Wilms' tumor protein (WT1) is a transcription factor which regulates the expression of numerous target genes, including EPO. This protein plays an essential role in the normal development of the urogenital system, including cellular development and cell survival, and it has both tumor suppressor and oncogenic roles in tumor formation.

Defects in the WT1 protein can lead to Wilms tumor, Frasier syndrome, Denys-Drash syndrome, nephrotic syndrome type 4, and Meacham syndrome.