Biology subjects

Wierda, K.

Publications and source records attributed to Wierda, K..

6 recordsLinked to original sources

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↗