Biology subjects

Seuntjens, E.

Publications and source records attributed to Seuntjens, E..

17 recordsLinked to original sources

bioRxiv2026

Protocol for calcium imaging of acute brain slices from Octopus vulgaris hatchlings during application of neurotransmitters

Octopus vulgaris and other cephalopods are of increasing interest as neurobiological model organisms. This protocol describes a method to record calcium activity from individual cells in acute brain slices from Octopus vulgaris hatchlings during exogenous application of neurotransmitters. Using this protocol, we characterized single-cell responses to specific neurotransmitters in the optic lobes, which process visual information. The approach is readily adaptable to other cephalopods and small invertebrate species. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=146 HEIGHT=200 SRC="FIGDIR/small/711860v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@1a3da0forg.highwire.dtl.DTLVardef@412424org.highwire.dtl.DTLVardef@abda7eorg.highwire.dtl.DTLVardef@958ebf_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2025

OCTRON - a general purpose segmentation and tracking pipeline for behavioral experiments

OCTRON is a pipeline for markerless segmentation and tracking of animals in behavioral experiments. By combining Segment Anything Models (SAM 2) for rapid annotation, YOLO11 models for training, and state-of-the-art multi-object trackers, OCTRON enables unsupervised segmentation and tracking of multiple animals with complex, deformable body plans. We validate its versatility across species - from transparent marine annelids to camouflaging cuttlefish - demonstrating robust, general-purpose applicability for behavioral analysis.

animal behavior and cognition↗

bioRxiv2025

Neurons, Muscles, and Venom: Identifying Drivers of Cephalopod Predation

Venom plays a central role in the predatory ecology of coleoid cephalopods (octopuses, squids, and cuttlefish), yet the mechanisms governing venom release from the posterior salivary gland (PSG) are unknown. Using a multimodal approach combining X-ray micro-histotomography, histological stainings, in situ hybridization, comparative phylogenetics, and ex vivo imaging across multiple coleoid species, we characterize the structural and neuronal regulatory organization of the PSG. We verified that the gland comprises two distinct tubular systems: secretory tubules specialized for venom production and smooth-striated tubules positioned to facilitate venom transport toward the beak for injection into its prey. Molecular localization of filamentous and -actin confirms a circular smooth muscle layer surrounding the tubules. Mapping of six neuronal markers, including neurofilament (NF-H), synapsin, and muscle-type nicotinic acetylcholine receptors, reveals dense and stereotyped neural innervation closely associated with the muscular compartments. Comparative phylogenetic analyses of cys-loop ligand-gated ion channel sequences indicate a predominancy of excitatory acetylcholine- and dopamine-gated receptors in coleoid venom glands, implicating potential molecular agents involved in neural control of venom release. Consistent with neural regulation, ex vivo stimulation of the PSG elicits calcium signaling throughout the gland. Together, our results reveal a conserved venom gland structure among octopuses, squids, and cuttlefish, with a spatially distinct neuromuscular tissue organization indicating venom production and release sites modulated by a network of neuronal agents. This work provides a mechanistic framework into venom gland organization and molecular regulation of venom release in one of the oldest venomous lineages.

neuroscience↗

bioRxiv2025

Novel dopaminergic neurotransmission in the Octopus visual system

Octopus vulgaris, the common octopus, has a complex brain that evolved independently from that of vertebrates, raising the possibility that it may be built using novel circuit motifs or non-canonical neurochemistry. Through systematic characterization of octopus ligand-gated ion channel genes, we identified novel ionotropic receptors for two neurotransmitters, dopamine and acetylcholine, that play key roles in visual circuits. One of these, DopC1, encodes a dopamine-gated cation channel expressed in deeper layers of the optic lobe (inner granular layer and medulla). A second, AChRB1, encodes an acetylcholine-gated anion channel expressed in photoreceptors and dopaminergic outer granular layer neurons. Dopamine drives excitation, particularly in deeper, DopC1 enriched layers, and thereby may play an important role in feed-forward excitation, whereas acetylcholine evokes inhibition, possibly mediating negative feedback from deeper layers. The octopus visual system thus shows fundamental differences in both neurochemistry and wiring compared to mammals, implying distinct mechanisms of visual information processing.

neuroscience↗

bioRxiv2025

Ultrasound-based prediction of spawning time in females of Octopus vulgaris

There has been a great interest in common octopus Octopus vulgaris aquaculture over recent years and commercial production is coming within reach. In addition, O. vulgaris is a short-lived semelparous species with a long spawning period. Therefore, monitoring ovary maturation in cultured octopuses can be useful in the scheduling of hatchery operations and management of culture resources. The present work aimed to assess the ovary maturity status in cultured and wild common octopus by means of a noninvasive technique, ultrasonography, to anticipate the time of spawning in aquaculture. A total of 27 octopuses (15 cultured and 12 wild ones) in different ovarian maturation stages were used in ultrasonographic procedures. Ultrasound-based ovary volumes were compared with real ovarian volumes and then the ultrasonography-based gonadosomatic index (GSIU) was estimated. Data from cultured females indicate that GSIU was initially below 0.3 cm3 per 100 g of body weight in immature animals, and attained a fast increase until reaching about 4.0 cm3 per 100 g of body weight right before spawning. The steep increase in relative volume occurred similarly in females of different body weights. In addition, the specific growth rate of cultured animals decreases with time, and with GSIU. Lastly, a linear mixed model indicated a significantly negative and logarithmic relationship between the time to spawning and GSIU in captive females. That relationship will be useful to predict spawning time in immature and maturing females, helping in the management of octopus broodstocks in research and production facilities.

zoology↗

bioRxiv2025

Loss of Elp3 impairs the maturation tempo of brain ependymal cells

Conditional deletion of Elp3 in the mouse forebrain leads to microcephaly at birth. In this study, we demonstrate that these mice also develop postnatal hydrocephalus, associated with an enlargement of the brain ventricles. In wild-type mice, ependymal motile cilia are properly aligned to facilitate the circulation of cerebrospinal fluid (CSF) within the ventricles. Our findings reveal that Elp3 loss induces endoplasmic reticulum (ER) stress and upregulation of ATF4 expression in ependymal cell progenitors, which compromises Notch signaling and accelerates their maturation. This is accompanied by a disruption in the establishment of rotational and translational polarities of the motile cilia of maturing ependymal cells, resulting in disorganized cilia bundles. Collectively, these molecular abnormalities lead to the premature and abnormal development of ependymal cells, culminating in cilia beating dysfunction, impaired CSF clearance, and the development of hydrocephalus.

neuroscience↗

bioRxiv2024

Early life growth and cellular heterogeneity in the short-lived African turquoise killifish telencephalon

The African turquoise killifish (Nothobranchius furzeri) is becoming a favorable model for neurobiological research. The combination of a short lifespan and a declining neuroregenerative capacity upon aging makes the killifish ideally suited for research on brain aging and regeneration. A remarkable cellular diversity makes up the young-adult killifish telencephalon, characterized by highly proliferative non-glial progenitors and four spatially distinct radial glia subtypes. In contrast to a relatively slow embryonic development, hatching is followed by a period of accelerated growth in the short-lived N. furzeri strain; GRZ. Accordingly, the brain of this teleost experiences a period of rapid expansion and maturation. In this study, we charted the growth progression of the killifish telencephalon during early post-embryonic development. We identified a dynamic cellular buildup of the neurogenic niches sustaining this explosive growth. Spatial data revealed specific differences between pallial and subpallial regions in terms of growth pace and cellular output. Spatial signatures comparable to zebrafish were identified for excitatory and inhibitory neuronal lineages, already present at hatching. Summary statementThis study charts the progenitor and neural diversity of the telencephalon from post-embryonic development, identifying the cellular building blocks during accelerated brain growth of the short-lived African Turquoise killifish.

neuroscience↗

bioRxiv2024

Altered Socio-Affective Communication and Amygdala Development in mice with Protocadherin10-deficient Interneurons

Autism Spectrum Disorder (ASD) is a group of neurodevelopmental conditions associated with deficits in social interaction and communication, together with repetitive behaviors. The cell adhesion molecule Protocadherin10 (Pcdh10) has been implicated in the etiology of ASD. Pcdh10 is expressed in the nervous system during embryonic and early postnatal development and has been linked to neural circuit formation. Here, we show strong expression of Pcdh10 in the ganglionic eminences and in the basolateral complex of the amygdala at mid and late embryonic stages, respectively. Both inhibitory and excitatory neurons expressed Pcdh10 in the basolateral complex at perinatal stages and genes linked to vocalization behavior were enriched in Pcdh10- expressing neurons in adult mice. To further investigate the involvement of Pcdh10 in neurodevelopment with relevance to ASD, and to assess the functional and behavioral consequences of loss of Pcdh10 in basolateral amygdala interneurons, we combined a ubiquitous and a conditional Pcdh10 knockout mouse model. Conditional knockout of Pcdh10 reduced the number of interneurons in the basolateral complex. Both models exhibited altered developmental trajectories of socio-affective communication through isolation-induced ultrasonic vocalizations in neonatal pups, characterized by increased emission rates in heterozygous pups. Furthermore, acoustic call features were affected and heterozygous conditional knockout pups emitted calls characterized by reduced peak frequencies but increased frequency modulation. Additionally, we identified distinct clusters of call subtypes with specific developmental trajectories, suggesting the vocalization repertoire is extensive and dynamic during early life. The nuanced alterations in socio-affective communication at the level of call emission rates, acoustic call features, and clustering of call subtypes were primarily seen in heterozygous pups of the conditional knockout and less prominent in the ubiquitous Pcdh10 knockout, suggesting that changes in anxiety levels associated with Gsh2-lineage interneurons might drive the observed behavioral effects. Together, this demonstrates that loss of Pcdh10 specifically in interneurons contributes to behavioral alterations in socio-affective communication with relevance to ASD.

neuroscience↗

bioRxiv2023

A chromosome-level reference genome for the common octopus, Octopus vulgaris (Cuvier, 1797)

Cephalopods are emerging animal models and include iconic species for studying the link between genomic innovations and physiological and behavioral complexities. Coleoid cephalopods possess the largest nervous system among invertebrates, both for cell counts and brain-to-body ratio. Octopus vulgaris has been at the center of a long-standing tradition of research into diverse aspects of cephalopod biology, including behavioral and neural plasticity, learning and memory recall, regeneration, and sophisticated cognition. However, no chromosome-scale genome assembly is available for O. vulgaris to aid in functional studies. To fill this gap, we sequenced and assembled a chromosome-scale genome of the common octopus, O. vulgaris. The final assembly spans 2.8 billion basepairs, 99.34% of which are in 30 chromosome-scale scaffolds. Hi-C heatmaps support a karyotype of 1n=30 chromosomes. Comparisons with other octopus species genomes show a conserved octopus karyotype, and a pattern of local genome rearrangements between species. This new chromosome-scale genome of O. vulgaris will further facilitate research in all aspects of cephalopod biology, including various forms of plasticity and the neural machinery underlying sophisticated cognition, as well as an understanding of cephalopod evolution.

genomics↗

bioRxiv2023

Neuroanatomical characterization of the Nmu-Cre knock-in mice reveals an interconnected network of unique neuropeptidergic cells

Neuromedin U (NMU) is an evolutionary conserved neuropeptide that has been implicated in multiple processes, such as circadian regulation, energy homeostasis, reward processing and stress coping. Although central expression of NMU has been addressed previously, the lack of specific and sensitive tools has prevented a comprehensive characterization of NMU-expressing neurons in the brain. We have generated a knock-in mouse model constitutively expressing Cre recombinase under the Nmu promoter. We have validated the model using a multi-level approach based on quantitative reverse-transcription polymerase chain reactions, in situ hybridization, a reporter mouse line and an adenoviral vector driving Cre-dependent expression of a fluorescent protein. Using the Nmu-Cre mouse, we performed a complete mapping of NMU expression in adult mouse brain, unveiling a potential midline NMU modulatory circuit with the ventromedial hypothalamic nucleus (VMH) as a key node. Moreover, immunohistochemical analysis suggested that NMU neurons in the VMH mainly constitute a unique population of hypothalamic cells. Taken together, our results suggest that Cre expression in the Nmu-Cre mouse model largely reflects NMU expression in the adult mouse brain, without altering endogenous NMU expression. Thus, the Nmu-Cre mouse model is a powerful and sensitive tool to explore the role of NMU neurons in mice.

neuroscience↗

bioRxiv2022

Optimization of Whole Mount RNA multiplexed in situ Hybridization Chain Reaction with Immunohistochemistry, Clearing and Imaging to visualize octopus neurogenesis

Gene expression analysis has been instrumental to understand the function of key factors during embryonic development of many species. Marker analysis is also used as a tool to investigate organ functioning and disease progression. As these processes happen in three dimensions, the development of technologies that enable detection of gene expression in the whole organ or embryo is essential. Here, we describe an optimized protocol of whole mount multiplexed RNA in situ hybridization chain reaction version 3.0 (HCR v3.0) in combination with immunohistochemistry (IHC), followed by fructose-glycerol clearing and light sheet fluorescence microscopy (LSFM) imaging on whole-mount Octopus vulgaris embryos. We developed a code to automate probe design which can be applied for designing HCR v3.0 type probe pairs for fluorescent in situ mRNA visualization. As proof of concept, neuronal (Ov-elav) and glial (Ov-apolpp) markers were used for multiplexed HCR v3.0. Neural progenitor (Ov-ascl1) and precursor (Ov-neuroD) markers were combined with an immunostaining for phosphorylated-histone H3, a marker for mitosis. After comparing several tissue clearing methods, fructose-glycerol clearing was found optimal in preserving the fluorescent signal of HCR v3.0. The expression that was observed in whole-mount octopus embryos matched with the previous expression data gathered from paraffin-embedded transverse sections. Three-dimensional reconstruction revealed additional spatial organization that had not been discovered using two-dimensional methods.

developmental biology↗

bioRxiv2022

MicroRNAs are deeply linked to the emergence of the complex octopus brain

Soft-bodied cephalopods such as the octopus are exceptionally intelligent invertebrates with a highly complex nervous system that evolved independently from vertebrates. Because of elevated RNA editing in their nervous tissues, we hypothesized that RNA regulation may play a major role in the cognitive success of this group. We thus profiled mRNAs and small RNAs in 18 tissues of the common octopus. We show that the major RNA innovation of soft-bodied cephalopods is a massive expansion of the miRNA gene repertoire. These novel miRNAs were primarily expressed in neuronal tissues, during development, and had conserved and thus likely functional target sites. The only comparable miRNA expansions happened, strikingly, in vertebrates. Thus, we propose that miRNAs are intimately linked to the evolution of complex animal brains. One-Sentence SummarymiRNAs are deeply linked to the emergence of complex brains.

evolutionary biology↗

bioRxiv2022

Cell type diversity in a developing octopus brain

Octopuses are mollusks that have evolved intricate neural systems comparable with vertebrates in terms of cell number, complexity and size. The cell types within the octopus brain that control their amazingly rich behavioral repertoire are still unknown. Here we profile cell diversity of the paralarval Octopus vulgaris brain to build a comprehensive cell type atlas that comprises mostly neural cells, as well as multiple glial subtypes, endothelial cells and fibroblasts. Moreover, we spatially map cell types within the octopus brain, including vertical and optic lobe cell types. Investigation of cell type conservation reveals a shared gene signature between glial cells of mice, fly and octopus. Genes related to learning and memory are enriched in vertical lobe cells, which show molecular similarities with Kenyon cells in Drosophila. Taken together, our data sheds light on cell type diversity and evolution of the complex octopus brain. Highlights & Key findingsO_LICharacterization of different cell types present in the early paralarval brain C_LIO_LICross-species comparisons reveal a conserved glial gene expression signature C_LIO_LIVertical lobe amacrine cells in octopus have molecular similarities to fly Kenyon cells C_LIO_LIHomeobox genes are defining transcription factors for cell type identity C_LIO_LIRecently expanded gene families may underlie cellular diversification C_LI

developmental biology↗

bioRxiv2021

Single-cell sequencing of the adult killifish (N. furzeri) brain identifies an atypical progenitor, glial and neuronal heterogeneity

The African turquoise killifish combines a short lifespan with spontaneous age-dependent loss of neuroregenerative capacity. The stem cell niches driving neuroregeneration and their molecular signatures remain elusive. To investigate this, we performed scRNA-seq of the adult telencephalon, combined with full-length transcriptomics using ISO-seq. Our results unveil about 25 cell types including neurons and progenitors of glial-and non-glial nature. Subclustering of progenitors identifies four radial glia (RG), and two non-glial progenitor (NGP) cell states. Combining the molecular profiles with spatial mapping of the RG clusters, reveals two spatially divergent astroglia, one ependymal, and one neuroepithelial-like subtype. We propose neuroepithelial-like RG and NGPs to be the start and intercessor populations of both neuro- and gliogenic lineages. Neuronal classification reveals distinct subtypes and lineages corresponding to excitatory and inhibitory neurons. This catalogue of telencephalon cell types is an extensive resource to understand the molecular basis of intrinsic plasticity shaping adult neuro- and gliogenesis. HighlightsO_LIScRNA-seq and ISO-seq identified a complete cell catalogue of the adult killifish telencephalon C_LIO_LIProgenitor diversity revealed the presence of spatially-defined (astro)glial subtypes C_LIO_LIA neuroepithelial radial glia population marks the start point of neurogenesis, accompanied by proliferative non-glial progenitors C_LIO_LIImmature neurons form transcriptional subgroups that correspond to excitatory and inhibitory mature neuronal cell types C_LIO_LIThis cellular atlas is a basis for studying neurogenesis and neuro-regeneration upon injury, disease and aging C_LI

neuroscience↗

bioRxiv2021

Identification of neural progenitor cells and their progeny reveals long distance migration in the developing octopus brain

Cephalopods have evolved nervous systems that parallel the complexity of mammalian brains in terms of neuronal numbers and richness in behavioral output. How the cephalopod brain develops has only been described at the morphological level, and it remains unclear where the progenitor cells are located and what molecular factors drive neurogenesis. Using histological techniques, we located dividing cells, neural progenitors and postmitotic neurons in Octopus vulgaris embryos. Our results indicate that progenitors are located outside the central brain cords in the lateral lips adjacent to the eyes, suggesting that newly formed neurons migrate into the cords. Lineage tracing experiments then showed that progenitors, depending on their location in the lateral lips, generate neurons for the different lobes. The finding that octopus newborn neurons migrate over long distances is reminiscent of vertebrate neurogenesis and suggests it might be a fundamental strategy for large brain development.

developmental biology↗

bioRxiv2021

Aging impairs the essential contributions of non-glial progenitors to neurorepair in the dorsal telencephalon of the Killifish N. furzeri

The aging central nervous system (CNS) of mammals displays progressive limited regenerative abilities. Recovery after loss of neurons is extremely restricted in the aged brain. Many research models fall short in recapitulating mammalian aging hallmarks or have an impractically long lifespan. We established a traumatic brain injury model in the African turquoise killifish (Nothobranchius furzeri), a regeneration-competent vertebrate model that evolved to naturally age extremely fast. Stab-wound injury of the aged killifish dorsal telencephalon unveils an impaired and incomplete regeneration response when compared to young individuals. Remarkably, killifish brain regeneration is mainly supported by atypical non-glial progenitors, yet their proliferation capacity appears declined with age. We identified a high inflammatory response and glial scarring to also underlie the hampered generation of new neurons in aged fish. These primary results will pave the way for further research to unravel the factor age in relation to neurorepair, and to improve therapeutic strategies to restore the injured and/or diseased aged mammalian CNS. HighlightsO_LIAging impairs neurorepair in the killifish pallium at multiple stages of the regeneration process C_LIO_LIAtypical non-glial progenitors support the production of new neurons in the naive and injured dorsal pallium C_LIO_LIThe impaired regeneration capacity of aged killifish is characterized by a reduced reactive proliferation of these progenitors followed by a decreased generation of newborn neurons that in addition, fail to reach the injury site C_LIO_LIExcessive inflammation and glial scarring surface as potential brakes on brain repair in the aged killifish pallium C_LI

neuroscience↗

bioRxiv2020

A practical staging atlas to study embryonic development of Octopus vulgaris under controlled laboratory conditions

BackgroundOctopus vulgaris has been an iconic cephalopod species for neurobiology research as well as for cephalopod aquaculture. It is one of the most intelligent and well-studied invertebrates, possessing both long- and short-term memory and the striking ability to perform complex cognitive tasks. Nevertheless, how the common octopus developed these uncommon features remains enigmatic. O. vulgaris females spawn thousands of small eggs and remain with their clutch during their entire development, cleaning, venting and protecting the eggs. In fact, eggs incubated without females usually do not develop normally, mainly due to biological contamination (fungi, bacteria, etc.). This high level of parental care might have hampered laboratory research on the embryonic development of this intriguing cephalopod. ResultsHere, we present a completely parameter-controlled artificial seawater standalone egg incubation system that replaces maternal care and allows successful embryonic development of a small-egged octopus species until hatching in a laboratory environment. We also provide a practical and detailed 1 staging atlas based on bright-field and light sheet fluorescence microscopy imaging for precise monitoring of embryonic development. The atlas has a comparative section to benchmark stages to the different scales published by Naef (1928), Arnold (1965) and Boletzky (2016). Finally, we provide methods to monitor health and wellbeing of embryos during organogenesis. ConclusionBesides introducing the study of O. vulgaris embryonic development to a wider community, this work can be a high-quality reference for comparative evolutionary developmental biology.

developmental biology↗