Notch3 Activation Is Sufficient but Not Required for Inducing Human T-Lineage Specification

Abstract

Although the role for the individual Notch receptors in early hematopoiesis have been thoroughly investigated in mouse, studies in human have been mostly limited to the use of pan-Notch inhibitors. However, such studies in human are important to predict potential side effects of specific Notch receptor blocking reagents because these are currently being considered as therapeutic tools to treat various Notch-dependent diseases. In this study, we studied the individual roles of Notch1 and Notch3 in early human hematopoietic lineage decisions, particularly during T-lineage specification. Although this process in mice is solely dependent on Notch1 activation, we recently reported Notch3 expression in human uncommitted thymocytes, raising the possibility that Notch3 mediates human T-lineage specification. Although expression of a constitutive activated form of Notch3 (ICN3) results in the induction of T-lineage specification in human CD34+ hematopoietic progenitor cells, similar to ICN1 overexpression, loss-of-function studies using blocking Abs reveal that only Notch1, but not Notch3, is critical in this process. Blocking of Notch1 activation in OP9-DLL4 cocultures resulted in a complete block in T-lineage specification and induced monocytic and plasmacytoid dendritic cell differentiation instead. In fetal thymus organ cultures, impeded Notch1 activation resulted in B and dendritic cell development. In contrast, Notch3 blocking Abs only marginally affected T-lineage specification and hematopoietic differentiation with a slight increase in monocyte development. No induction of B or dendritic cell development was observed. Thus, our results unambiguously reveal a nonredundant role for Notch1 in human T-lineage specification, despite the expression of other Notch receptors.

Inhibition of Notch 1 receptor influenced the differentiation of Lin-CD45RA-dendritic cell precursors within ovarian carcinoma microenvironment

“…Most studies were mainly focused on CD34+ hematopoietic progenitors and DCs stage. For instance,Els Waegemans et al reported that blocking of Notch1 signaling at the stage of CD34+ hematopoietic progenitors resulted in a complete block in T-lineage specification and induced monocytic and plasmacytoid dendritic cells [ 21 ]. However, another study, which repealed that MicroRNA-23b promoted tolerogenic properties of dendritic cells in vitro through inhibiting Notch1/NF-jB signalling pathways, was mainly focus on the mature DC stage [ 22 ].…”

GATA3 induces human T-cell commitment by restraining Notch activity and repressing NK-cell fate

“…In human, similar developmental stages of early T cell development exist, but the molecular processes that control them are less clear. While the requirement for strong NOTCH1 signalling to induce T-lineage specification is well-established 15 16 , studies from our lab and others have revealed some remarkable differences in how this pathway controls later stages of T cell development in human compared to in mouse, with strong Notch-dependent TCR-γδ development in human as the most remarkable difference 15 17 18 19 . However, these studies also revealed that Notch signalling is permissive for NK cell development 20 , indicating that Notch activation is not sufficient to induce T-cell commitment, in agreement with other studies 7 21 .…”

The Role of Notch3 in Cancer

“…Notch3 is expressed in the early stages of T‐cell development, but it normally becomes downregulated as cells transition to the double‐positive stage during maturation. Furthermore, Notch3 appears to be redundant for T‐cell development, whereas Notch1 is required . Even so, Notch3 expression is found in the majority of T‐cell acute lymphoblastic leukemia (T‐ALL) cases.…”