Biology subjects

Liu, Y.

Publications and source records attributed to Liu, Y..

At least 1,369 records · Page 76Linked to original sources

bioRxiv2023

Inhibition of KLK8 promotes pulmonary endothelial repair by restoring VE-cadherin/Akt/FOXM1 pathway

The tissue kallikrein-related peptidases (KLKs) are secreted serine proteases deeply involved in angiogenesis. However, whether KLKs are involved in the regulation of endothelial regeneration during sepsis remains unknown. By comparing the mRNA levels of 15 KLKs, we found that KLK8 was the highest induced KLK member in lung tissues or primary isolated mouse lung vascular endothelial cells (MLVECs) exposed to lipopolysaccharide (LPS). Adenovirus-mediated overexpression of KLK8 caused endothelial hyperpermeability both in vitro and in vivo. Inhibition of KLK8, by either gene knockout or KLK8 neutralizing antibodies, alleviated sepsis-induced endothelial hyperpermeability, acute lung injury and mortality. Mechanistically, transcription profiling of KLK8-overexpressed endothelial cells revealed a central role of forkhead box M1 (FOXM1) downregulation in mediating the pro-injury and anti-proliferation effects of KLK8. KLK8 cleaved VE-cadherin and consequently suppressed FOXM1 expression by inactivation of the VE-cadherin/Akt pathway. KLK8 deficiency or blockade rescued VE-cadherin/Akt/FOXM1 pathway, thus promoting endothelium regeneration. This study reveals a critical role for KLK8-induced inactivation of VE-cadherin/Akt/FOXM1 pathway in mediating the impairment of endothelial regeneration and the consequent lung vascular leakiness in response to sepsis. HighlightsO_LIUpregulated KLK8 mediates lung endothelial barrier dysfunction during sepsis C_LIO_LIKLK8 inactivates VE-cadherin/Akt/FOXM1, thus impairing endothelium regeneration C_LIO_LIKLK8 deficiency or blockade rescues VE-cadherin/Akt/FOXM1 signaling pathway C_LIO_LIKLK8 deficiency or blockade promotes endothelium regeneration during sepsis C_LIO_LIKLK8 deficiency or blockade attenuates sepsis-induced acute lung injury and mortality C_LI

physiology↗

bioRxiv2023

Mapping the shared and unique structural asymmetry abnormalities of young children with autism and developmental delay/intellectual disability with normative models and their multimodal cascade

To understand the neural mechanism of autism spectrum disorder (ASD) concurrent with developmental delay/intellectual disability (DD/ID), it is essential to comprehensively take genetic, brain, and behavioural measurements as a whole and focus on subjects at early age. However, such research is still lacking. Here, using the sMRI data of 1030 children under 8 years old, we employed developmental normative models to explore the atypical development of gray matter volume (GMV) asymmetry in individuals with ASD without DD/ID, ASD with DD/ID and DD/ID, and their associations with neurophysiological measures and transcription profiles. By computing the individual deviations from typical controls, we observed an ASD-specific abnormal GMV laterality pattern that was more rightwards in the inferior parietal cortex and precentral cortex and noted abnormal within-group heterogeneity in the temporal pole. Specifically, ASD with DD/ID children exhibited more regional abnormalities; ASD without DD/ID children showed higher within-group variability; while children with DD/ID showed no significant abnormalities. However, there were no significant differences among the three groups. The GMV laterality of ASD without DD/ID children was associated with ASD symptoms, whereas that of ASD with DD/ID children was associated with both ASD symptoms and verbal IQ. Last, the GMV laterality of the ASD with DD/ID, ASD without DD/ID, and DD/ID groups was associated with shared and unique gene expression profiles, but the associations of the latter two groups with intellectual genes showed opposite effects. Our findings illustrated the atypical development of regional structural lateralization in autistic children, which is associated with upstream genes and downstream behavioural performance. The differences and similarity between ASD and DD/ID additionally improve our standing to the neural mechanism of neurodevelopmental disorders comorbidity.

neuroscience↗

bioRxiv2023

Utilizing Non-Invasive Prenatal Test Sequencing Data Resource for Human Genetic Investigation

Non-invasive prenatal testing (NIPT) employs ultra-low-pass sequencing of maternal plasma cell-free DNA to detect fetal trisomy. With exceptional sensitivity, specificity, and safety, NIPT has gained global adoption, exceeding ten million tests, establishing it as one of the largest human genetic resources. This resource holds immense potential for exploring population genetic variations and their correlations with phenotypes. Here, we present comprehensive methods tailored for analyzing large, low-depth NIPT genetic datasets, involving customized algorithms and software for genetic variation detection, genotype imputation, and genome-wide association analysis. Through evaluations, we demonstrate that, when integrated with appropriate probabilistic models and population-specific haplotype reference panels, accurate allele frequency estimation and high genotype imputation accuracy (0.8 to 0.9) are achievable for genetic variants with alternative allele frequencies between 0.01 and 0.05, at sequencing depths of 0.1x to 0.25x. Additionally, we attained an R-square exceeding 0.9 for estimating genetic effect sizes across various sequencing platforms. These findings establish a robust theoretical and practical foundation for leveraging NIPT data in advancing medical genetic studies, not only in realms of maternal and child health, but also for long-term health outcomes. HighlightsO_LIIntroduction of probabilistic model integration for analyzing large-scale, low-pass non-invasive prenatal test (NIPT) sequencing data C_LIO_LIEvaluation of protocols for variant detection, genotype imputation, and genome-wide association analyses with NIPT data C_LI

bioinformatics↗

bioRxiv2023

Climate change has desynchronized insect and vegetation phenologies across Europe

Climate change is drastically affecting the phenologies of species worldwide, including shifts in development1-3. The potential impact of climate change on the synchronicity of plant-insect phenology is particularly concerning since the stability of pollination networks and food chains depends on their tight temporal dependencies4-6. Furthermore, the recently reported "insect armageddon"7 makes it urgent to establish trends and identify primary drivers of plant-insect phenological synchrony. Here, coupling high-resolution remote sensing and citizen science data across Europe over 34 years, we examine the differences in occurrence dates of 1,584 herbivorous insects across four orders and the corresponding dates of leaf unfolding. We find that 61.2% of the vegetation and insect phenologies have become highly asynchronous, with vegetation phenology advancing four-fold faster than insect phenology. These trends were modulated by insects life-cycles and taxonomic order. A primary driver of this phenological mismatch is the higher sensitivity of vegetation phenology than insect phenology to climate, which has prevented insects from matching the pace of plant phenological advance in the growing season. Our analyses provide a unique continental overview and underlying mechanisms of the asynchronicity between vegetation and insect phenologies, thus enhancing our ability to predict and manage its potential cascading ecological effects.

ecology↗

bioRxiv2023

Regulation of blood pressure by METTL3 via RUNX1b-eNOS pathway in endothelial cells

BackgroundEndothelial cells regulate vascular tone to control the blood pressure (BP) by producing both relaxing and contracting factors. Previously, we identified methyltransferase-like 3 (METTL3), a primary N6-methyladenosine (m6A) methyltransferase, as a key player in alleviating endothelial atherogenic progression. However, its involvement in BP regulation remains unclear. MethodsTo evaluate the role of METTL3 in vivo, mice with EC specific METTL3 deficiency (EC-Mettl3KO) with or without Ang II infusion were used to create a hypertensive model. Functional and MeRIP sequencing analysis were performed to explore the mechanism of METTL3-mediated hypertension. ResultsWe observed a reduction in endothelial METTL3 activity by Ang II in vitro and in vivo. Endothelial METTL3-deficient mice exhibited higher BP than controls, both before and after Ang II infusion. Through m6A sequencing and functional analysis, we identified m6A modification of various RUNX1 monomers resulted in endothelial dysfunction. Mutations in the 3'UTR region of RUNX1b abolished its luciferase reporter activity, and enhanced eNOS promoter luciferase reporter activity with or without METTL3 overexpression. Overexpression of METTL3 by adeno-associated virus reduced Ang II-induced BP elevation. ConclusionThis study reveals that METTL3 alleviates hypertension through m6A-dependent stabilization of RUNX1b mRNA, leading to upregulation of eNOS, thus underscoring the pivotal role of RNA transcriptomics in the regulation of hypertension.

cell biology↗

bioRxiv2023

Nuclear cytoophidia assembly represses transcriptional activity to control skeletal development and homeostasis

Compartmentation via filamentation is an evolutionarily conserved subcellular structure that fine-tunes the inherent activity of proteins. Cytoophidia represent a typical class of filamentous structures controlling enzymatic activities. Despite eukaryotic cells containing both cytoplasmic cytoophidia and nuclear cytoophidia, the physiological significance of nuclear cytoophidia is largely unknown. Here we show that nuclear filamentation inhibits the transcriptional activity of Impdh2 required for limb formation and bone resorption. Impdh2 deletion in mouse limb mesenchymal progenitors causes severe skeletal dysplasia by impairing endochondral ossification and chondrocyte differentiation. Additionally, Impdh2 deficiency in myeloid lineages leads to an increased bone mass via impeding osteoclast differentiation. Furthermore, Impdh2 regulates osteoclastic mitochondrial biogenesis and function. We propose that the nuclear compartmentalization of Impdh2 regulates the transcriptional activity during skeletal development and homeostasis.

cell biology↗

bioRxiv2023

Toward Best Practice in Identifying Subtle Differential Expression with RNA-seq: A Real-World Multi-Center Benchmarking Study Using Quartet and MAQC Reference Materials

Translating RNA-seq into clinical diagnostics requires ensuring the reliability of detecting clinically relevant subtle differential expressions, such as those between different disease subtypes or stages. Moreover, cross-laboratory reproducibility and consistency under diverse experimental and bioinformatics workflows urgently need to be addressed. As part of the Quartet project, we presented a comprehensive RNA-seq benchmarking study utilizing Quartet and MAQC RNA reference samples spiked with ERCC controls in 45 independent laboratories, each employing their in-house RNA-seq workflows. We assessed the data quality, accuracy and reproducibility of gene expression and differential gene expression and compared over 40 experimental processes and 140 combined differential analysis pipelines based on multiple ground truths. Here we show that real-world RNA-seq exhibited greater inter-laboratory variations when detecting subtle differential expressions between Quartet samples. Experimental factors including mRNA enrichment methods and strandedness, and each bioinformatics step, particularly normalization, emerged as primary sources of variations in gene expression and have a more pronounced impact on the subtle differential expression measurement. We underscored the pivotal role of experimental execution over the choice of experimental protocols, the importance of strategies for filtering low-expression genes, and optimal gene annotation and analysis tools. In summary, this study provided best practice recommendations for the development, optimization, and quality control of RNA-seq for clinical diagnostic purposes.

genomics↗

bioRxiv2023

Structural insights into specific recognition of PTENα/β-NTE by WDR5 in cancer progression

PTEN/{beta}, two variants of PTEN, play a key role in promoting tumor growth by interacting with WDR5 through their N-terminal extensions (NTEs). This interaction facilitates the recruitment of the SET1/MLL methyltransferase complex, resulting in histone H3K4 trimethylation and upregulation of oncogenes such as NOTCH3, which in turn promotes tumor growth. However, the molecular mechanism underlying this interaction has remained elusive. In this study, we determined the crystal structure of PTEN-NTE in complex with WDR5, which reveal that PTEN specifically binds to the WIN site of WDR5 through a novel binding motif specifically found in the NTE domain of PTEN/{beta}. Disruption of this interaction significantly impedes cell proliferation and tumor growth, highlighting the potential of the WIN site inhibitors of WDR5 as therapeutic agents for PTEN/{beta} associated cancers. These findings not only shed light on the important role of the PTEN/{beta}-WDR5 interaction in carcinogenesis, but also present a promising avenue for developing cancer treatments that target this pathway.

cancer biology↗

bioRxiv2023

SIRT5 variants from patients with mitochondrial disease are associated with reduced SIRT5 stability and activity, but not with neuropathology

SIRT5 is a sirtuin deacylase that represents the major activity responsible for removal of negatively-charged lysine modifications, in the mitochondrial matrix and elsewhere in the cell. In benign cells and mouse models, under basal non-stressed conditions, the phenotypes of SIRT5 deficiency are generally quite subtle. Here, we identify two homozygous SIRT5 variants in human patients suffering from severe mitochondrial disease. Both variants, P114T and L128V, are associated with reduced SIRT5 protein stability and impaired biochemical activity, with no evidence of neomorphic or dominant negative properties. The crystal structure of the P114T enzyme was solved and shows only subtle deviations from wild-type. Via CRISPR-Cas9, we generate a mouse model that recapitulates the human P114T mutation; homozygotes show reduced SIRT5 levels and activity, but no obvious metabolic abnormalities, neuropathology or other gross evidence of severe disease. We conclude that these human SIRT5 variants most likely represent severe hypomorphs, and are likely not the primary pathogenic cause of the neuropathology observed in the patients.

genetics↗

bioRxiv2023

Linking root-associated fungal and bacterial functions to root economics

Tree roots form symbioses with soil microbes to acquire nutrients, but the relationships between root nutrient acquisition strategies and microbial community composition remain poorly understood. Here, we measured root traits and root-associated fungal and bacterial guilds in 336 trees of 52 species from a subtropical forest. We found a fungal gradient from ectomycorrhizal to saprotrophic dominance, which corresponded with a shift from organic to mineral nutrient economics. This fungal gradient was aligned with the increase of root nitrogen concentration, suggesting a linkage from simple root trait to fungal-mediated carbon-nutrient cycling. We also found that the functional composition of fungal and bacterial communities was closely correlated with host root-zone pH, which often varied among coexisting trees. Root-zone pH was independent of the common root traits, underpinning a potential new gradient in the root trait space. Our findings integrate microbial functions into the root economics framework, thereby advancing the understanding of diversity of nutrient acquisition strategies across forest trees.

ecology↗

bioRxiv2023

A phosphorylation-dependent switch of the lysosomal V-ATPase assembly regulates α-synuclein clearance in glia

Glia serve as double-edged swords to modulate neuropathology in Parkinsons disease (PD), but how they react opposingly to be beneficial or detrimental under pathological conditions, like promoting or eliminating -synuclein (-syn) inclusions, remains elusive. Here we present evidence that dAuxilin (dAux), the Drosophila homolog of the PD risk factor Cyclin G-associated kinase (GAK), regulates the lysosomal degradation of -syn in glia. Lack of glial Gak/dAux increases the lysosome number and size, regulates lysosomal acidification and hydrolase activity, and ultimately blocks the degradation of substrates including -syn. Whereas -syn accumulated prominently in lysosomes devoid of glial dAux, levels of injected -syn preformed fibrils also further enhanced in the absence of microglial Gak. Mechanistically, dAux mediates phosphorylation at the serine 543 of Vha44, the V1C subunit of the vacuolar H+-ATPase (V-ATPase), regulates its assembly to control proper acidification of the lysosomal milieu. Expression of Vha44, but not the Vha44 variant lacking S543 phosphorylation, restores lysosome acidity, locomotor deficits, and DA neurodegeneration upon glial dAux depletion, linking this pathway to PD. Our findings identify a phosphorylation-dependent switch controlling the V-ATPase assembly for lysosomal -syn degradation in glia. Targeting the clearance of glial -syn inclusions via this lysosomal pathway could potentially be a therapeutical approach to ameliorate the disease progression in PD.

neuroscience↗

bioRxiv2023

GeneMAP: A discovery platform for metabolic gene function

Organisms maintain metabolic homeostasis through the combined functions of small molecule transporters and enzymes. While many of the metabolic components have been well-established, a substantial number remains without identified physiological substrates. To bridge this gap, we have leveraged large-scale plasma metabolome genome-wide association studies (GWAS) to develop a multiomic Gene-Metabolite Associations Prediction (GeneMAP) discovery platform. GeneMAP can generate accurate predictions, even pinpointing genes that are distant from the variants implicated by GWAS. In particular, our work identified SLC25A48 as a genetic determinant of plasma choline levels. Mechanistically, SLC25A48 loss strongly impairs mitochondrial choline import and synthesis of its downstream metabolite, betaine. Rare variant testing and polygenic risk score analyses have elucidated choline-relevant phenomic consequences of SLC25A48 dysfunction. Altogether, our study proposes SLC25A48 as a mitochondrial choline transporter and provides a discovery platform for metabolic gene function.

genomics↗

bioRxiv2023

Dietary restriction of individual amino acids stimulates unique molecular responses in mouse liver

Dietary protein and essential amino acid (EAA) restriction promote favorable metabolic reprogramming, although the extent to which shared or EAA-specific mechanisms facilitate diet-associated phenotypes remains unclear. Here, we compared the physiological and molecular effects of dietary methionine, leucine, or isoleucine depletion (Met-D, Leu-D, and Ile-D) in C57BL/6J mice. Each diet elicited responses not phenocopied by mTORC1 inhibition, including reduced fat mass and hepatic amino acid catabolism. Ile-D yielded additional distinct responses, highlighted by histone H2A/H4 hypoacetylation and maintained hepatic acetyl-CoA levels despite downregulated FA {beta}-oxidation. Multi-Omics Factor Analysis of 14,139 data points objectively affirmed Ile-D phenotypes are distinct from Met-D or Leu-D and identified several metabolic and chromatin features as primary discriminators. Metabolic and epigenetic responses to Ile-D were recapitulated in vitro, suggesting underlying mechanisms represent fundamental cellular properties. Together, these results demonstrate EAAs can stimulate unique phenotypes and highlight distinct molecular mechanisms by which EAAs may inform metabolic health.

biochemistry↗

bioRxiv2023

Role of Dusp5 KO on Vascular Properties of Middle Cerebral Artery in Rats

Vascular aging influences hemodynamics, elevating risks for vascular diseases and dementia. We recently demonstrated that knockout (KO) of Dusp5 enhances cerebral and renal hemodynamics and cognitive function. This improvement correlates with elevated pPKC and pERK1/2 levels in the brain and kidneys. Additionally, we observed that Dusp5 KO modulates the passive mechanical properties of cerebral and renal arterioles, associated with increased myogenic tone at low pressure, enhanced distensibility, greater compliance, and reduced stiffness. The present study evaluates the structural and mechanical properties of the middle cerebral artery (MCA) in Dusp5 KO rats. We found that vascular smooth muscle cell layers and the collagen content in the MCA wall are comparable between Dusp5 KO and control rats. The internal elastic lamina in the MCA of Dusp5 KO rats exhibits increased thickness, higher autofluorescence intensity, smaller fenestrae areas, and fewer fenestrations. Despite an enhanced myogenic response and tone of the MCA in Dusp5 KO rats, other passive mechanical properties, such as wall thickness, cross-sectional area, wall-to-lumen ratio, distensibility, incremental elasticity, circumferential wall stress, and elastic modulus, do not significantly differ between strains. These findings suggest that while Dusp5 KO has a limited impact on altering the structural and mechanical properties of MCA, its primary role in ameliorating hemodynamics and cognitive functions is likely attributable to its enzymatic activity on cerebral arterioles. Further research is needed to elucidate the specific enzymatic mechanisms and explore potential clinical applications in the context of vascular aging.

physiology↗

bioRxiv2023

Development of a human heart-on-a-chip model using induced pluripotent stem cells, fibroblasts and endothelial cells

In recent years, research on organ-on-a-chip technology has been flourishing, particularly for drug screening and disease model development. Fibroblasts and vascular endothelial cells engage in crosstalk through paracrine signaling and direct cell-cell contact, which is essential for the normal development and function of the heart. Therefore, to faithfully recapitulate cardiac function, it is imperative to incorporate fibroblasts and vascular endothelial cells into a heart-on-a-chip model. Here, we report the development of a human heart-on-a-chip composed of induced pluripotent stem cell (iPSC)-derived cardiomyocytes, fibroblasts, and vascular endothelial cells. Vascular endothelial cells cultured on microfluidic channels responded to the flow of culture medium mimicking blood flow by orienting themselves parallel to the flow direction, akin to in vivo vascular alignment in response to blood flow. Furthermore, the flow of culture medium promoted stronger junction formation between vascular endothelial cells, as evidenced by CD31 staining and lower apparent permeability. The triculture condition of iPSC-derived cardiomyocytes, fibroblasts, and vascular endothelial cells resulted in higher expression of the ventricular cardiomyocyte marker IRX4 and increased contractility compared to the biculture condition with iPSC-derived cardiomyocytes and fibroblasts alone. Such triculture-derived cardiac tissues exhibited cardiac responses similar to in vivo hearts, including an increase in heart rate upon noradrenaline administration. In summary, we have achieved the development of a heart-on-a-chip composed of cardiomyocytes, fibroblasts, and vascular endothelial cells that mimics in vivo cardiac behavior.

cell biology↗

bioRxiv2023

Modulation of Alzheimer's Disease Brain Pathology in Mice by Gut Bacterial Deletion: The Role of Il-17a and Microglial MyD88

Gut bacteria regulate brain pathology of Alzheimers disease (AD) patients and animal models; however, the underlying mechanism remains unclear. In this study, 3-month-old APP-transgenic female mice with and without knock-out of Il-17a gene, or haploinsufficiency of MyD88 in microglia were treated with antibiotics-supplemented or normal drinking water for 2 months. Antibiotic treatment eradicated gut bacteria, particularly in the phyla Bacteroidetes and Firmicutes, and reduced Il-17a-expressing CD4-positive T lymphocytes. Deletion of gut bacteria inhibited inflammatory activation in the brain and microglia, and reduced cerebral A{beta} levels in APP-transgenic mice, which was abolished by deficiency of Il-17a or haploinsufficiency of MyD88 in microglia. As possible mechanisms regulating A{beta} pathology, deletion of gut bacteria inhibited {beta}-secretase activity and increased the expression of Abcb1 and Lrp1 in the brain or at the blood-brain barrier, which were also reversed by the absence of Il-17a. Interestingly, a crossbreeding experiment between APP-transgenic mice and Il-17a knockout mice further showed that deficiency of Il-17a had already increased Abcb1 and Lrp1 expression at the blood-brain barrier. Thus, deletion of gut bacteria attenuates inflammatory activation and amyloid pathology in APP-transgenic mice via Il-17a and microglial MyD88-involved signalling pathways. Our study contributes to a better understanding of the gut-brain axis in AD pathophysiology.

neuroscience↗

bioRxiv2023

Spatially resolved molecular and cellular atlas of the mouse brain

A comprehensive atlas of genes, cell types, and their spatial distribution across a whole mammalian brain is fundamental for understanding function of the brain. Here, using snRNA-seq and Stereo-seq techniques, we generated a mouse brain atlas with spatial information for 308 cell clusters with single-cell resolution involving over 6 million cells as well as for 29,655 genes. We have identified new astrocyte clusters, and demonstrated that distinct cell clusters exhibit preference for cortical subregions. In addition, we identified 155 genes exhibiting regional specificity in the brainstem, and 513 long non-coding RNA exhibited regional specificity in the adult brain. Parcellation of brain regions based on spatial transcriptomic information showed large overlap with that by traditional method. Furthermore, we have uncovered 411 transcription factor regulons with spatiotemporal specificity during development. Thus, our study has discovered genes and regulon with spatiotemporal specificity, and provided a high-resolution spatial transcriptomic atlas of the mouse brain.

neuroscience↗

bioRxiv2023

The SCN8A p.(Gly1625Arg) variant associated with developmental and epileptic encephalopathy causes complex biophysical changes and reduced neuronal firing

BackgroundMutations in the SCN8A gene, encoding the voltage-gated sodium channel NaV1.6, lead to various neurodevelopmental disorders. The SCN8A p.(Gly1625Arg) mutation (NaV1.6G1625R) was identified in a patient diagnosed with developmental epileptic encephalopathy (DEE), presenting with moderate epilepsy and severe developmental delay. MethodsWe performed biophysical and neurophysiological characterizations of NaV1.6G1625R in Neuro-2a cells and cultured hippocampal neurons, followed by computational modeling to determine the impact of its heterozygous expression on cortical neuron function. FindingsVoltage-clamp analyses of NaV1.6G1625R demonstrated a heterogeneous mixture of gain-and loss-of-function properties, including reduced current amplitudes, a marked increase in the time constant of fast voltage-dependent inactivation and a depolarizing shift in the voltage dependence of inactivation. Recordings in transfected cultured neurons showed that these intricate biophysical properties had a minor effect on neuronal excitability when firing relayed on both endogenous and transfected NaV channels. Conversely, there was a marked reduction in the number of action potentials when firing was driven by the transfected mutant NaV1.6 channels. Computational modeling of mature cortical neurons further revealed a mild reduction in neuronal firing when mimicking the patients heterozygous NaV1.6G1625R expression. Structural modeling of NaV1.6G1625R and a double-mutant cycle analysis suggested the possible formation of pathophysiologically-relevant cation-{pi} interaction between R1625 and F1588, affecting the voltage dependence of inactivation. InterpretationOur analyses demonstrate a complex combination of gain and loss-of-function changes resulting in an overall mild reduction in neuronal firing, related to a perturbed interaction network within the voltage sensor domain. FundingISF, DFG, BMBF, The Hartwell Foundation, ICRF, ISCA Research in contextO_ST_ABSEvidence before this studyC_ST_ABSMutations in the SCN8A gene, encoding the voltage-gated sodium channel NaV1.6, result in multiple neurodevelopmental syndromes ranging from benign epilepsy to developmental delay without epilepsy or developmental epileptic encephalopathy (DEE). Recent studies established that most DEE-causing SCN8A mutations result in a gain of function effect. However, several SCN8A mutations that diverge from this pattern were described. Added value of this studyWe performed a multi-tiered study of the SCN8A p.(Gly1625Arg) variant (NaV1.6G1625R), identified in a patient with atypical DEE presentation, featuring moderate epilepsy that is well controlled by the sodium channel blocker Oxcarbazepine, along with profound stagnated developmental delay. This variant is positioned within the S4 segment of domain IV, a critical region for NaV1.6 function, where pathogenic variants were shown to cause either a loss or gain of channel function, but often with mixed biophysical alterations. Our biophysical characterization of NaV1.6G1625R in Neuro-2a cells demonstrated complex gain-and loss-of-function properties, cumulating to reduced firing in cultured hippocampal neurons and computational modeling of mature cortical neurons, demonstrating an overall loss-of-function effect. Implications of all the available evidenceOur results indicate the necessity for combined biophysical and neuronal characterization of individual SCN8A variants, especially those presenting with complex biophysical changes or atypical clinical presentation. Moreover, while sodium channel blockers are the recommended treatment for SCN8A variants associated with gain-of-function, additional considerations may be needed for DEE-causing variants that are associated with mild loss-of-function.

physiology↗