Towards a Molecular Characterization of an Imprinted QTL Affecting Muscle Mass in Pig

Valerie Amarger
Department of Animal Breeding and Genetics; Swedish University of Agricultural Sciences

We have identified a paternally expressed QTL affecting cardiac and skeletal muscle mass segregating in an intercross between the European Wild Boar and the Large White domestic pig (1). This QTL maps at the distal end of chromosome 2p, which is homologous to human chromosome 11p. This region harbors an important cluster of imprinted genes. Among them, the paternally expressed IGF2 gene was identified as a possible candidate and a pig genomic clone containing this gene was isolated and localized at chr2pl.7. A highly polymorphic microsatellite was found at the 3' end of IGF2, as previously reported in human and mice. This locus provides a unique opportunity for molecular characterization of a QTL. The identification of a putative third allele segregating in a cross between Pietrain and Large White suggests that multiple alleles are present at this QTL in pig (2). New markers in the region are isolated in order to define haplotypes associated with the QTL effect and narrow as much as possible the candidate region. Two BAC clones spanning around 200 kb have been isolated and shown to contain the genes for Tyrosine Hydroxylase, Insulin, IGF2 and H19 which are clustered in the homologous region on human chr11p. The complete region is in process to be sequenced. The aim is to characterize the entire region and to identify potential regulatory regions. Comparative sequencing of this region in animals carrying different QTL alleles will be performed in order to identify possible causative mutations. This work is carried out in collaboration with Prof. Michel Georges' group in Liege.


  1. Jeon et al., Nat. Genet. 21: 157-158, 1999.

  2. Nezer et al., Nat. Genet. 21: 155-156, 1999.