HOX-A10regulates hematopoietic lineage commitment: evidence for a monocyte-specific transcription factor

rified human cord-blood progenitors was examined by using in vitro assays. In fetal thymic organ cultures, a dramatic reduc- tion in cells expressing high levels of HOX-A10 was observed, along with ab- sence of thymocytes positive for CD31 T-cell receptor ab. Furthermore, in MS-5 stromal cell cultures, there was a 7-fold reduction in the number of natural killer cells and a 9-fold reduction in the number of B cells, thus showing a profound de- fect in differentiation toward the lym- phoid lineage in HOX-A10-transduced progenitors. In contrast, the number of CD141 monocytic cells in the stromal cell culture was 6-fold higher, suggesting an enhanced differentiation toward the my- eloid differentiation pathway of HOX-A10- transduced progenitors. However, there was a slight reduction in the number of CD151 granulocytic cells, which were blocked in their final maturation. These data show that HOX-A10 can act as an important key regulator of lineage deter- mination in human hematopoietic pro- genitor cells. (Blood. 2002;99:1197-1204)