Novel excision products of T cell receptor γ gene rearrangements and developmental stage specificity implied by the frequency of nucleotide insertions at signal joints

Abstract

We have cloned circular DNA excised by T cell receptor (TcR)γ1, γ2 and γ3 gene rearrangements in fetal and adult mouse thymocytes. Circular DNA contained a signal joint reciprocal to the genomic V-J coding joint. Although signal joints without nucleotide insertions are common in immunoglobulin (Ig) and TcR gene rearrangements, the signal joint of γ found in adult thymocytes contained non-germ-line element (N) insertions at high frequency, while no insertions were found in fetal thymocytes. Thus developmental stage specificity of TcR γ gene rearrangements is faithfully reflected on the signal joint of excision products. In addition, examination of γ gene excision products revealed circular DNA products of TcR γ-α transrearrangements, but no evidence for V_γ gene replacement in a rearranged segment.