Molecular characterization of different ataxia telangiectasia T-cell clones. I. A common breakpoint at the 14q11.2 band splits the T-cell receptor alpha-chain gene.

Using in situ chromosomal hybridization we have mapped the gene for the T-cell receptor alpha-chain in three different non-malignant T-cell clones occurring in ataxia telangiectasia. The constant region was translocated in each of the three clones. The variable region remained in its original position in two cases and was deleted in one clone which lost the derivative chromosome 14. We have therefore demonstrated that the T-cell receptor alpha-gene is split in at least two of these translocations. To our knowledge, this is the first direct evidence of the involvement of a gene from the immunoglobulin superfamily in chromosomal rearrangements in ataxia telangiectasia.