Description : Alpha-fetoprotein is a major plasma protein in the fetus, where it is produced by
the yolk sac and liver (Ingram et al., 1981). In the adult its concentration is very
low except when a tumor such as hepatoma or teratoma is present. The similarity in
physical properties of AFP and albumin (ALB; 103600) and the fact that their presence
is inversely related suggested that AFP is the fetal counterpart of serum albumin.
The alpha-fetoprotein and albumin genes are syntenic; this may represent an ontogenically
significant arrangement with switch from AFP to albumin, comparable to the hemoglobin
F to hemoglobin A switch (see 141800). Mammalian AFP and serum albumin genes are thought
to have arisen through duplication of an ancestral gene 300 to 500 million years ago.
The AFP gene is a member of a multigenic family that comprises the related genes encoding
ALB, alpha-albumin, or afamin (AFM; 104145), and vitamin D-binding protein, otherwise
known as group-specific component (GC; 139200) (Gabant et al., 2002).;