The role of hedgehog (Hh) signaling in B lymphopoiesis has remained unclear. We observed that proliferation of pro-B cells in stromal cocultures was impaired by inter-ruption of Hh signaling, prompting us to ask whether the target of Hh antagonism was intrinsic or extrinsic to the B lymphoid compartment. By conditional deletion of the pathway activator gene Smo we found that cell-autonomous Hh signaling is dispensable for B cell development, B lymphoid repopulation of bone marrow and humoral immune function. In contrast, depletion of Smo protein from stromal cells was associated with impaired generation of B lymphoid cells from hematopoietic stem progenitor cells (HSPC), while reciprocal removal of Smo from HSPC had no effect on production of B cell progenitors. Depletion of Smo from stromal cells was associated with coordinate downregulation of genes whose expression is associated with osteoblastoid identity and B lymphopoietic activity. Our results suggest that activity of the Hh pathway within stro-mal cells promotes B lymphopoiesis in a cell-nonautonomous fashion.
- Submitted December 14, 2011.
- Accepted April 10, 2012.
- Copyright © 2005 American Society of Hematology