HEB-Deficient T-Cell Precursors Lose T-Cell Potential and Adopt an Alternative Pathway of Differentiation

Abstract

Early thymocytes possess multilineage potential, which is progressively restricted as cells transit through the double-negative stages of T-cell development. DN1 cells retain the ability to become natural killer cells, dendritic cells, B cells, and myeloid cells as well as T cells, but these options are lost by the DN3 stage. The Notch1 signaling pathway is indispensable for initiation of the T-cell lineage and inhibitory for the B-cell lineage, but the regulatory mechanisms by which the T-cell fate is locked in are largely undefined. Previously, we discovered that the E-protein transcription factor HEBAlt promoted T-cell specification. Here, we report that HEB^−/− T-cell precursors have compromised Notch1 function and lose T-cell potential. Moreover, reconstituting HEB^−/− precursors with Notch1 activity enforced fidelity to the T-cell fate. However, instead of becoming B cells, HEB^−/− DN3 cells adopted a DN1-like phenotype and could be induced to differentiate into thymic NK cells. HEB^−/− DN1-like cells retained GATA3 and Id2 expression but had lower levels of the Bcl11b gene, a Notch target gene. Therefore, our studies have revealed a new set of interactions between HEB, Notch1, and GATA3 that regulate the T-cell fate choice in developing thymocytes.

ACKNOWLEDGMENTS

We thank J. Carlyle for critical reviews of the manuscript. We are also grateful to P. Rajkumar and A. Moore for assistance in genotyping of mice and G. Knowles and A. Khandani for sorting expertise.

This work was supported by research grants from the Canadian Institute for Health Research (MOP82861) and the Leukemia Research Fund to M.K.A. and by an Ontario Graduate Scholarship to M.B.

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.01034-10.