The NeuN protein is localized in nuclei and perinuclear cytoplasm of most of
the neurons in the central nervous system of mammals. Monoclonal antibodies to
the NeuN protein have been actively used in the immunohistochemical research of
neuronal differentiation to assess the functional state of neurons in norm and
pathology for more than 20 years. Recently, NeuN antibodies have begun to be
applied in the differential morphological diagnosis of cancer. However, the
structure of the protein, which can be revealed by antibodies to NeuN, remained
unknown until recently, and the functions of the protein are still not fully
clear. In the present mini-review, data on NeuN accumulated so far are
summarized and analyzed. Data on the structure and properties of the protein,
its isoforms, intracellular localization, and hypothesized functions are
reported. The application field of immunocytochemical detection of NeuN in
scientific and clinical studies, as well as the difficulties in the
interpretation of the obtained experimental data and their possible causes, is
described in details.