Myostatin Mutations Cause Double Muscling in Cattle

The differences between humans and farm animals are obvious, from body structure to diet to reproduction. Unlike humans, swine have litters of young; cattle are ruminants; and sheep are woolly. Despite such significant differences, growth and development of mammalian species is very similar. The biological controls that govern the establishment of body axes, induction and morphogenesis of tissues, and organogenesis are conserved from flies to man. Generally, the same genes and gene products regulate the same processes in a mouse as in a pig or cow, or human. Recently, it has been determined that mammalian species are highly similar even at the genomic level, with the same genes clustered in groups on chromosomes, a phenomenon called conserved synteny. This syntenic conservation is a consequence of the common evolution of mammals until relatively recent times (on an evolutionary time scale). As a result of the fundamental similarity among mammals, it has become clear in the last two or three decades that research being conducted in the biomedical fields can have direct impact on production agriculture. Although nonhuman species are thought of by the biomedical community as models for the study of human disease, from an agricultural perspective humans and mice can be considered model species for livestock. Since the level of financial support afforded to biomedical research is in staggering excess to that of animal agriculture, the success or failure of livestock genomic research is likely to be inevitably tied to progress in studies of humans and mice whose goal is not at all directed towards livestock. Numerous examples of the application of molecular genetic studies in mice and/or humans to livestock have already been reported. For example, human genetic and biochemical studies formed the basis by which it was determined that the malignant hyperthermia (halothane susceptibility) observed in swine is due to a genetic defect in a calcium release channel gene known as the ryanodine receptor (Fujii et al., 1991). This discovery has resulted in the ability of the swine production industry to more effectively manage their herds with regards to this heritable trait. A more recent example is the discovery of a mutation in the fibroblast growth factor 3 receptor (FGFR3) gene in sheep with spider lamb syndrome, a finding which was based on studies of mice having targeted disruptions of this gene (Beever et al., 1998).