Feline glucose-6-phosphate dehydrogenase cellular mosaicism. Application to the study of retrovirus-induced pure red cell aplasia.

Neoplasms result from the uncontrolled proliferation of abnormal or transformed cells. The early stages of this process are difficult to study because of the lack of sensitive and specific markers of clonal evolution in an experimental system. We have developed a cat model using cellular mosaicism for glucose-6-phosphate dehydrogenase (G-6-PD). Our findings confirm that the structural locus for feline G-6-PD is on the X-chromosome and demonstrate that it is randomly inactivated in somatic cells. Heterozygous cats have balanced ratios of G-6-PD enzyme types in peripheral blood cells and hematopoietic progenitors that remain stable over time. In our initial studies, we used the model to analyze the events surrounding marrow failure experimentally induced by selected strains of feline leukemia virus (FeLV). Two G-6-PD heterozygous cats, one F1 male hybrid and one domestic cat were infected with FeLV (C or KT) and developed pure red cell aplasia (PRCA). Colonies arising from the more mature erythroid colony-forming cell were not detected in marrow culture of anemic animals although erythroid bursts persisted, suggesting that the differentiation of early erythroid progenitors (BFU-E) was inhibited in vivo. The ratio of G-6-PD types in hematopoietic progenitors and peripheral blood cells from the heterozygous cats did not change when the animals developed PRCA. Thus, the anemia did not result from the clonal expansion of a transformed myeloid stem cell. With this experimental approach, one may prospectively assess clonal evolution and cellular interactions in other FeLV-induced diseases.