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Reversal of cell, circuit and seizure phenotypes in a mouse model of DNM1 epileptic encephalopathy

ABSTRACT: Pathogenic heterozygous missense mutations in the DNM1 gene result in a novel form of epileptic encephalopathy. DNM1 encodes for the large GTPase dynamin-1, an enzyme with an obligatory role in the endocytosis of synaptic vesicles (SVs) at mammalian nerve terminals. Pathogenic DNM1 mutations cluster within regions required for its essential GTPase activity, implicating disruption of this enzyme activity as being central to epileptic encephalopathy. We reveal that the most prevalent pathogenic mutation in the GTPase domain of DNM1, R237W, disrupts dynamin-1 enzyme activity and SV endocytosis when overexpressed in central neurons. To determine how this dominant-negative heterozygous mutant impacted cell, circuit and behaviour when expressed from its endogenous locus, we generated a mouse carrying the R237W mutation. Neurons isolated from heterozygous mice displayed dysfunctional SV endocytosis, which translated into altered excitatory neurotransmission and seizure-like phenotypes. Importantly, these phenotypes were corrected at the cell, circuit and in vivo level by the drug, BMS-204352, which accelerates SV endocytosis in wild-type neurons. This study therefore provides the first direct link between dysfunctional SV endocytosis and epilepsy, and importantly reveals that SV endocytosis is a viable therapeutic route for monogenic intractable epilepsies.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Brain

DISEASE(S): Early Infantile Epileptic Encephalopathy

SUBMITTER: Matthias Trost

LAB HEAD: Matthias Trost

PROVIDER: PXD039667 | Pride | 2023-08-14

REPOSITORIES: Pride

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Project description:BACKGROUND: While many authorities theorize that cancer vaccines are too weak to be widely effective, there are quite a few reports with clearly demonstrated, significant clinical benefit in some patients. The literature of cellular cancer immunotherapies shows that 53% (78/147) of phase II studies showed evidence of clinical activity. While not all reached their primary endpoints, 75% (12/16) of phase III studies had positive data. SV-BR-1-GM, derived from a patient with grade 2 (moderately differentiated) breast cancer, is a GM-CSF-secreting breast cancer cell line with properties of antigen-presenting cells we established. METHODS: We report detailed molecular and clinical findings from an open-label phase I, single-arm pilot study in breast (3 subjects) and ovarian (1 subject) cancer with irradiated SV-BR-1-GM cells (ClinicalTrials.gov Identifier NCT00095862). Inoculations of SV-BR-1-GM were preceded by low-dose cyclophosphamide and followed by injections of interferon-alpha2b into the SV-BR-1-GM inoculation sites. We assessed both cellular (delayed-type hypersensitivity (DTH) reactions) and humoral (anti-SV-BR-1 antibody) immune responses and conducted molecular analyses on patient blood cells and SV-BR-1-GM cells. RESULTS: Treatment was generally safe and well tolerated. Immune responses were elicited universally. Overall survival was more than 33 months for three of the four patients. As previously reported, one patient (Subject A002, with grade 2 breast cancer) had regression of metastases in lung, breast and soft tissue within 2 months of treatment initiation. At later relapse, with multiple metastases including several in the brain, rapid tumor response was again seen, including complete regression of CNS metastases. Consistent with a role of Class II HLA in contributing to SV-BR-1-GM’s mechanism of action, Subject A002 allele-matched SV-BR-1-GM at the HLA-DRB1 and HLA-DRB3 loci. Only the HLA-DRB1 alleles were clearly expressed in SV-BR-1-GM cells. However, interferon-gamma (possibly also present in situ) upregulated both HLA-DRB1 and HLA-DRB3 to substantial levels. Gene expression data supports the hypothesis that SV-BR-1-GM cells have retained some of the original breast cancer’s grade 2 character. CONCLUSIONS: We describe a whole-cell immunotherapy regimen with remarkable rapidity of response and a speedy rescue response, including complete resolution of CNS metastases after relapse. Class II HLA matches might be critical for SV-BR-1-GM’s therapeutic potential.

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Reversal of cell, circuit and seizure phenotypes in a mouse model of DNM1 epileptic encephalopathy

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