Biology subjects

Wierda, K.

Publications and source records attributed to Wierda, K..

14 recordsLinked to original sources

bioRxiv2026

A subtype-specific gene regulatory program controls differential circuit integration of deep CA3 pyramidal neurons

How closely related neuronal subtypes integrate into different circuits remains poorly understood. Deep and superficial hippocampal CA3 pyramidal neurons (PNs) differ in intrinsic firing and mossy fiber (MF) input at specialized postsynaptic structures termed thorny excrescences (TEs). Combining developmental single-nucleus multiomics with genetic targeting, morphological analysis and electrophysiology, we identify the transcription factor ST18 as a regulator of deep CA3 subtype identity. ST18 marks sparsely thorny and burst-firing neurons, and gene regulatory analyses predict that it represses a superficial-associated program involved in dendritic spine development, synaptic organization, and electrophysiological properties. Postnatal ST18 loss shifts the transcriptional and chromatin landscape of deep CA3 PNs toward a superficial-like state. These molecular changes are accompanied by increased TE elaboration approaching superficial levels, enhanced excitatory synaptic activity, and reduced burst-firing. Together, these findings identify ST18-dependent restriction of an alternative subtype program as a mechanism linking molecular identity to distinct input connectivity patterns and intrinsic firing properties during postnatal circuit maturation.

neuroscience↗

bioRxiv2026

Multimodal profiling and intersectional genetics reveal CA1 border inhibitory neuron diversity and postnatal emergence of retrosplenial connectivity

Inhibitory neurons (INs) at the stratum radiatum/stratum lacunosum-moleculare border of hippocampal CA1 comprise diverse populations, including long-range-projecting neurons that innervate the retrosplenial cortex (RSCtx). However, their molecular organization and developmental connectivity remain poorly understood. Here, we combine multimodal transcriptomic profiling, intersectional genetics, and retrograde tracing to characterize CA1 border INs. We identified two major caudal ganglionic eminence-derived, Cxcl14-enriched populations distinguished by Syt6/Cck-related and Ntng1-expressing transcriptional profiles. We then generated a Cxcl14-Cre mouse line that, when combined with an IN-specific viral enhancer, provides genetic access to CA1 border INs. Retrograde labeling established that CA1 INs projecting to the RSCtx belong to the Ntng1-expressing population, and that this long-range projection emerges during postnatal mouse development, between postnatal days 3 and 5. Finally, analysis of genes encoding cell-surface proteins, key regulators of connectivity, revealed distinct expression profiles in RSCtx-projecting and SYT6-positive INs. Together, these findings establish a molecular and developmental framework for CA1 border IN diversity and provide a genetic strategy for investigating the assembly and function of these inhibitory circuits.

neuroscience↗

bioRxiv2026

Extracellular neuroligin-ICAM5 coupling drives dendritic growth via actin remodeling

Neuroligins (NLGNs) organize neuronal connectivity by engaging a diverse set of interaction partners, yet how extracellular recognition couples to intracellular growth programs remains unclear. Using affinity proteomics, we identify intercellular adhesion molecule-5 (ICAM5), a cell-surface protein localized to dendritic filopodia, as a novel neuroligin interactor. Surface plasmon resonance and cell-based assays demonstrate direct binding between the ICAM5 and NLGN3 extracellular domains and reveal that ICAM5 engages all neuroligin isoforms. ICAM5 is required for NLGN-induced dendritic outgrowth, but the NLGN3-ICAM5 complex does not contribute to synaptogenesis. Mechanistically, ICAM5 sustains PAK-Cofilin signaling and F-actin organization in growth cones, positioning it as a downstream effector that links neuroligin engagement to actin remodeling. Together, these findings define a neuroligin-ICAM5 axis that couples extracellular recognition to intracellular actin remodeling to control neuronal structural development.

neuroscience↗

bioRxiv2025

MyeliMAP: Studying Oligodendrocyte Function in Brain Networks

Oligodendrocytes are the myelinating glia of the central nervous system (CNS), essential for rapid signal propagation, metabolic support, and neuronal health. While rodent-based cultures and organoid systems have provided insights into oligodendrocyte biology, they fall short of capturing human-specific features of myelination or integrating structural and functional readouts. Here, we present MyeliMAP (Myelination MAPping), a human pluripotent stem cell (hPSC) -derived microphysiological and electrophysiological platform that enables robust modeling of CNS myelination. The system combines inducible hPSC-derived neurons and oligodendrocytes in a custom-engineered microfluidic microstructure designed to mimic the developing brain microenvironment, promoting spatially organized axon-glia interactions and controlled myelin sheath formation. Within six weeks, we demonstrate myelin formation and maturation by immunofluorescence and ultrastructural validation using transmission electron microscopy (TEM), confirming compact multilayered wrapping of human axons. Importantly, the microstructure is directly integrated with a high-density microelectrode array (HD-MEA), enabling real-time, long-term functional assessment of network activity and myelin-dependent changes in signal conduction. This allowed us to demonstrate that oligodendrocyte-based myelinated neurons display enhanced conduction velocity of action potentials compared to neuron monocultures. Moreover, the presence of oligodendrocytes stabilized the temporal neuronal network activity by reducing variability in firing patterns and enhancing synchrony across the culture. This dual structure-function approach surpasses static end-point analyses by coupling morphological validation with dynamic, quantitative measurements of maturing circuit physiology. MyeliMAP provides a reproducible, human-relevant platform to dissect neuron-glia interactions and accelerate discovery of remyelination-promoting strategies for CNS disease.

neuroscience↗

bioRxiv2025

Presynaptic Release Probability Determines the Need for Sleep

Sleep is universal among animals with synapses, yet the synaptic functions determining the need for sleep remain elusive. By directly measuring synaptic transmission at anatomically defined synapses in Drosophila, we found that synaptic strength remained stable or declined after sleep deprivation in a circuit-specific manner. In contrast, presynaptic release probability (Pr) consistently decreased with sleep loss across circuits and species, stemming from reduced Ca2+ influx or weakened vesicle-channel coupling at presynaptic terminals, and recovered after sleep. Bidirectional manipulations of Pr altered sleep pressure, establishing a causal relationship between presynaptic function and sleep need. Non-synaptic sleep-regulatory signaling pathways consistently modulate Pr but not synaptic strength. Thus, our findings identify Pr, rather than synaptic strength, as the conserved synaptic substrate underlying sleep need.

neuroscience↗

bioRxiv2025

Human Myelin Spheres for In Vitro Oligodendrocyte Maturation, Myelination and Neurological Disease Modeling

Demyelinating diseases, such as multiple sclerosis, damage the protective myelin sheaths of the central nervous system. The development of effective therapies has been hampered by the lack of models that accurately replicate human myelin biology. Here we present a novel method to generate human myelin spheres (MyS) by coculturing of hPSC-derived neuronal and oligodendrocyte precursor cells, to create myelinated neurons. Using multimodal analyses including confocal and (electron)microscopy, single-nuclei transcriptomics, lipidomics, and electrophysiology, we demonstrate myelination in MyS as early as six weeks into coculture. These myelinated structures mature over time into multilamellar and compacted myelin sheaths with lipid compositions and transcriptomic profiles mirror the temporal dynamics of in vivo human oligodendrocyte development and neuronal myelination, resembling those of late fetal/postnatal oligodendrocytes. By employing lysolecithin-induced demyelination and Rabies virus infection experiments, we demonstrate the potential of MyS as an innovative, physiologically relevant platform for studying myelin-related neurodegeneration and neuroinfection.

neuroscience↗

bioRxiv2025

A dynamic gene regulatory code drives synaptic development of hippocampal granule cells

Connecting neurons into functional circuits requires the formation, maturation, and plasticity of synapses. While advances have been made in identifying individual genes regulating synapse development, the molecular programs orchestrating their action during circuit integration of neurons remain poorly understood. Here, we take a multiomic approach to reconstruct gene regulatory networks (GRNs), comprising transcription factors (TFs), regulatory regions, and predicted target genes, in hippocampal granule cells (GCs). We find a dynamic gene regulatory code, with early and late postnatal GRNs regulating cell morphogenesis and synapse organization and plasticity, respectively. Our results predict sequential regulations, with early-active TFs delaying the activation of later GRNs and their putative synaptic targets. Using a loss-of-function approach, we identify Bcl6 as a regulator of pre- and postsynaptic structural maturation, and Smad3 as a modulator of inhibitory synaptic transmission, in GCs. Together, these findings highlight the networks of key TFs and target genes orchestrating GC synapse development.

neuroscience↗

bioRxiv2025

Intracortical bipolar stimulation allows selective activation of neuronal populations in the cortex

BackgroundIntracortical electrical stimulation has emerged as a promising approach for sensory restoration, such as a cortical visual prosthesis, yet its effectiveness is limited by current spread and electrode density constraints. ObjectiveTo determine whether intracortical bipolar current steering--via modulation of the return electrode position--can enhance neural activation selectivity compared to traditional monopolar stimulation, with the aim of improving spatial precision in sensory restoration. MethodsWe applied intracortical stimulation and used two-photon calcium imaging on acute brain slices to directly visualize neural responses to bipolar stimulation. Biophysical computational modeling was used to complement the experimental results. The analysis included both cellular and population-level assessments to evaluate the impact of several stimulation patterns, such as current direction, electrode spacing and current amplitude, on recruitment patterns. ResultsBipolar stimulation selectively activated distinct neural populations based on the direction of the current flow. This approach decreased the overlap between activated groups and increased the number of independently addressable neural clusters by up to 9-fold relative to monopolar stimulation. Moreover, the electrode configuration and spacing critically influenced the spatial spread of activation. ConclusionsIntracortical bipolar current steering enhances neural activation selectivity by engaging independent neural populations through current directionality. These findings suggest that this strategy may improve the spatial precision of neural prosthetics and sensory restoration without the need for an increased electrode density.

neuroscience↗

bioRxiv2023

Human synaptic neoteny requires species-specific balancing of SRGAP2-SYNGAP1 cross-inhibition

Human-specific (HS) genes are potential drivers of brain evolution, but their impact on human neuron development and disease remains unclear. Here we studied HS genes SRGAP2B/C in human cortical projection neurons (CPNs) in vivo, using xenotransplantation in the mouse cortex. Downregulation of SRGAP2B/C in human CPNs greatly accelerated synaptic development, indicating their requirement for human-specific synaptic neoteny. SRGAP2B/C acted by downregulating their ancestral paralog SRGAP2A, thereby upregulating postsynaptic levels of SYNGAP1, a major intellectual deficiency/autism spectrum disorder (ID/ASD) gene. Combinatorial genetic invalidation revealed that the tempo of synaptogenesis is set by a balance between SRGAP2A and SYNGAP1, which in human CPNs is tipped towards neoteny by SRGAP2B/C. Our results demonstrate that HS genes can modify the phenotypic expression of ID/ASD mutations through regulation of synaptic neoteny. One-Sentence SummaryHuman-specific genes SRGAP2B/C control human cortical neuron neoteny by regulating the function of neurodevelopmental disorder gene SYNGAP1

neuroscience↗

bioRxiv2023

SYNGAP1 deficiency disrupts neoteny in human cortical neurons in vivo.

Intellectual deficiency (ID) and autism spectrum disorder (ASD) originate from disrupted development of human-specific cognitive functions. Human brain ontogeny is characterized by a considerably prolonged, neotenic, cortical neuron development. Neuronal neoteny could be disrupted in ID/ASD, but this was never tested because of the difficulties to study developing human cortical circuits. Here we use xenotransplantation of human cortical neurons into the mouse cortex to study the in vivo neuronal consequences of SYNGAP1 haploinsufficiency, a frequent cause of ID/ASD. We find that SYNGAP1 deficient neurons display strong acceleration of morphological and functional synaptic development. At the circuit level, SYNGAP1 haploinsufficient neurons display disrupted neoteny, with faster integration into cortical circuits and acquisition of sensory responsiveness months ahead of time. These data link neuronal neoteny to ID/ASD, with important implications for diagnosis and treatments.

neuroscience↗

bioRxiv2022

LRRC37B is a species-specific regulator of voltage-gated channels and excitability in human cortical neurons

The enhanced cognitive abilities characterizing the human species result from specialized features of neurons and circuits, but the underlying molecular mechanisms remain largely unknown. Here we report that the hominid-specific gene LRRC37B encodes a novel receptor expressed in a subset of human cortical pyramidal neurons (CPNs). LRRC37B protein localizes at the axon initial segment (AIS), the specialized domain triggering action potentials. LRRC37B ectopic expression in mouse CPNs in vivo leads to reduced intrinsic excitability, a distinctive feature of some classes of human CPNs. At the molecular level, LRRC37B acts as a receptor for the secreted ligand FGF13A and interacts with the voltage gated sodium channel (VGSC) beta subunit SCN1B, thereby inhibiting the channel function of VGSC, specifically at the AIS. Electrophysiological recordings in adult human cortical slices reveals that endogenous expression of LRRC37B in human CPNs reduces neuronal excitability. LRRC37B thus acts as a species-specific modifier of human cortical neuron function, with important implications for human brain evolution and diseases.

neuroscience↗

bioRxiv2022

Astrocyte-targeted gene delivery of interleukin 2 specifically increases brain-resident regulatory T cell numbers and protects against pathological neuroinflammation

The ability of immune-modulating biologics to prevent and reverse pathology has transformed recent clinical practice. Full utility in the neuroinflammation space, however, requires identification of both effective targets for local immune-modulation and a delivery system capable of crossing the blood-brain-barrier. The recent identification and characterization of a small population of regulatory T cells (Tregs) resident in the brain presents one such potential therapeutic target. Here we identified brain IL2 levels as a limiting factor for brain-resident Tregs. We developed a gene-delivery approach for astrocytes, with a small-molecule on-switch to allow temporal control, and enhanced production in reactive astrocytes to spatially-direct delivery to inflammatory sites. Mice with brain-specific IL2 delivery were protected from traumatic brain injury, stroke and multiple sclerosis models, without impacting the peripheral immune system. These results validate brain-specific IL2 gene-delivery as effective protection against neuroinflammation, and provide a versatile platform for delivery of diverse biologics to neuroinflammatory patients.

immunology↗

bioRxiv2021

Melanin Concentrating Hormone- and sleep-dependent synaptic downscaling is impaired in Alzheimer's Disease

In Alzheimers disease (AD), pathophysiological changes in the hippocampus cause deficits in episodic memory formation, leading to cognitive impairment 1,2. Neuronal hyperactivity is observed early in AD 3,4. Here, we find that homeostatic mechanisms transiently counteract increased neuronal activity in the hippocampal CA1 region of the AppNL-G-F humanized knock-in mouse model for AD 5, but ultimately fail to maintain neuronal activity at set-point. Spatial transcriptomic analysis in CA1 during the homeostatic response identifies the Melanin-Concentrating Hormone (MCH)-encoding gene. MCH is expressed in sleep-active lateral hypothalamic neurons that project to CA1 and modulate memory 6. We show that MCH regulates synaptic plasticity genes and synaptic downscaling in hippocampal neurons. Furthermore, MCH-neuron activity is impaired in AppNL-G-F mice, disrupting sleep-dependent homeostatic plasticity and stability of neuronal activity in CA1. Finally, we find perturbed MCH-axon morphology in CA1 early in AppNL-G-F mice and in AD patients. Our work identifies dysregulation of the MCH-system as a key player in aberrant neuronal activity in the early stages of AD.

neuroscience↗

bioRxiv2021

Corticotropin-Releasing Factor Induces Functional And Structural Synaptic Remodelling In Acute Stress

Biological responses to internal and external stress factors involve highly conserved mechanisms, using a tightly coordinated interplay of many factors. Corticotropin-releasing factor (CRF) plays a central role in organizing these lifesaving physiological responses to stress. We show that CRF rapidly and reversibly changes Schaffer Collateral input into hippocampal CA1 pyramidal cells (PC), by modulating both functional and structural aspects of these synapses. Host exposure to acute stress, in vivo CRF injection, and ex vivo CRF application all result in fast de novo formation and remodeling of existing dendritic spines. Functionally, CRF leads to a rapid increase in synaptic strength of Schaffer collateral input into CA1 neurons, e.g. increase in spontaneous neurotransmitter release, paired-pulse facilitation and repetitive excitability and improves long-term synaptic plasticity: LTP and LTD. In line with the changes in synaptic function, CRF increases the number of presynaptic vesicles, induces redistribution of vesicles towards the active zone increases active zone size, and improves the alignment of the pre- and post-synaptic compartments. Together, CRF rapidly enhances synaptic communication in the hippocampus, potentially playing a crucial role in the enhanced memory consolidation in acute stress.

neuroscience↗