In this review, we will focus on the roles of LIMK1, the most abundant and extensively studied family member, in the regulation of the dendritic spine, synaptic plasticity, memory, and its dysfunction in brain diseases, including Alzheimer’s disease, Parkinson’s disease, Williams–Beuren syndrome, schizophrenia, and autism (Table 1). The gene discussed is LIMK1; the disease is Parkinson disease.