Sl/Sld mice have an increased number of gap junctions in their bone marrow stromal cells.

To study the defect of the hematopoietic inductive microenvironment (HIM) in Sl/Sld mice, femoral bone marrow tissue of 10 of each mutant, (Sl/Sld and W/Wv) their normal littermates (Sl+/Sl+ and W+/W+), and 20 normal C57BL mice were examined by electron microscopy using morphometric and statistical methods. Gap junctions were observed in all strains of mice, in the following stromal cell types: 1) reticular cells, 2) between reticular cells and periarterial adventitial cells, and 3) between periarterial adventitial cells. The frequency of gap junctions in bone marrow stromal cells of Sl/Sld mice (mean = 2.2/9.4 X 10(-3) mm2) was significantly higher than in control mice. It is suggested that there is a relationship between the increased numbers of gap junctions in bone marrow stromal cells of Sl/Sld mice and the defect in HIM function in these genetically anemic animals.