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Pre-T cell receptor Self-MHC Sampling Restricts Thymocyte Dedifferentiation

ABSTRACT: Programming T lymphocytes to distinguish self from non-self is a vital, multi-step process arising in the thymus. Signalling through the pre-T cell receptor (preTCR), a CD3-associated heterodimer comprising an invariant pTα chain and a clone-specific β chain, constitutes a critical early checkpoint in thymocyte development within the αβ T-cell lineage. Recent work demonstrates that preTCRs arrayed on double negative (DN) thymocytes, like αβ TCRs appearing on double positive (DP) thymocytes, ligate peptides bound to MHC molecules (pMHC) on thymic stroma but via a different molecular docking strategy. Here we show the consequences of those distinctive interactions for thymocyte progression, using synchronized fetal thymic progenitor cultures differing in the presence or absence of pMHC on support stroma, determining single cell transcriptomes at key thymocyte developmental transitions. Although MHC negative stroma fosters αβ T lymphocyte differentiation, the absence of pMHC-preTCR interplay leads to deviant thymocyte transcriptional programming associated with de-differentiation. Highly proliferative DN and DP subsets with antecedent characteristics of T cell lymphoblastic and myeloid malignancies emerge. Thus, in addition to fostering β chain repertoire broadening for subsequent αβ TCR utilization, preTCR-pMHC interaction limits cellular plasticity to facilitate normal thymocyte differentiation and proliferation that, if absent, introduces significant developmental vulnerabilities.

ORGANISM(S): Mus musculus

PROVIDER: GSE186049 | GEO | 2022/10/18

REPOSITORIES: GEO

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Project description:Developmental checkpoints in stem/progenitor cells are critical to the determination, commitment and differentiation into distinct lineages. Cancer cells often retain expression of lineage-specific checkpoint proteins, but their potential impact in cancer remains elusive. T lymphocytes mature in the thymus following a highly orchestrated developmental process that entails the successive rearrangements and expression of T-cell receptor (TCR) genes. Low affinity recognition of self-peptide/MHC complexes (self-pMHC) presented by thymic epithelial cells by the TCR of CD4+CD8+ (DP) cortical thymocytes transduces positive selection signals that ultimately shape the developing T cell repertoire. DP thymocytes not receiving these signals die by lack of stimulation whereas those that recognize self-pMHC with high affinity undergo TCR-mediated apoptosis and negative selection. In T-cell acute lymphoblastic leukaemia (T-ALL), leukaemic transformation of maturating thymocytes results from the acquisition of multiple genetic and epigenetic alterations in oncogenes and tumour suppressor genes, that disrupt the normal regulatory circuits and drive clonal expansion of differentiation-arrested lymphoblasts. We show here that TCR triggering by negatively-selecting self-pMHC prevented T-ALL development and leukaemia maintenance in mice. Induction of TCR signalling by high affinity self-pMHC or treatment with monoclonal antibodies to the CD3 signalling chain (anti-CD3) caused massive leukaemic cell death and a gene expression program resembling that of thymocyte negative selection. Importantly, anti-CD3 treatment hampered leukaemogenesis in mice transplanted with either mouse or patient-derived T-ALLs. These data provide a rationale for targeted therapy based on anti-CD3 treatment of T-ALL patients and demonstrate that endogenous developmental checkpoint proteins are amenable to therapeutic intervention in cancer cells. Gene expression data from four culture conditions was performed for the following cells: ALL-SIL-TCRÎ±/Î²-GFP co-cultured on OP9-DL1 for 48 h, ALL-SIL-TCRÎ±/Î²-GFP without co-culture, ALL-SIL cells transduced with TLX shRNA (sh-TLX), and ALL-SIL transduced with sh-control vectors. All conditions are performed in two replicates.

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Pre-T cell receptor Self-MHC Sampling Restricts Thymocyte Dedifferentiation

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