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CD3- T cells with cis- or trans-acting mutations affecting expression of T cell receptor beta-chain mRNA
J G Wong1, S Kasibhatla, E A Nalefski
1Division of Tumour Virology, Dana-Farber Cancer Institute, Boston, MA 02115.
Abstract:
Mutants of an untransformed T cell clone that no longer respond to TCR/CD3 stimulation have been derived using a selection procedure based on the loss of functional response to Ag. This functional selection gives rise to clones of several different phenotypes. We have previously described mutants with a TCR/CD3+ cell surface phenotype whose TCR are uncoupled from cellular responses. We describe six additional mutants that do not express TCR/CD3 at the cell surface. One of the CD3- clones contains a deletion in the successfully rearranged TCR-alpha gene, whereas another carries a deletion in the successfully rearranged TCR-beta gene. TCR/CD3 expression in these deletion mutants can be restored by transfection of TCR-alpha or TCR-beta DNA. Four other clones do not express TCR-beta mRNA, yet contain no obvious deletions or rearrangements in the TCR-beta genes. One of these clones does not transcribe TCR-beta chain mRNA. The mutation in this clone does not reside in the TCR-beta gene itself, but may instead reside in a trans-acting regulatory element affecting TCR-beta gene expression, because the TCR-beta mRNA-phenotype is complemented by fusion with a TCR-alpha-beta- cell line. TCR-beta chain regulatory mutants will be valuable in contributing to our understanding of how TCR expression is regulated.
Insights
Researchers identified T-cell receptor (TCR) mutants lacking cell surface expression. These mutants, including gene deletions and regulatory element mutations, offer insights into TCR/CD3 regulation and T-cell signaling pathways.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- T-cell receptor (TCR) and CD3 complex are crucial for T-cell activation.
- Previous studies identified T-cell mutants with uncoupled TCR signaling.
- Understanding TCR/CD3 regulation is vital for T-cell function.
Purpose of the Study:
- To characterize novel T-cell mutants with defects in TCR/CD3 expression.
- To investigate the genetic basis of TCR/CD3 loss-of-function.
- To explore regulatory mechanisms of TCR-beta chain expression.
Main Methods:
- Functional selection of T-cell mutants based on antigen response.
- Phenotypic analysis of cell surface TCR/CD3 expression.
- Genetic analysis including gene deletion screening and mRNA expression analysis.
- Complementation studies using cell fusion.
Main Results:
- Six new T-cell mutants lacking surface TCR/CD3 were identified.
- Two mutants had deletions in TCR-alpha or TCR-beta genes, restorable by transfection.
- Four mutants showed no TCR-beta mRNA; one lacked TCR-beta transcription due to a trans-acting regulatory element defect.
- Complementation confirmed a trans-acting regulatory mutation affecting TCR-beta expression.
Conclusions:
- Functional selection can yield diverse TCR/CD3 deficient mutants.
- TCR gene deletions and regulatory element mutations impair TCR expression.
- Novel trans-acting regulatory mutants provide insights into TCR-beta gene expression control.
- These mutants are valuable tools for studying T-cell receptor regulation.