Gene Expression: Overview of Control

During development, cells can change the expression of their genes when influenced by both external and internal signals. Signals from outside the cell that influence gene expression include contact with other cells, growth factors, and hormones.

Growth factors are extracellular molecules that stimulate a cell to grow or proliferate. Examples include epidermal growth factor and fibroblast growth factor. Growth factors regulate gene expression indirectly through a network of intracellular signaling cascades.

Hormones are signaling molecules that endocrine cells secrete into the bloodstream. Some hormones, such as insulin, bind to cell surface receptors and affect gene expression through a network of intracellular signaling cascades. Other hormones, such as testosterone, pass through the cell membrane and bind to regulatory proteins in the cell that directly regulate transcription.