Transdifferentiation and metaplasia--switching cell types.

States of developmental commitment are encoded as combinations of transcription factors and changes in their expression can bring about transdifferentiation or metaplasia. For example, ectopic expressions of Vestigial can convert Drosophila leg to wing; of C/EBPbeta can convert pancreatic exocrine cells to hepatocytes; and expression of C/EBPalpha and PPARgamma can convert myoblasts to adipocytes.