Due to growth and differentiation defects induced by Brca1 and Gata3 deficiency 15, 19, 29-32, mice deficient for either Brca1 or Gata3 rarely develop tumors, making it difficult to identify the role of Brca1 and Gata3 loss in regulating EMT in tumor development and metastasis. The gene discussed is GATA3; the disease is neoplasm.