CGB

CGB Full Name

chorionic gonadotropin, beta polypeptide

CGB Introduction

CGB gene encodes the beta subunit of human chorionic gonadotropin (hCG) which exists as a glycoprotein hormone that trophoblast cells of the placenta produce mainly during pregnancy. The beta subunit of this hormone provides its specific biological function while differentiating it from other glycoprotein hormones including LH and FSH and TSH. CGB gene cluster on chromosome 19 contains multiple genes which work together to produce sufficient hCG needed for fetal development during early development. CGB gene produces hCG which enters maternal blood circulation after implantation to function as an early pregnancy biomarker.

Figure 1. Biosynthesis and maturation of hCG subunits in the secretory pathway and sequestration of free subunits and hCG-heterodimers following the cisternal maturation model.(Source: Merz WE, et al. 2007)

Functionally, the beta subunit of hCG participates in regulating the maternal endocrine environment by stabilizing the corpus luteum and promoting progesterone secretion, which is essential for maintaining the endometrium and supporting embryonic development. hCG hormone serves multiple functions in addition to its traditional role in reproduction because it helps develop trophoblast cells and creates blood vessels in the placenta and regulates immune responses between mother and fetus. The CGB-driven hCG beta subunit activates LHCGR receptors to start cAMP signaling pathways which regulate implantation and placental growth and fetal survival.

The activation of CGB genes leads to increased hCG beta protein production which causes various medical problems. The presence of high hCG levels in blood indicates three types of trophoblastic diseases which include hydatidiform mole and choriocarcinoma and specific germ cell tumors that develop because of abnormal CGB gene expression. The presence of low or insufficient hCG levels in blood can indicate three different conditions which include threatened miscarriage and ectopic pregnancy and placental insufficiency. The clinical use of free beta-hCG as a tumor marker has been established for non-trophoblastic cancers which include testicular cancer and ovarian cancer and specific gastrointestinal tumors because it shows CGB gene activation in these diseases.

Alternate Names for CGB

CGB; chorionic gonadotropin, beta polypeptide; CGB3; CGB5; CGB7; CGB8; hCGB; choriogonadotropin subunit beta; CG-beta; chorionic gonadotropin beta chain; chorionic gonadotrophin chain beta; chorionic gonadotropin beta subunit; chorionic gonadotropin beta 3 subunit;

• Immunohistochemistry Antibodies for Pathology

• 1.Merz WE, et al. Nonassembled human chorionic gonadotropin subunits and alphaalpha-homodimers use fast-track processing in the secretory pathway in contrast to alphabeta-heterodimers. Endocrinology. 2007, 148(12):5831-41.