LMO2 is essential to maintain the ability of progenitors to differentiate into T-cell lineage in mice.

Ken-Ichi Hirano,Hiroyuki Hosokawa,Takashi Yahata,Kiyoshi Ando,Yusuke Endo,Maria Koizumi,Katsuto Hozumi

doi:10.7554/elife.68227

Abstract

Notch signaling primarily determines T-cell fate. However, the molecular mechanisms underlying the maintenance of T-lineage potential in pre-thymic progenitors remain unclear. Here, we established two murine Ebf1-deficient pro-B cell lines, with and without T-lineage potential. The latter expressed lower levels of Lmo2; their potential was restored via ectopic expression of Lmo2. Conversely, the CRISPR/Cas9-mediated deletion of Lmo2 resulted in the loss of the T-lineage potential. Introduction of Bcl2 rescued massive cell death of Notch-stimulated pro-B cells without efficient LMO2-driven Bcl11a expression but was not sufficient to retain their T-lineage potential. Pro-B cells without T-lineage potential failed to activate Tcf7 due to DNA methylation; Tcf7 transduction restored this capacity. Moreover, direct binding of LMO2 to the Bcl11a and Tcf7 loci was observed. Altogether, our results highlight LMO2 as a crucial player in the survival and maintenance of T-lineage potential in T-cell progenitors via the regulation of the expression of Bcl11a and Tcf7.

Highlights

Hematopoietic stem cells (HSCs) have the ability to self-renew and differentiate into all blood cell types
We found that the expression levels of Lmo2 mRNA and protein were approximately threefold higher in pro-B(+) than pro-B(À) cells (Figure 1B,C), and enforced expression of Lmo2 markedly provided their capacity to differentiate into T-cell lineage following Notch stimulation in vitro (Figure 1D)
These results suggest that LMO2 plays a pivotal role in the maintenance of the capacity to differentiate into T-cell lineage driven by Notch signaling in Ebf1-deficient pro-B cells

Summary

Introduction

Hematopoietic stem cells (HSCs) have the ability to self-renew and differentiate into all blood cell types. HSCs begin to differentiate into various lineage cells, gradually losing their potential to become their descendants, hematopoietic progenitor cells (HPCs), and differentiate into mature blood cells (Doulatov et al, 2012; Kosan and Godmann, 2016). This sequence of processes has long been imagined as a ball rolling down a valley track (Goldberg et al, 2007). Cell fate decisions in hematopoietic cells are controlled by continuous interactions between environmental influences and intrinsic cellular mechanisms, such as transcription factor networks and epigenetic regulation (Wilson et al, 2009). Several transcription factors contribute to the acquisition of T-cell identity, including TCF1 (encoded by Tcf7), basic helix-loop-helix (bHLH) factors, E2A and HEB, PU., GATA3, Bcl11b, and Runx family members, all of which are essential for T-cell development in the thymus (Hosokawa and Rothenberg, 2021; Hosokawa et al, 2021a; Hosokawa et al, 2021b)

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