Carcinoembryonic Antigen Gene Family

The carcinoembryonic antigen (CEA) gene family belongs to the
immunoglobulin supergene family and can be divided into two main
subgroups based on sequence comparisons. In humans it is clustered
on the long arm of chromosome 19 and consists of approximately 20
genes. The CEA subgroup genes code for CEA and its classical
crossreacting antigens, which are mainly membrane-bound, whereas
the other subgroup genes encode the pregnancy-specific
glycoproteins (PSG), which are secreted. Splice variants of
individual genes and differential post-translational modifications
of the resulting proteins, e.g., by glycosylation, indicate a high
complexity in the number of putative CEA-related molecules. So far,
only a limited number of CEA-related antigens in humans have been
unequivocally assigned to a specific gene. Rodent CEA-related genes
reveal a high sequence divergence and, in part, a completely
different domain organization than the human CEA gene family,
making it difficult to determine individual gene counterparts.
However, rodent CEA-related genes can be assigned to human
subgroups based on similarity of expression patterns, which is
characteristic for the subgroups. Various functions have been
determined for members of the CEA subgroup in vitro, including cell
adhesion, bacterial binding, an accessory role for collagen binding
or ecto-ATPases activity. Based on all that is known so far on its
biology, the clinical outlook for the CEA family has been
reassessed.