Experimental conditions were identical to those described in the legend to Figure 6. In Transwell cultures, bone marrow MNC were placed within the Transwell inserts and separated from the Rab-9 monolayers by a 0.4-μm nylon membrane. Transwell inserts were not toxic to hematopoietic progenitors because the latter were able to proliferate vigorously in Transwells in the presence of IL-3 and GM-CSF (not shown). Colony assays were performed on day 8 of coculture in methylcellulose supplemented with SCF, IL-3, and GM-CSF. Total CFC (HPP-CFC, CFU-GM, CFU-G, CFU-M) were counted on day 8 of colony assays. For reference, the plating efficiency (or frequency of CFC) of cells harvested from the Rab-9/LMJSN coculture was 4%.

Mean ± SD; n = 3.