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

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.

Multi-modular structure of the gene regulatory network for specification and commitment of murine T cells

“…In addition, supporting results came from studies introducing into pro-T cells acute antagonists of key transcription factors, including the natural E protein antagonist ID2 (89) or an artificially constructed dominant repressor form of PU.1 (90). Additional supporting results came from earlier perturbation studies knocking out E protein genes Tcf3 (E2A) and Tcf12 (HEB) or Bcl11b (71, 79) and studies utilizing progenitor or pro-T cell lines and acute T-cell malignancies to interrogate roles of the early-acting transcription factors Lmo2 and Hhex (81,88,91). For data on normal developmental expression dynamics of these genes in pro-T cells, RNA-seq and single-cell RNA-seq datasets were used (92)(93)(94), corroborated by highly curated microarray data (95).…”

“…During early T cell development, Lyl1 is important to make ETP to DN2a progression possible and to turn on Gfi1 (200), which encodes a zinc finger repressor protein that is crucial for survival of early lymphoid progenitors in the presence of Notch signals (172). Recent studies also show a supportive role of Lmo2 in maintaining the T-lineage competence of immortalized progenitor-like cells (81,195). Thus, although silenced in mature T cells, Lmo2 and Lyl1 contribute to the T-lineage developmental competence of hematopoietic progenitors.…”

“…Lmo2 interacts with DNA replication complexes to regulate the DNA synthesis rate in hematopoietic progenitor cells, and it increases the pool of self-renewing population in Phase 1 in a gain-of-function setting (86,274,275). Also, Lmo2 upregulates Bcl2 expression in pro-T cells, which contributes to maintain the size of the Phase 1 cell pool 81), consistent with the effect of the Lmo2 partner Lyl1 on the ETP-DN2a pool size in vivo (200). Consistently, constitutive expression of Lmo2 in bone marrow progenitor cells results higher frequencies of ETPs in cell cycle upon bone marrow chimera reconstitution, which leads to T-ALL due to the accumulated number of ETP-like cells in the thymus (275).…”

“…These sources constitute RNA-seq and microarray results from studies of germline deletion of genes encoding the high mobility group factor TCF1 (encoded by Tcf7 ) ( 28 , 76 , 77 ), the basic helix-loop-helix E proteins E2A ( Tcf3 ) and HEB ( Tcf12 ) ( 78 , 79 ), and the later-activated zinc finger factor associated with T-cell lineage commitment, Bcl11b ( 28 , 80 ). In addition, we used studies of acute, stage-specific deletions of the ETS family subgroup member PU.1 (encoded by Spi1 , previously called Sfpi1 in mice) ( 28 , 48 ); of Lmo2 ( 81 ); of GATA3 ( 28 , 82 , 83 ); of Bcl11a ( 28 ); of Erg ( 28 ); of Notch1 and Notch2 together ( 67 ); and of Runx1 and Runx3 together ( 51 , 84 ). Although data for cells in the same developmental stages with complete disruption of Ikaros ( Ikzf1 ) were not available, differentially expressed genes that responded to Ikaros ( Ikzf1 ) zinc finger 4 deletion were also added ( 85 ).…”

Identification of Cellular Interactions in the Tumor Immune Microenvironment Underlying CD8 T Cell Exhaustion

“…BCL11A slows differentiation of T cells to maintain self-renewal [34]. It is required for normal lineage development of lymphocytes [35, 36]. PLAG1 helps to maintain self-renewal in hematopoietic stem cells [37].…”