Single-cell transcriptomics uncovers an instructive T-cell receptor role in adult γδ T-cell lineage commitment

Area of Science:

• Immunology
• Cell Biology
• Developmental Biology

Background:

• T-cell progenitors in the adult thymus differentiate into either alpha beta (αβ) or gamma delta (γδ) T cells.
• The role of the γδ T-cell receptor (TCR) in lineage commitment is debated: it may instruct the lineage or merely confirm a pre-existing state.

Purpose of the Study:

• To investigate whether γδ TCR signaling is instructive or confirmatory for γδ T-cell lineage commitment.
• To elucidate the role of LAT, an adaptor protein crucial for γδ TCR signaling, in T-cell development.

Main Methods:

• Utilized genetically modified mice lacking LAT expression to disrupt γδ TCR signaling.
• Analyzed T-cell development at the CD4- CD8- double-negative third (DN3) stage using flow cytometry.
• Employed single-cell transcriptomics to assess the lineage commitment status of LAT-deficient DN3 γδ T cells.

Main Results:

• LAT-deficient mice exhibited a block in T-cell development at the DN3 stage, with a small population of γδ T cells expressing intermediate γδ TCR levels (γδint).
• Single-cell transcriptomics revealed that these LAT-deficient DN3 γδint cells showed no commitment to the γδ T-cell lineage.
• Unexpectedly, a subset of these cells proliferated and progressed to the DN4 stage but failed to activate the γδ T-cell transcriptional program.

Conclusions:

• The γδ TCR-LAT signaling axis is crucial for instructing the γδ T-cell lineage specification.
• γδ T-cell lineage commitment is not pre-established but actively instructed by γδ TCR signaling, building upon an uncommitted state.