RBFOX3 (NEUN, neuronal nuclear antigen) is an RNA-binding protein that is localized in the nuclei and perinuclear cytoplasm of neurons. The protein is involved in neuronal differentiation and is a permanent regulator of the neuronal phenotype. This protein is a useful marker for post-mitotic neurons and neurocytomas. References: Acta Naturae. 2015 Apr-Jun; 7(2): 42–47; Pathol Res Pract. 2003;199(7):463-8;