MAPPING OF CD24 AND HOMOLOGOUS SEQUENCES TO MULTIPLE CHROMOSOMAL LOCI

The human cell surface antigen, CD24, is a glycosyl phosphatidylinosit ol (GPI)-linked glycoprotein that has been implicated in the different iation and activation of granulocytes and B lymphocytes. Changes in ex pression of the antigen occur at critical times during B lineage devel opment. CD24 was cloned by its homology to mouse heat-stable antigen. Southern blot analysis suggested the presence of multiple CD24 related sequences in the human genome. We have now mapped CD24 homologous seq uences to chromosomes 6q21, 15q21-q22, and Yq11 by screening a panel o f somatic cell hybrid DNAs and by in situ hybridization. At least two additional homologues, one located on chromosome 1 at band p36 and one tentatively mapped to chromosome 20, that are distantly related to CD 24 were identified. Southern analysis of male and female DNA samples c onfirmed the presence of CD24 homologous sequences on the human Y chro mosome. Sequencing of DNA fragments amplified from monochromosomal som atic cell hybrids showed that the CD24 cDNA was derived from a transcr ipt originating from a gene on chromosome 6. The CD24 gene on the Y ch romosome had many base changes compared to the cDNA but had retained a n open reading frame, leaving open the question of whether this gene i s functional. Both ATGs in the translation initiation region of CD24 h omologous sequences on chromosome 15 were converted to GTGs, making it unlikely that this gene, if functional, encodes a protein similar to CD24. CD24, therefore, is a member of a multigene family, but it remai ns to be determined whether any of the related genes are functional. ( C) 1994 Academic Press, Inc.