EXPRESSION OF ERYTHROID-SPECIFIC GENES IN MEGAKARYOBLASTIC DISORDERS

Currently available data indicate that erythroid and megakaryocytic di fferentiation pathways are closely related to each other, and there ma y exist progenitor cells common to those two lineages may exist. Acute megakaryoblastic leukemia (AML-M7) and transient myeloproliferative d isorder in Down's syndrome (TMD) are characterized by rapid growth of abnormal blast cells which express megakaryocytic markers. These blast cells express lineage-specific transcription factors such as GATA-1 c ommon to these lineages and frequently express erythroid-specific mRNA s such as gamma-globin and erythroid delta-aminolevulinate synthase (A LAS-E), indicating that most of the blasts in M7 and TMD cases have er ythroid and megakaryocytic phenotypes. These results suggest that blas ts in M7 and TMD may correspond to progenitors of both erythroid and m egakaryocytic lineages.