Alpha-Catenin Is Dispensable for Normal Hematopoietic Stem Cell Function.

Abstract 1438

Poster Board I-461

We previously demonstrated the loss of expression of alpha-E-Catenin, the product of the CTNNA1 gene, in primary leukemic stem cells isolated from patients with advanced Myelodysplastic Syndrome (MDS) and Acute Myeloid Leukemia (AML) associated with loss of all or part of the long arm of chromosome 5. To formally assess the impact of loss of Ctnna1 expression on hematopoiesis, we employed a murine model for the hematopoietic specific conditional loss of Ctnna1 expression. We demonstrate that Ctnna1 deficiency is associated with normal hematopoietic maturation and proliferation as assessed by peripheral blood examination and methycellulose colony assays. We assessed stem cell and early progenitor frequencies using both flow cytometry and functional assays. Ctnna1 deficiency was associated with equivalent frequencies of Sca1+C-Kit+CD135-Lineage- HSCs in both experimental animals and controls. Short term HSC and MPP frequencies were likewise unaltered. We assessed HSC function using transplantation studies. In competitive repopulation experiments, HSCs deficient for Ctnna1 maintained stable engraftment of recipient mice for up to 1 year. Limiting dilution analyses detected no significant difference in HSC frequency between wild type and Ctnna1 deficient mice. We examined the potential role of Ctnna1 deficient hematopoietic stem cells in two murine models for myeloid neoplasms 1.) exposure to mutagen ENU and 2.) a model for murine AML driven by the HoxA9-Nup98 fusion product. Following exposure of HSCs to ENU, loss of Ctnna1 was not associated with an increased risk of development of a myeloid neoplasm. Expression of the HoxA9-Nup98 fusion product by retroviral infection of Ctnna1 deficient and wild type Sca1+C-Kit+Lineage- cells resulted in no difference in time to development of the previously characterized myeloproliferative disorder or acute leukemia. Taken together, these data demonstrate that in the absence of specific genetic abnormalities, loss of Ctnna1 expression in primary murine HSCs is not associated with aberrant HSC function or the development of myeloid neoplasms. Further studies are necessary to define a role for of loss of Ctnna1 expression in human myeloid malignancies.