In this report, we characterize an alternate gene element of the murine TCR β-chain. First, we have looked at the expression of the alternate exon, Cβ0, in normal T cell clones, as well as in fetal vs adult whole thymus. The Cβ0 exon is expressed in only 1% or less of TCR-β messages in four of four mature T cell clones examined. Cβ0 is found at 10-fold higher levels in both fetal and adult thymus mRNA. Thus C̄0 is developmentally regulated by T cells, although expression of the alternate exon is relatively constant from the fetal thymus to the adult thymus. Second, evolutionary conservation of the Cβ0 gene element was studied in both the rat and the human. The rat β-locus contains a gene element highly homologous to the mouse Cβ0 gene, but the rat Cβ0 gene contains mutations in both splice sites that probably prevent the gene element from being spliced into mRNA. We have also sequenced the first exon of rat Cβ1, and find that the Cβ0 exon and the intron around Cβ0 are conserved between rat and mouse to the same level as the Cβ1 coding region. The intron around Cβ1, in contrast, shows the decrease in conservation between the two species that is expected for a noncoding region. Analysis of the putative Cβ0-containing region in the human reveals no sequences homologous to the Cβ0 gene element. Because the mouse is the only species that has conserved a functional Cβ0 gene, we conclude that the Cβ0 exon does not play a general role in T cell development.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of Immunology|
|State||Published - 1989|
ASJC Scopus subject areas
- Immunology and Allergy