VPS13B

Researchers have not determined the role of the VPS13B gene (frequently called the COH1 gene) in the human body. Studies have shown that it has some similarities to a gene found in yeast that is involved in sorting and transporting proteins inside the cell. The human VPS13B gene is normally turned on in most cells of the body, which suggests that it plays an important role in cellular function. It may be particularly important in the formation of blood cells and the development and function of the eye and brain.

Cohen syndrome - caused by mutations in the VPS13B gene

At least 73 different mutations in the VPS13B gene have been shown to cause Cohen syndrome. Most of these mutations result in a premature stop signal in the instructions for making the VPS13B protein. Researchers believe that this genetic change leads to the production of an abnormally short, nonfunctional version of the protein. It is not known how the absence of the VPS13B protein leads to the signs and symptoms of Cohen syndrome.

In the Finnish population, 75 percent of individuals with Cohen syndrome have a mutation in the VPS13B gene that deletes two DNA building blocks (base pairs). This mutation is sometimes written as 3348_3349delCT. The deletion causes a premature stop signal in the instructions for making the VPS13B protein.

Two common mutations are seen in the Old Order Amish population. The first mutation inserts one base pair and is sometimes written as 9258_9259insT. This mutation creates a premature stop signal in the instructions for making the VPS13B protein. The second mutation changes a single protein building block (amino acid) in the VPS13B protein. Specifically, this mutation replaces the amino acid isoleucine with the amino acid threonine at position 2820 (written as Ile2820Thr or I2820T). Outside the Finnish and Amish populations, nearly all mutations in the VPS13B gene are seen in only one or a small number of families.