2019 Grant Recipient – Colleen Carpenter

Dissecting the Interplay Between Genetic and Metabolic Deficits in LGS using Zebrafish

Dr. Colleen Carpenter, PhD

University of California, San Francisco

Highlights:

• Model 40 different single-gene mutations that represents catastrophic childhood epilepsies in zebrafish
• Evaluate electrophysiological, behavioral, neuro-anatomical, survival and pharmacological assays.
• Phenotypes with unprovoked electrographic seizure activity were identified in zebrafish lines for 8 genes.
• Created an open-source database containing sequencing information, survival curves, behavioral profiles and representative electrophysiology data.
• We offer all zebrafish lines as a resource to the neuroscience community.

Results:

Genetic engineering techniques have contributed to the now widespread use of zebrafish to investigate gene function, but zebrafish-based human disease studies, particularly for neurological disorders, are limited. Here we used CRISPR-Cas9 to generate single-gene mutant zebrafish lines representing catastrophic childhood epilepsies. We evaluated larval phenotypes using electrophysiological, behavioral, neuro-anatomical, survival, and pharmacological assays. Local field potential recordings (LFP) were used to screen larvae. Phenotypes with unprovoked electrographic seizure activity (i.e., epilepsy) were identified in zebrafish lines for eight genes associated with LGS. We also created an open-source database containing sequencing information, survival curves, behavioral profiles, and representative electrophysiology data. We offer all zebrafish lines as a resource to the neuroscience community and envision them as a starting point for further functional analysis and/or identification of new therapies.

Phenotypic analysis of catastrophic childhood epilepsy genes

Lay Abstract:

Seizures are due to abnormal activity along the electrical networks in the brain and may lead to sudden uncontrolled jerky movements, loss of consciousness, confusion, and death. Epilepsy is a debilitating, chronic brain disorder where individuals experience spontaneous, recurrent seizures. Lennox-Gastaut Syndrome (LGS) is currently one of the most severe childhood-onset epilepsies. In addition to frequent seizures, patients often exhibit serious cognitive, behavioral, and psychiatric problems. The prognosis for LGS is poor. There is no cure, and many of the available antiepileptic drugs are ineffective in controlling LGS seizures. Thus, an urgent unmet need remains to improve the current drug discovery process for LGS.

The first step in treating a disease is to gain a concrete understanding of its etiology using an experimental animal model. The second step is to use this information to identify new therapies. Our strategy, based on work pioneered in the Baraban laboratory, is to generate zebrafish models for genetic forms of epilepsy. Using these models, we then perform large-scale drug screening to identify lead compounds. In a very short time (less than five years), this approach has already proved successful in Dravet syndrome (DS), another childhood epilepsy. Drugs discovered only in our zebrafish DS model show efficacy in DS patients and are moving on to FDA-approved clinical trials. Here we hope to apply a similar strategy targeted to LGS.