THE ROLE OF HOMEOBOX GENES IN HEMATOPOIESIS

Homeobox genes encode transcription factors containing a common DNA-bi nding motif found in virtually all animal species. Different homeobox gene families have evolved which encode homeodomains of different type s or classes and thus far approximately 170 homeobox genes have been c loned. Homeoproteins are involved in the control of animal development and several lines of evidence strongly suggest that they may contribu te to the regulation of hematopoiesis. Many members of this large fami ly are expressed in blood cells. Moreover, homeobox containing genes h ave been involved in translocation events occurring in certain leukemi as and lymphomas. Furthermore a number of studies indicate that modula tion of homeobox gene expression may induce alterations in proliferati ve, differentiative or phenotypic characteristics of hematopoietic cel ls. Although the function of each individual gene has not been clearly defined there is strong evidence for cooperativity among homeoprotein s indicating that regulatory combinations of homeobox genes may play a pivotal role in controlling survival, proliferation and differentiati on of hematopoietic cells.