Biology subjects

Hill, S. F.

Publications and source records attributed to Hill, S. F..

4 recordsLinked to original sources

bioRxiv2026

Epilepsy and premature mortality driven by inhibitory neuron dysfunction in a mouse model of SCN1A gain-of-function neurodevelopmental disorder

The gene most commonly implicated in epilepsy, SCN1A, encodes the neuronal voltage-gated sodium channel subunit NaV1.1. SCN1A variants that reduce sodium current ("loss of function" variants) cause Dravet syndrome, a neurodevelopmental disorder defined by treatment-resistant temperature-sensitive epilepsy with onset at/around 5 months of age, developmental delay/intellectual disability, and features of or formal diagnosis autism. However, an emerging group of variants cause "gain of function" (GoF) effects on NaV1.1 and result in a distinct presentation with earlier onset than Dravet syndrome and prominent movement disorder but without temperature sensitivity. We developed the first mouse model of SCN1A GoF epilepsy with heterozygous Cre-dependent expression of the recurrent patient variant Scn1a-p.R1636Q. Global expression of this variant causes premature mortality in 100% (64/64) of mutant mice between postnatal day 12-18 due to spontaneous, convulsive seizures. Activation of the mutant allele in parvalbumin interneurons (Dlx5/6-Cre or PV-Cre), but not excitatory neurons (Slc17a7-Cre) or other interneuron subtypes (VIP-Cre or Sst-Cre), recapitulates the premature mortality and epilepsy phenotypes. Treatment of Scn1a-p.R1636Q mutant mice with the sodium channel blocker GS967 markedly prolongs lifespan. This work is the first study of SCN1A GoF epilepsy in a preclinical model in vivo. Further investigation in the Scn1aflox(R1636Q)mouse will yield new mechanistic insights into disease mechanisms to drive advances in the treatment of SCN1A GoF epilepsy.

neuroscience↗

bioRxiv2026

Developmental dysregulation of chandelier cell excitability in a mouse model of Dravet Syndrome

Chandelier cells (ChCs) are a rare and highly specialized sub-type of inhibitory neuron in the cerebral cortex that specifically and exclusively form synapses onto the axon initial segment of excitatory neurons and thereby exert powerful control of excitability. We applied a newly developed, cell type-specific enhancer element to label ChCs and assess their electrophysiological and morphological properties across development in Dravet Syndrome (Scn1a+/- mice), a prominent neurodevelopmental disorder defined by epilepsy and features of autism spectrum disorder. Dravet Syndrome is known to predominantly impact GABAergic interneurons. We found that ChCs from juvenile Scn1a+/- mice (postnatal day, P18-21) exhibit impaired excitability, and that deficits largely persist in young adulthood (P35-56). These findings are distinct from prior observations in the more common subtype of parvalbumin-positive interneurons, basket cells. We found no differences in the axonal or dendritic morphology of ChCs at either time point. Our results suggest a role for ChCs in the pathogenesis of Dravet Syndrome and constitute the first targeted study of ChC function in a specific genetically-defined neurodevelopmental disorder.

neuroscience↗

bioRxiv2025

Novel mouse model reveals neurodevelopmental origin of PMM2-CDG brain pathology

Congenital disorders of glycosylation (CDG) are a group of neurogenetic conditions resulting from disruptions in the cellular glycosylation machinery. The majority of CDG patients have compound heterozygous pathogenic variants in the phosphomannomutase 2 (PMM2) gene. Individuals with PMM2-CDG exhibit multi-systemic symptoms, prominently featuring neurological deficits with nearly all patients exhibiting cerebellar hypoplasia and ataxia. To overcome embryonic lethality caused by whole body knock-out of Pmm2 and mimic patient-related compound heterozygous pathogenic variants, we paired a Pmm2 flox allele (Pmm2fl) with a catalytically inactive knock-in allele (Pmm2R137H), commonly present in PMM2-CDG patients. Mice with post-mitotic loss of PMM2 from neurons or astrocytes are indistinguishable from unaffected littermates, including in a broad battery of neurological assessments. In contrast, removal of PMM2 from embryonic neural precursor cells leads to cerebellar hypoplasia, ataxia, seizures, and early lethality. Comprehensive multi-omics profiling, including metabolomics, glycomics, single-cell transcriptomics, proteomics, and glycoproteomics, reveal widespread molecular disturbances throughout the brain, with the cerebellum showing the most pronounced disruption. These findings highlight the heightened dependency of the developing cerebellum on intact N-glycosylation, aligning with clinical observations in PMM2-CDG patients. Importantly, glycoproteomic alterations identified in our mouse model are corroborated in PMM2-CDG patient post-mortem cerebellar tissue, underscoring the translational relevance of our findings and implicating impaired synaptic transmission as a key pathogenic mechanism.

neuroscience↗

bioRxiv2024

Attenuated ectopic action potential firing in parvalbumin expressing interneurons in a mouse model of Dravet Syndrome

Dravet syndrome is caused by heterozygous loss-of-function variants in SCN1A, which encodes the voltage-gated sodium channel Nav1.1. Our recent work suggests that a primary pathogenic mechanism of Dravet syndrome is impaired action potential propagation along axons of cortical parvalbumin-positive fast-spiking GABAergic interneurons (PVINs). Ectopic action potentials (EAPs) are action potentials that initiate distal to the axon initial segment. We recently demonstrated that a large proportion of PVINs fire EAPs during periods of increased excitation. Although their function remains unknown, EAPs may play a role in amplifying (when occurring in excitatory cells) and/or preventing seizures (when occurring in interneurons). Regardless of function, their generation in distal axons suggests that EAP frequency could be a useful proxy for distal axonal excitability. We hypothesized that EAPs are attenuated in PVINs from Dravet syndrome (Scn1a+/-) mice due to dysfunction of the distal axon. We induced EAPs in PVINs in acute brain slices prepared from male and female wildtype (WT) and Scn1a+/- mice at P18-21 and P35-56, when we have previously identified axonal conduction deficits in Scn1a+/- PVINs. We elicited EAPs in 17/22 (77%) of WT PVINs, including 6 (22%) that exhibited barrages of EAPs. In contrast, Scn1a+/- PVINs never fired barrages (0%), and only 8/23 (34%) exhibited even single EAPs. This finding adds to the body of evidence supporting impaired action potential propagation in Dravet syndrome PVINs, and is the first evidence of impaired EAP firing in a disease model, suggesting that dysregulation of EAPs could be involved in the pathophysiology of human disease.

neuroscience↗