Nonsense CD247 mutations show dominant-negative features in T-cell receptor expression and function.

Area of Science:

• Immunology
• Molecular Biology

Background:

• The invariant TCR ζ/CD247 homodimer is essential for TCR/CD3 expression and signaling via its 3 ITAMs.
• CD247 mutations can cause immunodeficiency, but the impact of other CD247 variants on TCR function is unclear.

Purpose of the Study:

• To analyze and model the effects of heterozygous nonsense CD247 mutations on T-cell receptor (TCR) expression and function.
• Investigate potential dominant-negative effects in patients with immunodeficiency or autoimmunity.

Main Methods:

• Jurkat T cells (WT and CD247-deficient ZKO) were engineered using CRISPR/Cas9.
• Cells were transduced with WT CD247 or variants with mutated ITAMs (Q142X, Q101X, Q70X).

Main Results:

• Two heterozygous nonsense CD247 mutations (p.Y152X, p.Q101X) were identified in patients, affecting ITAM-2 and/or ITAM-3.
• Mutated CD247 variants reduced surface CD3 expression and impaired T-cell signaling (CD69 induction).
• Expression of CD247 variants lacking ITAMs in ZKO cells failed to restore normal CD3 levels; in WT cells, it reduced CD3 expression.

Conclusions:

• CD247 variants with absent ITAMs, resulting from nonsense mutations, are defective in TCR assembly.
• These variants exert a dominant-negative effect on TCR expression and signaling in vitro.
• This in vitro effect may correlate with observed clinical symptoms in patients.