Biology subjects

Dogra, D.

Publications and source records attributed to Dogra, D..

3 recordsLinked to original sources

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↗

bioRxiv2021

Myostatin is a negative regulator of adult neurogenesis in zebrafish

Intrinsic and extrinsic inhibition of axonal and neuronal regeneration obstruct spinal cord (SC) repair in mammals. In contrast, adult zebrafish achieve functional recovery after SC damage. While studies of innate SC regeneration have focused on axon regrowth as a primary repair mechanism, how local neurogenesis impacts functional recovery is unknown. We uncovered dynamic expression of myostatin b (mstnb) in a niche of dorsal ependymal progenitors after complete SC transection in zebrafish. Genetic loss-of-function in mstnb impaired functional recovery, although glial and axonal bridging across the lesion were unaffected. Using a series of transgenic reporter lines, we quantified the numbers of stem, progenitor, and neuronal cells in the absence of mstnb. We found neural stem cell proliferation was reduced, while newborn neurons were increased in mstnb null tissues, suggesting mstnb is a negative regulator of neurogenesis. Molecularly, neuron differentiation genes were upregulated, while the neural stem cell maintenance gene fgf1b was downregulated in mstnb mutants. Finally, we show that human FGF1 treatment rescued neuronal gene expression in mstnb mutants. These studies uncover unanticipated neurogenic functions for mstnb in adult zebrafish, and establish the importance of local neurogenesis for functional SC repair.

neuroscience↗

bioRxiv2021

Neuronal KGB-1 JNK MAPK signaling regulates the dauer developmental decision in response to environmental stress in C. elegans

In response to stressful growth conditions of high population density, food scarcity and elevated temperature, young larvae of nematode Caenorhabditis elegans can enter a developmentally arrested stage called dauer that is characterized by dramatic anatomic and metabolic remodeling. Genetic analysis of dauer formation of C. elegans has served as an experimental paradigm for the identification and characterization of conserved neuroendocrine signaling pathways. Here, we report the identification and characterization of a conserved JNK-like mitogen-activated protein kinase (MAPK) pathway that is required for dauer formation in response to environmental stressors. We observed that loss-of-function mutations in the MLK-1-MEK-1-KGB-1 MAPK pathway suppress dauer entry. Loss-of-function mutation in the VHP-1 MAPK phosphatase, a known negative regulator of KGB-1 signaling, results in constitutive dauer formation which is dependent on the presence of dauer pheromone but independent of diminished food levels or elevated temperatures. Our data suggest that KGB-1 pathway acts in the sensory neurons, in parallel to established insulin and TGF-{beta} signaling pathways, to transduce the dauer-inducing environmental cues of diminished food levels and elevated temperature.

developmental biology↗