Functional Characterisation of ELF2 in Haemopoietic Development

Abstract

ELF2 (E74-like factor 2), a member of the Ets family of transcription factors, has been reported to regulate genes important in B cell development, cell cycle progression, and angiogenesis. The two ELF2 isoforms, ELF2-A and ELF2-B, arise from alternative promoter usage and have been shown to exert opposing effects on target gene expression; ELF2-A activates while ELF2-B represses. While the balance of isoform expression has been suggested to maintain normal cellular function, the function of each isoform and their influence on haemopoietic development is poorly understood. This project explored the role of ELF2 in vitro and in vivo by overexpression studies. In vitro overexpression of ELF2-A and ELF2-B resulted in distinct biological effects. ELF2-B overexpression resulted in a significant reduction in cell proliferation and clonogenic capacity, induced apoptotic cell death and a partial cell-cycle block at the G2-M phase. ELF2-A overexpression showed a modest decrease in clonogenic capacity and a slight increase in apoptotic activity, whilst cell proliferation was unaffected. Removal of the ELF2-B-specific N-terminal region decreased apoptotic cell death, suggesting that this domain was important for ELF2-B function. The role of the ELF2 isoforms in haemopoietic development was explored in vivo using a murine bone marrow reconstitution model. ELF2 overexpressing mice displayed perturbations in early B cell development, and multiple stages of the T cell development. However, mature B cells, T cells and myeloid cells were unaffected. Importantly, no differences in B and T cell development were observed between the different ELF2 isoforms. Taken together, we describe ELF2 as an important regulator of apoptosis and cell cycle regulation. Given that both processes are critical in the haemopoiesis, we postulate that the effects of ELF2 on B and T cell development may be due to its role in apoptosis and cell cycle regulation.