CLN5 gene
The CLN5 gene provides instructions for a protein involved in lysosomal function, with mutations leading to CLN5 disease, a condition affecting mental and motor development.
Normal Function
The CLN5 gene provides instructions for making a protein whose function is not well understood. Cells produce an inactive CLN5 preprotein containing extra segments. For the protein to become active, these segments must be removed through processing steps. The active CLN5 protein is then transported to lysosomes, where it is suggested to play a role in breaking down or recycling damaged or unneeded proteins.
Health Conditions Related to Genetic Changes
CLN5 disease
At least 35 mutations in the CLN5 gene have been found to cause CLN5 disease. This condition impairs mental and motor development, often causing difficulty with walking, intellectual decline, recurrent seizures (epilepsy), and vision loss. Symptoms typically appear around age 5 but can begin in adolescence or adulthood.
Most mutations interfere with the processing of the preprotein or alter its structure, preventing the protein from reaching the lysosomes. A lack of functional CLN5 protein impairs the breakdown of certain proteins, which accumulate in cells. Nerve cells are particularly vulnerable to these accumulations, and their widespread loss leads to severe symptoms and early death.
In cases where the disease develops in adolescence or adulthood, it is thought that the mutations result in a protein with reduced function that is broken down earlier than normal. Because the altered protein can function for a limited time, substances accumulate more slowly, delaying the onset of symptoms.