The gene encoding the palmitoylated erythrocyte membrane protein, p55, originates at the CpG island 3' to the factor VIII gene.

A CpG island 30 kb 3' to the human factor VIII gene in Xq28 is associated with a 2-kb transcript. This gene encodes a previously described palmitoylated membrane protein, p55, containing a src homology motif, SH3. Although originally described in reticulocytes, the transcript is expressed in a wide variety of human tissues. The gene is also present in the mouse and expressed in all mouse tissues examined. No known factor VIII gene deletions extend into the p55 gene. Since the function of the p55 protein is not known, the p55 gene is formally a candidate for any of the 19 or more disease genes that have not been isolated but are closely linked genetically to the factor VIII gene.