Search

National audience; This article outlines the main steps and the contribution of INRA to the development of genomics, which has revolutionised over the last two decades the knowledge of livestock genome structure and function. The development in the 1990’s of the first microsatellite marker maps quickly allowed the first major genes to be localised and numerous quantitative trait loci to be detected. Meanwhile, cytogenetics and comparative genomics studies allowed livestock genomics to benefit from advances in the knowledge of human and mouse genomes. At the end of the 1990’s, the construction of high-density mapping tools such as radiation hybrid maps and large insert libraries made it possible to develop fine mapping programmes and to identify the first causative mutations. The early 2000’s have been marked by the development of systematic gene expression tools, i.e. micro-arrays and DNA chips, the start of the first animal genome sequencing projects, and the rise of genomic databases and bioinformatics. Available sequence data then made it possible to detect in silico their variations, in particular the numerous single point polymorphisms (SNP) and to finely characterise the structure of livestock population genomes. Genomics has also renewed breeding programmes, with the development of programmes for marker-assisted selection, for the characterisation and the management of genetic variability and of parentage control or traceability applications.; Cet article retrace les principales étapes et la contribution de l’INRA au développement de la génomique, qui révolutionne depuis deux décennies les connaissances sur la structure et le fonctionnement du génome des animaux d’élevage. L’élaboration, dans les années 90, des premières cartes de marqueurs microsatellites a rapidement permis de mettre en évidence de nombreux locus à effets quantitatifs et de localiser les premiers gènes majeurs. En parallèle, les travaux de cytogénétique et de génomique comparative permettaient de tirer parti de l’avancée des connaissances sur le génome de l’homme et de la souris. A la fin des années 90, la construction d’outils de cartographie à haute densité, cartes d’hybrides d’irradiation et banques de grands fragments, a permis l’essor des travaux de cartographie fine et l’identification des premières mutations causales. Le début des années 2000 a été marqué par le développement des outils d’étude systématique de l’expression des gènes, micro-réseaux et puces à ADN, le démarrage du séquençage des premiers génomes d’animaux d’élevage, et l’essor des bases de données génomiques et de la bioinformatique. La connaissance des séquences permet ensuite de détecter in silico leurs variations, en particulier les très nombreuses variations ponctuelles (SNP) et de caractériser finement la structure des génomes des populations animales. La génomique a également renouvelé les méthodes d’amélioration génétique des populations, avec la mise en place de programmes de sélection assistée par marqueurs, de caractérisation et de gestion de la variabilité génétique et le développement d’applications en matière de contrôle de généalogie ou de traçabilité.

Introduction to the Symposium on Pig Biodiversity, which was held in the Spanish city of Córdoba during 7-9th November 2002

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 $F_{ m ST} = 0.27$ ), 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 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.