Question

Explain why myo D acts as a master switch and sets a cell down a particular developmental pathway. You may also want to review briefly what transcription factors are. (Please try to keep it short)

Answer 1

The expression of Myod is sufficient to convert a fibroblast to a skeletal muscle cell and hence, is a model system in developmental biology for studying how a single initiating event can orchestrate a highly complex and predictable response. The identification of Myod as a master regulatory gene of skeletal muscle differentiation provided the opportunity to assess the roles of tissue-specific transcription factors and chromatin-associated proteins in regulating cell differentiation.

The azacytidine-mediated demethylation of the Myod gene results in the conversion of 10T1/2 cells to skeletal muscle, because the Myod gene is heavily methylated and not expressed in 10T1/2 cells but becomes relatively demethylated and is expressed following treatment with 5-azacytidine. Genetic experiments have shown that either Myod or Myf5 can specify the skeletal muscle lineage in mice. Mouse muscle develops relatively normally without either Myod or Myf5, but disrupting OF both genes results in the absence of skeletal muscle cells, indicating that these genes are necessary to establish a viable muscle lineage.

Hence, The ability of Myod to convert cells of many different lineages and differentiation states to skeletal muscle suggests that it has the characteristics of a pioneer transcription factor.