Identifying DNA polymorphisms in human TCRA/D variable genes by direct sequencing of PCR products

Area of Science:

• Immunology
• Genetics
• Molecular Biology

Background:

• The T-cell receptor (TCR) is crucial for adaptive immunity, recognizing peptide antigens presented by MHC molecules.
• The TCR's high variability is encoded by germline gene segments, particularly the Variable (V) segments.

Purpose of the Study:

• To identify germline polymorphisms within the variable (V) gene segments of the human TCRA/D locus using a sequence-based approach.
• To investigate the potential functional impact of these polymorphisms on TCR structure and function.

Main Methods:

• Amplification of 30 different V gene segments from multiple unrelated individuals.
• Sequencing of amplified V gene segments using low melting point agarose.
• Analysis of sequence data to identify single nucleotide substitutions, insertions/deletions, and repeat variations.

Main Results:

• Identification of 27 polymorphisms across 15 V gene segments.
• Variations included single nucleotide substitutions, insertion/deletion polymorphisms, and variable length dinucleotide repeats.
• Nine polymorphisms resulted in amino acid changes, primarily at non-conserved residues within hypervariable regions.

Conclusions:

• Germline variations in TCR V gene segments are common.
• These polymorphisms may alter TCR interaction with MHC and peptide, influencing immune response.
• TCR gene variations could contribute to individual susceptibility to autoimmune diseases.