NeuN expression in health and disease: A histological perspective on neuronal heterogeneity.

Neuronal nuclei (NeuN), also known as Rbfox3, is a widely used neuronal marker for identifying postmitotic neurons in both basic neuroscience and diagnostic neuropathology. Since its discovery, NeuN immunoreactivity has enabled accurate neuron counting, injury assessment, and anatomical mapping. However, accumulating evidence demonstrates that NeuN is not universally expressed across all mature neurons. Specific neuron types, such as olfactory mitral cells, cerebellar Purkinje cells, and retinal photoreceptors, consistently lack NeuN immunostaining despite functional maturity. Moreover, NeuN expression is dynamically regulated under pathological conditions. In ischemia-reperfusion (I/R) injury,…