Cloning of a Carcinoembryonic Antigen Gene Family Member Expressed in Leukocytes of Chronic Myeloid Leukemia Patients and Bone Marrow

The carcinoembryonic antigen (CEA) gene family belongs to the
immunoglobulin superfamily and can be subdivided into the CEA and
pregnancy-specific glycoprotein subgroups. The basic structure of
the encoded proteins consists of, in addition to a leader, one
IgV-like and 2, 3, or 6 IgC-like domains. These domains are
followed by varying COOH-terminal regions responsible for
secretion, transmembrane anchoring, or insertion into the membrane
by a glycosyl phosphatidylinositol tail. Here we report on the
characterization of CGM6, a new member of the CEA gene subgroup, by
complementary DNA cloning. The deduced coding region comprises 349
amino acids and consists of a leader, one IgV-like, two IgC-like
domains, and a hydrophobic region, which is replaced by a glycosyl
phosphatidylinositol moiety in the mature protein. CGM6 transcripts
were only found thus far in leukocytes of chronic myeloid leukemia
patients, in normal bone marrow, and in marginal amounts in normal
granulocytes. The CGM6 gene product might, therefore, represent a
myeloid marker. Analyses of CGM6 protein-expressing HeLa
transfectants with monoclonal antibodies strongly indicate that the
CGM6 gene codes for the CEA family member NCA-95.