Publication Date:
2005-11-16
Description:
The Wnt and Notch signaling pathways have critical roles in cell fate decisions. However, the interaction of these pathways is poorly understood. Using highly purified Wnt3a and immobilized Notch ligand, Delta1ext-IgG, we investigated the mechanisms involved in Wnt and Notch signaling interactions during hematopoietic stem cell differentiation. When CD34+CD38- cord blood stem cells were cultured for 2 to 3 weeks with five growth factors (SCF 300ng/ml, Flt-3L 300ng/ml, TPO 100ng/ml, IL-6 100ng/ml, and IL-3 10ng/ml), most precursor cells lost CD34 expression and differentiated into mature cells, most of which were monocytes. However, as we previously reported, when cells were cultured with Delta1ext-IgG, we found an increased percentage of lymphoid progenitors (CD34+CD7+) and more mature lymphoid precursors (CD34-CD7+) in the cell population. The addition of purified Wnt3a (100ng/ml) alone without Delta1ext-IgG did not significantly change the percentage of CD7+ cells (1% vs. 3%). However, when both Wnt3a and Delta1ext-IgG were added, we saw an increased percentage of CD7+ cells (11% with Delta1ext-IgG alone to 27% with both) (Fig. 1A). Wnt3a also enhanced gene expression of CD3ε and preTα induced by Delta1ext-IgG. These results suggest that Wnt3a enhances the effect of Notch signaling on T-cell lineage development. To test the role of endogenous Wnt signaling, we added Dickkopf1, an inhibitor of Wnt signaling. When CD34+CD38- cells were cultured with Dickkopf1 (300ng/ml) alone for a 2 week, the percentage and number of CD56+ NK cells was unaffected. However, when cultured with Dickkopf1 and Delta1ext-IgG, the percentage and number of CD56+ NK precursor cells were increased (2% with Delta1ext-IgG alone vs. 17% with Dickkopf1 and Delta1ext-IgG; 0.2 ×105 vs. 1.5×105, p
Print ISSN:
0006-4971
Electronic ISSN:
1528-0020
Topics:
Biology
,
Medicine
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