Biology subjects

Kurrasch, D. M.

Publications and source records attributed to Kurrasch, D. M..

4 recordsLinked to original sources

bioRxiv2026

SCN1A haploinsufficiency disrupts neural progenitor networks and accelerates neurogenesis in human Dravet syndrome forebrain assembloids

Dravet syndrome is a severe childhood neurological disorder caused mostly due to mutations in the sodium channel gene SCN1A. Although the disorder is widely attributed to dysfunction of inhibitory neurons, growing evidence suggests that disease mechanisms may begin much earlier during brain development. To investigate the developmental consequences of SCN1A haploinsufficiency, we generated patient-derived dorsal-ventral forebrain assembloids that model key features of human corticogenesis. We found that SCN1A was expressed in ventricular zone neural progenitors and that its reduced expression was associated with impaired growth, disrupted ventricular zone organization, and progressive depletion of progenitor populations. We further demonstrated reduced progenitor proliferation and self-renewal, accelerated cell-cycle exit, and premature neuronal differentiation, leading to increased production of excitatory neurons and enhanced network excitability. Single cell transcriptomic analyses revealed reduced cycling radial glial cells, accelerated progenitor maturation, and dysregulation of gap junction and calcium signaling pathways. Following these findings, we examined progenitor calcium activity and found that SCN1A haploinsufficiency disrupted coordinated functional network organization, resulting in reduced recurrent connectivity and fragmentation of functional cellular assemblies. These abnormalities occurred despite preserved intrinsic electrophysiological properties of individual progenitors, indicating a defect in population-level coordination rather than single cell electrophysiology. Together, our findings identify disrupted progenitor communication as an early developmental consequence of SCN1A haploinsufficiency and suggest that abnormalities within neural progenitor populations contribute to altered corticogenesis, excitatory neurogenesis, and circuit hyperexcitability in Dravet syndrome. This work expands current disease models beyond interneuron dysfunction and highlights the developing ventricular zone as a potential therapeutic target.

neuroscience↗

bioRxiv2024

Epileptic phenotypes in slc13a5 loss-of-function zebrafish are rescued by blocking NMDA receptor signaling

SLC13A5 encodes a citrate transporter highly expressed in the brain important for regulating intra- and extracellular citrate levels. Mutations in this gene cause a rare infantile epilepsy characterized by lifelong seizures, developmental delays, behavioral deficits, poor motor progression, and language impairments. SLC13A5 individuals respond poorly to treatment options; yet drug discovery programs are limited due to a paucity of animal models that phenocopy human symptoms. Here, we used CRISPR/Cas9 to create loss-of-function mutations in slc13a5a and slc13a5b, the zebrafish paralogs to human SLC13A5. slc13a5 mutant larvae showed cognitive dysfunction and sleep disturbances, consistent with SLC13A5 individuals. These mutants also exhibited fewer neurons and a concomitant increase in apoptosis across the optic tectum, a region important for sensory processing. slc13a5 mutants displayed hallmark features of epilepsy, including an imbalance in glutamatergic and GABAergic excitatory-inhibitory gene expression, disrupted neurometabolism, and neuronal hyperexcitation as measured in vivo by extracellular field recordings and live calcium imaging. Mechanistically, we tested the involvement of NMDA signaling in slc13a5 mutant epilepsy-like phenotypes. Slc13a5 protein co-localizes with excitatory NMDA receptors in wild-type zebrafish and blocking NMDA receptors in slc13a5 mutant larvae rescued bioenergetics, hyperexcitable calcium events, and behavioral defects. These data provide empirical evidence in support of the hypothesis that excess extracellular citrate over-chelates the ions needed to regulate NMDA receptor function, leading to sustained channel opening and an exaggerated excitatory response that manifests as seizures. These data show the utility of slc13a5 mutant zebrafish for studying SLC13A5 epilepsy and open new avenues for drug discovery.

neuroscience↗

bioRxiv2022

kcna1a mutant zebrafish as a model of episodic ataxia type 1 and epilepsy

ObjectiveKCNA1 mutations are associated with a rare neurological movement disorder known as episodic ataxia type 1 (EA1), with epilepsy as a common comorbidity. Current medications only provide partial relief to ataxia and/or seizures, making new drugs needed. Here, we investigate the utility of zebrafish kcna1a-/- as a model of EA1 with epilepsy by characterizing its phenotype and comparing the efficacy of the first-line therapy carbamazepine in kcna1a-/- zebrafish to Kcna1-/- rodents. MethodsWe used CRISPR/Cas9 mutagenesis to introduce a mutation in the sixth segment of the zebrafish Kcna1 protein. Behavioral and electrophysiological assays were performed on kcna1a-/- larvae to assess ataxia- and epilepsy-related phenotypes. We also carried out real-time qPCRs to measure the transcript levels of brain hyperexcitability markers and bioenergetic profiling of kcna1a-/- larvae to evaluate their metabolic health. Carbamazepine efficacy was tested using behavioral assessments in kcna1a-/- zebrafish and seizure frequency in Kcna1-/- mice. Resultskcna1a-/- zebrafish showed uncoordinated movements and locomotor deficits. The mutants also exhibited impaired startle responses when exposed to light-dark flashes and acoustic stimulation. Extracellular field recordings and upregulated fosab transcript levels showed hyperexcitability of the kcna1a-/- brain. Further, vglut2a and gad1b transcript levels were altered, indicative of neuronal excitatory/inhibitory imbalance in the kcna1a-/- brain. Metabolic health was also compromised in kcna1a-/- as seen by a significant reduction in measures of cellular respiration. Notably, carbamazepine reduced the impaired startle response in kcna1a-/- zebrafish but had no effect on the seizure frequency in Kcna1-/- mice, suggesting that this EA1 zebrafish model might better translate to human efficacy compared to rodents. SignificanceWe conclude that zebrafish kcna1a-/- larvae show ataxia and epilepsy-related phenotypes and that they are responsive to carbamazepine treatment, consistent with EA1 patients. This study supports the notion that these zebrafish disease models can be useful for drug screening as well as studying the underlying disease biology. KEY POINTSO_LIZebrafish kcna1a-/- larvae display dynamic behavioral changes, along with ataxia-like uncoordinated movements and brain hyperexcitability C_LIO_LIkcna1a-/- larvae have dysfunctional neuronal excitatory/inhibitory balance and perturbed metabolic health C_LIO_LISimilar to its effectiveness in patients, carbamazepine treatment improves behavioral deficits in kcna1a-/- larvae C_LI

neuroscience↗

bioRxiv2019

A Highly Conserved Shh Enhancer Coordinates Hypothalamic and Craniofacial Development

Enhancers that are conserved deep in evolutionary time regulate characteristics held in common across taxonomic classes. Here, deletion of the highly conserved Shh enhancer SBE2 (Shh brain enhancer 2) markedly reduced Shh expression within the embryonic brain specifically in the rostral diencephalon; however, no abnormal anatomical phenotype was observed due to compensatory low levels of expression mediated by a second enhancer. In contrast, a further reduction of Shh levels, achieved by crossing the SBE2 deletion with the Shh null allele, disrupted brain and craniofacial tissue; thus, linking SBE2 regulated Shh expression to multiple defects and further enabling the study of the effects of differing levels of Shh on embryogenesis. Development of the hypothalamus, derived from the rostral diencephalon, was disrupted along both the anterior-posterior (AP) and the dorsal-ventral (DV) axes. Expression of DV patterning genes and subsequent neuronal population induction were particularly sensitive to Shh expression levels, demonstrating a novel morphogenic context for Shh. The role of SBE2, which is highlighted by DV gene expression, is to step-up expression of Shh above the minimal activity of the second enhancer, ensuring the necessary levels of Shh in a regional-specific manner. We also show that low Shh levels in the diencephalon disrupted neighbouring craniofacial development, including mediolateral patterning of the bones along the cranial floor and viscerocranium. Thus, SBE2 contributes to hypothalamic morphogenesis and ensures there is coordination with the formation of the adjacent midline cranial bones that subsequently protects the neural tissue.

developmental biology↗