RELN (Reelin): RELN (Reelin) encodes a large secreted extracellular matrix protein called reelin, which is essential for neuronal migration and positioning during brain development. It influences the layering of neurones in the cerebral cortex and cerebellum. Changes or mutations in RELN expression have been linked to several neuropsychiatric disorders, including autism, schizophrenia, and bipolar disorder. Reelin also contributes to synaptic plasticity in the adult brain, affecting learning and memory.