T cell receptor γ and δ gene junctional sequences in SCID mice : excessive P nucleotide insertion

The severe combined immunodeficiency (SCID) mutation has been postulated to affect a V(D)J recombinase activity involved in coding joint formation. Analysis of 38 joints from 34 distinct sequences of normally rearranged T cell receptor (TCR) gamma and delta genes from adult, SCID thymocytes reveals coding joints with an increased number of P nucleotides. One-third of P sequences are greater than or equal to 4 nucleotides in length and P elements of up to 15 bases are observed. This suggests that the SCID defect deregulates P nucleotide addition. Consequently, essential V(D)J recombination intermediates may seldom be generated.