Search Results (620)

Autism spectrum disorder (ASD) and Fragile X syndrome (FXS) are neurodevelopmental disorders marked by deficits in communication and social interaction, often accompanied by anxiety, seizures, and intellectual disability. FXS, the most common monogenic cause of ASD, results from silencing of the FMR1 gene and consequent loss of FMRP, a regulator of synaptic protein synthesis. Disruptions in cyclic nucleotide (cAMP and cGMP) signaling underlie both ASD and FXS contributing to impaired neurodevelopment, synaptic plasticity, learning, and memory. Notably, reduced cAMP levels have been observed in platelets, lymphoblastoid cell lines and neural cells from FXS patients as well as Fmr1 KO and dfmr1 Drosophila models, linking FMRP deficiency to impaired cAMP regulation. Phosphodiesterase (PDE) inhibitors, which prevent the breakdown of cAMP and cGMP, have emerged as promising therapeutic candidates due to their ability to modulate neuronal signaling. Several PDE isoforms—including PDE2A, PDE4D, and PDE10A—have been implicated in ASD, and FXS, as they regulate pathways involved in synaptic plasticity, cognition, and social behavior. Preclinical and clinical studies show that PDE inhibition modulates neuroplasticity, neurogenesis, and neuroinflammation, thereby ameliorating autism-related behaviors. BPN14770 (a PDE4 inhibitor) has shown promising efficacy in FXS patients while cilostazol, pentoxifylline, resveratrol, and luteolin have showed improvements in children with ASD. However, challenges such as isoform-specific targeting, optimal therapeutic window, and timing of intervention remain. Collectively, these findings highlight PDE inhibition as a novel therapeutic avenue with the potential to restore cognitive and socio-behavioral functions in ASD and FXS, for which effective targeted treatments remain unavailable. Full article

EZH2, the catalytic subunit of polycomb repressive complex 2 (PRC2), plays a critical role in neural development by regulating gene expression through the trimethylation of lysine 27 on histone H3 (H3K27me3), which promotes chromatin remodeling and transcriptional repression. Although PRC2 is known to regulate cell fate specification and gliogenesis, its in vivo functions during vertebrate neurodevelopment, particularly at the level of neuronal subtype differentiation, remain incompletely understood. Here, we investigated the consequences of ezh2 loss-of-function during zebrafish brain development, focusing on oligodendrocyte differentiation, cerebellar neurogenesis, and the formation of neurotransmitter-specific neuronal populations. Using whole-mount in situ hybridization, we found that ezh2 inactivation does not alter the expression of oligodendrocyte lineage markers, indicating that early oligodendrocyte precursor cell specification and myelination are preserved. However, a significant reduction in cerebellar proliferation was observed in ezh2-deficient larvae, as evidenced by the downregulation of pcna and cyclin A2, while other brain regions remained unaffected. Notably, the expression of atoh1c, a key marker of glutamatergic cerebellar progenitors, was strongly reduced at 5 days post fertilization, suggesting a selective role for ezh2 in maintaining cerebellar progenitor identity. This was associated with impaired differentiation of both glutamatergic granule cells and GABAergic Purkinje cells in specific cerebellar subregions. In contrast, the expression of markers for other major neurotransmitter systems remained unaffected, indicating a region-specific requirement for ezh2 in neuronal development. Finally, behavioral analysis revealed a hyperlocomotor phenotype in ezh2^−/− larvae, consistent with cerebellar dysfunction. Together, these findings identify ezh2 as a key regulator of progenitor maintenance and neuronal differentiation in the cerebellum, highlighting its crucial role in establishing functional cerebellar circuits. Full article

Myelin is a membranous structure critically important for human health. Historically, it was believed that myelin remained largely unchanged in the adult brain. However, recent research has shown that myelin is remarkably dynamic, capable of adjusting axonal conduction velocity and playing a role in learning, memory, and recovery from injury, in response to both physiological and pathological signals. Axons are more efficiently insulated in myelinated fibers, where segments of the axonal membrane are wrapped by the myelin sheath. Although extensive data are available on the electrical properties of myelin, its structural and mechanical characteristics—as well as the role of its lipid composition—are also relevant, although much less explored. The objective of our review is derived from this point since alterations in lipid components can lead to axonal dysfunction, giving rise to neurological disorders such as multiple sclerosis and other demyelinating conditions. In this review, concerning the lipid composition of myelin, we focus on two distinct classes of lipids: sphingolipids and long-chain fatty acids, emphasizing the differential contributions of saturated versus polyunsaturated species. We analyze studies that correlate the mechanical vulnerability of myelin with its lipid composition, particularly sphingomyelin, thereby underscoring its role in protecting neurons against physical stress and providing a robust microstructural network that reinforces the white matter as a whole. From a biochemical perspective, we examine the susceptibility of myelin to oxidative stress, metabolic disorders, and extreme nutritional deficiencies in relation to the role of long-chain fatty acids. Both perspectives highlight that the aforementioned lipids participate in a complex biomechanical balance that is essential for maintaining the stability of myelin and, consequently, the integrity of the central and peripheral nervous systems. Full article

RAC3 encodes a small Rho-family GTPase essential for cytoskeletal regulation and neurodevelopment, and de novo RAC3 variants typically act as gain-of-function alleles that cause severe neurodevelopmental disorders. In this study, we analyzed a fetus with multisystem congenital anomalies and identified a de novo RAC3 p.(T17R) variant by genome sequencing. To elucidate the pathogenicity of this variant, we combined in silico variant prioritization, structural and energetic modeling, and pathogenicity prediction with in vitro biochemical assays, including GDP/GTP exchange, GTP hydrolysis, effector pull-down, and luciferase reporter analyses in COS7 cells, as well as morphological analysis of primary hippocampal neurons. Furthermore, we performed in vivo analyses using a mouse in utero electroporation to assess cortical neuron migration, axon extension, and dendritic development. Our biochemical results suggest that RAC3-T17R exhibits markedly increased GDP/GTP exchange, with a preference for GDP binding, and undetectable GTP hydrolysis. The mutant displayed minimal binding to canonical RAC effectors (PAK1, MLK2, and N-WASP) and failed to activate SRF-, NFκB-, or AP1-dependent transcription. Neuronal overexpression of RAC3-T17R impaired axon formation in vitro, while in vivo expression delayed cortical neuron migration and axon extension and reduced dendritic arborization. Clinically, the fetus exhibited corpus callosum agenesis, microcephaly, organomegaly, and limb contractures. Collectively, these findings indicate that the RAC3 p.(T17R) variant may represent a signaling-deficient allele with pleiotropic, variant-specific mechanisms that disrupt corticogenesis and broader organogenesis. Our multi-tiered in silico–in vitro–in vivo approach demonstrates that noncanonical RAC3 variants can produce complex, multisystem developmental phenotypes beyond previously recognized RAC3-related neurodevelopmental disorders. Full article

Demyelinating diseases, such as multiple sclerosis, involve oligodendrocyte death, myelin loss, and neuronal death. These processes have been extensively studied, and a causal relationship has been demonstrated between them: destruction of oligodendrocytes results in myelin deficiency, which subsequently leads to neurodegeneration and the consequent loss of sensory, motor, and cognitive functions. Currently, myelinopathies lack fully effective treatments. Available drugs primarily focus on controlling the immune response without directly promoting myelin regeneration or restoring neuronal functionality. Alongside these treatments, pharmaceutical research has increasingly focused on developing therapies that stimulate oligodendroglial lineage differentiation and myelin sheath regeneration. Despite these advances, the lack of suitable preclinical models has been a significant obstacle in evaluating new therapeutic compounds. In this review, we present the main animal models used in the preclinical phase for the study of myelin-related diseases and their role in the development of new therapies. In addition, we highlight the usefulness of R-Ras animal models for assessing the efficacy of compounds that promote oligodendrocyte differentiation. Full article

Neuropeptides (NPs) are small molecular messengers synthesized in large dense core vesicles (LDCVs) and secreted to the extracellular space. In the central nervous system (CNS), NPs are secreted to the synaptic space, playing crucial roles in modulating neurons, astrocytes, microglia, oligodendrocytes, and other glial cells, through G-protein-coupled receptors, thereby influencing complex multicellular responses. During neuroinflammation, NPs regulate glial and neuronal reactions to inflammatory signals, promoting resolution and preventing chronic, non-resolving inflammation. For example, NPs inhibit apoptosis in neurons and oligodendrocytes while inducing anti-inflammatory effects in microglia and astrocytes, modulating cytokine secretion. Here, we present the notion that neuropeptides could participate in neuroinflammatory progression, altering glial responses, leading to excessive, non-resolutive inflammation when dysregulated. NP signaling—whether excessive or deficient—can disrupt specific cellular processes, leading to pathological inflammation, gliosis, and functional loss—hallmarks of neurodegenerative diseases. Despite their significance, the precise mechanisms underlying NP-mediated effects remain incompletely understood. This review synthesizes experimental and translational evidence highlighting the pivotal role of NPs in resolving neuroinflammation and explores how targeting NPs or their receptors could offer novel therapeutic strategies for neurodegenerative disorders. Further research is needed to elucidate the specific signaling pathways and receptor dynamics involved, which could pave the way for innovative treatments that address the root causes of these debilitating conditions. Full article

The pituitary adenylate cyclase-activating polypeptide receptor 1 (PAC1) plays a pivotal role in central nervous system development and homeostasis. Comparisons of PAC1 knockout (PAC1^−/−), heterozygous (PAC1^+/−) and wild-type (PAC1^+/+) mice demonstrate that PAC1 deficiency severely impairs pre-weaning survival and results in marked developmental deficits, including reduced postnatal weight and altered locomotor behavior. PAC1^−/− mice exhibited hyperlocomotion, reduced anxiety-like behavior, and transient deficits in motor coordination. Gene expression analyses revealed widespread dysregulation of oligodendrocyte-associated markers, with significant myelin reduction and decreased mature oligodendrocyte density in the corpus callosum. ER stress was evidenced in both white matter and motor cortex, as indicated by altered expression of UPR-related genes and increased phosphorylated (p)IRE1⁺ neurons. Retinal morphology was compromised in PAC1^−/− animals, with reduced overall retinal and ganglion cell layer thickness. Notably, no gross morphological or molecular abnormalities were detected in the spinal cord regarding myelin content or MBP expression; however, synaptic marker expression was selectively reduced in the ventral horn of PAC1-deficient mice. Together, these findings highlight a critical role for PAC1 in oligodendrocyte maturation, retinal development, and synaptogenesis, providing new insights with relevance in multiple sclerosis and other neurodevelopmental and neurodegenerative conditions. Full article

After spinal cord injury, pathological changes predominantly proceed caudal to the site of injury. To what extent these changes contribute to abnormalities during regeneration is poorly understood. Here, we addressed this question with a low-thoracic compression injury mouse model. The total numbers of immunohistochemically stained neuronal and glial cell types in the lumbar spinal cord were stereologically determined 6 weeks after injury. We also investigated injured mice deficient in close homolog of L1 (CHL1), which had been reported to recover better after injury than their wild-type littermates. We here report that there were no differences between genotypes in uninjured animals. In both injured CHL1-deficient and wild-type littermates, gray and white matter volumes were decreased as compared with uninjured mice. Numbers of motoneurons and parvalbumin-expressing interneurons were also reduced in both genotypes. Numbers of interneurons in injured mutant mice were lower than in wild-type littermates. Whereas injury did not affect numbers of astrocytes and oligodendrocytes in the gray matter, numbers of microglia/macrophages were increased. In the mutant white matter, numbers of oligodendrocytes were reduced, with no changes in numbers of astrocytes and microglia. A loss of motoneurons and interneurons was observed in both genotypes, but loss of interneurons was more prominent in the absence of CHL1. We propose that, after injury, CHL1 deficiency causes deficits in structural outcome not seen after injury of wild-type mice. Full article

Background: The pathophysiology of epilepsy is characterized by increased neuronal activity due to an excess of the excitatory neurotransmitter glutamate and a deficiency in the inhibitory neurotransmitter gamma–aminobutyric acid (GABA). Epilepsy presents with seizures, neuronal loss, and hyperactivity in the subthalamic nucleus (STN). Astrocytes play a crucial role by absorbing extracellular glutamate through glutamate transporter–1 (GLT–1), thereby reducing neuronal excitation. Upregulating the expression of astrocytic GLT–1 is a promising therapeutic strategy for epilepsy. Sulbactam (SUL), a β–lactam antibiotic, has been demonstrated to exert neuroprotective effects by upregulating GLT–1 expression. Objectives: This study investigated the impact of SUL on neuronal and behavioral changes in epilepsy by using a pentylenetetrazol (PTZ)-induced rat model of epilepsy. Methods: Rats were treated with saline, SUL (50 and 150 mg/kg), or a combination of SUL and the GLT–1 blocker dihydrokainate (DHK) for 20 days. Subsequently, behavioral tasks were conducted to assess recognition, anxiety, and memory. Results: Histological analyses revealed that SUL ameliorated neuronal deficits, increased astrocytic GLT–1 expression, and reduced hyperactivity in the STN. Additionally, SUL promoted astrocyte proliferation, indicating a new dimension of its neuroprotective properties. However, the beneficial effects of SUL were prevented by DHK. Conclusions: This pioneering study highlights multiple benefits of SUL, including seizure suppression, increased GLT–1 expression, and astrocyte proliferation, underscoring its high potential as a treatment for epilepsy. Full article

Background/Objectives: The Reelin–Dab1 signaling pathway, known for its crucial role in neurodevelopment, particularly in neuronal migration and the formation of cortical layers, has been a subject of extensive research. However, its involvement in gastrointestinal organogenesis is a relatively unexplored area. Our study investigates the expression patterns of Dab1, Reelin, PGP9.5, and Sox2 during stomach development in yotari (Dab1^−/−) mice and aims to shed light on how Dab1 inactivation affects epithelial–mesenchymal signaling dynamics, thereby contributing to a deeper understanding of this pathway’s non-neural functions. Methods: Embryonic stomach tissues from yotari and wild-type mice, collected at developmental stages E13.5 and E15.5, were examined by immunofluorescenceto evaluate the difference in expression of Dab1, Reelin, PGP9.5, and Sox2. Semi-quantitative scoring and quantitative image analysis were used to assess protein localization and intensity within epithelial and mesenchymal compartments. Results: Dab1 expression was significantly increased in both the epithelium and mesenchyme of yotari mice at E13.5 and E15.5. Reelin expression in the epithelium showed a visible but statistically non-significant decrease in yotari at E15.5, while mesenchymal expression remained low and significantly lower than controls. PGP9.5 expression was significantly reduced in yotari epithelium at E13.5, then strongly upregulated at E15.5. Mesenchymal PGP9.5 remained consistently high. Sox2 showed no statistically significant changes but increased semi-quantitatively in yotari epithelium and mesenchyme at E15.5. These findings highlight compartment-specific disruptions and potential compensatory mechanisms following Dab1 inactivation. Conclusions: Our findings indicate that Dab1 deficiency leads to distinct molecular changes in epithelial and mesenchymal compartments of the developing stomach. The Reelin–Dab1 axis appears critical for epithelial–mesenchymal coordination, while PGP9.5 and Sox2 upregulation in yotari mice may represent potential compensatory responses that could support epithelial integrity, although this remains speculative without functional validation. Full article

It is widely accepted that chronic inflammation constitutes a significant mechanism that promotes the biological aging process. The pineal gland is regarded as being closely related to the control of the “life clock”. The present study aimed to determine the inflammation associated with pinealectomy in the rat hippocampus and to investigate the extent to which age stage impacts the severity of this inflammation. We evaluated the expression of the Akt/NF-kB signaling pathway in neurons and gliosis level in the dorsal hippocampus (dHipp) of rats subjected to sham surgery or pinealectomy at 3, 14, or 18 months of age. The assessment was conducted using immunohistochemistry. Removal of the pineal gland resulted in significant, region-specific increases in NF-kB expression in neurons of the dHipp in the youngest and middle-aged groups. However, the change in expression of the phosphorylated form of Akt (pAkt1) in neurons went in the opposite direction in these two age groups, and there were also regional differences. Pinealectomy triggered microgliosis in both young and old rats, but middle-aged rats were resistant to microglia activation. Conversely, astrogliosis was observed in young adult and middle-aged groups with melatonin deficiency in certain regions of the dHipp. It is noteworthy that young adult rats demonstrated the highest degree of vulnerability to inflammation associated with the loss of melatonin as a hormone. In contrast, middle-aged rats with pinealectomy exhibited a complex and partial adaptive response. These findings emphasize the dynamic and age-dependent nature of neuroinflammation following pinealectomy, underscoring the developmental stage as a critical determinant of inflammatory susceptibility. Full article

Fatty-acid-hydroxylase-associated neurodegeneration (FAHN) is a rare neurodegenerative disorder caused by loss-of-function mutations in the FA2H gene, leading to impaired enzymatic activity and resulting in myelin sheath instability, demyelination, and axonal degeneration. In this study, we established a human in vitro model using neurons and oligodendrocytes derived from induced pluripotent stem cells (hiPSCs) of a FAHN patient. This coculture system enabled the investigation of myelination processes and myelin integrity in a disease-relevant context. Analyses using immunofluorescence and Western blot revealed impaired expression and localisation of key myelin proteins in oligodendrocytes and cocultures. FA2H-deficient cells showed reduced myelination, shortened internodes, and disrupted formation of the nodes of Ranvier. Additionally, we identified autophagy defects—a hallmark of many neurodegenerative diseases—including reduced p62 expression, elevated LC3B levels, and impaired fusion of autophagosomes with lysosomes. This study presents a robust hiPSC-based model to study FAHN, offering new insights into the molecular pathology of the disease. Our findings suggest that FA2H mutations compromise both the structural integrity of myelin and the efficiency of the autophagic machinery, highlighting potential targets for future therapeutic interventions. Full article

Background/Objectives: An important new consideration when studying autism spectrum disorder (ASD) is the bioenergetic mechanisms underlying the relatively recent rapid evolutionary expansion of the human brain, which pose fundamental risks for mitochondrial dysfunction and calcium signaling abnormalities and their potential role in ASD, as recently highlighted by insights from the BTBR mouse model of ASD. The rapid brain expansion taking place as Homo sapiens evolved, particularly in the parietal lobe, led to increased energy demands, making the brain vulnerable to such metabolic disruptions as are seen in ASD. Methods: Mitochondrial dysfunction in ASD is characterized by impaired oxidative phosphorylation, elevated lactate and alanine levels, carnitine deficiency, abnormal reactive oxygen species (ROS), and altered calcium homeostasis. These dysfunctions are primarily functional, rather than being due to mitochondrial DNA mutations. Calcium signaling plays a crucial role in neuronal ATP production, with disruptions in inositol 1,4,5-trisphosphate receptor (ITPR)-mediated endoplasmic reticulum (ER) calcium release being observed in ASD patient-derived cells. Results: This impaired signaling affects the ER–mitochondrial calcium axis, leading to mitochondrial energy deficiency, particularly in high-energy regions of the developing brain. The BTBR mouse model, with its unique Itpr3 gene mutation, exhibits core autism-like behaviors and metabolic syndromes, providing valuable insights into ASD pathophysiology. Conclusions: Various interventions have been tested in BTBR mice, as in ASD, but none have directly targeted the Itpr3 mutation or its calcium signaling pathway. This review presents current genetic, biochemical, and neurological findings in ASD and its model systems, highlighting the need for further research into metabolic resilience and calcium signaling as potential diagnostic and therapeutic targets for ASD. Full article

B-raf (rapidly accelerated fibrosarcoma) is a crucial player within the ERK/MAPK signaling pathway. In the CNS, B-raf has been implicated in neuronal differentiation, long-term memory, and major depression. Mice with forebrain neuron-specific B-raf knockout show behavioral deficits in spatial learning tasks and impaired hippocampal long-term potentiation (LTP). To elucidate the mechanism(s) underlying diminished synaptic plasticity in B-raf-deficient mice, we performed whole-cell recordings from CA1 pyramidal cells in hippocampal slices of control and B-raf mutant mice. We found that the NMDA/AMPA ratio of excitatory postsynaptic currents (EPSCs) at the Schaffer collateral—CA1 pyramidal cell synapses was significantly reduced in B-raf mutants, which would at least partially account for their impaired LTP. Interestingly, the reduced NMDA component of field postsynaptic potentials in mutant preparations was partially reinstated by blocking the apamin-sensitive small-conductance Ca²⁺-activated K⁺ (SK) channels, which have also been reported to modulate hippocampal LTP and learning tasks. To determine the impact of B-raf-dependent signaling on SK current, we isolated the apamin-sensitive tail current after a strong depolarizing event and found indeed a significantly bigger SK current in B-raf-deficient cells compared to controls, which is consistent with the reduced action potential firing and the stronger facilitating effect of apamin on CA1 somatic excitability in B-raf-mutant hippocampus. Our data suggest that B-raf signaling readjusts the delicate balance between NMDA receptors and SK channels to promote synaptic plasticity and facilitate hippocampal learning and memory. Full article

Due to their clinical heterogeneity, nonspecific symptoms, and the limitations of existing biomarkers and imaging modalities, metabolic brain diseases (MBDs), such as mitochondrial encephalopathies, lysosomal storage disorders, and glucose metabolism syndromes, pose significant diagnostic challenges. This review examines the growing potential of cell-free DNA (cfDNA) derived from cerebrospinal fluid (CSF) epigenetic profiling as a dynamic, cell-type-specific, minimally invasive biomarker approach for MBD diagnosis and monitoring. We review important technological platforms and their use in identifying CNS-specific DNA methylation patterns indicative of neuronal injury, neuroinflammation, and metabolic reprogramming, including cfMeDIP-seq, enzymatic methyl sequencing (EM-seq), and targeted bisulfite sequencing. By synthesizing current findings across disorders such as MELAS, Niemann–Pick disease, Gaucher disease, GLUT1 deficiency syndrome, and diabetes-associated cognitive decline, we highlight the superior diagnostic and prognostic resolution offered by CSF cfDNA methylation signatures relative to conventional CSF markers or neuroimaging. We also address technical limitations, interpretive challenges, and translational barriers to clinical implementation. Ultimately, this review explores CSF cfDNA epigenetic analysis as a liquid biopsy modality. The central objective is to assess whether epigenetic profiling of CSF-derived cfDNA can serve as a reliable and clinically actionable biomarker for improving the diagnosis and longitudinal monitoring of metabolic brain diseases. Full article