Somatic hypermutation and junctional diversification at Ig heavy chain loci in the nurse shark.

摘要: We estimate there are approximately 15 IgM H chain loci in the nurse shark genome and have characterized one locus. It consists of V, two D, J germline gene segments, constant (C) region can be distinguished from all others by a unique combination restriction endonuclease sites Cmu2. On basis these Cmu2 markers, 22 cDNA clones were selected an epigonal organ library same individual; their C sequences proved to up polyadenylation site. With identification corresponding CDR3 rearrangements could analyzed precisely, for first time. Considerable diversity was generated trimming N addition at three junctions varied recombination patterns D segments. The originated independent events, most carried both single contiguous substitutions. 53 point mutations occurred with bias transition changes (53%), whereas 78 tandem substitutions, mostly 2-4 bp long, do not (36%). nature substitution is as mutants six L isotypes, showing that somatic hypermutation events very similar genes this early vertebrate. cis-regulatory elements targeting must already existed ancestral Ig gene, before divergence.