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NeuN

NeuN, also known as neuronal nuclei, is a neuron-specific nuclear protein expressed predominantly in the nuclei and cytoplasm of post-mitotic neurons throughout the vertebrate central and peripheral nervous systems, serving as a widely used immunohistochemical marker for identifying mature neurons due to its high specificity and stability in most neuronal cell types.^[1]^[2] Discovered in 1992 through the generation of monoclonal antibodies (clone A60) against murine neural antigens, NeuN was initially characterized as a soluble, DNA-binding protein appearing as three bands of 46–48 kDa on immunoblots, with expression beginning postnatally in the developing mouse brain and persisting in adulthood across species including humans.^[1]^[3] Although highly conserved and detected in the majority of neuronal populations, NeuN immunoreactivity is absent or reduced in certain cell types such as cerebellar Purkinje cells, olfactory mitral cells, and photoreceptor cells, as well as in some pathological conditions like neurodegeneration or injury, highlighting limitations in its use as a universal neuronal label.^[1]^[2] In 2009, NeuN was molecularly identified as an epitope of the RNA-binding protein Fox-3 (Rbfox3), a member of the Fox-1 family of splicing factors that regulates alternative splicing of neuron-specific transcripts by binding to UGCAUG elements in pre-mRNA, thereby influencing neuronal differentiation, maturation, and function beyond its role as a mere histological marker.^[4] This revelation expanded understanding of NeuN's biological significance, linking it to RNA processing pathways critical for neural development, with Rbfox3 knockout studies in mice demonstrating disrupted splicing and neuronal phenotypes.^[4]^[2] Since its discovery, anti-NeuN antibodies have become indispensable in neuroscience research for quantifying neuronal density, mapping brain regions, and studying disease models, though researchers must account for its variable expression in subsets of neurons and under stress conditions to avoid misinterpretation.^[2]

History and Discovery

Initial Identification

NeuN was first identified in 1992 through a study employing monoclonal antibodies raised against purified nuclei from mouse brain cells. Researchers generated a panel of antibodies via repeated immunizations in mice, screening them for immunoreactivity specific to neuronal nuclei. One such antibody, designated A60, specifically labeled the nuclei of neurons across various regions of the adult mouse central nervous system, revealing a novel antigen termed NeuN for its neuronal nuclear specificity.^[1] Initial observations characterized NeuN as a soluble nuclear protein expressed in the majority of central nervous system (CNS) neurons in mammals, with immunostaining patterns demonstrating prominent nuclear localization and weaker perinuclear staining in mouse brain sections. This immunoreactivity was absent in non-neuronal cells such as glia and was notably missing in certain neuronal subtypes, including cerebellar Purkinje cells, mitral cells of the olfactory bulb, and retinal photoreceptors. The protein appeared post-mitotically, coinciding with neuronal differentiation and withdrawal from the cell cycle, as evidenced by its detection in maturing neurons during embryonic development and in vitro models like retinoic acid-stimulated P19 carcinoma cells.^[1] Early immunohistochemical applications of the A60 antibody extended NeuN's specificity to mature neurons in a range of vertebrates, including rats, chickens, humans, and salamanders, highlighting its conserved role as a marker of post-mitotic neuronal identity. In fixed tissue sections, the staining protocol involved immunofluorescence or immunoperoxidase methods, which consistently showed NeuN enrichment in neuronal nuclei, facilitating its use in mapping neuronal populations and studying differentiation timelines. Subsequent molecular studies identified NeuN as the RNA-binding protein Rbfox3, but its initial discovery established it as a reliable histological tool for neuronal identification.^[1]

Molecular Characterization

The molecular identity of NeuN, a widely used neuronal marker, was elucidated in 2009 through biochemical approaches that linked its immunoreactivity to the RNA-binding protein Rbfox3 (also known as Fox-3). Researchers performed immunoprecipitation of brain nuclear extracts using the monoclonal anti-NeuN antibody (clone A60), followed by mass spectrometry analysis of the precipitated proteins, which identified peptides uniquely matching the predicted sequence of Rbfox3. Complementary cloning of full-length Rbfox3 cDNA and expression in heterologous systems confirmed that the recombinant protein exhibited immunoreactivity indistinguishable from endogenous NeuN on Western blots, revealing characteristic doublet bands around 45-48 kDa and additional higher-molecular-weight species consistent with post-translational modifications.^[4] Further validation came from immunological correlations between anti-NeuN and anti-Rbfox3 antibodies. Immunoprecipitation with anti-NeuN specifically pulled down Rbfox3 isoforms, as detected by anti-Rbfox3 Western blotting, while reciprocal immunoprecipitation with anti-Rbfox3 recovered the NeuN-reactive proteins. These findings established that the epitopes recognized by both antibodies overlap on Rbfox3, ruling out alternative candidates and confirming Rbfox3 as the antigenic target of the anti-NeuN antibody.^[4] Genetic confirmation was provided by studies in Rbfox3 knockout mice, where deletion of the Rbfox3 gene resulted in complete loss of NeuN immunoreactivity in neuronal nuclei across brain regions, as assessed by immunohistochemistry. This absence of staining in homozygous knockouts, contrasted with robust labeling in wild-type littermates, directly demonstrated that Rbfox3 expression is required for NeuN detection.^[5] Recent proteomics investigations from 2023 to 2025 have reaffirmed this identification in high-resolution analyses of neuronal proteomes. For instance, single-nucleus proteomics of mouse brain tissue, using fluorescence-activated nuclei sorting with anti-NeuN antibodies to isolate neuronal nuclei, identifies Rbfox3 as a neuron-specific protein in the nuclear proteome, supporting its role as the core antigen without evidence of additional targets.^[6] These validations underscore the specificity of anti-NeuN antibodies for Rbfox3 in diverse experimental contexts.

Gene and Structure

Genomic Features

The RBFOX3 gene, encoding the neuronal nuclear protein NeuN, is located on the long arm of human chromosome 17 at cytogenetic band 17q25.3.^[7] The orthologous Rbfox3 gene in mice resides on chromosome 11.^[8] In humans, RBFOX3 spans approximately 522 kb of genomic DNA and consists of 15 exons, with extensive alternative splicing producing at least 39 distinct transcript isoforms that contribute to functional diversity.^[9] These isoforms arise primarily from cassette exons and mutually exclusive splicing events, enabling tissue-specific regulation.^[10] RBFOX3 demonstrates high sequence conservation across vertebrate species, reflecting its essential role in neural development; homologs in non-mammals, such as the duplicated genes rbfox3a and rbfox3b in zebrafish (Danio rerio), exhibit over 70% identity in key RNA-binding domains and display analogous neuron-enriched expression.^[11] This conservation underscores the evolutionary stability of Rbfox family-mediated splicing mechanisms in the vertebrate nervous system.^[12] The promoter and upstream regulatory elements of RBFOX3 drive its restricted expression in postmitotic neurons during development, with RE1-silencing transcription factor (REST, also known as NRSF) repressing RBFOX3 in non-neuronal cells to ensure neuron-specific expression.^[13]

Protein Composition

NeuN, encoded by the RBFOX3 gene, is a predominantly nuclear protein with an observed molecular weight of 45–48 kDa on SDS-PAGE, though the predicted mass of the canonical isoform is approximately 40 kDa, attributable to post-translational modifications.^[14] The main isoform comprises about 355 amino acids, featuring a modular structure that includes an N-terminal proline-rich region, a central RNA recognition motif (RRM) spanning roughly 80 amino acids for specific RNA binding, and a C-terminal alanine-rich domain with sequences conserved across the RBFOX family, particularly homologous to Fox-1 in the RRM and adjacent areas.^[14] The RRM, located near the center of the protein (approximately residues 120–200 in the canonical sequence), exhibits 95–100% identity to the corresponding motif in Fox-1 and enables sequence-specific interactions with UGCAUG elements in pre-mRNA targets.^[14] Additionally, the C-terminal region harbors a hydrophobic proline-tyrosine nuclear localization signal (hPY-NLS), which directs the protein to the nucleus and is encoded by exon 15 in certain isoforms.^[10] This NLS contributes to the protein's primary nuclear enrichment in postmitotic neurons. Alternative splicing generates multiple RBFOX3 isoforms, typically detected as bands ranging from 45 kDa to over 75 kDa on Western blots, with variations arising from inclusion or exclusion of exons such as 15 and 15A that alter the C-terminal extension and NLS presence, thereby influencing subcellular localization between nuclear and cytoplasmic compartments.^[10]^[15] Post-translational phosphorylation occurs at several serine, threonine, and tyrosine residues (at least six sites in the homologous mouse protein), potentially modulating protein stability and localization dynamics, though specific neuronal impacts remain under investigation.^[16]

Expression and Localization

Cellular Distribution

NeuN exhibits predominant nuclear localization within post-mitotic neurons, serving as a reliable marker for neuronal identity through immunohistochemical detection. In mature neurons, the protein is primarily confined to the nucleus, where it appears as distinct staining patterns, though some perinuclear cytoplasmic staining is observed, particularly in larger neurons such as motor neurons in the spinal cord.^[4]^[17] This subcellular distribution underscores NeuN's role as a nuclear antigen, with the cytoplasmic component potentially reflecting isoform variations or transport dynamics in differentiated cells.^[10] Expression of NeuN is highly specific to neurons and absent in glial cells, neural progenitors, and the vast majority of non-neuronal cells across vertebrate species. It is not detected in astrocytes, oligodendrocytes, or microglia, reinforcing its utility as a neuron-exclusive biomarker in histological analyses. Notable exceptions occur within certain neuronal subtypes, where NeuN immunoreactivity is lacking, including cerebellar Purkinje cells, mitral cells of the olfactory bulb, and photoreceptor cells. These absences highlight limitations in NeuN's coverage, as it fails to label specific neuronal populations despite its broad neuronal specificity.^[1]^[4]^[18] NeuN is expressed throughout the central and peripheral nervous systems of vertebrates, including mammals, birds, amphibians, and humans, but shows no detectable presence in non-neural tissues such as liver, kidney, or muscle. Immunohistochemical studies reveal NeuN in most mature neurons of the brain, spinal cord, and peripheral ganglia, with detection rates encompassing the majority of post-mitotic neuronal populations in typical neural circuits. This tissue-restricted pattern confirms NeuN's conservation as a pan-neuronal marker across evolutionary lineages, absent from proliferative or non-neuronal compartments.^[1]^[3]

Developmental Timing

NeuN expression first appears in post-mitotic neurons during early embryonic development, marking the onset of neuronal differentiation. In mice, detectable expression begins around embryonic day 10.5 (E10.5) in post-mitotic neurons of the midbrain, extending to the hindbrain and spinal cord by E12.5, coinciding with the withdrawal from the cell cycle and initial differentiation processes.^[19] This timing aligns with the absence of NeuN in proliferating neural stem cells, which remain unlabeled, underscoring its specificity to non-dividing neuronal populations.^[20] In rats, a similar pattern emerges, with immunohistochemical detection shortly after cells exit mitosis, typically around equivalent embryonic stages adjusted for gestational length.^[1] As neurons mature, NeuN expression undergoes upregulation, correlating with key developmental milestones such as synapse formation during the transition from embryonic to postnatal stages. In mice, levels increase progressively in differentiating neurons, reaching a stable peak in adulthood where it is maintained in terminally differentiated cells throughout the central nervous system.^[17] This progression reflects the protein's role as a marker of neuronal maturation, with expression intensifying as cells establish synaptic connections and functional circuits. However, in certain stress or pathological conditions, such as neurodegeneration or reactive states, NeuN can be downregulated without implying cell death, highlighting its dynamic nature in response to environmental or disease-related pressures.^[21] Species comparisons reveal conserved temporal dynamics, adapted to developmental timelines. In humans, NeuN emerges as early as 8–10 weeks of gestation in spinal motor neurons and dorsal root ganglion cells, with progressive labeling of cortical plate neurons by 19–22 weeks, primarily in deeper layers destined for 4–6, and widespread expression by 24 weeks.^[22] This pattern mirrors the rodent onset in post-mitotic stages but extends over a protracted fetal period, peaking in postnatal maturity akin to mice and rats, where it persists robustly into adulthood barring stress-induced alterations.^[17]

Biological Functions

Role in RNA Splicing

NeuN, also known as Rbfox3, functions as a key splicing factor in postmitotic neurons, where it binds to the intronic UGCAUG motif in pre-mRNA to promote the inclusion of alternative exons during RNA splicing. This RNA recognition motif (RRM) domain in Rbfox3 exhibits high affinity for the UGCAUG sequence, typically located in downstream introns relative to regulated exons, thereby facilitating position-dependent enhancement of exon inclusion. The nuclear isoform of Rbfox3 predominantly drives this splicing activity, while cytoplasmic variants may influence mRNA stability or translation indirectly; sequestration in the nucleus ensures targeted regulation of neuronal transcripts. Rbfox3 cooperates with other Rbfox family members (Rbfox1 and Rbfox2) through shared binding sites and multiprotein complexes, amplifying splicing efficiency across overlapping targets without requiring direct protein-protein interactions for core function. Among its targets, Rbfox3 regulates the alternative splicing of the MAPT gene encoding tau protein, binding UGCAUG in intron 10 to enhance exon 10 inclusion and increase the proportion of 4-repeat tau isoforms, which are essential for microtubule stability in axons.^[23] Similarly, Rbfox3 promotes inclusion of specific exons in the VAMP1 gene, modulating synaptic vesicle release and thereby influencing neuronal excitability and seizure susceptibility.^[24] These splicing events contribute to fine-tuning neuronal signaling, as disruptions alter synaptic function and circuit balance without affecting gross neuronal viability. In Rbfox3 knockout mice, widespread mis-splicing of neuronal transcripts leads to altered hippocampal excitability, increased seizure propensity, and behavioral deficits such as reduced anxiety and impaired spatial memory, yet these animals exhibit no overt neurodegeneration or cell loss. Restoration of key targets like VAMP1 in GABAergic neurons partially rescues seizure phenotypes, underscoring the splicing-dependent role of Rbfox3 in maintaining circuit homeostasis.

Involvement in Neuronal Maturation

NeuN, also known as RBFOX3, contributes to the establishment of post-mitotic neuronal identity by regulating the alternative splicing of key differentiation genes, such as Numb, which promotes the progression of neuronal maturation in postmitotic cells.^[25] In vertebrate development, RBFOX3-dependent inclusion of Numb exon 12 generates a neuron-specific isoform that enhances cell polarity and suppresses Notch signaling, thereby facilitating the expression of differentiation markers like LIM homeodomain transcription factors (e.g., Lim1/2, Isl1) without altering progenitor proliferation.^[25] This splicing-mediated mechanism ensures the transition to a mature neuronal state, as evidenced by RNA interference knockdown experiments in chick spinal cord neurons and P19 embryonic carcinoma cells, where RBFOX3 depletion reduced these markers by over 50% and delayed overall differentiation, an effect rescued by ectopic expression of the mature Numb isoform.^[25] RBFOX3 interacts indirectly with transcription factors through its splicing regulation of transcripts involved in neuronal signaling pathways, influencing downstream gene expression critical for maturation.^[5] For instance, in hippocampal circuits, RBFOX3 modulates presynaptic release probability and synaptic plasticity by splicing targets that affect transcription factor-responsive elements, as shown in knockout mice exhibiting altered expression of plasticity-related genes like Arc and Egr4.^[5] Evidence from triple knockout studies of RBFOX family members, including RBFOX3, demonstrates delayed dendrite formation and reduced dendritic complexity in cultured cortical neurons, with splicing defects in cytoskeletal genes (e.g., Add1, Tpm1) leading to impaired structural maturation and up to 30% fewer primary dendrites compared to controls.^[26] In response to neuronal stress, RBFOX3 expression is downregulated in injury models, impacting neuronal survival and resilience. Following traumatic brain injury (TBI) or axotomy, RBFOX3/NeuN immunoreactivity is significantly reduced in affected neurons, such as facial motoneurons where it is nearly abolished by day 3 post-injury, correlating with disrupted splicing programs that compromise synaptic integrity and increase vulnerability to degeneration.^[27] This downregulation is observed in chronic phases after TBI and correlates with neuroinflammation and neuronal damage in hippocampal regions.^[28] Homozygous knockout models demonstrate persistent deficits in adult hippocampal neurogenesis and synaptogenesis, with RBFOX3 absence resulting in a 40-50% reduction in proliferating (Ki67+) and immature (DCX+) neurons, alongside increased excitatory synapse density but impaired functionality, manifesting as deficits in spatial learning and novel object recognition tasks.^[29] Similarly, excitotoxic injury models reveal decreased RBFOX3 levels linked to altered tau splicing and cognitive impairments, suggesting that RBFOX3 decline contributes to hippocampal circuit imbalances and memory loss in neurodegenerative contexts.^[30]

Applications

Neuronal Biomarker in Research

NeuN serves as a standard biomarker in immunohistochemistry (IHC) protocols to label mature neurons in fixed brain tissue slices and primary neuronal cultures, enabling precise visualization of neuronal nuclei and morphology.^[17] In flow cytometry, anti-NeuN antibodies facilitate the isolation and quantification of post-mitotic neuronal populations from dissociated brain tissue or cell cultures, allowing for high-throughput analysis of neuronal heterogeneity.^[31] These techniques leverage NeuN's nuclear localization to distinguish neurons from non-neuronal cells with high fidelity. In basic neuroscience research, NeuN is widely applied to quantify neuronal loss in animal models of neurological disorders, such as stroke and epilepsy. For instance, IHC staining with NeuN reveals region-specific reductions in neuronal density following ischemic insults in rodent stroke models, providing a metric for assessing infarct size and recovery.^[32] Similarly, in epilepsy models induced by status epilepticus, NeuN-positive cell counts in hippocampal and cortical regions track selective neuronal vulnerability and degeneration over time.^[33] Beyond injury models, NeuN IHC evaluates the efficiency of neuronal differentiation from stem cells, measuring the proportion of mature neurons generated during protocols for neural progenitor expansion.^[34] A key advantage of NeuN as a biomarker is its high specificity for post-mitotic neurons, which emerges shortly after cell cycle exit and persists throughout adulthood, making it ideal for studies of neuronal maturation and stability.^[17] Established protocols support multiplexing NeuN with cytoplasmic markers like microtubule-associated protein 2 (MAP2) to simultaneously assess nuclear and dendritic features in the same tissue section, enhancing resolution in complex analyses such as neuronal arbor reconstruction.^[35] Recent studies from 2023 to 2025 have incorporated NeuN in assays using induced pluripotent stem cell (iPSC)-derived neurons for drug screening, particularly in high-content imaging platforms to evaluate compound effects on neuronal viability and function. For example, a 2023 high-throughput screen miniaturized iPSC neuron cultures stained with NeuN to identify neurotoxic liabilities, achieving single-cell resolution for toxicity profiling.^[36] In 2025, tri-culture models of iPSC-derived neurons co-stained for NeuN and other markers supported electrophysiological drug testing, demonstrating NeuN's role in confirming neuronal maturity during personalized medicine screens.^[37]

Diagnostic and Clinical Uses

NeuN immunohistochemistry serves as a cornerstone in diagnostic neuropathology for identifying neuronal elements in formalin-fixed paraffin-embedded (FFPE) tissues, particularly in cases involving brain tumors and traumatic injuries. The monoclonal antibody clone A60 recognizes NeuN with high sensitivity and specificity, producing robust nuclear and perinuclear staining in postmitotic neurons while sparing non-neuronal structures. This application enhances the visualization of neuronal architecture in surgical and autopsy specimens, facilitating the confirmation of neuronal identity amid heterogeneous pathological changes.^[38] In brain tumors, NeuN staining is instrumental for delineating neuronal components, as demonstrated in gangliogliomas, dysembryoplastic neuroepithelial tumors, and central neurocytomas, where it highlights mature neuronal differentiation. Expression is widespread across most primary brain tumor subtypes, including diffuse astrocytomas, ependymomas, oligodendrogliomas, glioblastomas, and medulloblastomas, but absent in pilocytic astrocytomas, aiding in differential diagnosis. For instance, in clear cell tumors, positive NeuN immunoreactivity carries a 76.9% predictive value for central neurocytoma, while negativity supports oligodendroglioma. In injury contexts, such as traumatic brain lesions, NeuN confirms preserved or lost neuronal populations in FFPE sections, guiding prognostic assessments.^[38]^[39] NeuN is widely employed in biopsies from neurodegenerative diseases to quantify neuronal density and evaluate loss patterns. In Alzheimer's disease, stereological analysis reveals approximately 35% reduction in entorhinal cortex neurons during preclinical or very mild stages, correlating with cognitive decline and exceeding neurofibrillary tangle counts.^[40] This marker's nuclear staining precisely delineates affected pyramidal neurons, supporting histopathological confirmation of atrophy in affected regions like the hippocampus and temporal cortex. In Parkinson's disease, NeuN immunohistochemistry demonstrates rostrocaudal declines in neuronal density within the anterior olfactory nucleus, with significant reductions in bulbar portions compared to non-PD controls, highlighting early olfactory pathway involvement in α-synucleinopathy. These quantifications inform disease staging and progression monitoring in clinical biopsies.^[41] Clinical protocols for NeuN leverage the validated A60 clone, which has been extensively tested on human FFPE tissues for diagnostic reliability, yielding consistent results across central and peripheral nervous system samples. Integration with advanced imaging, such as MRI-guided biopsies, allows NeuN-stained sections to correlate histopathological findings with radiological features, enhancing accuracy in intraoperative consultations and postoperative evaluations. Standardized protocols recommend antigen retrieval and visualization via immunoperoxidase methods, ensuring compatibility with multiplex panels for comprehensive tumor or degeneration profiling.^[38] In specific diagnostic scenarios, NeuN plays a key role in identifying neuronal differentiation in glioneuronal and neuronal tumors under the 2021 WHO classification of CNS tumors (5th edition), for example confirming mature neuronal components in low-grade lesions like gangliogliomas to distinguish them from higher-grade diffuse gliomas and guide therapeutic decisions. This application refines integrated diagnoses, where NeuN complements molecular markers like BRAF fusions to stratify prognosis in pediatric and adult cases. However, NeuN expression can be absent or reduced in certain neuronal subtypes (e.g., Purkinje cells) or pathological conditions, necessitating complementary markers for accurate assessment.^[38]^[39]

Nomenclature and Family

Origin of the Fox Designation

The designation "Fox" originates from the gene fox-1 in the nematode Caenorhabditis elegans, identified in 1994 as a key regulator in sex determination. This gene, an acronym for "Feminizing locus on X," encodes an RNA-binding protein that promotes hermaphrodite development in XX individuals by repressing the master sex-determination gene xol-1 through alternative splicing. The discovery highlighted fox-1's role in dosage compensation and tissue-specific RNA processing on the X chromosome.^[42] In vertebrates, the Fox family expanded into the Rbfox (RNA-binding Fox-1 homolog) genes, recognized as orthologs of C. elegans fox-1 starting in the early 2000s.^[43] These homologs, including Rbfox1, Rbfox2, and Rbfox3, similarly bind UGCAUG elements in pre-mRNA to regulate tissue-specific alternative splicing, extending the ancestral function beyond sex determination to broader developmental processes.^[44] The Rbfox nomenclature reflects their evolutionary conservation and shared RNA-binding domain.^[45] For NeuN specifically, the protein—initially identified in 1992 as a neuronal nuclear antigen— was renamed Rbfox3 in 2009 upon sequencing, revealing its identity as a member of the Rbfox family. This reclassification linked NeuN to the conserved splicing regulatory mechanism, though the "NeuN" term persists in immunohistochemical contexts due to the specificity of the original monoclonal antibody. Evolutionarily, the splicing function of Fox/Rbfox proteins has been conserved from invertebrates like C. elegans to mammals, underscoring their fundamental role in metazoan RNA regulation across diverse tissues.^[45]

Relation to Rbfox Proteins

NeuN, also known as Rbfox3, belongs to the Rbfox family of RNA-binding proteins, which includes three mammalian paralogs: Rbfox1 (also called A2BP1), Rbfox2 (RBM9), and Rbfox3. These proteins share a conserved RNA recognition motif (RRM) domain that enables them to bind the intronic (U)GCAUG sequence motif, thereby regulating alternative splicing of pre-mRNA targets primarily involved in neuronal development and function.^[12]^[46] While the Rbfox family members exhibit functional redundancy in splicing regulation, their expression patterns differ significantly. Rbfox1 is predominantly expressed in neurons, heart, and skeletal muscle; Rbfox2 shows broader, ubiquitous expression including in embryonic tissues, stem cells, and various progenitor cells; and Rbfox3 is restricted to post-mitotic neurons. Despite these overlaps, the splicing targets of the Rbfox proteins are partially redundant but largely non-overlapping, allowing for tissue-specific fine-tuning of gene expression. For instance, Rbfox3 primarily influences neuronal maturation-related transcripts, whereas Rbfox1 and Rbfox2 regulate a wider array of cytoskeletal and synaptic genes across tissues.^[47]^[46]30023-0) A key distinction lies in their subcellular localization and roles. Rbfox3 is predominantly localized to the nucleus in neurons, where it facilitates splicing events, though cytoplasmic isoforms exist that may influence mRNA stability. In contrast, Rbfox1 exhibits significant cytoplasmic localization, contributing to post-transcriptional regulation of mRNA levels and stability, while Rbfox2 is primarily nuclear but supports broader splicing programs due to its widespread expression. Genetically, the Rbfox genes are encoded by distinct loci on separate chromosomes—Rbfox1 on 16p13.3, Rbfox2 on 22q12.3, and Rbfox3 on 17q25.3—reflecting their evolutionary divergence. This genetic separation, combined with partial functional compensation, results in milder phenotypes in single Rbfox3 knockout mice, such as increased seizure susceptibility and altered anxiety behaviors, compared to the severe neurodevelopmental defects observed in triple knockouts.^[15]^[44]^[48]^[49]^[50]

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Dose-dependent action of the RNA binding protein FOX-1 to relay X ...
FOX-1, an RNA recognition motif protein, triggers hermaphrodite development in XX embryos by causing non-productive alternative pre-mRNA splicing of xol-1, the ...Missing: origin designation
[44]
Homologues of the Caenorhabditis elegans Fox-1 protein ... - PubMed
A vertebrate homologue of the Fox-1 protein from C. elegans was recently shown to bind to the element GCAUG and to act as an inhibitor of alternative splicing ...
[45]
Article Cytoplasmic Rbfox1 Regulates the Expression of Synaptic ...
Jan 6, 2016 · Human genetic studies have focused attention on RBFOX1, a vertebrate homolog of the Caenorhabditis elegans Feminizing gene 1 on X (also ...
[46]
Fox-1 family of RNA-binding proteins | Cellular and Molecular Life ...
Aug 18, 2009 · The Fox-1 family of RNA-binding proteins are evolutionarily conserved regulators of tissue-specific alternative splicing in metazoans.
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Rbfox proteins regulate splicing as part of a large multiprotein ...
The Rbfox family of splicing regulators includes three mammalian paralogs Rbfox1 (A2BP1), Rbfox2 (RBM9), and Rbfox3 (NeuN) that are all expressed in neurons and ...
[48]
Novel Rbfox2 isoforms associated with alternative exon usage in rat ...
Aug 30, 2017 · RBFOX3/NeuN, a neuronal maturity marker, is strangely depleted in suprachiasmatic nucleus (SCN) neurons, and may be compensated by a change in Rbfox2 ...<|control11|><|separator|>
[49]
Identification of a classic nuclear localization signal at the N ...
Dec 1, 2016 · In contrast to Rbfox1 and Rbfox3 which localize to both the nucleus and the cytoplasm [13,14,16], Rbfox2 is thought to be exclusively nuclear, ...
[50]
RBFOX3/NeuN is Required for Hippocampal Circuit Balance and ...
Dec 1, 2015 · Rbfox3 knockout mice displayed increased seizure susceptibility and decreased anxiety-related behaviors. Focusing on hippocampal phenotypes, we ...
[51]
Rbfox Splicing Factors Promote Neuronal Maturation and Axon ...
Feb 21, 2018 · Our data show that the Rbfox-regulated splicing program plays a crucial role in structural and functional maturation of postmitotic neurons.