June 5, 2006 Thanks to a recent study on the genetic factors that promote muscular hypertrophy among Texel sheep, Prof. Michel Georges' team at the University of Liège has discovered a new kind of mutation that could be at the origin of many phenotypes in various species, among which humans, including genetic predispositions to certain hereditary diseases. This discovery is of significant interest to the international scientific community. The results are published in this week's edition of the American journal Nature Genetics.
The authors describe the discovery of a novel class of mutations that disrupt the function of a gene and thereby cause a specific phenotype. The mutation created the appearance of an "illegitimate" microRNA (miRNA) recognition site in a gene that did not have it in its normal form.
In this study, the gene concerned is the myostatin. This gene is expressed in the skeletal muscle and the function of the derived protein is to inhibit muscular growth. The mutation discovered among sheep exposed a recognition site for two miRNAs that are highly expressed in the muscle. In "mutant" animals, these miRNAs will consequently target the myostatin gene and block its translation. The result is that the absence of myostatin provokes a muscular hypertrophy among Texel sheep.
A mechanism observed in other species as well
However, Michel Georges' team investigated further. Pursuing the study using bioinformatic approaches, the team identified polymorphisms (common mutations) among humans and mice that are likely to act in the same way as they do in the Texel breed. It appears, therefore, that this new kind of mutation, discovered while studying sheep, could contribute significantly to the phenotypic variation observed in many species – among which humans – including the hereditary predisposition to various diseases.
Researchers at ULg have thus produced a database available online that compiles all these mutations (the Patrocles database: http://www.patrocles.org). It will assist researchers around the world in discovering similar phenomena for other phenotypes including hereditary diseases.
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