NeuN

Rat hippocampus stained with antibody to NeuN (green), myelin basic protein (red) and DNA (blue). Antibodies and image courtesy of EnCor Biotechnology Inc.
Antibody staining for Fox-3/NeuN in the adult rat cerebellum in green. The Fox-3/NeuN antibody binds to the small cerebellum granule cell neurons, which form a prominent layer. In contrast antibody to the close relative of Fox-3/NeuN, Fox-2, is shown in red. Fox-2 antibody stains Purkinje neurons and Golgi cell which are not recognized by the Fox-3/NeuN antibody. The Purkinje cells form a layer above the much more abundant granule cells, and an occasional Golgi cell, also positive for Fox-2 but negative for Fox-3/NeuN, can be seen in the granule cell layer. DNA is shown in blue. Antibodies and image courtesy of EnCor Biotechnology Inc.

NeuN (Feminizing Locus on X-3, Fox-3, Rbfox3, or Hexaribonucleotide Binding Protein-3), a homologue to sex-determining genes in Caenorhabditis elegans, is a neuronal nuclear antigen that is commonly used as a biomarker for neurons.

History

NeuN was first described in 1992 by Mullen et al., who raised a series of monoclonal antibodies to mouse antigens with the original intent of finding mouse species specific immunological markers for use in transplantation experiments.[1] In the event they isolated a hybridoma line, called mAb A60, which proved to bind an antigen expressed only in neuronal nuclei and to a lesser extent the cytoplasm of neuronal cells, and which appeared to work on all vertebrates. This unknown antigen was therefore known as NeuN for "Neuronal Nuclei". In 2009, Kim et al. used proteomic methods to show that NeuN corresponds to a protein known as Fox3, also known as Rbfox3, a mammalian homologue of Fox-1, a protein originally found in the nematode worm C. elegans.[2]

Structure

Western blotting shows that mAb A60 binds to two bands of apparent molecular weight 46kDa and 48kDa on SDS-PAGE. These two forms are generated from a single gene by alternate splicing. Both forms are expressed only in neurons and as a result the mAb A60 antibody and other similar antibodies to Fox3/NeuN have become very widely used as a robust marker of neurons.

Uses as a Neuronal Biomarker

NeuN antibodies are widely used to label neurons, despite some shortcomings, and a September 2016 Medline search using the keyword "NeuN" produced 2565 hits.[3] A few neuronal cell types are not recognized by NeuN antibodies, such as cerebellar Purkinje cells and Golgi cells, olfactory Mitral cells, retinal photoreceptors and gamma motor neurons. However the vast majority of neurons are strongly NeuN positive, and NeuN immunoreactivity has been widely used to identify neurons in tissue culture and in sections and to measure the neuron/glia ratio in brain regions.[4] NeuN immunoreactivity becomes obvious as neurons mature, typically after they have downregulated expression of Doublecortin, a marker seen in the earliest stages of neuronal development.

Feminizing Locus on X Homologue

Fox-3 is one of a family of mammalian homologues of the Fox-1 protein, originally discovered in the nematode worm C. elegans as a gene involved in sex determination.[5] Fox is, in fact, an acronym of "Feminizing locus on X". The mammalian genome contains three genes homologous to C. elegans Fox-1, called Fox-1, Fox-2 and Fox-3. The Fox proteins are all about 46kDa in size, and each includes a central, highly conserved ~70 amino acid RRM or RNA recognition motif. RRM domains are one of the most common in the human genome and are found in numerous proteins which bind RNA molecules. NeuN/Fox-3 and the other Fox proteins function in the regulation of mRNA splicing and bind specific RNA sequences. For a review of the Fox family of proteins see this reference.[6] An alternate name for Fox-3 is hexaribonucleotide binding protein 3.

References

As of 15 June 2011, this article is derived in whole or in part from EnCor Biotechnology Inc.. The copyright holder has licensed the content in a manner that permits reuse under CC BY-SA 3.0 and GFDL. All relevant terms must be followed. The original text was at "Monoclonal Antibody to Fox3/NeuN".

  1. ↑ Mullen, RJ; Buck, CR; Smith, AM (1992). "NeuN, a neuronal specific nuclear protein in vertebrates". Development (Cambridge, England). 116 (1): 201–11. PMID 1483388.
  2. ↑ Kim, K. K.; Adelstein, R. S.; Kawamoto, S. (2009). "Identification of Neuronal Nuclei (NeuN) as rbfox3, a member of the Fox-1 Gene Family of Splicing Factors". Journal of Biological Chemistry. 284 (45): 31052–61. doi:10.1074/jbc.M109.052969. PMC 2781505Freely accessible. PMID 19713214.
  3. ↑ "NeuN - PubMed - NCBI".
  4. ↑ Herculano-Houzel, S.; Lent, R (2005). "Isotropic Fractionator: A Simple, Rapid Method for the Quantification of Total Cell and Neuron Numbers in the Brain". Journal of Neuroscience. 25 (10): 2518–21. doi:10.1523/JNEUROSCI.4526-04.2005. PMID 15758160.
  5. ↑ Hodgkin, J; Zellan, JD; Albertson, DG (1994). "Identification of a candidate primary sex determination locus, fox-1, on the X chromosome of Caenorhabditis elegans". Development (Cambridge, England). 120 (12): 3681–9. PMID 7821230.
  6. ↑ Underwood JG, Boutz PL, Dougherty JD, Stoilov P, Black DL (2005). "Homologues of the Caenorhabditis elegans Fox-1 protein are neuronal splicing regulators in mammals". Mol. Cell. Biol. 25: 10005–10016. doi:10.1128/MCB.25.22.10005-10016.2005. PMC 1280273Freely accessible. PMID 16260614.
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