Organization of the T-cell receptor alpha-chain gene and rearrangement in human T-cell leukaemias.

The structure and rearrangement of the human T-cell receptor alpha-chain gene have been analysed. The constant region segment is comprised of four exons, with the 3' non-coding region present as a separate exon. Two J alpha segments have been identified by sequence analysis about 4 X 10(3) and 15 X 10(3) base-pairs upstream from the constant region segment. Analysis of alpha-chain rearrangements in a panel of T-cells reveals the presence of at least four more J alpha segments within 19 X 10(3) base-pairs of C alpha and suggests the existence of additional J alpha segments further upstream. This dispersed organization of the J alpha region contrasts with the clustered organization observed in other lymphoid rearranging genes. The use of J alpha probes in diagnostic purposes for T-cell leukaemia is not, therefore, convenient and will require a number of different probes to ensure complete analysis of the locus.