Functions of E2A-HEB heterodimers in T-cell development revealed by a dominant negative mutation of HEB.
Lymphocyte development and differentiation are regulated by the basic helix-loop-helix (bHLH) transcription factors encoded by the E2A and HEB genes. These bHLH proteins bind to E-box enhancers in the form of homodimers or heterodimers and, consequently, activate transcription of the target genes. E2A homodimers are the predominant bHLH proteins present in B-lineage cells and are shown genetically to play critical roles in B-cell development. E2A-HEB heterodimers, the major bHLH dimers found in thymocyte extracts, are thought to play a similar role in T-cell development. However, disruption of either the E2A or HEB gene led to only partial blocks in T-cell development. The exact role of E2A-HEB heterodimers and possibly the E2A and HEB homodimers in T-cell development cannot be distinguished in simple disruption analysis due to a functional compensation from the residual bHLH homodimers. To further define the function of E2A-HEB heterodimers, we generated and analyzed a dominant negative allele of HEB, which produces a physiological amount of HEB proteins capable of forming nonfunctional heterodimers with E2A proteins. Mice carrying this mutation show a stronger and earlier block in T-cell development than HEB complete knockout mice. The developmental block is specific to the alpha/beta T-cell lineage at a stage before the completion of V(D)J recombination at the TCRbeta gene locus. This defect is intrinsic to the T-cell lineage and cannot be rescued by expression of a functional T-cell receptor transgene. These results indicate that E2A-HEB heterodimers play obligatory roles both before and after TCRbeta gene rearrangement during the alpha/beta lineage T-cell development.
Barndt
R J
RJ
Department of Immunology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Dai
M
M
Zhuang
Y
Y
D000483:Alleles; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D019070:Cell Lineage; D004254:DNA Nucleotidyltransferases; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D019281:Dimerization; D018628:Gene Dosage; D015870:Gene Expression; D015333:Gene Rearrangement, beta-Chain T-Cell Antigen Receptor; D019672:Genes, T-Cell Receptor; D018257:Helix-Loop-Helix Motifs; D006410:Hematopoiesis; D006801:Humans; D019891:Leukopoiesis / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D016296:Mutagenesis; D010641:Phenotype; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics; D013601:T-Lymphocytes / Q000166:cytology*; D051820:TCF Transcription Factors; D013950:Thymus Gland; D058125:Transcription Factor 7-Like 1 Protein; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D019076:Transgenes; D045567:VDJ Recombinases
D051792:Basic Helix-Loop-Helix Proteins; D004254:DNA Nucleotidyltransferases; D004268:DNA-Binding Proteins; D016693:Receptors, Antigen, T-Cell, alpha-beta; D051820:TCF Transcription Factors; D058125:Transcription Factor 7-Like 1 Protein; D014157:Transcription Factors; D045567:VDJ Recombinases; C544912:TCF7L1 protein, human; C489532:Tcf12 protein, mouse; C544913:Tcf7l1 protein, mouse; C073366:TCF12 protein, human