GATA1 is mutated in TMD and AMKL. Positions of the various alterations in GATA1. All of the mutations are located within exon 2 or the proximal nucleotides of the downstream intron. Translation that initiates at Met1 produces the 50-kDa full-length protein, whereas use of the alternate initiation codon at Met84 generates a shorter 40-kDa isoform.