ORGANIZATION, POLYMORPHISM, AND EXPRESSION OF THE HUMAN T-CELL RECEPTOR AV1 SUBFAMILY

At least 32 mostly single-member subfamilies of T-cell receptor alpha variable (TCRAV) genes have been described in humans. The AV1 subfamil y is the largest, estimated by hybridization to contain as many as fiv e members. However, a search of nucleotide sequence databases reveals a much greater number of unique sequences corresponding to this subfam ily. In order to resolve this discrepancy between hybridization and nu cleotide sequencing data, and to better understand the nature of varia bility among variable genes within a large subfamily, a genomic charac terization of the AV1 subfamily in humans was carried out. Total genom ic DNA, as well as isolated genomic clones spanning the TCRA region we re screened for members of the AV1 subfamily by polymerase chain react ion (PCR) and nucleotide sequencing as well as by hybridization. A tot al of eight AV1 genes were identified and their nucleotide sequences w ere determined. Three of the sequences represent new genes. Based on s tructural features and the results of PCR screening of cDNA, none of t hese new genes appear to be functional. Several additional previously reported AV1 sequences were determined to represent alleles of AV1 gen es, and simple PCR restriction digest assays were established for thei r detection. Use of each of the identified AV1 genes as hybridization probes failed to reveal any additional hybridizing bands. Thus the AV1 genes represent the largest TCRAV subfamily with a maximum of eight me mbers, several of which have common allelic forms.