The distribution of gene segments in T-cell receptor gamma gene rearrangements demonstrates the need for multiple primer sets

Abstract

Limited data exist regarding the distribution of gene segments used in T-cell receptor gamma gene rearrangements (TCR gamma GR) in T-cell lymphoproliferative disorders. The reported efficacy of TCR gamma GR protocols ranges from 60% to greater than 90%. Laboratories reporting a lower detection rate tend to use a limited set of primers. The goal of our study was to provide TCR gamma GR data to demonstrate the molecular biological basis for needing multiple primer sets targeting all gene segments. Sixty cases with a confirmed histological diagnosis of a T-cell lymphoproliferative disorder and TCR gamma GR were identified in our lymphoma registry from 1995 to 2001. DNA was obtained from fresh/frozen tissue, cell lysates, or paraffin-embedded tissue. Variable (V gamma) region gene segments were identified using denaturing gradient gel electrophoresis, which was used to select the cases in the study. Capillary electrophoresis using fluorescent-labeled joining (J gamma) region primers was performed to identify J gamma segments. Sixty cases contained a total of 98 TCR gamma GR, as some cases have more than one rearrangement. The most frequent gene segment combination involved the V gamma 1-8 and J gamma 1/2 segments. If a single primer set directed at these two segments were used for clinical diagnosis, that pair of primers would only diagnose 67% of cases as positive for TCR gamma GR. Our gene segment distribution data emphasize the importance of using a comprehensive set of V gamma and J gamma primers for an optimal detection rate of TCR gamma GR. Protocols with limited numbers of primers should be reconsidered.

Figure 1.

Denaturing gradient gel electrophoresis: two cases exhibiting a rearrangement in the Vγ10 segment (arrows). CEM, HSB2, and Jurkat are T-cell lines for positive controls and CEM shows a biallelic rearrangement.

Figure 2.

Capillary electrophoresis method showing biallelic clonal rearrangements with the Jγ1/2 (black) and JγP1/2 (green) primers in a case of peripheral T-cell lymphoma. The heights of the clonal peaks are greater than two times the polyclonal background. x axis, nucleotide length; y axis, intensity of signal.