B lymphopoiesis in long-term bone marrow cultures from Cx43+/− and Cx43+/+ mice.

(A) After establishment of confluent adherent layers from Cx43+/+ or Cx43+/− bone marrow cells, cultures were recharged from the same pool of Cx43+/+ or Cx43+/− bone marrow, respectively, and maintained under myeloid long-term culture conditions for 3 weeks before transfer to B lymphoid culture conditions. Cells were harvested from cultures at weekly intervals thereafter and the frequency of CD45R⁺sIgM⁻ and CD45R⁺sIgM⁺ cells determined. Groups different at ** = P < .0005; * = P < .005. There were no significant differences in cellularity between the cultures established with Cx43+/+ and Cx43+/− bone marrow (data not shown). Data are based on individual analysis of 8 cultures per experimental group. (B) Expression of Cx43 mRNA in sorted Lin⁻, Sca-1⁺, c-kit⁺ stem cells, sorted CD43⁺CD45R⁺ pro-B cells, and heterogeneous bone marrow stroma depleted of hematopoietic cells. RT-PCR was performed as described in “Materials and methods.”