Hematopoietic progenitor cell abnormalities in Hoxc-8 null mutant mice

The mammalian Hox genes encode a family of conserved transcription factors that control the establishment of the body plan during embryogenesis. Many Hox genes are also known to be expressed in hematopoietic cells. We found t hat Hoxc-8, a member of the Hox C cluster, is expressed in the mouse hemato poietic organs, fetal liver and adult bone marrow. To determine the role of Hoxc-8 gene in hematopoiesis, we compared progenitor cell numbers in the f etal liver and adult bone marrow cells. We observed a significant reduction in the number of erythroid burst-forming unit (BFU-E) and in granulocyte/m acrophage colony-forming unit (CFU-GM) in the Hoxc-8 null mice, although th e peripheral blood cell counts were normal. The hematopoietic cells from th e homozygote animals exhibited normal expansion capability in a liquid cult ure system, suggesting that the decreased number of progenitor cells may be due to a defect extrinsic to the hematopoietic cells, such as in the inter action with the microenvironment. J. Exp. Zool. 283:186-193, 1999. (C) 1999 Wiley-Liss, Inc.