Haematopoiesis In Mice Heterozygous For the W Trait: Defective Formation of Transient Endogenous Spleen Colonies

It has been determined that W/+ and W^v/+ heterozygous mice, as compared with normal +/+ homozygous littermates, form significantly lower numbers of transient 5-day endogenous spleen colonies in response to X-irradiation. This defect was evident for doses of irradiation between 2–6 Gy (200–600 rad) and was associated with a slightly increased radiosensitivity of the assayed precursor cells (TE-CFU) in W heterozygotic mice. Moreover, the defect was transplantable, i.e., intrinsic to the marrow cells and not to the microenvironment, and was not associated with a similar decrease in cells which form erythropoietic bursts in vitro (BFUe). This study provides a cellular basis for increased radiosensitivity of W/+ and W^v/+ mice and suggests that the ‘W’ mutation is semi-dominant, both with respect to the white spotting and TE-CFU formation.