Identification of a new murine lectin-like gene in close proximity to CD94

The cytolytic activities of natural killer (NK) cells are controlled by immune receptors expressed on the NK cell surface that interact with MHC I molecules on the target cell. In the murine system, the receptors that perform this function are members of the c-type lectin superfamily and are found in a 4 Mbp cluster termed the natural killer gene complex (NKC) on chromosome 6. To date, over 30 receptor genes, which largely exhibit lymphoid-restricted expression, have been cloned from this region. With the completion of genomic sequencing in this region, computer prediction of genes based in part on expressed sequence tag (EST) evidence has allowed the identification of potential new genes in the cluster. In this study, we investigated one of these predicted genes and showed that it is a bona fide gene, which is transcribed in both the mouse and rat but is not present in humans. A phylogenetic comparison also showed that the novel gene, Klre-1, is most closely related to CD94. Strikingly, the Klre-1 gene is located within very close proximity (2.3 kb) to the CD94 gene. Consequently, we examined the expression patterns of Klre-1 by quantitative real-time polymerase chain reaction and found a correlation between expression of CD94 and Klre-1 in primary cells as well as cell lines. This discovery presents further possibilities for characterising transcriptional control of genes in the NKC.