The invention provides isolated nucleic acid molecules, designated TANGO 281, which encode proteins downregulated in megakaryocytes that fail to express the gata-1 transcription factor (a factor critical for blood cell formulation) and can, therefore, represent direct or indirect gata-1 targets. The invention also provides antisense nucleic acid molecules, expression vectors containing the nucleic acid molecules of the invention, host cells into which the expression vectors have been introduced, and non-human transgenic animals in which a nucleic acid molecule of the invention has been introduced or disrupted. The invention still further provides isolated polypeptides, fusion polypeptides, antigenic polypeptides and antibodies. Diagnostic, screening and therapeutic methods utilizing compositions of the invention are also provided.