Drebrins (developmentally regulated brain proteins) are cytoplasmic proteins that bind F-actin in the brain and are involved in cell migration, extension of neuronal processes and plasticity of dendrites. There are three isoforms: two embryonic types (E1 and E2); and an adult type (A), generated by alternative RNA splicing from a single Drebrin gene. Drebrins are expressed mainly in brain neurons but are also found in skeletal muscle, heart, placenta, pancreas and kidney. Drebrin has been designated as a marker of the dendritic spine. Decreases in Drebrin levels in the brain have been been associated with Alzheimer s disease and Down syndrome.