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AFTER YEARS of speculation, scientists are finally peering into the black box of differentiation, the prophetic moment during development when a cell closes off all options but one and commits to a singular lineage. It has long been postulated that this moment is controlled, not by a cohort of genes, but by a "master regulatory switch," a single gene that, once activated, sets in motion the cell's machinery to make only one cell type.
In 1987, the first master regulatory gene was identified by a team led by Harold Weintraub, MD, PhD, at the Fred Hutchinson Cancer Research Center, Seattle, Wash. Called MyoD, this gene is thought to activate the entire program of skeletal muscle differentiation.
Furthermore, when researchers transfect MyoD into primary cultures of other cell types—such as fibroblasts, adipocytes, and brain cells—these cells also convert to muscle. This capacity has been demonstrated repeatedly in cell types derived from
Randall T. Gene Scene: A Master Control Switch for Myogenesis Muscles Its Way Into the Clinic. JAMA. 1992;267(3):337-338. doi:10.1001/jama.1992.03480030015006