Pre-mRNA alternative splicing regulator. Regulates alternative splicing of RBFOX2 to enhance the production of mRNA species that are targeted for nonsense-mediated decay (NMD). Widely expressed in brain, including in cerebral cortex, hippocampus, thalamus, caudate/putamen, cerebellum, as well as in the spinal cord (at protein level). Not expressed in all neuronal cells within a region, in cerebellum, expression is absent in Purkinje cells (at protein level). Expressed in the retina in the ganglion cells and some cells in the inner nuclear layer, but absent from the photoreceptor cells and most cells in the inner nuclear layer (at protein level). In the neural tube, expressed as early as 9.5 dpc and expression is confined to the nervous system. By 12.5 dpc, can be found in the developing ventral horns and is also detected in the developing dorsal horns as well as in the dorsal root ganglion. Not detected in the ventricular zone, roof plate, floor plate or marginal zone (developing white matter). It is expressed from embryonic stage to adulthood. By retinoic acid. Expression is up-regulated in P19 cells during neural differentiation upon retinoic acid treatment (at the protein level). Phosphorylated. Knockout mice have significantly reduced brain weight, impaired neurofilament expression and decreased white matter volume, but normal total body mass. They show increased susceptibility to seizures and reduced anxiety-related behaviors compared with wild type littermates, as well as defective hippocampal gene expression and deficits in synaptic transmission and plasticity in the dentate gyrus. Initial characterization was derived from usage of a monoclonal antibody (A60) directed to an unknown protein called NeuN (PubMed:15605376 and PubMed:1483388), but later identified as RBFOX3.