A NUP98-HOXD13 Fusion Gene Induces a Transplantable Myelodysplastic Syndrome in Mice.

The myelodysplastic syndromes (MDSs) are a group of hematologic stem cell disorders characterized by ineffective hematopoiesis and dysplasia. A large number of chromosomal aberrations including deletions, amplifications, inversions, and translocations, some of which involve the NUP98 gene, have been associated with MDS. Recently an MDS mouse model expressing a NUP98-HOXD13 (NHD13) fusion gene was developed, which faithfully recapitulates all of the key features of MDS. Although it is well-established that acute myeloid leukemia (AML) is transplantable, there is no evidence that MDS is a transplantable condition. Therefore, in order to develop evidence for MDS as a hematopoietic stem cell (HSC) disease, we attempted to transfer MDS to normal recipients through bone marrow transplantation (BMT). All the recipients transplanted with bone marrow (BM) cells from NHD13 mice with MDS showed anemia, leukopenia, lymphopenia, and neutropenia when compared to recipients of wild-type (WT) littermates. The homing efficiency of the NHD13 primitive progenitor cells (Lineage negative [Lin⁻], Sca-1+) was about 2 fold higher than WT, and there was no significant difference in BM cellularity between the recipients of NHD13 and WT BM, indicating that the NHD13 recipients had ineffective hematopoiesis. These phenomena were reproduced in secondary recipients using primary recipients of NHD13 BM as donor mice. In secondary transplantation assays, 3 out of 5 recipients developed acute myeloid leukemia (AML) at 16 weeks post-transplantation. Morphological features of MDS, including nuclear-cytoplasmic asynchrony, binucleate cells, hypersegmented neutrophils, and giant platelets were detected in BM and peripheral blood of NHD13 donor, primary and secondary recipients by cytospin preparations. In competitive repopulation assays, mice transplanted with equal numbers of WT and NHD13 BM cells showed a decreased percentage of NHD13 cells in the peripheral blood, but an increased percentage of NHD13 cells in the BM, again providing evidence of ineffective hematopoiesis of the NHD13 cells. The transplantation of lineage depleted cells from BM has shown that the transplantable cells for MDS reside in the Lin⁻ population of NHD13 BM. These findings demonstrate that MDS can be transferred to healthy recipients by BMT, supporting the concept that MDS originates in a transplantable multilineage hematopoietic stem cell.