Investigating the role of CONNEXIN43 in marrow

Abstract

We have found connexin43 (Cx43) gap junctions in mouse haemopoietic tissue and proposed that they play a part in the division of primitive haemopoietic stem cells (PHSC, Rosendaal et al., 1997). Normal resting haemopoiesis, which produced the circulating blood cells, is carried out by progenitors, formed by the division of PHSC. They divide when their progeny are needed to repopulate a severely depleted blood-forming system, e.g. when the definitive haemopoietic system is founded in the embryo and neonate or after treating an adult with a cytotoxic drug which selectively deletes dividing haemopoietic cells (e.g. 5-fluorouracil). To divide, PHSC must receive signals and we believe that communication via Cx43 gap junctions is involved. We graft into toe-notched reporter mice, all of whose stem cells have been deleted by busulphan, a competing mixture of two kinds of congenic stem cells with different glucose-phosphate isomerase markers, 1a and 1b. The competing populations of stem cells have different degrees of expression of Cx43, +/+1a versus +/+1b, or +/+1a versus +/− 1b, or +/+1a versus −/−1b. At intervals thereafter we assay the proportions of Gpi-1a and 1b in five blood cells. This allows three levels of comparison, (1) of repopulation of donors by stem cells, (2) of repopulation of reporter mice by grafted stem cells and (3) of repopulation of reporter mice after subsequent challenge.(1) We treat donor 1a and 1b mice with 5-fluorouracil and then compete the same femoral fractions of their marrow in reporter mice.(2) We compete untreated 1a and 1b foetal liver stem cells from +/+, +/− or −/− in reporter mice.(3) We stress with different cytotoxic drugs the blood-forming systems of reporter mice after they have been grafted with these combinations of stem cells.Rosendaal et al. (1997) Leukemia 11, 1281–9.