Axon Guidance Research Articles

Different subsets of V2a propriospinal neurons respond differently to spinal cord injury

While propriospinal neurons play a crucial role in recovering function post-spinal cord injury, it remains unclear whether these neurons exhibit largely similar responses to injury or if their diversity requires distinct alterations in gene expression. Here, we focused on one population of spinal neurons, the V2a class, previously shown to be important for recovery of locomotor and respiratory function after spinal cord injury. Using single nuclei gene expression analyses, we delineate substantial molecular and cellular heterogeneity of V2a propriospinal neurons subtypes in adult mice and examine how individual subtypes are altered by injury. Remarkably, a subset of V2a neurons expressing Rbms3+/Nav3+ and enriched for synaptic transmission and axon guidance molecules were found to be nearly absent following injury. The remaining V2a populations exhibited distinctive transcriptional alterations, indicating a potential rewiring of cellular interactions within the spinal cord microenvironment. Thus, our study reveals the diverse responses of propriospinal neurons to injury. These analyses provide a foundation for understanding changes in propriospinal neurons that may lead to adaptive (or maladaptive) changes in circuit function following injury. NIH R01 NS112255 (PI:Crone) Spinal Circuitry for Ventilatory Control and Compensation Craig H. Neilsen Foundation- Spinal Cord Injury Research on the Translational Spectrum (PI: Crone) Targeting propriospinal neurons to improve breathing following injury. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

CNTN4 modulates neural elongation through interplay with APP.

The neuronal cell adhesion molecule contactin-4 (CNTN4) is genetically associated with autism spectrum disorder (ASD) and other psychiatric disorders. Cntn4-deficient mouse models have previously shown that CNTN4 plays important roles in axon guidance and synaptic plasticity in the hippocampus. However, the pathogenesis and functional role of CNTN4 in the cortex has not yet been investigated. Our study found a reduction in cortical thickness in the motor cortex of Cntn4 -/- mice, but cortical cell migration and differentiation were unaffected. Significant morphological changes were observed in neurons in the M1 region of the motor cortex, indicating that CNTN4 is also involved in the morphology and spine density of neurons in the motor cortex. Furthermore, mass spectrometry analysis identified an interaction partner for CNTN4, confirming an interaction between CNTN4 and amyloid-precursor protein (APP). Knockout human cells for CNTN4 and/or APP revealed a relationship between CNTN4 and APP. This study demonstrates that CNTN4 contributes to cortical development and that binding and interplay with APP controls neural elongation. This is an important finding for understanding the physiological function of APP, a key protein for Alzheimer's disease. The binding between CNTN4 and APP, which is involved in neurodevelopment, is essential for healthy nerve outgrowth.

Identifying candidate genes associated with hippocampal dysfunction in a hemiparkinsonian rat model by transcriptomic profiling

ABSTRACT Parkinson’s disease (PD) often results in hippocampal dysfunction, which leads to cognitive and emotional challenges and synaptic irregularities. This study attempted to assess behavioral anomalies and identify differentially expressed genes (DEGs) within the hippocampus of a hemiparkinsonian rat model to potentially uncover novel genetic candidates linked to hippocampal dysfunction. Striatal 6-hydroxydopamine (6-OHDA) infusions were performed unilaterally in the brains of adult SD rats, while dopaminergic impairments were verified in rats with 6-OHDA-lesioned striata. RNA sequencing and gene expression analysis unveiled 1018 DEGs in the ipsilateral rat hippocampus following 6-OHDA infusion: 631 genes exhibited upregulation, while 387 genes were downregulated (with FDR-adjusted p-value < 0.05 and absolute fold-change > 1.5). Gene ontology analysis of DEGs indicated that alterations in the hippocampi of 6-OHDA-lesioned rats were primarily associated with synaptic signaling, axon development, behavior, postsynaptic membrane, synaptic membrane, neurotransmitter receptor activity, and peptide receptor activity. The Kyoto Encyclopedia of Genes and Genomes analysis of DEGs demonstrated significant enrichment of the neuroactive ligand–receptor interaction, calcium signaling pathway, cAMP signaling pathway, axon guidance, and notch signaling pathway in rat hippocampi that had been subjected to striatal 6-OHDA infusion. STRING analysis confirmed a notable upregulation of eight hub genes (Notch3, Gng4, Itga3, Grin2d, Hgf, Fgf11, Htr3a, and Col6a2), along with a significant downregulation of two hub genes (Itga11 and Plp1), as validated by reverse transcription-quantitative polymerase chain reaction. This study provides a comprehensive transcriptomic profile of the hippocampi in a hemiparkinsonian rat model, thereby offering insights into the signaling pathways underlying hippocampal dysfunction.

Distinct transcriptomic profile of satellite cells contributes to preservation of neuromuscular junctions in extraocular muscles of ALS mice.

Amyotrophic lateral sclerosis (ALS) is a fatal neuromuscular disorder characterized by progressive weakness of almost all skeletal muscles, whereas extraocular muscles (EOMs) are comparatively spared. While hindlimb and diaphragm muscles of end-stage SOD1G93A (G93A) mice (a familial ALS mouse model) exhibit severe denervation and depletion of Pax7+satellite cells (SCs), we found that the pool of SCs and the integrity of neuromuscular junctions (NMJs) are maintained in EOMs. In cell sorting profiles, SCs derived from hindlimb and diaphragm muscles of G93A mice exhibit denervation-related activation, whereas SCs from EOMs of G93A mice display spontaneous (non-denervation-related) activation, similar to SCs from wild-type mice. Specifically, cultured EOM SCs contain more abundant transcripts of axon guidance molecules, including Cxcl12, along with more sustainable renewability than the diaphragm and hindlimb counterparts under differentiation pressure. In neuromuscular co-culture assays, AAV-delivery of Cxcl12 to G93A-hindlimb SC-derived myotubes enhances motor neuron axon extension and innervation, recapitulating the innervation capacity of EOM SC-derived myotubes. G93A mice fed with sodium butyrate (NaBu) supplementation exhibited less NMJ loss in hindlimb and diaphragm muscles. Additionally, SCs derived from G93A hindlimb and diaphragm muscles displayed elevated expression of Cxcl12 and improved renewability following NaBu treatment in vitro. Thus, the NaBu-induced transcriptomic changes resembling the patterns of EOM SCs may contribute to the beneficial effects observed in G93A mice. More broadly, the distinct transcriptomic profile of EOM SCs may offer novel therapeutic targets to slow progressive neuromuscular functional decay in ALS and provide possible 'response biomarkers' in pre-clinical and clinical studies.

Distinct transcriptomic profile of satellite cells contributes to preservation of neuromuscular junctions in extraocular muscles of ALS mice

Amyotrophic lateral sclerosis (ALS) is a fatal neuromuscular disorder characterized by progressive weakness of almost all skeletal muscles, whereas extraocular muscles (EOMs) are comparatively spared. While hindlimb and diaphragm muscles of end-stage SOD1G93A (G93A) mice (a familial ALS mouse model) exhibit severe denervation and depletion of Pax7+satellite cells (SCs), we found that the pool of SCs and the integrity of neuromuscular junctions (NMJs) are maintained in EOMs. In cell sorting profiles, SCs derived from hindlimb and diaphragm muscles of G93A mice exhibit denervation-related activation, whereas SCs from EOMs of G93A mice display spontaneous (non-denervation-related) activation, similar to SCs from wild-type mice. Specifically, cultured EOM SCs contain more abundant transcripts of axon guidance molecules, including Cxcl12, along with more sustainable renewability than the diaphragm and hindlimb counterparts under differentiation pressure. In neuromuscular co-culture assays, AAV-delivery of Cxcl12 to G93A-hindlimb SC-derived myotubes enhances motor neuron axon extension and innervation, recapitulating the innervation capacity of EOM SC-derived myotubes. G93A mice fed with sodium butyrate (NaBu) supplementation exhibited less NMJ loss in hindlimb and diaphragm muscles. Additionally, SCs derived from G93A hindlimb and diaphragm muscles displayed elevated expression of Cxcl12 and improved renewability following NaBu treatment in vitro. Thus, the NaBu-induced transcriptomic changes resembling the patterns of EOM SCs may contribute to the beneficial effects observed in G93A mice. More broadly, the distinct transcriptomic profile of EOM SCs may offer novel therapeutic targets to slow progressive neuromuscular functional decay in ALS and provide possible ‘response biomarkers’ in pre-clinical and clinical studies.

SEMA3B inhibits TGFβ-induced extracellular matrix protein production and its reduced levels are associated with a decline in lung function in IPF.

Idiopathic pulmonary fibrosis (IPF) is marked by the activation of fibroblasts, leading to excessive production and deposition of extracellular matrix (ECM) within the lung parenchyma. Despite the pivotal role of ECM overexpression in IPF, potential negative regulators of ECM production in fibroblasts have yet to be identified. Semaphorin class 3B (SEMA3B), a secreted protein highly expressed in lung tissues, has established roles in axonal guidance and tumor suppression. However, the role of SEMA3B in ECM production by fibroblasts in the pathogenesis of IPF remains unexplored. Here, we show the downregulation of SEMA3B and its cognate binding receptor, neuropilin 1 (NRP1), in IPF lungs compared with healthy controls. Notably, the reduced expression of SEMA3B and NRP1 is associated with a decline in lung function in IPF. The downregulation of SEMA3B and NRP1 transcripts was validated in the lung tissues of patients with IPF, and two alternative mouse models of pulmonary fibrosis. In addition, we show that transforming growth factor-β (TGFβ) functions as a negative regulator of SEMA3B and NRP1 expression in lung fibroblasts. Furthermore, we demonstrate the antifibrotic effects of SEMA3B against TGFβ-induced ECM production in IPF lung fibroblasts. Overall, our findings uncovered a novel role of SEMA3B in the pathogenesis of pulmonary fibrosis and provided novel insights into modulating the SEMA3B-NRP1 axis to attenuate pulmonary fibrosis.NEW & NOTEWORTHY The excessive production and secretion of collagens and other extracellular matrix proteins by fibroblasts lead to the scarring of the lung in severe fibrotic lung diseases. This study unveils an antifibrotic role for semaphorin class 3B (SEMA3B) in the pathogenesis of idiopathic pulmonary fibrosis. SEMA3B functions as an inhibitor of transforming growth factor-β-driven fibroblast activation and reduced levels of SEMA3B and its receptor, neuropilin 1, are associated with decreased lung function in idiopathic pulmonary fibrosis.

Genome-wide association analyses identify 95 risk loci and provide insights into the neurobiology of post-traumatic stress disorder.

Post-traumatic stress disorder (PTSD) genetics are characterized by lower discoverability than most other psychiatric disorders. The contribution to biological understanding from previous genetic studies has thus been limited. We performed a multi-ancestry meta-analysis of genome-wide association studies across 1,222,882 individuals of European ancestry (137,136 cases) and 58,051 admixed individuals with African and Native American ancestry (13,624 cases). We identified 95 genome-wide significant loci (80 new). Convergent multi-omic approaches identified 43 potential causal genes, broadly classified as neurotransmitter and ion channel synaptic modulators (for example, GRIA1, GRM8 and CACNA1E), developmental, axon guidance and transcription factors (for example, FOXP2, EFNA5 and DCC), synaptic structure and function genes (for example, PCLO, NCAM1 and PDE4B) and endocrine or immune regulators (for example, ESR1, TRAF3 and TANK). Additional top genes influence stress, immune, fear and threat-related processes, previously hypothesized to underlie PTSD neurobiology. These findings strengthen our understanding of neurobiological systems relevant to PTSD pathophysiology, while also opening new areas for investigation.

In vitro human cell culture models in a bench-to-bedside approach to epilepsy.

Epilepsy is the most common chronic neurological disease, affecting nearly 1%-2% of the world's population. Current pharmacological treatment and regimen adjustments are aimed at controlling seizures; however, they are ineffective in one-third of the patients. Although neuronal hyperexcitability was previously thought to be mainly due to ion channel alterations, current research has revealed other contributing molecular pathways, including processes involved in cellular signaling, energy metabolism, protein synthesis, axon guidance, inflammation, and others. Some forms of drug-resistant epilepsy are caused by genetic defects that constitute potential targets for precision therapy. Although such approaches are increasingly important, they are still in the early stages of development. This review aims to provide a summary of practical aspects of the employment of invitro human cell culture models in epilepsy diagnosis, treatment, and research. First, we briefly summarize the genetic testing that may result in the detection of candidate pathogenic variants in genes involved in epilepsy pathogenesis. Consequently, we review existing invitro cell models, including induced pluripotent stem cells and differentiated neuronal cells, providing their specific properties, validity, and employment in research pipelines. We cover two methodological approaches. The first approach involves the utilization of somatic cells directly obtained from individual patients, while the second approach entails the utilization of characterized cell lines. The models are evaluated in terms of their research and clinical benefits, relevance to the invivo conditions, legal and ethical aspects, time and cost demands, and available published data. Despite the methodological, temporal, and financial demands of the reviewed models they possess high potential to be used as robust systems in routine testing of pathogenicity of detected variants in the near future and provide a solid experimental background for personalized therapy of genetic epilepsies. PLAIN LANGUAGE SUMMARY: Epilepsy affects millions worldwide, but current treatments fail for many patients. Beyond traditional ion channel alterations, various genetic factors contribute to the disorder's complexity. This review explores how invitro human cell models, either from patients or from cell lines, can aid in understanding epilepsy's genetic roots and developing personalized therapies. While these models require further investigation, they offer hope for improved diagnosis and treatment of genetic forms of epilepsy.

Role of Cxcl12a on habenular axon projection in Danio rerio

The habenula is a forebrain region that is responsible for many emotional responses. The habenular axons project posteriorly to the interpeduncular nucleus (IPN), a region in midbrain. Correct projection of these habenular axons depend on chemokine signaling. Components of this signaling pathway include chemokine ligand, Cxcl12a, and chemokine receptor, Cxcr4b. Cxcr4b is made in the habenula, while Cxcl12a is made along the path of the habenular axons. Loss of either Cxcl12a or Cxcr4b results in abnormal anterior growth of habenular axons. However, the exact function of Cxcl12a as a directional cue at the habenula is not known. To explore this, overexpression of cxcl12a is being performed. Overexpression of cxcl12a is induced by heat shock in larvae carrying a transgenic line that produces GFP in the habenula and its axons. Heat shock is performed at 33 hours post fertilization (hpf), several hours prior to initial axon outgrowth. However, there have been challenges confirming overexpression of cxcl12a at this time point. Once overexpression is confirmed we will examine the habenular axons at 5 days post fertilization (dpf). We hypothesize that the overexpression of cxcl12a in larval zebrafish will cause a disruption in the growth of the axons of the habenula, implying that Cxcl12a is an attractant in habenular axon guidance. If no habenular axon disruption is noted, this implies that 33 hpf is not the correct window for chemokine signaling at the habenula or that excess Cxcl12a is insufficient in disrupting habenular axon pathfinding.

The role of Cxcl12b in habenular axon pathfinding in zebrafish

The habenula is a complex region of the forebrain with multiple populations of neurons making different neurotransmitters such as dopamine, serotonin, GABA, norepinephrine, and acetylcholine. The habenula is involved in behavioral response to pain, stress, sleep, anxiety and reward.​ The habenula provides the fundamental mechanism in both survival and decision making. Axons of the habenula project to the interpeduncular nucleus (IPN) of the midbrain. Chemokine signaling has been shown to help axons reach this target. Chemokine receptor Cxcr4b is made in the habenula, while ligand Cxcl12b is produced anterior and posterior to the developing habenula. Based on this expression pattern, we hypothesize that Cxcl12b is working as a repellant and therefore, without Cxcl12b the habenular axons will project incorrectly in the anterior/posterior direction. We have identified cxcl12b mutants carrying a transgenic line that labels the habenula and its axons with GFP. However, we have not identified any males carrying the cxcl12b mutation and the transgenic line. Due to this, we will be using the gene editing technology CRISPR to cause mutation in the cxcl12b gene injust one generation. This mutation will permit us to explore the role of Cxcl12b on habenular axon pathfinding.

The role of axon guidance molecules in the pathogenesis of epilepsy.

Current treatments for epilepsy can only manage the symptoms of the condition but cannot alter the initial onset or halt the progression of the disease. Consequently, it is crucial to identify drugs that can target novel cellular and molecular mechanisms and mechanisms of action. Increasing evidence suggests that axon guidance molecules play a role in the structural and functional modifications of neural networks and that the dysregulation of these molecules is associated with epilepsy susceptibility. In this review, we discuss the essential role of axon guidance molecules in neuronal activity in patients with epilepsy as well as the impact of these molecules on synaptic plasticity and brain tissue remodeling. Furthermore, we examine the relationship between axon guidance molecules and neuroinflammation, as well as the structural changes in specific brain regions that contribute to the development of epilepsy. Ample evidence indicates that axon guidance molecules, including semaphorins and ephrins, play a fundamental role in guiding axon growth and the establishment of synaptic connections. Deviations in their expression or function can disrupt neuronal connections, ultimately leading to epileptic seizures. The remodeling of neural networks is a significant characteristic of epilepsy, with axon guidance molecules playing a role in the dynamic reorganization of neural circuits. This, in turn, affects synapse formation and elimination. Dysregulation of these molecules can upset the delicate balance between excitation and inhibition within a neural network, thereby increasing the risk of overexcitation and the development of epilepsy. Inflammatory signals can regulate the expression and function of axon guidance molecules, thus influencing axonal growth, axon orientation, and synaptic plasticity. The dysregulation of neuroinflammation can intensify neuronal dysfunction and contribute to the occurrence of epilepsy. This review delves into the mechanisms associated with the pathogenicity of axon guidance molecules in epilepsy, offering a valuable reference for the exploration of therapeutic targets and presenting a fresh perspective on treatment strategies for this condition.

Mucopolysaccharidosis type II zebrafish model exhibits early impaired proteasomal-mediated degradation of the axon guidance receptor Dcc.

Most of the patients affected by neuronopathic forms of Mucopolysaccharidosis type II (MPS II), a rare lysosomal storage disorder caused by defects in iduronate-2-sulfatase (IDS) activity, exhibit early neurological defects associated with white matter lesions and progressive behavioural abnormalities. While neuronal degeneration has been largely described in experimental models and human patients, more subtle neuronal pathogenic defects remain still underexplored. In this work, we discovered that the axon guidance receptor Deleted in Colorectal Cancer (Dcc) is significantly dysregulated in the brain of ids mutant zebrafish since embryonic stages. In addition, thanks to the establishment of neuronal-enriched primary cell cultures, we identified defective proteasomal degradation as one of the main pathways underlying Dcc upregulation in ids mutant conditions. Furthermore, ids mutant fish-derived primary neurons displayed higher levels of polyubiquitinated proteins and P62, suggesting a wider defect in protein degradation. Finally, we show that ids mutant larvae display an atypical response to anxiety-inducing stimuli, hence mimicking one of the characteristic features of MPS II patients. Our study provides an additional relevant frame to MPS II pathogenesis, supporting the concept that multiple developmental defects concur with early childhood behavioural abnormalities.

Discovery of long non-coding RNAs in naïve CD4+ T cells in response to initiating antiretroviral therapy at acute or chronic phase of HIV-1 infection

Long non-coding RNAs (lncRNAs) have gained prominence due to their involvement in various cellular processes, but their specific roles remain elusive. Dysregulation of lncRNAs has been implicated in the pathogenesis of several diseases. In this study, we aimed to shed light on the role of lncRNAs in individuals infected with human immunodeficiency virus type 1 (HIV-1) by examining their changes in the expression patterns related to the initiation of antiretroviral therapy (ART) during acute or chronic phases of infection, compared to healthy controls. We found 316 differentially expressed (DE) lncRNAs in patients receiving long-term ART, shedding light on their potential roles. We also observed interactions between these DE lncRNAs and specific microRNAs (miRNAs). Some of these miRNAs, such as hsa-miR-574-5p, hsa-miR-765, hsa-miR-6165, hsa-miR-1207-5p, and hsa-miR-378i, are associated with cancer progression or suppression, while others, including hsa-miR-328-5p, hsa-miR-4753-3p, and MiR-664, play roles in immune system regulation. Furthermore, our study revealed substantial enrichment in distinct Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, such as axon guidance, PI3K-Akt signaling, and MAPK signaling pathways. Although our results indicate possible molecular processes impacted by the discovered lncRNAs, we cannot explicitly establish causality or specific connections between lncRNAs and genes in these pathways, fostering more specific studies. Furthermore, Gene Ontology (GO) analysis highlighted terms such as cytoskeletal protein binding, ion channel function, synaptic processes, neuron projection, and the somatodendritic compartment, underscoring the relevance of lncRNAs in these cellular components within the context of HIV-1 infection and ART treatment. In conclusion, our study emphasizes the need for further exploration of lncRNAs as potential biomarkers and therapeutic targets in HIV-1-infected patients, with a particular focus on CD4+ T cells. Understanding the functions of lncRNAs in these contexts may pave the way for novel treatment strategies and improved patient outcomes, aligning with the broader goals of our research.

Integrative analysis of the lncRNA-miRNA-mRNA interactions in smooth muscle cell phenotypic transitions.

Objectives: We previously found that the pluripotency factor OCT4 is reactivated in smooth muscle cells (SMC) in human and mouse atherosclerotic plaques and plays an atheroprotective role. Loss of OCT4 in SMC in vitro was associated with decreases in SMC migration. However, molecular mechanisms responsible for atheroprotective SMC-OCT4-dependent effects remain unknown. Methods: Since studies in embryonic stem cells demonstrated that OCT4 regulates long non-coding RNAs (lncRNAs) and microRNAs (miRNAs), making them candidates for OCT4 effect mediators, we applied an in vitro approach to investigate the interactions between OCT4-regulated lncRNAs, mRNAs, and miRNAs in SMC. We used OCT4 deficient mouse aortic SMC (MASMC) treated with the pro-atherogenic oxidized phospholipid POVPC, which, as we previously demonstrated, suppresses SMC contractile markers and induces SMC migration. Differential expression of lncRNAs, mRNAs, and miRNAs was obtained by lncRNA/mRNA expression array and small-RNA microarray. Long non-coding RNA to mRNA associations were predicted based on their genomic proximity and association with vascular diseases. Given a recently discovered crosstalk between miRNA and lncRNA, we also investigated the association of miRNAs with upregulated/downregulated lncRNA-mRNA pairs. Results: POVPC treatment in SMC resulted in upregulating genes related to the axon guidance and focal adhesion pathways. Knockdown of Oct4 resulted in differential regulation of pathways associated with phagocytosis. Importantly, these results were consistent with our data showing that OCT4 deficiency attenuated POVPC-induced SMC migration and led to increased phagocytosis. Next, we identified several up- or downregulated lncRNA associated with upregulation of the specific mRNA unique for the OCT4 deficient SMC, including upregulation of ENSMUST00000140952-Hoxb5/6 and ENSMUST00000155531-Zfp652 along with downregulation of ENSMUST00000173605-Parp9 and, ENSMUST00000137236-Zmym1. Finally, we found that many of the downregulated miRNAs were associated with cell migration, including miR-196a-1 and miR-10a, targets of upregulated ENSMUST00000140952, and miR-155 and miR-122, targets of upregulated ENSMUST00000155531. Oppositely, the upregulated miRNAs were anti-migratory and pro-phagocytic, such as miR-10a/b and miR-15a/b, targets of downregulated ENSMUST00000173605, and miR-146a/b and miR-15b targets of ENSMUST00000137236. Conclusion: Our integrative analyses of the lncRNA-miRNA-mRNA interactions in SMC indicated novel potential OCT4-dependent mechanisms that may play a role in SMC phenotypic transitions.

HMGB1 prefers to interact with structural RNAs and regulates rRNA methylation modification and translation in HeLa cells

BackgroundHigh-mobility group B1 (HMGB1) is both a DNA binding nuclear factor modulating transcription and a crucial cytokine that mediates the response to both infectious and noninfectious inflammation such as autoimmunity, cancer, trauma, and ischemia reperfusion injury. HMGB1 has been proposed to control ribosome biogenesis, similar as the other members of a class of HMGB proteins.ResultsHere, we report that HMGB1 selectively promotes transcription of genes involved in the regulation of transcription, osteoclast differentiation and apoptotic process. Improved RNA immunoprecipitation by UV cross-linking and deep sequencing (iRIP-seq) experiment revealed that HMGB1 selectively bound to mRNAs functioning not only in signal transduction and gene expression, but also in axon guidance, focal adhesion, and extracellular matrix organization. Importantly, HMGB1-bound reads were strongly enriched in specific structured RNAs, including the domain II of 28S rRNA, H/ACA box snoRNAs including snoRNA63 and scaRNAs. RTL-P experiment showed that overexpression of HMGB1 led to a decreased methylation modification of 28S rRNA at position Am2388, Cm2409, and Gm2411. We further showed that HMGB1 overexpression increased ribosome RNA expression levels and enhanced protein synthesis.ConclusionTaken together, our results support a model in which HMGB1 binds to multiple RNA species in human cancer cells, which could at least partially contribute to HMGB1-modulated rRNA modification, protein synthesis function of ribosomes, and differential gene expression including rRNA genes. These findings provide additional mechanistic clues to HMGB1 functions in cancers and cell differentiation.

Insights from the neural guidance factor Netrin-1 into neurodegeneration and other diseases.

Netrin-1 was initially discovered as a neuronal growth cue for axonal guidance, and its functions have later been identified in inflammation, tumorigenesis, neurodegeneration, and other disorders. We have recently found its alterations in the brains with Alzheimer's disease, which might provide important clues to the mechanisms of some unique pathologies. To provide better understanding of this promising molecule, we here summarize research progresses in genetics, pathology, biochemistry, cell biology and other studies of Netrin-1 about its mechanistic roles and biomarker potentials with an emphasis on clinical neurodegenerative disorders in order to expand understanding of this promising molecular player in human diseases.

Plexin B3 guides axons to cross the midline in vivo.

During the development of neural circuits, axons are guided by a variety of molecular cues to navigate through the brain and establish precise connections with correct partners at the right time and place. Many axon guidance cues have been identified and they play pleiotropic roles in not only axon guidance but also axon fasciculation, axon pruning, and synaptogenesis as well as cell migration, angiogenesis, and bone formation. In search of receptors for Sema3E in axon guidance, we unexpectedly found that Plexin B3 is highly expressed in retinal ganglion cells of zebrafish embryos when retinal axons are crossing the midline to form the chiasm. Plexin B3 has been characterized to be related to neurodevelopmental disorders. However, the investigation of its pathological mechanisms is hampered by the lack of appropriate animal model. We provide evidence that Plexin B3 is critical for axon guidance in vivo. Plexin B3 might function as a receptor for Sema3E while Neuropilin1 could be a co-receptor. The intracellular domain of Plexin B3 is required for Semaphorin signaling transduction. Our data suggest that zebrafish could be an ideal animal model for investigating the role and mechanisms of Sema3E and Plexin B3 in vivo.

353 Eph/Ephrin Signaling Influences Innervation of Outer Hair Cells in Cochlea

OBJECTIVES/GOALS: 48,000,000 people in the U.S. have hearing loss, negatively impacting quality of life and work. Unveiling axon guidance for auditory type II spiral ganglia neurons (SGNs) will aid development of new therapies. I study the role of Eph/Ephrin and planar cell polarity (PCP) signaling during type II SGN turning and outer hair cell (OHC) innervation. METHODS/STUDY POPULATION: This quantitative study was conducted on Efna3 and Vangl2 null mice possessing Neurog1CreERT2 and R26RtdTomato mutations. Spontaneous Cre activity within the Neurogenin1CreERT2 line causes recombination and expression of fluorescent Rosa26 Reporter (R26R)tdTomatoin a restricted number of SGNs, including type IIs. Together, these lines permit SGN sparse labeling. Immunostaining and confocal imaging were used to analyze dsRed in Efna3 and Vangl2 mice and quantify type II SGN turning. In combination, Imaris 3D renderings were used to quantify type II SGN turning, branching, navigation features and temporal effects of EPHRIN-A3-Fc on type IIs via cochlear cultures (a gain-of-function manipulation). For both sexes, 5-6 cochleae per genotype were analyzed and compared by t-test to wildtype (WT) controls. RESULTS/ANTICIPATED RESULTS: Efna3 nulls showed a small rise in type II SGNs incorrectly turning toward the apex at an error rate of 16.0% compared to WTs (n=6; p=0.05). P0 Efna3 nulls had reduced branch number compared to WTs, 4.1 and 7.2, respectively (n=129; p=&lt;0.0001), suggesting EPHRIN-A3 acts as a positive growth cue. In cochlear cultures, EPHRIN-A3-Fc led to type II SGN collapse at E15.5, indicating a repulsive function. However, at P0, EPHRIN-A3-Fc treatment led to type II SGNs with elevated branch numbers compared to Control-Fc treatment: 18.1 and 11.4, respectively (n=116; p=&lt;0.0001). This indicates a positive growth function. At E16.5, EPHRIN-A3 protein immunoreactivity on Deiters’ and pillar cells appears reduced in Vangl2 nulls compared to WT cochleae, suggesting that EPHRIN-A3 acts downstream of PCP signaling. DISCUSSION/SIGNIFICANCE: Results suggest that Eph/Ephrin signaling acts downstream of PCP signaling to mediate type II SGN guidance and EPHRIN-A3 switches its mode of activation. The clinical implications of these findings are that therapeutics targeting EPHRIN-A3 and/or VANGL2 in their given pathways could stimulate new OHC innervation following auditory damage.

Tet controls axon guidance in early brain development through glutamatergic signaling

Mutations in ten-eleven translocation (TET) proteins are associated with human neurodevelopmental disorders. We find a function of Tet in regulating Drosophila early brain development. The Tet DNA-binding domain (TetAXXC) is required for axon guidance in the mushroom body (MB). Glutamine synthetase 2 (Gs2), a key enzyme in glutamatergic signaling, is significantly down-regulated in the TetAXXC brains. Loss of Gs2 recapitulates the TetAXXC phenotype. Surprisingly, Tet and Gs2 act in the insulin-producing cells (IPCs) to control MB axon guidance, and overexpression of Gs2 in IPCs rescues the defects of TetAXXC. Feeding TetAXXC with metabotropic glutamate receptor antagonist MPEP rescues the phenotype while glutamate enhances it. Mutants in Tet and Drosophila Fmr1, the homolog of human FMR1, have similar defects, and overexpression of Gs2 in IPCs also rescues the Fmr1 phenotype. We provide the first evidence that Tet controls the guidance of developing brain axons by modulating glutamatergic signaling.

MICRO-RNA AS DIAGNOSTIC MODALITY OF MAJOR DEPRESSIVE DISORDER

Introduction – Major Depressive Disorder (MDD) is a chronic mental health disorder, with suicidal ideation, but until now an exact diagnostic approach has not been found. For the limitations of the current diagnosis, such as subjective reports of patients or their families with mental status examinations, there is still a lack of objective diagnostic results. In this case, it is still a challenge for researchers. Neutropic factors, hypothalamic-pituitary-adrenal hormones (HPA), indicators of inflammation, and metabolic factors, were found to be novel biomarkers for MDD. However, these biomarkers show limited sensitivity and specificity. The most recent diagnostic development effort is the use of microRNA as a diagnostic modality approach for MDD. Methods – This study uses a qualitative method by collecting valid journals with certain inclusion and exclusion criteria. The keywords used were MDD, microRNA, and Diagnostic. There are journals used as the source of this literature review which come from valid scientific sources such as NCBI, ScienceDirect, and PubMed which were published in the last 10 years. Results – The results of the miRNA-124-3p expression test showed a significant difference between the healthy control group and the MDD patient group. The specificity and sensitivity of miRNA-221-3p, miRNA-451a, miRNA-34a-5p, and let-7d-3p showed high accuracy in the diagnosis of MDD. Discuss – The unknown etiology of MDD makes some patients have no results or significant progress of their depression in clinical settings which is contributed by gene regulatory pathway that shows high significance associated with neural function brain in depressive disorders such as apoptotic pathway, P13K-Akt signaling, axon guidance, neurotrophin signaling pathway, mTOR signaling pathway. Conclusion- The diagnostic effectiveness of miRNA in major depressive disorder can be significantly enhanced by using miRNA expression coding and has been proven by various tests. Therefore, this research is expected to be an innovation in diagnosing MDD for further research. Keywords: MDD, depression, microRNA, diagnostic