B cell lineage progression and identity are impeded synergistically in EBF1 and Runx1 haploinsuficient mice (36.13)

Abstract

Abstract The transcription factors Early B cell factor 1 (EBF1) and Runx1 are essential for B cell development. B lymphopoiesis is arrested at an early state and hematopoiesis is ablated in the absence of EBF1 and Runx1, respectively. Previously, we demonstrated synergistic activity of EBF1 and Runx1 in the activation of the B cell-specific gene mb-1(Cd79a). To identify cooperative functions of these factors in vivo, we generated Ebf(Ehet)Runx(Rhet)-double haploinsufficient(ERhet) mice. Significant compound effects were observed in ERhet mice. B cell numbers in the bone marrow and spleen were reduced greatly. Generation of pre-B and immature B cells in ERhet mice is impeded by: 1) reduced frequencies of Ig light chain gene rearrangements and 2) significant alterations in B cell-specific gene expression. Notably, repression of c-kit and activation of Aiolos were delayed. Interestingly, a high percentage of pro- and pre-B cells from ERhet mice expressed the NK cell markers NK1.1, CD160 and 2B4. Co-expressions of these NK cell markers with genes indicative of B cell commitment was demonstrated using multiplex, single cell PCR. Retroviral complimentation of Ebf1 and Runx1 deficiencies eliminated the promiscuous expression of NK cell genes in ERhet pro-B cells. Thus, appropriate dosage of Ebf1 and Runx1 is necessary for efficient activation of the B cell-specific program and suppression of lineage inappropriate genes. Our data solidify EBF1’s role in controlling B cell lineage commitment.