Missense mutations in transcription factor GATA1 underlie several distinct forms of anemia and thrombocytopenia. Clinical severity depends on the site and type of substitution, and distinct substiutions of the same residue produce disparate phenotypes. To investigate the effect of GATA1 missense mutations on erythroid differentiation we expressed conditionally activated wild type or mutant versions of GATA1 in GATA1-null G1E cells. We used gene expression microarrays to explore how GATA1 missense mutations affect erythroid transcription programs. GATA1-null G1E cells ectopically expressing conditionally activated versions of GATA1 (GATA1-ER, GATA1(R216Q)-ER, GATA1(R216W)-ER, GATA1(D218G)-ER, or GATA1(D218Y)-ER) were treated with estradiol for 24 hours to initiate erythroid differentiation. Total RNA from treated cells was extracted for Affymetrix microarray. All data were generated from three biological replicates. Transcript levels were compared in wild type vs. mutant lines.