Heterogeneity of NeuN Protein Distribution as a Marker of Morphological Personalization of Cerebral Cortex Neurons: an Experimental Study

Aim. To identify personalized morphological neuronal phenotypes based on the distribution pattern of the neuronal protein NeuN in the cerebral cortex layers.

Materials and Methods. A histologic study of the cerebral cortex was performed in rats (N=10). Tissue sections were stained with hematoxylin and eosin, and the neuronal nuclear protein NeuN was visualized by immunohistochemical staining. Analysis was performed by microscopy and image analysis software.

Results. NeuN immunohistochemical staining revealed distinct localization and intensity patterns within cortical neurons. Contrary to the definition of NeuN as a nuclear neuronal protein, its localization was observed in both the nucleus and cytoplasm in most neurons. The following neuronal phenotypes were identified based on NeuN staining patterns: 1) Neurons with stained nuclei but unstained cytoplasm; 2) Neurons with stained cytoplasm but unstained nuclei; 3) Neurons with stained nuclei and cytoplasm; 4) Fully stained neurons with no visible nuclei; 5) Neurons with stained processes (dendrites/axons). A significant difference was found between mean intensity of NeuN-positive neurons depending on the localization in the layers of the cerebral cortex.

Conclusion. Given the critical biological role of NeuN, the identified neuronal phenotypes based on NeuN localization warrant further research as they may reflect the functional states of neurons. The interpretation of the absence of NeuN staining as a marker of neuronal damage is not scientifically justified. Future studies using NeuN immunohistochemical staining should consider not only the total number of NeuN-positive neurons, but also their distinct phenotypes.

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