CLN3

The CLN3 gene provides instructions for making a protein whose function is unknown. Although the CLN3 protein is found in cells throughout the body, it appears to play a particularly important role in the survival of nerve cells (neurons) in the brain.

The CLN3 protein is found in several different parts of cells, including the cell membrane. Researchers have proposed many potential functions for this protein. These include protein transport (trafficking), cell-to-cell communication, and the transmission of chemical signals. The CLN3 protein may also be involved in the organization of the cell's structural framework (cytoskeleton) and in the self-destruction of cells (apoptosis). Additionally, the protein appears to be important for the normal function of cell structures called lysosomes. Lysosomes are compartments in the cell that normally break down toxic substances and recycle different types of molecules. Researchers propose that the CLN3 protein may help regulate the size and relative acidity (pH) of lysosomes. Additional functions of this protein are under study.

juvenile Batten disease - caused by mutations in the CLN3 gene

More than 40 mutations in the CLN3 gene have been identified in people with juvenile Batten disease. The most common mutation deletes about 1,000 DNA building blocks (base pairs) in the CLN3 gene. This mutation, which is usually called the 1 kb deletion, removes a critical part of the gene. The effects of the 1 kb deletion are not well understood, although this mutation likely disrupts the normal function of the CLN3 protein or prevents cells from making any functional CLN3 protein.

Researchers are working to determine how mutations in the CLN3 gene lead to the characteristic features of juvenile Batten disease. These mutations somehow disrupt the function of lysosomes, allowing a fatty substance called a lipopigment to build up abnormally within these cell structures. The buildup of this substance is thought to damage neurons and may ultimately cause these cells to die. Over time, the progressive death of neurons in the brain leads to vision loss, seizures, and a decline in thinking ability (cognition) in affected individuals.

Although lipopigment also accumulates within other types of cells, the signs and symptoms of juvenile Batten disease primarily affect the brain. Studies suggest that neurons may be particularly vulnerable to damage caused by the buildup of lipopigment in lysosomes.