Gene structure of the mouse leukocyte cell surface molecule Ly9

The Ly9 glycoprotein is a member of the immunoglobulin (Ig) superfamily, wh ich is expressed on the cell surface of B and T lymphocytes. With two allel es (Ly9.1 and Ly9.2), it was first described as an alloantigenic marker of lymphocyte differentiation. Ly9 consists of four Ig-like domains with the s tructural features of the CD2 subfamily, which includes CD2, CD48. CD58, 2B 4, CD84, and CDw150 (SLAM). Here, we report the isolation and characterizat ion of the Ly9 gene, which encompasses at least 19 kb and contains ten sepa rated exons. with sizes ranging from 54 to 355 bp. Each Ig-like domain is e ncoded by an individual exon. Sequence analysis of a 1.5-kb fragment upstre am from the start translational codon revealed the absence of appropriately located TATA and CAAT boxes. However, potential binding sites for the tran scription factors PU.1, Ikaros, AP-1, GATA-2, NF-GMa, NFAT-1, and Oct-2, wh ich are involved in the early development and maturation of lymphocytes, we re found. To further characterize the two allotypes of Ly9, cDNA of Balb/C and C57BL/6 mouse strains were sequenced and the predicted polypeptides com pared. Nine discrepancies were found, four of them in the first Ig-like dom ain. The characterization of the genomic organization of Ly9 presented in t his paper may improve understanding of the molecular mechanisms that regula te Ly9 expression, and the production of a construct to disrupt the Ly9 gen e in ES cells in order to produce deficient mice.