Indeed, enforced expression of Gata3 in the T-cell lineage caused a maturation arrest in the cytotoxic T-cell lineage and promoted the formation of thymic lymphoblastoid tumours [41], and overexpression of Gata3 at early fetal thymocyte stages redirected their differentiation towards the mast cell lineage [42]. The gene discussed is GATA3; the disease is neoplasm.