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 for V(gamma) gene replacement in a rearranged segment.