A high proportion of purebred Hampshire pigs carries the dominant RN- mutation, which causes high glycogen content in skeletal muscle. The mutation has beneficial effects on meat content but detrimental effects on processing yield. Here, it is shown that the mutation is a nonconservative substitution (R200Q) in the PRKAG3 gene, which encodes a muscle-specific isoform of the regulatory gamma subunit of adenosine monophosphate-activated protein kinase (AMPK). Loss-of-function mutations in the homologous gene in yeast (SNF4) cause defects in glucose metabolism, including glycogen storage. Further analysis of the PRKAG3 signaling pathway may provide insights into muscle physiology as well as the pathogenesis of noninsulin-dependent diabetes mellitus in humans, a metabolic disorder associated with impaired glycogen synthesis.

Abstract

A quantitative trait locus (QTL) analysis of growth and fatness data from a three-generation experimental cross between Meishan (MS) and Large White (LW) pig breeds is presented. Six boars and 23 F1 sows, the progeny of six LW boars and six MS sows, produced 530 F2 males and 573 F2 females. Nine growth traits, i.e. body weight at birth and at 3, 10, 13, 17 and 22 weeks of age, average daily gain from birth to 3 weeks, from 3 to 10 weeks and from 10 to 22 weeks of age, as well as backfat thickness at 13, 17 and 22 weeks of age and at 40 and 60 kg live weight were analysed. Animals were typed for a total of 137 markers covering the entire porcine genome. Analyses were performed using two interval mapping methods: a line-cross (LC) regression method where founder lines were assumed to be fixed for different QTL alleles and a half-/full-sib (HFS) maximum likelihood method where allele substitution effects were estimated within each half-/full-sib family. Both methods revealed highly significant gene effects for growth on chromosomes 1, 4 and 7 and for backfat thickness on chromosomes 1, 4, 5, 7 and X, and significant gene effects on chromosome 6 for growth and backfat thickness. Suggestive QTLs were also revealed by both methods on chromosomes 2 and 3 for growth and 2 for backfat thickness. Significant gene effects were detected for growth on chromosomes 11, 13, 14, 16 and 18 and for backfat thickness on chromosome 8, 10, 13 and 14. LW alleles were associated with high growth rate and low backfat thickness, except for those of chromosome 7 and to a lesser extent early-growth alleles on chromosomes 1 and 2 and backfat thickness alleles on chromosome 6.

-A set of eleven pig breeds originating from six European countries, and including a small sample of wild pigs, was chosen for this study of genetic diversity. Diversity was evaluated on the basis of 18 microsatellite markers typed over a total of 483 DNA samples collected. Average breed heterozygosity varied from 0.35 to 0.60. Genotypic frequencies generally agreed with Hardy-Weinberg expectations, apart from the German Landrace and Schwäbisch-Hällisches breeds, which showed significantly reduced heterozygosity. Breed differentiation was significant as shown by the high among-breed fixation index (overall F ST = 0.27), and confirmed by the clustering based on the genetic distances between individuals, which grouped essentially all individuals in 11 clusters corresponding to the 11 breeds. The genetic distances between breeds were first used to construct phylogenetic trees. The trees indicated that a genetic drift model might explain the divergence of the two German * Correspondence and reprints E-mail: glaval@toulouse.inra.fr 188 G. Laval et al.breeds, but no reliable phylogeny could be inferred among the remaining breeds. The same distances were also used to measure the global diversity of the set of breeds considered, and to evaluate the marginal loss of diversity attached to each breed. In that respect, the French Basque breed appeared to be the most "unique" in the set considered. This study, which remains to be extended to a larger set of European breeds, indicates that using genetic distances between breeds of farm animals in a classical taxonomic approach may not give clear resolution, but points to their usefulness in a prospective evaluation of diversity.genetic diversity / molecular marker / conservation / pig / European breed Résumé -Diversité génétique de onze races porcines européennes. Un ensemble de onze races porcines en provenance de six pays européens, et incluant un petit echantillon de sangliers, aété choisi pour uneétude de diversité génétique. Cette diversité aétéévaluée sur la base de 18 marqueurs microsatellites typés sur un total de 483échantillons d'ADN. Les racesétudiées manifestent un taux d'hétérozygotie allant de 0,35à 0,60. Les locus sont enéquililibre de Hardy-Weinbergà l'exception du cas des races allemandes Landrace et Schwäbisch-Hällisches, qui manifestent un déficit d'hétérozygotes. L'indice de différenciation entre races estélevé (F ST global de 0,27) et les distances génétiques entre individus permettent de les regrouper pratiquement en 11 ensembles distincts, correspondant aux 11 races considérées. Les distances génétiques entre races ont d'abordété utilisées pour construire des arbres phylogénétiques. Ces arbres suggèrent qu'un modèle de dérive génétique pourrait expliquer la divergence des deux races allemandes, mais aucune phylogénie fiable n'a puêtreétablie entre les races restantes. Les mêmes distances ont ensuiteété utilisées pour mesurer la diversité génétique globale de l'ensemble etévaluer la perte marginale de diversité associéeà chacune des racesétudiée...

International audienceA quantitative trait locus (QTL) analysis of growth and fatness data from a three-generation experimental cross between Meishan (MS) and Large White (LW) pig breeds is presented. Six boars and 23 F1 sows, the progeny of six LW boars and six MS sows, produced 530 F2 males and 573 F2 females. Nine growth traits, i.e. body weight at birth and at 3, 10, 13, 17 and 22 weeks of age, average daily gain from birth to 3 weeks, from 3 to 10 weeks and from 10 to 22 weeks of age, as well as backfat thickness at 13, 17 and 22 weeks of age and at 40 and 60 kg live weight were analysed. Animals were typed for a total of 137 markers covering the entire porcine genome. Analyses were performed using two interval mapping methods: a line-cross (LC) regression method where founder lines were assumed to be fixed for different QTL alleles and a half-/full-sib (HFS) maximum likelihood method where allele substitution effects were estimated within each half-/full-sib family. Both methods revealed highly significant gene effects for growth on chromosomes 1, 4 and 7 and for backfat thickness on chromosomes 1, 4, 5, 7 and X, and significant gene effects on chromosome 6 for growth and backfat thickness. Suggestive QTLs were also revealed by both methods on chromosomes 2 and 3 for growth and 2 for backfat thickness. Significant gene effects were detected for growth on chromosomes 11, 13, 14, 16 and 18 and for backfat thickness on chromosome 8, 10, 13 and 14. LW alleles were associated with high growth rate and low backfat thickness, except for those of chromosome 7 and to a lesser extent early-growth alleles on chromosomes 1 and 2 and backfat thickness alleles on chromosome 6

-A set of eleven pig breeds originating from six European countries, and including a small sample of wild pigs, was chosen for this study of genetic diversity. Diversity was evaluated on the basis of 18 microsatellite markers typed over a total of 483 DNA samples collected. Average breed heterozygosity varied from 0.35 to 0.60. Genotypic frequencies generally agreed with Hardy-Weinberg expectations, apart from the German Landrace and Schwäbisch-Hällisches breeds, which showed significantly reduced heterozygosity. Breed differentiation was significant as shown by the high among-breed fixation index (overall F ST = 0.27), and confirmed by the clustering based on the genetic distances between individuals, which grouped essentially all individuals in 11 clusters corresponding to the 11 breeds. The genetic distances between breeds were first used to construct phylogenetic trees. The trees indicated that a genetic drift model might explain the divergence of the two German * Correspondence and reprints E-mail: glaval@toulouse.inra.fr 188 G. Laval et al.breeds, but no reliable phylogeny could be inferred among the remaining breeds. The same distances were also used to measure the global diversity of the set of breeds considered, and to evaluate the marginal loss of diversity attached to each breed. In that respect, the French Basque breed appeared to be the most "unique" in the set considered. This study, which remains to be extended to a larger set of European breeds, indicates that using genetic distances between breeds of farm animals in a classical taxonomic approach may not give clear resolution, but points to their usefulness in a prospective evaluation of diversity.genetic diversity / molecular marker / conservation / pig / European breed Résumé -Diversité génétique de onze races porcines européennes. Un ensemble de onze races porcines en provenance de six pays européens, et incluant un petit echantillon de sangliers, aété choisi pour uneétude de diversité génétique. Cette diversité aétéévaluée sur la base de 18 marqueurs microsatellites typés sur un total de 483échantillons d'ADN. Les racesétudiées manifestent un taux d'hétérozygotie allant de 0,35à 0,60. Les locus sont enéquililibre de Hardy-Weinbergà l'exception du cas des races allemandes Landrace et Schwäbisch-Hällisches, qui manifestent un déficit d'hétérozygotes. L'indice de différenciation entre races estélevé (F ST global de 0,27) et les distances génétiques entre individus permettent de les regrouper pratiquement en 11 ensembles distincts, correspondant aux 11 races considérées. Les distances génétiques entre races ont d'abordété utilisées pour construire des arbres phylogénétiques. Ces arbres suggèrent qu'un modèle de dérive génétique pourrait expliquer la divergence des deux races allemandes, mais aucune phylogénie fiable n'a puêtreétablie entre les races restantes. Les mêmes distances ont ensuiteété utilisées pour mesurer la diversité génétique globale de l'ensemble etévaluer la perte marginale de diversité associéeà chacune des racesétudiée...