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

Abstract

Neoplasms result from the uncontrolled clonal 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-6PD). 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.

Retrovirus-induced feline pure red cell aplasia. Hematopoietic progenitors are infected with feline leukemia virus and erythroid burst-forming cells are uniquely sensitive to heterologous complement.

“…The animals used for these studies were the female F. offspring of matings between Geoffroy and domestic cats (6). The protocols for infection, for obtaining and processing specimens, and for the assay of feline CFU-E-, BFU-E-, and CFU-GM-derived colonies in methylcellulose culture have been reported (6,8).…”

“…The animals used for these studies were the female F. offspring of matings between Geoffroy and domestic cats (6). The protocols for infection, for obtaining and processing specimens, and for the assay of feline CFU-E-, BFU-E-, and CFU-GM-derived colonies in methylcellulose culture have been reported (6,8). Unless specifically noted, cells were cultured in the presence of0.5 U/ml ofpartially purified human urinary erythropoietin and a 5% concentration of medium conditioned by feline embryonic fibroblasts (FEA) infected with FeLV-A/Glasgow-l (9).…”

“…disorders in cats including leukemia, lymphoma, myelodysplastic syndromes, immunosuppression, and nonregenerative anemia (1)(2)(3). In the laboratory, cats infected with FeLV subgroup C/Sarma (FeLV-C) develop pure red cell aplasia (PRCA) characterized by severe anemia, reticulocytopenia, and the absence of hemoglobinized cells in the marrow (4)(5)(6). Despite this abnormality in erythropoiesis, granulocytic and megakaryocytic morphology and maturation are normal.…”

“…When marrow from cats with PRCA is cultured in vitro, no erythroid colonies (from erythroid colony-forming cells [CFU-E]) are detected. However, normal numbers of erythroid bursts (from erythroid burst-forming cells [BFU-EJ) persist, implying that BFU-E can differentiate in vitro to the hemoglobinized cells comprising erythroid bursts but not in vivo to CFU-E (6).…”

Clonal origin of leukemia – revisited. A tribute to Philip J Fialkow, MD

“…Similarly, he supported development of another experimental model, an interspecific feline hybrid, in which G6PD was the marker used to investigate a virally induced leukemia. 5 The pathogenesis of a virally associated human malignancy, Burkitt's lymphoma, had also been extensively studied. 6,7 Furthermore, Fialkow wrote many papers on clinical genetics and other medical topics.…”