THE DEVELOPMENT OF HEMATOPOIETIC-CELLS IS BIASED IN EMBRYONIC STEM-CELL CHIMERAS

The haematopoietic development of embryonic stem (ES) cell injection c himaeras was analysed using beta-galactosidase expression from an X-li nked transgene as a marker to distinguish the ES-derived cell populati on from the host cells. The number of cells in the different haematopo ietic cell subpopulations was determined by flow cytometry. When the p roportions of ES-derived cells in the antigen-positive lineages were c ompared to the ES cell contribution to all cells in the organs, we fou nd an unexpected bias in the haematopoietic differentiation of ES-deri ved cells. ES descendants were overrepresented in the bone marrow B ly mphoid cell population and the splenic myeloid cells but were underrep resented in the CD4-positive T lymphoid cells in the spleen, These res ults were obtained by comparison with control female animals that were X chromosome mosaic for beta-galactosidase expression. These findings of uneven contribution to haematopoietic development by ES cells indi cate that the commitment of ES cell descendants may be different from that of the host cells. (C) 1995 Acaaemic Press, Inc.