In a dominant mouse ethylnitrosurea mutagenesis screen for genes regulating erythropoiesis, we identified a pedigree with a novel microcytic hypochromia caused by a V235G missense mutation in
Dynamin 2 (Dnm2). Mutations in Dnm2, a
GTPase, are highly disease-specific and have been implicated in four forms of human diseases:
centronuclear myopathy, Charcot-Marie Tooth neuropathy and, more recently, T-cell leukaemia and
Hereditary Spastic Paraplegia, but red cell abnormalities have not been reported to date. The V235G mutation lies within a crucial
GTP nucleotide-binding pocket of Dnm2, and resulted in defective
GTPase activity and incompatibility with life in the homozygous state. Dnm2 is an essential mediator of
clathrin-mediated endocytosis, which is required for the uptake of
transferrin (Tf) into red cells for incorporation of
haem. Accordingly, we observed significantly reduced Tf uptake by Dnm2+/V235G cells, which led to impaired endosome formation. Despite these deficiencies, surprisingly all
iron studies were unchanged, suggesting an unexplained alternative mechanism underlies microcytic anaemia in Dnm2+/V235G mice. This study provides the first in vivo evidence for the requirements of Dnm2 in normal erythropoiesis.