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

We have cloned circular DNA excised by T cell receptor (TcR) gamma 1, gamma 2 and gamma 3 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 gamma 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 gamma gene rearrangements is faithfully reflected on the signal joint of excision products. In addition, examination of gamma gene excision products revealed circular DNA products of TcR gamma-alpha transrearrangements, but no evidence of V gamma gene replacement in a rearranged segment.