Transdifferentiation induced by gene transfer.

While for many tissues the differentiation process is well characterized, little is known about 'master switch' genes determining a specific differentiation pathway and having the potential to induce this process in a cell designed for a different differentiation pathway. Based on heterokaryon and 5-aza-cytidine-induced hypomethylation experiments, the muscle determination gene MyoD1 was identified and isolated, which was shown to induce myogenic differentiation even in cells of ectodermal lineage. Since transdifferentiation studies could also be performed in drosophila in vivo by 'false' expression of developmental genes, it is tempting to speculate that experimentally induced transdifferentiation mimics processes during embryonic development and tissue maturation.