GATA 3 is a transcription factor important in T cell development and is known to be mutated in certain syndromes(hypoparathroidism, deafness, renal dysplasia). Missense, frameshift and insertion/deletion mutations in the zinc finger domain have been reported in 10-15% of early T cell precursor ALL and may be associated with biallelic mutations or concomitant deletion of the second allele.