The C9orf72 gene gives instructions for making a protein that is found in multiple tissues. The protein is prevalent in neurons (nerve cells) in the outer layers of the cerebral cortex (brain) and in specialized neurons in the brain and spinal cord that control movement (motor neurons). The C9orf72 protein is thought to be located at the tip of the neuron in a region called the presynaptic terminal. This area is important for sending and receiving signals between neurons. It is believed the C9orf72 protein takes part in many processes involving ribonucleic acid (RNA) and influences the production of RNA from genes, the production of proteins from RNA, and the transport of RNA within the cell. The C9orf72 gene consists of a segment of DNA which is a series of six DNA building blocks (nucleotides), four guanines and two cytosines (GGGGCC). This segment, which is called a hexanucleotide repeat, can happen once or repeat multiple times in a row.