Phenotypic comparisons of: (top) “double muscled” bull homozygous for loss-of-function allele at the myostatin (MSTN) locus. Photograph courtesy of Michel Georges, University of Liège, Belgium. (Middle) Forelimb of GDF-8 (myostatin) knockout mouse (left) versus wild-type littermate (right). Photograph courtesy of Se-Jin Lee, Johns Hopkins University School of Medicine, Baltimore. Reprinted with copyright permission from Nature Publishing Group © 1997, from McPherron et al. 1997 (http://www.nature.com/). (Lower) Child at age of 6 d (left) and 7mo(right) homozygous for loss-of-function allele in the myostatin gene. Photograph courtesy of Markus Schuelke, University Medical Center, Berlin. Reprinted with copyright permission from the Massachusetts Medical Society and the New England Journal of Medicine © 2004, from Schuelke et al. 2004.
