Biology subjects

Das, A.

Publications and source records attributed to Das, A..

At least 163 records · Page 9Linked to original sources

bioRxiv2022

Patterns of secondary invasion in the understory of exotic, invasive timber stands

Current climate and land cover change threaten global mountaintops with increased spread of invasive species. Long-established plantations of exotic and invasive trees on these mountaintops can alter their surroundings, further increasing invader-facilitated or secondary invasion. Identifying the ecological conditions that promote such specific associations can help develop better management interventions. The Western Ghatss Shola Sky Islands (>1400m MSL) host vast stretches of exotic and invasive tree plantations that sustain colonisation of other invasive woody, herbaceous and fern species in their understories. Here we analysed vegetation and landscape variables from 232 systematically-placed plots in randomly selected grids using NMDS and Phi Coefficient approaches, to examine patterns of association (positive interactions) between secondary understory invasive species with specific exotic and invasive overstory species. We also conducted GLMM with zero inflation to determine the influence of environmental variables where such associations occur. We find that secondary invasion of multiple species under the canopy of other exotic invasives is widespread across the Shola Sky Islands. Stands of Eucalyptus host the colonisation of 70% of non-native invasive species surveyed across the Shola Sky Islands. In particular, Lantana camara invasion is strongly associated with Eucalyptus stands. We also found that climatic variables affect the colonisation of understorey woody invasive species, while invasion by exotic herbaceous species is associated with the density of road networks.. Canopy cover impacts all invasives negatively, while incidence of fire was negatively associated with invasion by Lantana spp and the Pteridium spp. While the restoration of natural habitats largely targets the highly invasive Acacia, less invasive Eucalyptus and Pine are often not included. Our study suggests that retaining such exotic species in natural habitats, particularly protected areas, can hinder ongoing restoration efforts by facilitating further invasions by multiple woody and herbaceous species.

ecology↗

bioRxiv2022

Electron Videography of a Lipid-Protein Tango

Biological phenomena ranging from enzymatic catalysis to synaptic transmission find their origins in the morphological fluctuations of biomolecules and biomolecular assemblies in liquid water. However, directly imaging these nanoscopic dynamics without probes or labels has been a fundamental methodological challenge. Here we developed an approach for molecular videography--combining liquid-phase transmission electron microscopy with molecular modelling--with which we filmed the nanoscale morphological fluctuations of individual, freely suspended, and unlabelled membrane protein nanodiscs in liquid. These unprecedented observations enabled us to quantify fingerprints of nanoscale lipid-protein interactions directly, revealing that nanodisc shape undulations are defined by the molecular mechanics of encircling scaffold proteins, whereas lipid interactions with a membrane protein reach across surprisingly long ranges to delineate dynamically modified membrane domains and increase nanodisc stability. Overall, this work illustrates an experimental approach to image, quantify, and understand biomolecular dynamics at the nanometre scale.

biophysics↗

bioRxiv2022

Equalizing epigenetically imprinted centromeres in early mammalian embryos

The CENP-A histone variant epigenetically defines centromeres, where its levels and locations are precisely maintained through mitotic cell divisions. However, differences in centromere CENP-A propagation in soma versus female/male germline remains poorly understood. Here, we generated CenpamScarlet mice and followed CENP-A dynamics in gametes, zygotes, and embryos. We found that, unlike somatic cells, progenitor female and male germ cells carry high centromeric CENP-A levels that decrease upon terminal differentiation. The reduction in CENP-A is differentially regulated between sexes, resulting in a ten-fold higher level in oocytes compared to sperm. In the zygote, the parent-of-origin CENP-A asymmetry is equalized prior to initial S-phase by redistribution of nuclear CENP-A from maternal to paternal chromosomes. Redistribution of CENP-A requires both CDK1/2 and PLK1 centromeric machinery. These experiments provide direct evidence for resetting of epigenetically imprinted centromeres in early pronuclear stage embryos and imply a mechanism to sense the non-equivalency of parental chromosomes. HighlightsO_LIIncreased CENP-A density at centromeres is a conserved property of germline stem cells while CENP-A reduction is coincident with germ cell differentiation C_LIO_LIPaternal and maternal CENP-A containing nucleosomes are intergenerationally inherited C_LIO_LICENP-A density at centromeres differs between male and female mature gametes C_LIO_LIUpon fertilization, maternal nuclear CENP-A is redistributed to equalize with parental CENP-A C_LIO_LICENP-C and MIS18BP1 are asymmetrically enriched in the parental pronuclei in accordance with CENP-A asymmetry. C_LIO_LILicensing for centromere equalization begins before zygotic DNA replication C_LI

developmental biology↗

bioRxiv2022

TWO DISULFIDE-REDUCING PATHWAYS ARE REQUIRED FOR THE MATURATION OF PLASTID C-TYPE CYTOCHROMES IN CHLAMYDOMONAS REINHARDTII

AO_SCPLOWBSTRACTC_SCPLOWIn plastids, conversion of light energy into ATP relies on cytochrome f, a key electron carrier with a heme covalently attached to a CXXCH motif. Covalent heme attachment requires reduction of the disulfide bonded CXXCH motif by CCS5 and CCS4, a protein of unknown function. CCS5 receives electrons from the oxido-reductase CCDA at the thylakoid membrane. In Chlamydomonas reinhardtii, loss of CCS4 or CCS5 function yields a partial cytochrome f assembly defect. Here we report that the {Delta}ccs4ccs5 double mutant displays a synthetic photosynthetic defect due to a complete loss of holocytochrome f assembly, a phenotype that can be chemically corrected by reducing agents. In {Delta}ccs4, the CCDA protein accumulation is decreased, indicating that one function of CCS4 is to stabilize CCDA. Dominant suppressor mutations mapping to the CCS4 gene were identified in photosynthetic revertants of the {Delta}ccs4ccs5 mutants. The suppressor mutations correspond to changes in the stroma-facing domain of CCS4 and restore holocytochrome f assembly above the residual levels detected in {Delta}ccs5. Because disulfide reduction via CCS5 no longer takes place in {Delta}ccs5, we hypothesize the suppressor mutations enhance the supply of reducing power independently of CCS5, uncovering the participation of CCS4 in a distinct redox pathway. CCS4-like proteins occur in the green lineage and are related to mitochondrial COX16, a protein involved in a disulfide reducing pathway. We discuss the operation of two pathways controlling the redox status of the heme-binding cysteines of apocytochrome f and the possible function of CCS4 as a shared component between the two pathways. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=163 SRC="FIGDIR/small/512171v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@7f496forg.highwire.dtl.DTLVardef@ae5229org.highwire.dtl.DTLVardef@942b20org.highwire.dtl.DTLVardef@19b7576_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical abstract.C_FLOATNO The {Delta}ccs4ccs5 mutant exhibits a photosynthetic growth defect due to a complete loss of cytochrome c assembly. Reduction of apocytochrome f in the thylakoid lumen requires the provision of reducing power through two different pathways, pathway 1 and 2. CCDA and CCS5, components of pathway 1, deliver electrons from stroma to apocytochrome f via thiol - disulfide exchange. CCS4 is involved in pathway 1 by stabilizing CCDA, but also functions through a CCS5 - independent pathway (pathway 2). In the absence of CCS5, gain - of - function mutations in the C terminus of CCS4 (indicated by a yellow star) enhance the delivery of reducing power either via CCDA or independently of CCDA to yet-to-be-discovered reductases C_FIG

genetics↗

bioRxiv2022

Genome-wide investigation of Cytochrome P450 superfamily of Aquilaria agallocha: association with terpenoids and phenylpropanoids biosynthesis

P450 superfamily (CYPs) has been known as contributors to the metabolites diversity and their promiscuous nature has led to the flexibility in substrate specificity and functional diversity. Current study was designed to investigate CYPs in the genome of an agarwood producing plant species named Aquilaria agallocha. Agarwood, the resinous fragrant wood with numerous phytochemicals, produced when an Aquilaria plant respond to wound and microbial infection. These chemicals are of great interest to industries ascribing it a high economic value. However, the pathways for the biosynthesis of these metabolites have not been studied in context of Aquilaria CYPs. We identified 136 A. agallocha CYP proteins from the genome, characterized and classified them into 8 clans and 38 families. Functional analysis unveiled their participation in terpenoids, phenolics, flavonoids and other valuable metabolites biosynthesis. Conserved motifs were detected and evolutionary analysis revealed duplicated and orthologous pairs. Potential members for the biosynthesis of sesquiterpenoids and phenylpropanoids reported in Aquilaria and agarwood were elucidated and validated through expression profiles in stress induced callus tissues and infected Aquilaria tress. This study provides a strong foundation for biochemical characterization of Aquilaria CYPs which will aid heterologous production of valuable phytochemicals and untangle molecular mechanism of agarwood formation.

plant biology↗

bioRxiv2022

Cryo-EM structure of the Agrobacterium tumefaciens type IV secretion system-associated T-pilus reveals stoichiometric protein-phospholipid assembly

Agrobacterium tumefaciens is a plant pathogen that causes crown gall disease by the horizontal transfer of oncogenic DNA that is integrated into the hosts genome. The conjugation is mediated by the conjugative VirB/D4 type 4 secretion system (T4SS). A. tumefaciens T4SS assembles an extracellular filament, the T-pilus, that is involved in the formation of a mating pair between A. tumefaciens and the recipient plant cell by a not fully understood mechanism. Here, we present a 3 [A] cryo-EM structure of the T-pilus, solved by helical reconstruction. Our structure reveals that the T-pilus comprises the major pilin protein VirB2 and phosphatidylglycerol (PG) phospholipid at a 1:1 stoichiometric ratio with 5-start helical symmetry. We further show that PG-headgroups and the positively charged Arg 91 residues of VirB2 protomers form extensive electrostatic interactions in the lumen of the T-pilus. Mutagenesis of Arg 91 destabilized the VirB2 protein and completely abolished pilus formation. While our T-pilus structure shows architectural similarity with previously published conjugative pili structures, positively charged sidechains protrude into the lumen and the lumen is narrower, raising questions whether the T-pilus is a conduit for ssDNA transfer. We also show that the VirB2 subunits in T-pilus filament are not cyclic, as previously thought.

microbiology↗

bioRxiv2022

Conformational Changes Regulate Metal Coordination in the Catalytic Sites of Cas9

The control of CRISPR-Cas9 activities plays an essential role in its safe adoption for clinical and research applications. Previous studies have identified conformational dynamics of Cas9 as a key regulatory element for its enzymatic activity. The molecular basis for how conformations influence the catalytic processes at both nuclease domains, however, remains elusive. Here we present well-resolved cryo-EM structures of the active Acidothermus cellulolyticus Cas9 (AceCas9) complexes representing pre-cleavage (2.9 [A]), two reaction intermediate (2.2 [A] and 2.4 [A]) and two post-cleavage (2.6 [A] and 2.7 [A]) states that reveal active site rearrangement during DNA binding and phosphodiester bond breakage by Cas9. Strikingly, large domain rearrangements in Cas9 triggered by the cognate DNA result in subtle changes in active sites that facilitate coordination of metal ions required for catalysis. The two reaction intermediate structures further reveal small oscillations in domain conformations, which alternates the reactive states of the two catalytic centers, thereby coupling cleavage of the two DNA strands. Consistent with the roles of conformations in organizing the active sites, adjustments of metal coordination ligands lead to altered metal specificity.

biochemistry↗

bioRxiv2022

Photoelectrochemical imaging of action potentials for single cardiomyocytes through contact force manipulation of organoids

Accurate monitoring of cardiomyocyte action potentials (APs) is essential to understand disease propagation and for trials of novel therapeutics. Patch clamp techniques offer gold standard measurements in this field, but are notoriously difficult to operate and only provide measurements of a single cell. Here we propose photoelectrochemical imaging (PEI), in conjunction with a setup for controlling the contact force between the cardiomyocyte organoids and the sensor surface, for measuring APs with high sensitivity. The method was validated through the use of drugs, and the results successfully visualized the expected electrophysiological changes to the APs. PEI allows for several cells to be monitored simultaneously, opening further research to the electrophysiological interactions of adjoining cells. This method expands the applications of PEI to three-dimensional geometries and provides the fields of stem cell research, drug trials and heart disease modelling with an invaluable tool to further investigate the role of APs.

biophysics↗

bioRxiv2022

Nodulin 16 of Lotus japonicus (Nlj16) regulates the recruitment of Leghemoglobin (LegH) to the infected nodule cell membrane during symbiotic nitrogen fixation

Nitrogenase that catalyses anaerobic symbiotic nitrogen fixation (SNF) in legumes is synthesized by rhizobium. Legume root cells express nodulin proteins after infection with rhizobia. Nodulins have been classified as early and late, reflecting the time points of their expression. Leghemoglobin (LegH), which is a classic example of a late nodulin, sequesters oxygen inside the nodule to protect the nitrogenase from oxygen toxicity to sustain SNF. Previous data from our laboratory demonstrated that phosphorylated LegH at S45 showed compromised oxygen sequestration in vitro due to structural disruption of the porphyrin binding pocket responsible for its oxygen binding. Moreover, we have demonstrated by using co-immunoprecipitation that LegH interacts both in vitro with Nodulin 16 of Lotus japonicus (Nlj16), another late nodulin. Fluorescence Immunohistochemistry (IHC) data shows that both LegH and Nlj16 are localized in the membrane and cytosol of infected cells. Notably, serine phosphorylation of LegH and interaction of Nlj16 with LegH respectively reduces and increases its in vitro oxygen sequestration ability. In this report, to further elucidate the spatio-temporal regulation of this interaction, we generated hairy root transgenic Lotus japonicus plants where Nlj16 has been knocked down by using siRNA. Most interestingly, our data shows that the membrane localization of LegH is obliterated in the Nlj16 knocked-down root cells infected with the cognate Rhizobia suggesting a distinct role of Nlj16 in its recruitment to the membrane of nodule cells.

plant biology↗

bioRxiv2022

Selection of an Ideal Machine Learning Framework for Predicting Perturbation Effects on Network Topology of Bacterial KEGGPathways

Biological networks for bacterial species are used to assign functional information to newly sequenced organisms but network quality can be largely affected by poor gene annotations. Current methods of gene annotation use homologous alignment to determine orthology, and have been shown to degrade network accuracy in non-model bacterial species. To address these issues in the KEGG pathway database, we investigated the ability for machine learning (ML) algorithms to re-annotate bacterial genes based on motif or homology information. The majority of the ensemble, clustering, and deep learning algorithms that we explored showed higher prediction accuracy than CD-hit in predicting EC ID, Map ID, and partial Map ID. Motif-based, machine-learning methods of annotation in new species were more accurate, faster, and had higher precisionrecall than methods of homologous alignment or orthologous gene clustering. Gradient boosted ensemble methods and neural networks also predicted higher connectivity of networks, finding twice as many new pathway interactions than blast alignment. The use of motif-based, machine-learning algorithms in annotation software will allow researchers to develop powerful network tools to interact with bacterial microbiomes in ways previously unachievable through homologous sequence alignment. CCS CONCEPTS* Applied computing [->] Computational biology; Life and medical sciences; Bioinformatics; * Computing methodologies [->] Machine learning algorithms; Machine learning approaches. ACM Reference FormatMichael Robben, Mohammad Sadegh Nasr, Avishek Das, Manfred Huber, Justyn Jaworski, Jon Weidanz, and Jacob Luber. 2022. Selection of an Ideal Machine Learning Framework for Predicting Perturbation Effects on Network Topology of Bacterial KEGG Pathways. In The 13th ACM Conference on Bioinformatics, Computational Biology, and Health Informatics, August 07-10, 2022, Chicago, IL. ACM, New York, NY, USA, 11 pages. https://doi.org/XXXXXXX.XXXXXXX

bioinformatics↗

bioRxiv2022

Enhanced mitochondrial biogenesis promotes cell survival in human stem cell derived retinal ganglion cells of the central nervous system

Mitochondrial dysfunctions are widely afflicted in central nervous system (CNS) disorders with minimal understanding on how to improve mitochondrial homeostasis to promote neuroprotection. Here we used human stem cell differentiated retinal ganglion cells (hRGCs) of the CNS, which are highly sensitive towards mitochondrial dysfunctions due to their unique structure and function, to identify mechanisms for improving mitochondrial quality control (MQC). We found that hRGCs are efficient in maintaining mitochondrial homeostasis through rapid degradation and biogenesis of mitochondria under acute damage. Using a glaucomatous Optineurin mutant (E50K) stem cell lines, we saw that at basal level mutant hRGCs possess less mitochondrial mass and suffer mitochondrial swelling due to excess ATP production load. Activation of mitochondrial biogenesis through pharmacological inhibition of the Tank binding kinase 1 (TBK1) restored energy homeostasis, mitigated mitochondrial swelling with neuroprotection against acute mitochondrial damage for glaucomatous E50K hRGCs, revealing a novel neuroprotection mechanism.

neuroscience↗

bioRxiv2022

Molecular Mechanism of Active Cas7-11 in Processing CRISPR RNA and Interfering Target RNA

Cas7-11 is a Type III-E CRISPR Cas effector that confers programmable RNA cleavage and has potential applications in RNA interference. Cas7-11 encodes a single polypeptide containing four Cas7- and one Cas11-like segments that obscures the distinction between the multi-subunit Class 1 and the single-subunit Class-2 CRISPR-Cas systems. We report a cryo-EM structure of the active Cas7-11 from Desulfonema ishimotonii (DiCas7-11) that reveals the molecular basis for RNA processing and interference activities. DiCas7-11 arranges its Cas7- and Cas11-like domains in an extended form that resembles the backbone made up by four Cas7 and one Cas11 subunits in the multi-subunit enzymes. Unlike the multi-subunit enzymes, however, the backbone of DiCas7-11 contains evolutionarily different Cas7 and Cas11 domains, giving rise to their unique functionality. The first Cas7-like domain nearly engulfs the last 15 direct repeat nucleotides and is responsible for processing and recognition of the CRISPR RNA. Whereas both the second and the third Cas7-like domains mediate target RNA cleavage, they differ in metal requirement for catalysis. The long variable insertion to the fourth Cas7-like domain has little impact to RNA processing or targeting, suggesting the possibility for engineering a compact and programmable RNA interference tool. One Sentence SummaryStructures of Cas7-11 reveal the molecular basis for processing CRISPR RNA and for cleaving target RNA.

biophysics↗

bioRxiv2022

Recording large-scale, cellular-resolution neuronal activity from freely-moving mice

Current methods for recording large-scale neuronal activity from behaving mice with single-cell resolution require either fixing the mouse head under a microscope or attachment of a recording device to the animals skull. Both of these options significantly affect the animal behavior and hence also the recorded brain activity patterns. Here, we introduce a new method to acquire snapshots of single-cell cortical activity maps from freely-moving mice using a calcium sensor called CaMPARI. CaMPARI has a unique property of irreversibly changing its color from green to red inside active neurons when illuminated with 400nm light. We capitalize on this property to demonstrate cortex-wide activity recording without any head fixation or attachment of a miniaturized device to the mouses head. Multiple cortical regions were recorded while the mouse was performing a battery of behavioral and cognitive tests. We identified task-dependent activity patterns across motor and somatosensory cortices, with significant differences across sub-regions of the motor cortex. This new CaMPARI-based recording method expands the capabilities of recording neuronal activity from freely-moving and behaving mice under minimally-restrictive experimental conditions and provides large-scale volumetric data that are not accessible otherwise.

neuroscience↗

bioRxiv2022

Site-specific decreases in DNA methylation in replicating cells following exposure to oxidative stress

Oxidative stress is a common feature of inflammation-driven cancers, and promotes genomic instability and aggressive tumour phenotypes. It is known that oxidative stress transiently modulates gene expression through the oxidation of transcription factors and associated regulatory proteins. Activated neutrophils produce hypochlorous acid and chloramines that can disrupt DNA methylation via methionine oxidation. The goal of the current study was to determine whether chloramine exposure results in sequence-specific modifications in DNA methylation that enable long-term alterations in transcriptional output. Proliferating Jurkat T-lymphoma cells were exposed to sublethal doses of glycine chloramine and differential methylation patterns were compared using Illumina EPIC 850K bead chip arrays. There was a substantial genome-wide decrease in methylation four hours after exposure that correlated with altered RNA expression for 24 and 48 hours, indicating sustained impacts on exposed cells. A large proportion of the most significant differentially methylated CpG sites were situated towards chromosomal ends, suggesting that these regions are most susceptible to inhibition of maintenance DNA methylation. This may contribute to epigenetic instability of chromosomal ends in rapidly dividing cells, with potential implications for the regulation of telomere length and cellular longevity.

molecular biology↗

bioRxiv2022

Active emulsions in living cell membranes driven by contractile stresses and transbilayer coupling

The spatiotemporal organisation of proteins and lipids on the cell surface has direct functional consequences for signaling, sorting and endocytosis. Earlier studies have shown that multiple types of membrane proteins including transmembrane proteins that have cytoplasmic actin binding capacity and lipid-tethered GPI-anchored proteins (GPI-APs) form nanoscale clusters driven by active contractile flows generated by the actin cortex. To gain insight into the role of lipids in organizing membrane domains in living cells, we study the molecular interactions that promote the actively generated nanoclusters of GPI-APs and transmembrane proteins. This motivates a theoretical description, wherein a combination of active contractile stresses and transbilayer coupling drive the creation of active emulsions, mesoscale liquid ordered (lo) domains of the GPI-APs and lipids, at temperatures greater than equilibrium lipid-phase segregation. To test these ideas we use spatial imaging of homo-FRET combined with local membrane order and demonstrate that mesoscopic domains enriched in nanoclusters of GPI-APs are maintained by cortical actin activity and transbilayer interactions, and exhibit significant lipid order, consistent with predictions of the active composite model.

cell biology↗

bioRxiv2022

B cell receptor repertoire analysis unveils dynamic antibody response and severity markers in COVID-19 patients

Humoral and cell mediated immunity are critical against viral infections. The knowledge of composition, diversity, gene usage of the B cell repertoires helps in determining the immune response to SARS-CoV-2 infection. Examining B cell response provides insights on therapeutic antibodies, disease severity markers and aids in predicting vaccine response. We have analyzed public domain immunoglobulin sequencing data from PBMCs of SARS-CoV-2 infected individuals to gain a better understanding of B cell repertoire in patients. Public clonotypes showed increased usage of IGHV3, IGHV4, IGKV1, IGKV3, IGLV3 and IGLV2 family genes during the acute phase infection. Identical CDR3 sequences were identified for heavy (H), kappa (K) and lambda (L) chains across individuals, indicating the convergence of B cell selection during SARS-CoV-2 infection. While the immune repertoire dynamically changed over the course of convalescence, there were persistent clones across early and late timepoints. The diversity of antibody repertoire, measured by Shannon-Weiner diversity index for H and K chains, reduced during the acute phase of infection. In addition, the repertoire diversity was low in severe patients compared to patients with mild or moderate symptoms. Increased usage of IGHV4-59 gene was observed in COVID-19 patients with severe symptoms requiring ventilator support at 2 weeks and 3 weeks post symptom onset. IGHV4-59 is reported to have rheumatoid factor (RF) activity with high affinity for IgG and the elevated level of IGHV4-59 provides a potential mechanism for the increased autoimmune responses in severe patients. Correlation of the clinical features with the B cell receptor repertoire dynamics elucidated public antibody clonotypes and disease severity markers for COVID-19.

immunology↗

bioRxiv2022

Activation of the neonatal immune system in healthy neonates within hours of birth.

It is now established that immune maturation occurs along a defined trajectory in the weeks and months after birth, but the immediate changes that occur within immune cells following birth is less clear. In this study, we monitored the immune profile of neonates via analysis of paired samples (n= 28) of cord blood and heel prick blood taken at varying times post term delivery by caesarean section. This paired approach accounted for the between-subject variability often observed over the first week of life. We identified rapid changes in immune cell populations within hours of birth. Specifically, we observed increased proliferation in effector T cells (but not regulatory T cells) that exhibited an increase in cytokine producing ability and also an increase in the percentage of CD3 T cells over this short time frame. This indicates that the mobilisation of the immune system is immediate post birth, presumably as a response to sudden exposure to the external environment, antigen or stress. Hence, immune development may start to occur more rapidly than previously proposed and as such, to study this trajectory, blood sampling should begin as soon after birth as possible.

immunology↗

bioRxiv2022

Conserved basal lamina proteins, laminin and nidogen, are repurposed to organize mechanosensory complexes responsible for touch sensation.

The sense of touch is conferred by the conjoint function of somatosensory neurons and skin cells. These cells meet across a gap filled by a basal lamina, an ancient structure found in metazoans. Using Caenorhabditis elegans, we show that membrane-matrix complexes containing laminin, nidogen, and the MEC-4 mechano-electrical transduction channel reside at this interface and are instrumental for proper touch sensation. These complexes fail to coalesce in touch-insensitive extracellular matrix mutants and in dissociated neurons. MEC-4, but not laminin or nidogen, is destabilized by point mutations in the C-terminal Kunitz domain of the extracellular matrix component, MEC-1. Thus, neuron-epithelial cell interfaces are instrumental in mechanosensory complex assembly and function. Loss of nidogen reduces the density of mechanoreceptor complexes and the amplitude of the touch-evoked currents they carry. These findings imply that somatosensory neurons secrete proteins that actively repurpose the basal lamina to generate special-purpose mechanosensory complexes responsible for vibrotactile sensing.

cell biology↗