The WT1 gene provides instructions for making a protein that is necessary for the development of the kidneys and gonads (ovaries in females and testes in males) before birth. After birth, WT1 protein activity is limited to a structure known as the glomerulus, which filters blood through the kidneys. The WT1 protein plays a role in cell growth, the process by which cells mature to perform specific functions (differentiation), and the self-destruction of cells (apoptosis). To carry out these functions, the WT1 protein regulates the activity of other genes by attaching (binding) to specific regions of DNA. On the basis of this action, the WT1 protein is called a transcription factor.