CPG15

CPG15, commonly known as neuritin, is a neuronal protein encoded by the NRN1 gene in humans. It was identified as Candidate Plasticity Gene 15 (CPG15) owing to its strong upregulation in response to neural activity, suggesting a role in synaptic plasticity. The protein is a small, glycosylphosphatidylinositol (GPI)-anchored cell-surface factor, and is also found in secreted form. It is mainly expressed in brain regions such as the hippocampus and cortex, with higher levels during development.

Functionally, neuritin promotes neurite outgrowth, increases dendritic branching and spine formation, and supports synapse maturation. Through cell-surface signaling, it modulates structural remodeling of neural circuits and enhances synaptic strength in an activity-dependent manner. Mechanistically it can influence cytoskeletal dynamics and signaling cascades associated with plasticity, though exact pathways remain under study.

Regulation and expression: Expression is induced by neuronal activity and neurotrophic signals, and is higher during development. It is produced by various neuronal populations and can be released from the cell surface through proteolytic shedding.

Clinical and research relevance: CPG15/neuritin is investigated for its roles in neural development, regeneration after injury, and synaptic plasticity-related processes underlying learning and memory. Altered expression or function has been explored in models of neurodevelopmental and neurodegenerative conditions, but concrete clinical implications remain to be established.

History: The gene was named Candidate Plasticity Gene 15 following discovery of its activity-dependent regulation, later renamed NRN1 in humans with the protein commonly referred to as neuritin.