Authors :
Presenting Author: Dulcie Lai, PharmD, PhD – CHOP
Icnelia Huerta-OCampo, MD – CHOP
Mika Houserova, PhD – CHOP
Brandon Brown, PhD – CHOP
Maximilian Gessner, BS – CHOP
Shareen Nelson, BS – CHOP
Elisa Waxman, PhD – CHOP
Benjamin Prosser, PhD – Penn
Beverly Davidson, PhD – CHOP
Rationale:
Syntaxin binding protein 1 (STXBP1, also known as MUNC18-1) plays an essential role in neurotransmitter release by regulating presynaptic vesicle fusion. Pathogenic variants in the STXBP1 gene primarily result in haploinsufficiency and present clinically as neurodevelopmental abnormalities accompanied by epilepsy. Current treatments for patients with STXBP1-related disorder (STXBP1-RD) are limited and focus on symptom management. To facilitate preclinical development of translatable STXBP1-RD gene therapies, we performed comprehensive phenotyping using mouse and human models of STXBP1-RD.
Methods:
To evaluate disease relevant phenotypes, Stxbp1-RD mice underwent a battery of behavioral tests including open field, light-dark assay, horizontal ladder, and Barnes maze.
For EEG characterization adult Stxbp1-RD mice (aged 16–30 weeks) were anesthetized, and electrodes implanted bilaterally in the motor, barrel, auditory, and visual cortices, as well as in the CA1 region of the hippocampus. Following a 48-hour postoperative recovery period, each mouse was connected to an Intan low-noise amplifier chip and data acquisition board via a lightweight tether. Mice were housed individually, and neural activity was continuously recorded for 48 to 72 hours.
To investigate network phenotypes in vitro using a human model, we used induced pluripotent stem cells (iPSCs) generated by reprogramming blood obtained from a patient with a pathogenic splice site mutation in STXBP1 (c663+1G >C) in conjunction with multielectrode array (MEA) recordings. A matched isogenic control was also generated with CRISPR-editing.
Results:
Behavioral phenotyping of Stxbp1-RD mice confirm disease-relevant phenotypes including hyperactivity, anxiety-like behaviors, locomotor deficits, and memory deficits. Furthermore, multielectrode EEG in these mice revealed an increase in delta power during wakefulness, a reduction in alpha/delta ratio, irregular spiking activity, and prolonged ( >1s) spike-wave discharges across brain regions. In vitro, MEA recordings of iPSC-derived cortical neurons reveal increased burst count and decreased burst duration in patient derived networks compared to the isogenic control indicating changes in network dynamics.
Conclusions:
Collectively, we have identified disease-relevant phenotypes spanning multiple species and platforms that will aid in the development of gene therapies to treat STXBP1-RD.
Funding:
Center for Epilepsy and Neurodevelopmental Disorders (ENDD).