Biology subjects

Suzuki, I.

Publications and source records attributed to Suzuki, I..

18 recordsLinked to original sources

bioRxiv2026

Coupled transcriptomic divergence establishes a human-specific synaptic glial precursor state

The mammalian cerebral cortex is built from a conserved developmental program, yet exhibits profound species-specific complexity. To decode the regulatory changes driving human brain evolution, we reconstructed and aligned continuous single-cell differentiation trajectories across the developing human, macaque, mouse, and ferret cortices. This comparative framework revealed a fundamental principle of transcriptomic evolution during mammalian cortical development: while stable expression is the mammalian default, genes that diverge strictly shift their allocation to cell differentiation trajectories and developmental timing in tandem. By isolating these coupled regulatory shifts to the human lineage, we revealed that a canonical synaptic gene network uniquely redeployed into early human oligodendrocyte precursor cells (OPCs). Human, chimpanzee, and gorilla cortical organoids confirmed that this neuron-like OPC state is an exclusively human innovation. Spatial transcriptome analysis found that these specialized OPCs engage adjacent neural progenitors (outer radial glia) via synaptic-adhesion signaling during neurogenetic period. These findings demonstrate that this coupled spatiotemporal rewiring establishes novel developmental microenvironments, providing a discrete molecular engine for human cortical evolution.

genomics↗

bioRxiv2026

Combination siRNA delivery as a therapeutic strategy for ADPKD

Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic kidney disease worldwide, characterized by progressive cyst growth and inflammation, yet effective targeted therapies remain limited. Here we show that TMEM16A and MCP-1, key mediators of cyst-lining epithelial expansion and inflammatory macrophage recruitment respectively, are consistently upregulated in cyst-lining collecting duct (CD) epithelia across murine, porcine, and human ADPKD models. In human ADPKD patient cells, although individual silencing of TMEM16A or MCP-1 transcripts reduced cyst growth, combined silencing produced superior therapeutic efficacy, establishing the rationale for evaluating dual-target delivery. To achieve dual gene silencing in the kidneys, we delivered Tmem16a and Mcp-1 siRNA using peptide amphiphile micelles (PAMs), an ultrasmall nanoparticle platform that enables efficient renal targeting. To redirect siRNA-loaded PAMs to CD epithelia, we functionalized their surface with a CD-targeting peptide (CDM), which enabled preferential accumulation in cyst-lining CD epithelia. In an inducible Pkd1-deficient mouse model, co-delivery of CDMs loaded with Tmem16a and Mcp-1 siRNA reduced kidney enlargement, cystic burden, tubular injury, and macrophage infiltration, with efficacy exceeding non-targeted siRNA delivery at equivalent doses. CDM demonstrated enhanced uptake in primary human ADPKD patient-derived CD cells and dual gene silencing reduced target gene expression and cyst expansion, establishing translational relevance. These findings establish CD peptide-functionalized micelles as a route to cell-type-selective RNAi in the kidney, delivering siRNA to cyst-lining CD cells. Furthermore, because both targets, TMEM16A and MCP-1, are transcribed within CD cells, our siRNA-loaded CD-targeting micelles silence two drivers of cyst expansion, and their simultaneous suppression represents an effective therapeutic strategy for ADPKD.

bioengineering↗

bioRxiv2026

Collecting Duct-Targeted Lipid Nanoparticles Deliver Pkd2 mRNA to Restore Polycystin-2 and Attenuate ADPKD

Autosomal dominant polycystic kidney disease (ADPKD), a leading genetic cause of kidney failure, is caused by mutations in the PKD1 or PKD2 genes, resulting in functional polycystin 1 (PC1) or polycystin 2 (PC2) deficiency, and is characterized by progressive cyst expansion in the kidneys. However, no approved therapy directly restores polycystin expression, and current treatments target downstream pathways rather than the genetic defect. Gene replacement therapy offers a direct route to functional rescue, but efficient delivery to cyst-lining renal epithelia remains a major barrier. To meet this challenge, we developed a lipid nanoparticle (LNP) that incorporates a collecting duct (CD) targeting peptide (CD LNPs) to enable delivery of Pkd2 mRNA (CD-mPkd2) to renal CD epithelia, the predominant site of cyst origin. CD LNPs increased renal accumulation and targeted CD cells in vivo, outperforming non-targeted formulations. In a Pkd2-deficient mouse model, repeated administration of CD-mPkd2 induced reversal of established cystic disease, restored renal architecture, and reduced the fibrotic and inflammatory microenvironment characteristic of ADPKD. Furthermore, CD-mPkd2 was well tolerated without detectable off-target toxicity. Given that PC2 supplementation can attenuate disease in Pkd1-deficient models, we further demonstrate that a single dose of CD-mPkd2 reduces cyst burden and improves renal function across this distinct genetic background. These findings establish CD-mPkd2 as a potential therapeutic strategy for ADPKD across genetic backgrounds.

bioengineering↗

bioRxiv2025

Advanced neural activity mapping in brain organoids via field potential imaging with ultra-high-density CMOS microelectrodes.

Human iPSC-derived brain organoids and assembloids have emerged as promising in vitro models for recapitulating human brain development, neurological disorders, and drug responses. However, detailed analysis of their electrophysiological properties requires advanced measurement techniques. Here, we present a novel analytical approach utilizing ultra-high-density (UHD) CMOS microelectrode arrays (MEAs) containing 236,880 electrodes (10.52 m x 10.52 m each) distributed over a broad sensing area of 32.45 mm2 for field potential imaging (FPI) of brain organoids. Neuronal activity was recorded simultaneously from over 46,000 electrodes interfaced with brain organoids, allowing for the identification of single-cell firing events and the assessment of neuronal network connectivity based on individual spikes. In midbrain organoids, administration of L-DOPA revealed both excitatory and inhibitory cellular responses, with a dose-dependent increase in the proportion of excitatory responses, suggesting enhanced network connectivity. Capitalizing on the spatial and temporal resolution of UHD-CMOS-MEAs, we introduced new endpoints for network activity: propagation velocity and propagation area. In cortical organoids, application of the GABAA receptor antagonist picrotoxin led to increased propagation velocity, whereas the NMDA receptor antagonist MK-801 resulted in a broad reduction of propagation area, along with localized increases. As FPI enables direct recording of electrical potential waveforms, frequency-domain analyses were also conducted. Spontaneous activity in cortical organoids exhibited region-specific frequency distributions, with gamma-band activity displaying distinct patterns compared to other frequency bands. Additionally, in midbrain-striatal assembloids, electrophysiological activity was observed in both regions. Connectivity analysis showed that treatment with 4-aminopyridine enhanced inter-organoid connection strength. This large-scale, single-cell-resolved recording approach using UHD-CMOS-MEAs facilitates comprehensive analysis of network connectivity, propagation velocity and propagation area, and frequency characteristics. It represents a powerful platform for advancing our understanding of the electrophysiological functions of brain organoids and assembloids, and holds significant potential for drug screening and disease modeling in human neuroscience research.

neuroscience↗

bioRxiv2025

Development of a Microelectrode Array System for Simultaneous Measurement of Field Potential and Glutamate Release in Brain Slices

Disorders of the central nervous system and complex side effects caused by abnormal neurotransmitter release have been widely reported. If neurotransmitter release and field potential (FP) could be simultaneously measured in real time, it would be possible to capture the relationship between changes in neurotransmitter release and alterations in electrical activity. In this study, we developed a novel microelectrode array (MEA) system capable of simultaneously measuring FP and electrochemical (EC) signals. Additionally, we developed an enzyme-modified carbon nanotube (CNT)-MEA capable of detecting glutamate, a major neurotransmitter, with high sensitivity in the range of several nM to several hundred nM. Using the developed enzyme-modified CNT-MEA and the simultaneous FP/EC measurement system, we successfully recorded extracellular potentials and glutamate release from hippocampal brain slices, detecting both an increase in oscillatory activity and temporal changes in glutamate release following caffeine administration. Furthermore, we also achieved the recording of dopamine release from brain slices using this system. We believe that the enzyme-modified CNT-MEA and the simultaneous FP/EC measurement system, which enable the real-time, simultaneous measurement of FP, glutamate release, and dopamine release, will contribute to a deeper understanding of brain circuit mechanisms, pathological brain conditions, and the evaluation of pharmacological compounds. HighlightsO_LIThe MEA system was customized to facilitate real-time simultaneous measurement of field potential (FP) and electrochemical (EC) signals. C_LIO_LIThe enzyme-modified CNT-MEA demonstrated the capability to detect glutamate at concentrations ranging from a few nM to several hundred nM. C_LIO_LIUsing the enzyme-modified CNT-MEA and the simultaneous FP/EC measurement system, we concurrently recorded FP and glutamate release from hippocampal brain slices, as well as their dynamic changes induced by caffeine administration. C_LIO_LIThe developed enzyme-modified CNT-MEA successfully detected dopamine release from brain slices. C_LIO_LIThe simultaneous recording of neural activity, glutamate release, and dopamine release achieved in this study is expected to contribute to elucidating the principles of brain circuit function, investigating brain pathologies, and evaluating compounds for drug discovery. C_LI

neuroscience↗

bioRxiv2025

Analysis of β rhythm induction in acute brain slices using field potential imaging with ultra-high-density CMOS-based microelectrode array.

Carbachol-induced beta rhythms in acute brain slices provide a promising ex vivo platform for evaluating compound effects under arousal-like hippocampal activity. Although microelectrode array (MEA) systems offer a non-invasive means of recording network dynamics, conventional MEAs have been limited by low electrode counts and small sensing areas, allowing only fragmented evaluation of neural activity. In this study, we applied field potential imaging (FPI) using an ultra-high-density (UHD) CMOS-MEA comprising 236,880 electrodes to simultaneously and spatially resolve carbachol-induced activity changes in the hippocampus and neocortex. Treatment with 10 {micro}M carbachol reliably induced oscillatory activity in the hippocampus at 1.33 {+/-} 0.33 Hz. Repetitive and temporally precise firing patterns originated in the CA3 region and propagated toward CA1. The average duration of individual oscillatory events was 52.82 {+/-} 6.44 ms, corresponding to a frequency of 18.93 {+/-} 3.03 Hz--within the beta frequency band. Cluster analysis based on waveform morphology revealed spatial groupings that reflected underlying anatomical structures. Beta-band power was significantly enhanced in both hippocampal and cortical regions following carbachol treatment. These findings demonstrate that the FPI platform enables high-resolution mapping of relationships between anatomical structures and brain function in acute slices, and holds promise as a pharmacological evaluation tool for assessing compound effects on hippocampal and cortical networks under wakefulness-like conditions.

neuroscience↗

bioRxiv2025

Field potential Imaging in human iPSC- derived Cardiomyocytes using UHD-CMOS-MEA

Evaluation using beat propagation analysis of human iPS cardiomyocytes is an effective approach for assessing human cardiac safety in drug development. However, current applications are primarily focused on detecting QT prolongation and arrhythmia risk, while its ability to comprehensively detect cardiotoxicity remains insufficient. Additionally, predicting the mechanism of action, which is crucial in drug development, remains challenging. In this study, we employed field potential imaging (FPI) using an ultra-high-density (UHD) CMOS microelectrode array (MEA) comprising 236,880 electrodes with high spatiotemporal resolution, capable of recording the activity of a monolayer of cardiomyocytes with tens of electrodes per cell. This method enabled the establishment of novel electrophysiological endpoints, including the number of excitation origins, fluctuations in origin positions, conduction velocity, and propagation area. Pharmacological characterization revealed drug-specific effects: isoproterenol increased excitation origins, mexiletine reduced conduction velocity, and E-4031 decreased propagation area while inducing early afterdepolarizations. Multivariate analysis of 13 compounds across 17 electrophysiological endpoints distinguished conduction velocity and propagation patterns based on their mechanisms of action. Additionally, 0.1 M doxorubicin exposure for 24 hours significantly reduced conduction velocity and propagation area, allowing early detection of chronic cardiotoxicity. These findings suggest that UHD-CMOS-MEA-based FPI enhances cardiotoxicity detection at low concentrations and precisely characterizes ion channel activity across different drug concentrations. The integration of novel electrophysiological endpoints derived from UHD-CMOS-MEA-based FPI, including excitation origin analysis, conduction velocity, and propagation area, along with multivariate analysis, is anticipated to establish a next-generation in vitro platform for comprehensive cardiotoxicity risk assessment and mechanism-based prediction of drug candidates.

pharmacology and toxicology↗

bioRxiv2025

Allometric studies on human- and pig-sized Delphinidae to understand resting metabolic rates with respiratory measurements

Exponential relationships between basal metabolic rate (BMR) and body mass are known in both terrestrial and marine mammals, with elevated BMR in the latter. However, it remains unclear whether the exponential relationship in marine mammals is different from that in terrestrial mammals. Metabolic rates of animals while resting at the water surface (resting metabolic rates: RMRs) were measured by breath-by-breath respirometry in two species of Delphinidae from temperate regions to elucidate the relationship between RMR and body mass in pantropical spotted dolphins (Stenella attenuate) and Rissos dolphins (Grampus griseus) with body masses ranging from 71 to 386 kg. The RMRs of rough-toothed dolphins (83-123 kg), common bottlenose dolphins (143-220 kg), and killer whales (3,364-5,318 kg) were obtained from the literature for allometric analyses. Measured RMRs were 344 {+/-} 39 and 1398 {+/-} 160 ml O2 min-1, respectively, which were 1.2-2.1 times higher than those predicted for similar-sized terrestrial mammals. A linear mixed-effects model showed the allometric mass exponent of 0.65 (95% CI: 0.54-0.76), which was closer to the 2/3-power of body mass than that of the widely observed 3/4-power commonly reported across a broad range of taxa. The new scaling relationship observed in the Delphinidae indicates that larger dolphins require less energy in aquatic environments, which is consistent with the theory of heat loss associated with a narrower surface area relative to larger volumes. This study suggested a different scaling relationship between aquatic and terrestrial mammals.

zoology↗

bioRxiv2024

Genome-wide mapping of autonomously replicating sequences in the marine diatom Phaeodactylum tricornutum

Autonomously replicating sequences (ARSs) are important accessories in episomal vectors that allow them to be replicated and stably maintained within transformants. Despite their importance, no information on ARSs in diatoms have been reported. Therefore, we attempted to identify ARS candidates in the model diatom, Phaeodactylum tricornutum, via chromatin immunoprecipitation sequencing. In this study, subunits of the origin recognition complex (ORC), ORC2 and ORC4, were used to screen for ARS candidates. ORC2 and ORC4 bound to 355 sites on the P. tricornutum genome, of which 69 were constantly screened after multiple attempts. The screened ARS candidates had an AT-richness of approximately 50% (44.39-52.92%) and did not have conserved sequences. In addition, ARS candidates were distributed randomly but had a dense distribution pattern at several sites. Their positions tended to overlap with those of the genetic region (73.91%). Compared to the ARSs of several other eukaryotic organisms, the characteristics of the screened ARS candidates are complex. Thus, our findings suggest that the diatom has a distinct and unique native ARSs.

molecular biology↗

bioRxiv2024

Development of a novel microphysiological system for neurotoxicity prediction using human iPSC-derived neurons with morphological deep learning

Microphysiological system (MPS) is an in vitro culture technology that reproduces the physiological microenvironment and functionality of humans, and is expected to be applied for drug screening. In this study, we developed a MPS for structured culture of human iPSC-derived neurons, then predict drug-induced neurotoxicity by morphological deep learning. For human iPSC-derived cortical neurons, after administration of three different amyloid {beta} (A{beta}) peptides, neurotoxicity effects were evaluated by a deep learning image analysis, training two artificial intelligence (AI) models on neurites and PSD-95 images. The combined results indicated that A{beta} 1-42 and 1-40, but not 1-28, induced synaptic degeneration, which is close to clinical reports. For human iPSC-derived sensory neurons, after administration of representative CIPN-related anti-cancer drugs, the toxic effects on soma and axons were evaluated by AI model using neurites images. Significant toxicity was detected in positive drugs and could be classified by different effects on soma or axon, suggesting that the current method provides an effective evaluation of chemotherapy-induced peripheral neuropathy. Taken together, it suggests that the present MPS combined with morphological deep learning is a useful platform for in vitro neurotoxicity assessment.

pharmacology and toxicology↗

bioRxiv2024

The effect of a harmful algal bloom (Karenia selliformis) on the benthic invertebrate community and the sea otter (Enhydra lutris) diet in eastern Hokkaido.

In recent decades, the locally extinct sea otter (Enhydra lutris lutris) has been recolonizing the coast of eastern Hokkaido. Their diet includes benthic invertebrates such as bivalves, sea urchins, snails, and chitons. In the fall of 2021, a harmful algal bloom (HAB) of Karenia selliformis occurred across Hokkaidos northern and eastern coasts, leading to a massive mortality of sea urchins. This dinoflagellate produces a neurotoxin (gymnodimine) implicated in shellfish poisoning. To determine the effect of the HAB on the marine community, we conducted benthic surveys using SCUBA and visually monitored the prey items of the sea otters in the affected area from 2020 to 2023. Following the HAB, we observed an 82% decrease in benthic sea urchin density (number m2), leading to their complete absence from the diet of sea otters. Conversely, bivalve density increased six-fold, accompanied by a nearly two-fold rise in their percentage in the sea otters diet. Minimal changes were observed in the density of chitons and snails, with no significant alteration in the sea otters diet. Despite these changes, the impact of the HAB on otters dietary preferences was temporary, as the percentage of dietary sea urchins began recovering one year later. Sea otters augmented their diet with bivalves to compensate for the reduced availability of sea urchins during the HAB with no apparent effects on the number of sea otters or their health. Our results highlight the adaptability of sea otters to adjust their diet according to prey availability.

ecology↗

bioRxiv2022

An in vitro microfluidic culture device for peripheral neurotoxicity prediction at low concentration based on deep learning

In this study, a microfluidic culture device was developed including related evaluation methods using deep learning for the purpose of constructing a rapid assessment platform for peripheral neuropathy caused by compounds. Primary rodent dorsal root ganglion was cultured in the microfluidic culture device that could separate the cell body and neurites, and the neurites morphological changes were analyzed by immunofluorescence images. Separated neurites successful culture in the microfluidic device for more than 1 month indicated that a series of test processes from culture to drug stimulation and fluorescence observation is possible. Additionally, cultured samples were treated with several anticancer drugs known to cause peripheral neurotoxicity (i.e., vincristine, oxaliplatin, and paclitaxel) and analyzed the neurites morphological changes by deep learning for image analysis. After training, artificial intelligence (AI) could identify neurite morphological changes caused by each compound and precisely predicted the toxicity positivity, even at low concentrations. For testing compounds, AI could also precisely detect toxicity negative and positive based on neurite images, even at low concentrations. Therefore, this microfluidic culture system is supposed to be useful for in vitro toxicity assessment.

pharmacology and toxicology↗

bioRxiv2022

Large-area electrical imaging having single neuron resolution using 236,880 electrodes CMOS-MEA technology

The electrophysiological technology having a high spatio-temporal resolution at the single-cell level, and noninvasive measurements of large areas provides insights on underlying neuronal function. Here, we used a complementary metal-oxide semiconductor (CMOS)-microelectrode array (MEA) that uses 236,880 electrodes each with an electrode size of 11.22 x 11.22 {micro}m and 236,880 covering a wide area of 5.5 x 5.7 mm in presenting a detailed and single-cell-level neural activity analysis platform for brain slices, human iPS cell-derived cortical networks, peripheral neurons, and human brain organoids. Propagation pattern characteristics between brain regions changes the synaptic strength into compounds based on single-cell time-series patterns, classification based on single DRG neuron firing patterns and compound responses, axonal conduction characteristics and changes to anticancer drugs, and network activities and transition to compounds in brain organoids were extracted. This detailed analysis of neural activity at the single-cell level using our CMOS-MEA provides a new understanding the basic mechanisms of brain circuits in vitro and ex vivo, on human neurological diseases for drug discovery, and compound toxicity assessment.

neuroscience↗

bioRxiv2021

Transcriptomic analysis of astaxanthin hyper-producing Coelastrum sp. mutant obtained by chemical mutagenesis

A newly isolated green microalga, Coelastrum sp. has the capability to produce and accumulate astaxanthin under various stress conditions. At present, a mutant G1-C1 of Coelastrum sp. obtained through chemical mutagenesis using ethyl methane sulfonate displayed an improvement in astaxanthin accumulation, which was 2-fold higher than that of the wild-type. However, lack of genomic information limits the understanding of the molecular mechanism that leads to a high level of astaxanthin in the mutant G1-C1. In this study, transcriptome sequencing was performed to compare the transcriptome of astaxanthin hyper-producing mutant G1-C1 and wild-type of Coelastrum sp. with respect to astaxanthin biosynthesis. This is to clarify why the mutant produced higher astaxanthin yield compared to the wild-type strain. Based on the transcriptomic analysis, the differentially expressed genes involved in astaxanthin biosynthesis were significantly upregulated in the mutant G1-C1 of Coelastrum sp. Genes coding phytoene synthase, phytoene desaturase,{zeta} -carotene desaturase, and lycopene {beta}-cyclase involved in {beta}-carotene biosynthesis in the mutant cells were upregulated by 10-, 9.2-, 8.4-, and 8.7-fold, respectively. Genes coding beta-carotene ketolase and beta-carotene 3-hydroxylase involved in converting {beta}-carotene into astaxanthin were upregulated by 7.8- and 8.0-fold, respectively. In contrast, the lycopene {varepsilon}-cyclase gene was downregulated by 9.7-fold in mutant G1-C1. Together, these results contribute to higher astaxanthin accumulation in mutant G1-C1. Overall, the data in this study provided molecular insight for a better understanding of the differences in astaxanthin biosynthesis between the wild-type and mutant G1-C1 strains.

molecular biology↗

bioRxiv2020

Subcellular mRNA localization and local translation of Arhgap11a in radial glial cells regulates cortical development

mRNA localization and local translation enable exquisite spatial and temporal control of gene expression, particularly in highly polarized and elongated cells. These features are especially prominent in radial glial cells (RGCs), which serve as neural and glial precursors of the developing cerebral cortex, and scaffolds for migrating neurons. Yet the mechanisms by which distinct sub-cellular compartments of RGCs accomplish their diverse functions are poorly understood. Here, we demonstrate that subcellular RNA localization and translation of the RhoGAP Arhgap11a controls RGC morphology and mediates cortical cytoarchitecture. Arhgap11a mRNA and protein exhibit conserved localization to RGC basal structures in mice and humans, conferred by a 5'UTR cis-element. Proper RGC morphology relies upon active Arhgap11a mRNA transport and localization to basal structures, where ARHGAP11A is locally synthesized. Thus, RhoA activity is spatially and acutely activated via local translation in RGCs to promote neuron positioning and cortical cytoarchitecture. Altogether, our study demonstrates that mRNA localization and local translation mediate compartmentalization of neural progenitor functions to control brain development. HighlightsO_LIArhgap11a in radial glia non-cell autonomously promotes neuronal migration and lamination C_LIO_LIArhgap11a mRNA localizes to radial glial endfeet via a 5 UTR cis element C_LIO_LIARHGAP11A expression in basal process and endfeet depends upon its localized mRNA C_LIO_LILocalized mRNA and RhoA-GAP activity in endfeet control radial glial morphology C_LI

neuroscience↗

bioRxiv2020

CROCCP2 acts as a human-specific modifier of cilia dynamics and mTOR signalling to promote expansion of cortical progenitors.

The primary cilum is a central component of signalling during neural development, from regional patterning to neuronal differentiation. Here we focus on CROCCP2, a hominid-specific gene duplicate from CROCC (Ciliary Rootlet Coiled Coil), also known as rootletin, that encodes the major protein component of the ciliary rootlet. We find that CROCCP2 is highly expressed in the human fetal brain and not in other primate species. CROCCP2 gain of function in the mouse embryonic cortex results in decreased ciliogenesis, increased mTOR signalling, and increased cell size of radial glial cells, leading to increased generation of intermediate/basal progenitors and increased neuronal output. CROCCP2 impacts cilia dynamics and neurogenesis by inhibition of the IFT20 ciliary trafficking protein. Our data identify a human-specific protein that drives cortical basal progenitor expansion through modulation of ciliary dynamics.

neuroscience↗

bioRxiv2020

Versatile live-cell activity analysis platform for characterization of neuronal dynamics at single-cell and network level

Chronic imaging of neuronal networks in vitro has provided fundamental insights into mechanisms underlying neuronal function. Existing labeling and optical imaging methods, however, cannot be used for continuous and long-term recordings of the dynamics and evolution of neuronal networks, as fluorescence indicators can cause phototoxicity. Here, we introduce a versatile platform for label-free, comprehensive and detailed electrophysiological live-cell imaging of various neurogenic cells and tissues over extended times. We report on a novel dual-mode high-density microelectrode array, which can simultaneously record in i) full-frame mode with 19,584 recording sites and ii) high-signal-to-noise mode with 246 channels. We set out to demonstrate the capabilities of this platform with recordings from primary and iPSC-derived neuronal cultures and tissue preparations over several weeks, providing detailed morpho-electrical phenotypic parameters at subcellular, cellular and network level. Moreover, we developed reliable analysis tools with drastically increased throughput for extracting axonal morphology and conduction parameters.

neuroscience↗

bioRxiv2020

Plastidic Δ6 Fatty-Acid Desaturases With Distinctive Substrate Specificity Regulate The Pool Of C18-PUFAs In The Ancestral Picoalga Ostreococcus tauri

Eukaryotic {Delta}6-desaturases are microsomal enzymes which balance the synthesis of {omega}-3 and {omega}-6 C18-polyunsaturated-fatty-acids (PUFA) accordingly to their specificity. In several microalgae, including O. tauri, plastidic C18-PUFA are specifically regulated by environmental cues suggesting an autonomous control of {Delta}6-desaturation of plastidic PUFA. Sequence retrieval from O. tauri desaturases, highlighted two putative {Delta}6/{Delta}8-desaturases sequences clustering, with other microalgal homologs, apart from other characterized {Delta}-6 desaturases. Their overexpression in heterologous hosts, including N. benthamiana and Synechocystis, unveiled their {Delta}6-desaturation activity and plastid localization. O. tauri lines overexpressing these {Delta}6-desaturases no longer adjusted their plastidic C18-PUFA amount under phosphate starvation but didnt show any obvious physiological alterations. Detailed lipid analyses from the various overexpressing hosts, unravelled that the substrate features involved in the {Delta}6-desaturase specificity importantly involved the lipid head-group and likely the non-substrate acyl-chain, in addition to the overall preference for the {omega}-class of the substrate acyl-chain. The most active desaturase displayed a broad range substrate specificity for plastidic lipids and a preference for {omega}-3 substrates, while the other was selective for {omega}-6 substrates, phosphatidylglycerol and 16:4-galactolipid species specific to the native host. The distribution of plastidial {Delta}6-desaturase products in eukaryotic hosts suggested the occurrence of C18-PUFA export from the plastid. One sentence summaryOsteococcus tauri plastidic lipid C18-PUFA remodelling involves two plastid-located cytochrome-b5 fused {Delta}6-desaturases with distinct preferences for both head-group and acyl-chain.

biochemistry↗