platelet derived growth factor subunit B
The PDGFB gene provides instructions for making one version (isoform) of the platelet derived growth factor (PDGF) protein. This protein is involved in many cellular processes, including cell growth and division (proliferation), maturation (differentiation), and movement. The PDGFB gene provides instructions for a precursor protein that must be processed to be able to perform its function. Before processing, the precursor PDGFB protein attaches (binds) to another PDGFB protein or a similar protein called the PDGFA precursor protein, forming a structure known as a dimer. Once the dimer is formed, the precursor proteins are processed by being cut at specific locations, which forms the functional (active) PDGF proteins, called PDGF-BB and PDGF-AB.
The active PDGF-BB or PDGF-AB protein binds to a PDGF receptor, which initiates cellular signaling. PDGF signaling activates many pathways important in cell proliferation, differentiation, and movement.
Dermatofibrosarcoma protuberans, a rare type of cancer that causes a tumor in the deep layers of skin, is characterized by a somatic mutation involving the PDGFB gene. Somatic mutations are not inherited, but are acquired during a person's lifetime and are present only in certain cells. Dermatofibrosarcoma protuberans is associated with a rearrangement (translocation) of genetic material between chromosomes 17 and 22. This translocation, written as t(17;22), fuses part of the PDGFB gene on chromosome 22 with part of another gene on chromosome 17 called COL1A1. The translocation is found on one or more extra chromosomes that can be either the normal linear shape or circular. The resulting combined (fusion) gene is called COL1A1-PDGFB.
The COL1A1-PDGFB fusion gene provides instructions for making a fusion protein. In the translocation, the PDGFB gene loses the part of its DNA that inhibits its activity, and production of the COL1A1-PDGFB fusion protein is controlled by COL1A1 gene sequences. As a result, the gene fusion leads to the production of large amounts of the fusion protein. The COL1A1-PDGFB protein forms a dimer and is processed like the normal PDGFB precursor protein. Processing removes the COL1A1 portion, which forms a protein that researchers believe functions like the active PDGF-BB protein. Excess PDGF-BB protein abnormally stimulates cells to proliferate and differentiate, leading to the tumor formation seen in dermatofibrosarcoma protuberans.
Primary familial brain calcification