Tandem arrangement of the closely linked desmoglein genes on human chromosome 18

The desmogleins, together with the desmocollins, both members of the cadherin superfamily, are the adhesive proteins of the desmosome type of cell junction, characteristically found in epithelial cells. Three different human desmoglein isoforms are encoded by separate genes (DSG1, DSG2, and DSG3) located on chromosome 18q12.1. DSG2 has been shown to be the most widely expressed in all desmosome-containing tissues, whereas DSG1 and DSG3 are expressed only in certain tissues, mostly stratified squamous epithelia. The desmoglein isoforms are expressed in a stratification-related manner in human epidermis, DSG1 being suprabasally expressed and DSG3 at a lower level, while DSG2 expression is weak and basal. Yeast artificial chromosome clones carrying all three known human desmoglein genes have now been isolated. The smallest clone containing all three DSG genes was 275 kb, and the three desmoglein genes were clustered within a region of less than 150 kb. From the types of clone obtained and from restriction enzyme analysis the order of the DSG genes and their orientation was deduced to be 5'-DSG1-DSG3-DSG2-3'. There thus appears to be some correspondence between the order of DSG genes and their expression within tissues, raising the intriguing possibility that the organization of the desmoglein gene cluster is required for properly regulated gene expression.