A dose‐dependent role for EBF1 in repressing non‐B‐cell‐specific genes

Abstract

Summary In the absence of EBF1, B cell development is arrested at an uncommitted progenitor stage that exhibits increased lineage potentials. Previously, we investigated the roles of EBF1 (E) and its DNA binding partner Runx1 (R) by evaluating B lymphopoiesis in single (Ehet and Rhet) and compound haploinsufficent (ERhet) mice. Here, we demonstrate that reduced Ebf1 gene dosage results in the inappropriate expression of NK cell lineage-specific genes in B cell progenitors. Moreover, prolonged expression of Ly6a/Sca-1 suggested the maintenance of a relatively undifferentiated phenotype. These effects were exacerbated by reduced expression of Runx1 and occurred despite expression of Pax5. Repression of inappropriately expressed genes was restored in most pre-B and all immature B cells of ERhet mice. Enforced EBF1 expression repressed promiscuous transcription in pro-B cells of ERhet mice and in Ebf1−/−Pax5−/− fetal liver cells. Together, our studies suggest that normal levels of EBF1 are critical for maintaining B cell identity by directing repression of non-B cell-specific genes.

Early B-cell Factor 1 Regulates the Expansion of B-cell Progenitors in a Dose-dependent Manner

“…Also interesting with regard to leukemia development is the finding that reduced transcription factor dose may result in lineage plasticity in B-cell progenitors. Although our functional analysis did not reveal any dramatic increase in lineage instability of B-lineage cells, it has been reported that monoallelic loss of Ebf1 leads to aberrant expression of NK-lineage genes in B-lymphoid progenitors (22). This indicates that alternative lineage programs cannot be properly silenced, and it should not be excluded that combined heterozygote deletions of Pax5 and Ebf1 may impact lineage commitment in a more dramatic manner than the heterozygote loss of either of these proteins alone.…”

“…Furthermore, low levels of PAX5 expression in hematopoietic progenitors result in an expansion of cells expressing a combination of myeloid and lymphoid genes similar to what can be observed in biphenotypic leukemia (19). Functional transcription factor dose is also of crucial importance in normal B-cell development, where reduced levels of E-proteins (E2A, HEB, and E2-2) (20) or loss of one allele of Ebf1 alone or in combination with E2a or Runx1 results in disturbed B-cell development (5,(21)(22)(23). Hence, transcription factor dose is of critical importance for malignant transformation in leukemia as well as normal B-cell differentiation, creating a link between development and disease.…”

Ebf1 heterozygosity results in increased DNA damage in pro-B cells and their synergistic transformation by Pax5 haploinsufficiency

“…[6][7][8] Ebf1 levels are also of relevance in leukemia because mutations resulting in reduced functional EBF1 dose 9,10 and increased expression of post-transcriptional inhibitors of EBF1, ZNF521, 11 or ZNF423 12 are found in B-cell acute lymphoblastic leukemia (B-ALL). 13,14 A direct role for Ebf1 dose in malignant transformation was supported by the findings that combined expression of constitutively active Stat5 (caStat5) and heterozygous loss of either Ebf1 or Pax5 results in B-cell leukemia in mice.…”

Tumor suppressors BTG1 and BTG2 regulate early mouse B-cell development

“…These findings are partially overlapping with the phenotype observed in Ebf1 and Pax5 knockout mice, where it has been shown that EBF1 and PAX5 are critical regulators of B-lineage specification and commitment by repressing alternative non-B-cell fates. [13][14][15] As the expression of Ebf1 and Pax5 itself is not inhibited in Btg1 -/-…”