quality and early growth. In order to expand the comparative map between pig and human, eight genes residing on the human homologue (chromosome 3) were chosen and FISH mapped. The results revealed conservation of gene content but also a number of intra chromosomal rearrangements between pig and human. In a FISH analysis the IGF2 gene was assigned to the distal tip of chromosome 2p. QTL analysis using markers from the IGF2 region revealed a paternally expressed locus with large effect on muscle development. IGF2, which also is paternally imprinted became a strong candidate gene. The results further confirms the conserved terminal location of this gene through evolution. The QTL can have practical use, since males having the favourable IGF2 allele can be selected for breeding. The Dominant White locus in pig is one of the major coat colour loci. Four alleles have hitherto been described, one of them was found in this study. The dominant Belt gene causes a white belt across the shoulders and front legs in Hampshire pigs. A genome scan assigned Belt to the centromeric region of chromosome 8 (SSCS). EDNRA, which was an alternative candidate gene, was FISH mapped to the q-arm of SSC8 and thus excluded. Complete cosegregation in 105 informative meiosis and its phenotypic effect strongly suggested that Belt is a fourth allele at the KIT locus. A quantitative PCR analysis showed that Belt is not associated with a duplication. PFGE analysis was carried out and a BAC contig was constructed to characterize the duplication of KIT in white pigs. The size of the duplication was estimated at about 450 kb. The results showed that the entire coding sequence of KIT was duplicated but not the flanking genes PDGFRA and KDR.

Keywords

Pig; Genome Analysis; Physical Mapping; FISH; trait loci

Published in

Acta Universitatis Agriculturae Sueciae. Veterinaria
2000, number: 96
ISBN: 91-576-5913-3
Publisher: Swedish University of Agricultural Sciences

SLU Authors

• Törnsten, Anna

  • Department of Animal Biosciences, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Animal and Dairy Science


Permanent link to this page (URI)

https://res.slu.se/id/publ/107626