Biology subjects

Seal, R. P.

Publications and source records attributed to Seal, R. P..

7 recordsLinked to original sources

bioRxiv2026

Noninvasive Focal Gene Delivery of Functional Neural Actuators to the Primate Spinal Cord using Focused Ultrasound

Pathologies of the spinal cord -- from degenerative diseases to chronic pain -- represent a substantial global health burden. Although surgical and pharmacological treatments for spinal cord pathologies have advanced considerably, therapies capable of addressing the cellular mechanisms underlying these conditions remain limited. Viral gene therapies present a compelling alternative, allowing for delivery of therapeutic genes that directly target the pathological processes in specific cell-types. Effective viral delivery to the spinal cord, however, remains constrained by a fundamental tradeoff between procedural invasiveness and spatial precision. As such, there remains a need for clinically tractable methods -- that are both noninvasive and focal -- to deliver gene therapeutics across the restrictive vascular boundaries of the blood-spinal cord barrier (BSCB). Here, we demonstrate noninvasive, focal disruption of the BSCB and delivery of systemically administered chemogenetic gene payloads to the cervical and thoracic spinal cord in marmoset nonhuman primates (Callithrix jacchus) using focused ultrasound (FUS). Through systematic testing of ultrasonic pressures and central frequencies, we establish a FUS parameter set optimized for robust, spatially constrained molecular delivery across the marmoset BSCB. Using these optimized parameters, we show that FUS BSCB disruption permitted focal penetrance of systemically administered viral vectors for transduction of both fluorescent transgenes and excitatory chemogenetics within targeted spinal segments. Positron emission tomography (PET) imaging following chemogenetic actuation revealed significantly increased metabolic demand within the targeted region of the spinal cord, demonstrating in vivo evidence of functional transgene expression. Behavioral and histopathological assessments demonstrated preserved neurological function and tissue integrity, supporting the safety of FUS BSCB disruption and viral delivery in nonhuman primates. To facilitate broad application of this platform for noninvasive delivery of receptor-based gene therapeutics in marmosets, we generated an ultra-high-resolution (74 m) multimodal MRI/CT spinal cord template for precise targeting and anatomical localization. We also provide open-access engineering drawings and CAD files for our M-FRAME system (Marmoset Fixation and Reorientation Apparatus for Multimodal Experiments), enabling precise and repeatable spinal targeting without surgical fixation. Together, these results establish FUS-mediated BSCB disruption as a safe and effective approach for noninvasive, focal gene delivery to the primate spinal cord.

neuroscience↗

bioRxiv2025

Persistence of vestibular function in the absence of glutamatergic transmission from hair cells

Quantal synaptic transmission in vestibular end-organs is glutamatergic. Although genetic deletion of Slc17a8 (termed Vglut3) leads to deafness in mice, the dependence of vestibular function on VGLUT3-mediated quantal transmission is unknown. Here, we investigated the vestibular phenotype of Vglut3-/- mice at the cellular, systems, and behavioral levels. The type-II vestibular hair cells (VHCs) in Vglut3+/+mice were strongly immunoreactive for VGLUT3, while type-I VHCs showed poor immunoreactivity. In Vglut3-/- mice quantal synaptic transmission in utricular calyces was reduced in rate and amplitude by > 95%. In vivo recordings of spontaneous activity in the vestibular nerve revealed similar action potential rates and regularity in Vglut3+/+and Vglut3-/- mice, suggesting a divergent underlying mechanism compared to the silent Vglut3-/- auditory nerve. In behavioral studies, Vglut3-/- mice did not exhibit considerable sensorimotor or balance deficits. Collectively, these data support the view that non-quantal transmission is the predominant mode of neurotransmission between type I VHCs and vestibular calyceal afferent neurons. We propose that non-quantal transmission alone underlies the apparently normal vestibular nerve physiology and behavioral function in Vglut3-/- mice.

neuroscience↗

bioRxiv2025

A molecular and spinal circuit basis for the functional segregation of itch and pain

Recent advances reveal an extensive cellular diversity within the dorsal horn. How this complexity processes distinct sensations, like itch and pain, remains a fundamental question. We discovered hidden within a population of neurons expressing the gastrin-releasing peptide receptor (Grpr+), thought to be itch-specific, are highly homologous yet functionally distinct subtypes distinguished by expression of Tachykinin-1 (Tac1). While the Tac1- subtype mediates itch, the Tac1+ subtype mediates mechanical allodynia across diverse pain states. Inhibitory populations and differential sensitivities to GRP serve as key modulators of the Grpr+ neuron subtypes, shaping modality specific output. Leveraging computationally designed genomic enhancers to silence the Tac1- population reverses itch while silencing the Tac1+ subtype reverses mechanical allodynia broadly. The work demonstrates the nuance of differential sensory modality coding within the dorsal horn and the power of genomic enhancer-based strategies for modality-specific targeting.

neuroscience↗

bioRxiv2025

Combining Machine Learning and Multiplexed, In Situ Profiling to Engineer Cell Type and Behavioral Specificity

A promising strategy for the precise control of neural circuits is to use cis-regulatory enhancers to drive transgene expression in specific cells. However, enhancer discovery faces key challenges: low in vivo success rates, species-specific differences in activity, challenges with multiplexing adeno-associated viruses (AAVs), and the lack of spatial detail from single-cell sequencing. In order to accelerate enhancer discovery for the dorsal spinal cord--a region critical for pain and itch processing--we developed an end-to-end platform, ESCargoT (Engineered Specificity of Cargo Transcription), combining machine learning (ML)-guided enhancer prioritization, modular AAV assembly, and multiplexed, in situ screening. Using cross-species chromatin accessibility data, we trained ML models to predict enhancer activity in oligodendrocytes and in 15 dorsal horn neuronal subtypes. We first demonstrated that an initial enhancer, Excit-1, targeted excitatory dorsal horn neurons and drove reversal of mechanical allodynia in an inflammatory pain model. To enable parallel profiling of a 27-enhancer-AAV library delivered intraspinally in mice, we developed a Spatial Parallel Reporter Assay (SPRA) by integrating a novel Golden-Gate assembly pipeline with multiplexed, in situ screening. Regression adjustment for spatial confounding enabled specificity comparisons between enhancers, demonstrating the ability to screen enhancers targeting diverse cell types (oligodendrocytes, motoneurons, dorsal neuron subtypes) in one experiment. We then validated two candidates, targeting Exc-LMO3 and Exc-SKOR2 neurons, respectively. In a companion paper by Noh et al, our colleagues show that the functional specificity of the Exc-SKOR2-targeting enhancer, unlike Excit-1, is capable of blocking the sensation of chemical itch in mice. These enhancers were derived from the macaque genome but displayed functional sensitivity in mice. This platform enables spatially resolved, multiplexed in vivo enhancer profiling to accelerate discovery of cell-targeting tools and gene therapy development.

neuroscience↗

bioRxiv2024

Dopamine mediated plasticity preserves excitatory connections to direct pathway striatal projection neurons and motor function in a mouse model of Parkinson's disease

The cardinal symptoms of Parkinsons disease (PD) such as bradykinesia and akinesia are debilitating, and treatment options remain inadequate. The loss of nigrostriatal dopamine neurons in PD produces motor symptoms by shifting the balance of striatal output from the direct (go) to indirect (no-go) pathway in large part through changes in the excitatory connections and intrinsic excitabilities of the striatal projection neurons (SPNs). Here, we report using two different experimental models that a transient increase in striatal dopamine and enhanced D1 receptor activation, during 6-OHDA dopamine depletion, prevent the loss of mature spines and dendritic arbors on direct pathway projection neurons (dSPNs) and normal motor behavior for up to 5 months. The primary motor cortex and midline thalamic nuclei provide the major excitatory connections to SPNs. Using ChR2-assisted circuit mapping to measure inputs from motor cortex M1 to dorsolateral dSPNs, we observed a dramatic reduction in both experimental model mice and controls following dopamine depletion. Changes in the intrinsic excitabilities of SPNs were also similar to controls following dopamine depletion. Future work will examine thalamic connections to dSPNs. The findings reported here reveal previously unappreciated plasticity mechanisms within the basal ganglia that can be leveraged to treat the motor symptoms of PD.

neuroscience↗

bioRxiv2023

Symmetry in frontal but not motor and somatosensory corticocortical and corticostriatal circuitry

Neocortex and striatum are topographically organized for sensory and motor functions. While sensory and motor areas are lateralized for touch and motor control, respectively, frontal areas are involved in decision making, where lateralization of function may be less important. This study contrasted the topographic precision of cell type-specific ipsilateral and contralateral cortical projections while varying the injection site location in transgenic mice of both sexes. While sensory cortical areas had strongly topographic outputs to ipsilateral cortex and striatum, they were weaker and not as topographically precise to contralateral targets. Motor cortex had somewhat stronger projections, but still relatively weak contralateral topography. In contrast, frontal cortical areas had high degrees of topographic similarity for both ipsilateral and contralateral projections to cortex and striatum. Corticothalamic organization is mainly ipsilateral, with weaker, more medial contralateral projections. Corticostriatal computations might integrate input outside closed basal ganglia loops using contralateral projections, enabling the two hemispheres to act as a unit to converge on one result in motor planning and decision making. Significance StatementEach cerebral hemisphere is responsible for sensation and movement of the opposite side of the body. Many axonal projections cross the midline to target contralateral areas. Crossed corticocortical, corticostriatal, and corticothalamic projections originate from much of neocortex, but how these projections vary across cortical regions and cell types is unknown. We quantify differences in the strength and targeting of ipsilateral and contralateral projections from frontal, motor, and somatosensory areas. The contralateral corticocortical and corticostriatal projections are proposed to play a larger role in frontal areas than in sensory or motor ones as a circuit basis for unifying computation across hemispheres in motor planning, while contralateral connectivity plays a smaller role in sensory and motor processing.

neuroscience↗

bioRxiv2022

A striatal plasticity that supports the long-term preservation of motor function in Parkinsonian mice.

Motor deficits of Parkinsons disease (PD) such as rigidity, bradykinesia and akinesia result from a progressive loss of nigrostriatal dopamine neurons. No therapies exist that slow their degeneration and the most effective treatments for the motor symptoms: L-dopa -the precursor to dopamine, and deep brain stimulation can produce dyskinesias and are highly invasive, respectively. Hence, alternative strategies targeted to slow the progression or delay the onset of motor symptoms are still highly sought. Here we report the identification of a long-term striatal plasticity mechanism that delays for several months, the onset of motor deficits in a mouse PD model. Specifically, we show that a one-week transient daily elevation of midbrain dopamine neuron activity during depletion preserves the connectivity of direct but not indirect pathway projection neurons. The findings are consistent with the balance theory of striatal output pathways and suggest a novel approach for treating the motor symptoms of PD.

neuroscience↗