Consistent with published studies that showed overexpression of Gata1s can rescue anemia caused by the absence of GATA1 (20), we surmise that the increased expression of GATA1s is sufficient to overcome the hypomorphic activity of the Gata1s isoform, accounting for the rescue of ineffective erythropoiesis. The gene discussed is GATA1; the disease is anemia (phenotype).