In 1997 in the September issue Science, a European team led by Michel Georges of the University of Liège in Belgium reported that the visibly distinct muscular hypertrophy, commonly known as double muscling, is caused by a mutation in the bovine version of a recently discovered gene that makes a protein called myostatin. Two other groups, one co-led by Tim Smith of the U.S. Department of Agriculture (USDA) lab in Clay Center, Nebraska (Genome Research reference), and the other by Sejin Lee of Johns Hopkins University, also found that the myostatin gene is mutated in Belgian Blues and have linked mutations in the gene to double muscling in a second breed of cattle, the Piedmontese, and in mice as well.