E2A Promotes the Survival of Precursor and Mature B Lymphocytes

Abstract

The basic helix-loop-helix transcription factor E2A is an essential regulator of B lymphocyte lineage commitment and is required to activate the expression of numerous B lineage-specific genes. Studies involving ectopic expression of Id proteins, which inhibit E2A as well as other basic helix-loop-helix proteins such as HEB, suggest additional roles of E2A at later stages of B cell development. We use E2A-deficient and E2A and HEB double-deficient pre-B cell lines to directly assess the function of E2A and HEB in B cell development after lineage commitment. We show that, in contrast to the established role of E2A in lineage commitment, elimination of E2A and HEB in pre-B cell lines has only a modest negative impact on B lineage gene expression. However, E2A single and E2A and HEB double-deficient but not HEB single-deficient cell lines show dramatically enhanced apoptosis upon growth arrest. To address the possible role of E2A in the regulation of B cell survival in vivo, we crossed IFN-inducible Cre-transgenic mice to E2A conditional mice. Cre-mediated E2A deletion resulted in a block in bone marrow B cell development and a significant reduction in the proportion and total number of splenic B cells in these mice. We show that Cre-mediated deletion of E2A in adoptively transferred mature B cells results in the rapid depletion of the transferred population within 24 h of Cre induction. These results reveal that E2A is not required to maintain B cell fate but is essential in promoting pre-B and B cell survival.

E2A and HEB Are Required to Block Thymocyte Proliferation Prior to Pre-TCR Expression

“…To examine the expression pattern of Cre and the efficiency of HEB deletion in developing thymocytes, we assessed the presence of floxed and deleted bands in DN2-4-sorted thymocytes from HEB flox/flox Cre ϩ mice. Serial dilutions of control DNA with predetermined ratios of floxed to deleted ranging from 100% floxed to 100% deleted were used to estimate the amount of deletion in HEB flox/flox Cre ϩ mice (20). PCR analysis shows that deletion of HEB occurs during the DN stage of thymocyte development, starting as early as the DN2 stage and persisting through the DN4 subset, where deletion appears to be at least 75% complete (Fig.…”

“…Toe DNA from a HEB flox/flox E2A flox/flox Cre Ϫ mouse was used as a negative control. To quantify deletion, a standard curve was generated by mixing known numbers of HEB Ϫ/Ϫ E2A Ϫ/Ϫ and HEB flox/flox E2A flox/flox pre-B cells together in the following ratios: 100% deleted (del), 90% del: 10% flox, 75% del: 25% flox, 50% del: 50% flox, 25% del: 75% flox, 10% del: 90% flox, 100% flox (20).…”

Zinc transporter SLC39A10/ZIP10 facilitates antiapoptotic signaling during early B-cell development

“…A Zn finger transcriptional factor BCL6 is critical for cell survival at the pre-B-cell transitional stage (41). In addition, E2A is also essential for B-cell development, and its absence results in growth arrest (42) and caspase-dependent apoptosis (43). These findings suggest that the ZIP10-Zn signaling axis may also affect transcriptional control in early B-cell development.…”

Stage-specific functions of E-proteins at the β-selection and T-cell receptor checkpoints during thymocyte development

“…These conditional ko animals have revealed various E-protein functions, further defining previously suggested roles and identifying novel roles. We have also established several other genetic models to further manipulate E-protein activity or to use in combination with our E-protein targetings [17,[35][36][37]. Together, these studies provide a broader view of E-protein function across an array of cell types and stages.…”