GATA proteins comprise a group of transcription factors that are related by the presence of conserved zinc finger DNA-binding domains, which bind directly to the nucleotide sequence core element GATA . There are six vertebrate GATA proteins, designated GATA-1 to GATA-6 .GATA-3 is a critical regulator of development of various systems in both mouse and human. GATA-3 mouse embryos die between E11 and E12 due to growth retardation and deformities in the brain and spinal cord. The function of GATA-3 has been extensively studied in T cell development and has recently been shown to be a downstream target of Notch in Notch-mediated differentiation of TH2 cells . It is expressed in both hematopoietic and non-hematopoietic tissues, including the kidney, skin, mammary gland, and central nervous system. Decreased expression of GATA-3 in luminal breast cancer is associated with poor clinical outcome. GATA-3 expression level may therefore be a promising prognostic biomarker. Haploinsufficiency of GATA-3 results in Barakat syndome in humans, a condition characterized by sensorineural deafness and renal dysplasia.