Authors :
Presenting Author: Brandon Brown, PhD – CHOP
Icnelia Huerta-OCampo, MD – CHOP
Mika Houserova, PhD – CHOP
Dulcie Lai, PharmD, PhD – CHOP
Maximilian Gessner, BS – CHOP
Alex Felix, PhD – University of Pennsylvania
Benjamin Prosser, PhD – Penn
Beverly Davidson, PhD – CHOP
Rationale:
Synaptic Ras-GTPase-activating protein (SYNGAP1) plays a key role in synaptic development and synaptic plasticity by coupling presynaptic neurotransmitter release with postsynaptic maturation. Pathogenic variants in the SYNGAP1 gene result in haploinsufficiency, which presents clinically as neurodevelopmental encephalopathy, intellectually disability, and epilepsy. Current treatments for patients with SYNGAP1-related disorder (SYNGAP1-RD) are limited and focus on symptom management. To facilitate the development of SYNGAP1-RD gene therapies we have developed a humanized mouse model and optimized novel functional readouts in vitro.Methods:
To produce humanized SYNGAP1-RD mice we crossed our recently developed humanized SYNGAP1 mouse line with Syngap1-RD mice. To characterize disease relevant behavioral phenotypes, juvenile (4-6 weeks old) and aged (30-33 weeks old) mice were subject to a battery of behavioral assays. Adult mice were also implanted with custom multielectrode EEGs to record from the motor cortex, barrel cortex, visual cortex, auditory cortex, and hippocampus.
For functional readouts in vitro we’ve utilized a high speed, subcellular localized genetically encoded calcium sensor to evaluate single neuron activity and network dynamics from SYNGAP1-RD cortical neuron cultures. Results:
The humanized SYNGAP1-RD mice, produced here, show disease related phenotypes including hyperactivity, memory deficits, and locomotor impairments, some of which are age dependent. Additionally, EEG in humanized Syngap1-RD mice reveal increased spiking and altered power density spectra across brain regions. In vitro we are able to reliably express high-speed calcium sensors in cortical neuron cultures via adeno-associated viral transduction, and preliminary analyses reveal increased firing rates of Syngap1-RD cultures. Analyses to characterize the rate of network maturation and network dynamics are ongoing. Conclusions: The humanized SYNGAP1-RD mouse model generated here provides a novel platform allowing for human gene targeted therapies to be assessed, and
in vitro high-speed calcium imaging allows for assessment of single neuron firing and neuronal network dynamics related to SYNGAP1-RD. The models and tools presented here recapitulate disease relevant phenotypes across model systems and will assist in the development of gene therapies to treat
SYNGAP1-RD.
Funding:
- Center for Epilepsy and Neurdevelopmental Disorders