KEY-WORDS: Bovine ; stature ; genome sequence

Scientists from INRA, Allice and foreign scientists all members of the 1000 cattle Consortium have explored the genetic determinism for size in cattle.

Scientists identified 163 regions of the bovine genome implicated in the variability of the stature of the animals. They identified most of the genes implicated in each region. Within these regions, the majority of the mutations responsible for stature variability are located in the non-coding regions of the genes and they play a role in gene expression regulation. The metabolic pathway for the growth hormone IGF2 is particularly concerned, even though this gene does not have mutations that affect size. A significant fraction of the genes implicated in the stature variability of cattle also play a similar role in other mammals including man and horses. Amongst these genes, several such as PLAG1 (Pleomorphic adenoma gene 1) or LCOR (ligand corepressor gene) along with the genomic regions that surround them show no variability in some breeds, suggesting there has been an important selection pressure on them and therefore on animal size.

These genomic regions help explain the reduced size of miniature animals for the Angus, Hereford and Belted Galloway breeds. However, they only explain 14% of the variability observed for the size of seven bovine populations for the Simmental, Limousine, Hereford, Charolaise, Angus and Brown Swiss breeds.

This wide-ranged study strengthened by the scientific resources shared by the partners of the international consortium "1000 bovine genomes", revealed for the first time how complex the genetic determinism is for bovine stature. This complexity is similar to that observed in man - the genes identified only explain 10-20% of the variability, on the contrary to what is found in dogs for which dozens of genes explain most of the variability, in particular between breeds.

Analogical analyses are currently underway for other traits.