Haussler_et_al_2023_MolecularNeurobiology

Häussler_et_al_2023_Molecular Neurobiology

Downregulation of Ubiquitin-Specific Protease 15 (USP15) Does Not Provide Therapeutic Benefit in Experimental Mesial Temporal Lobe Epilepsy

Molecular Neurobiology, 2023, https://doi.org/10.1007/s12035-023-03692-2

Structural epilepsies display complex immune activation signatures. However, it is unclear which neuroinflammatory pathways drive pathobiology. Transcriptome studies of brain resections from mesial temporal lobe epilepsy (mTLE) patients revealed a dysregulation of transforming growth factor β, interferon α/β and nuclear factor erythroid 2-related factor 2 pathways. Since these pathways are regulated by ubiquitin-specific proteases (USP), in particular USP15, we hypothesized that USP15 blockade may provide therapeutic relief in treatment-resistant epilepsies. For validation, transgenic mice which either constitutively or inducibly lack Usp15 gene expression underwent intrahippocampal kainate injections to induce mTLE. We show that the severity of status epilepticus is unaltered in mice constitutively lacking Usp15 compared to wildtypes. Cell death, reactive gliosis and changes in the inflammatory transcriptome were pronounced at 4 days after kainate injection. However, these brain inflammation signatures did not differ between genotypes. Likewise, induced deletion of Usp15 in chronic epilepsy did not affect seizure generation, cell death, gliosis or the transcriptome. Concordantly, siRNA-mediated knockdown of Usp15 in a microglial cell line did not impact inflammatory responses in form of cytokine release. Our data show that a lack of USP15 is insufficient to modulate the expression of relevant neuroinflammatory pathways in an mTLE mouse model and do not support targeting USP15 as a therapeutic approach for pharmacoresistant epilepsy.

Dataset

Here, we provide the dataset of intrahippocampal in vivo recordings and images of immunohistochemical stainings presented and analyzed in the paper.

Electrophysiology

Recordings from each mouse are presented in a separate folder. The folders are named after the individual mouse name (breeding number) and delta for conditional USP15 knockout mice (e.g. 146_delta) or con for mice with a floxed USP15 allele but without expression of cre recombinase, i.e. wildtypes (e.g. 154_con). Within each folder, all recordings of a mouse are presented in the following fashion: Recordingdate_UCB_recordinghour_mousenumberi.smr, e.g. 031219_UCB_001_146i.smr

Recording date: Each mouse was recorded to the following scheme: 5 consecutive days or recording; 2 days off; 5 days of tamoxifen injection (no recordings) to induce USP15 knockdown; 2 days off; 5 consecutive days of recording; 2 days off; 5 consecutive days of recording; 2 days off; 5 consecutive days of recording (the last five days were not done in all mice, so not all folders contain these).

Recording hour: Each mouse was recorded for 2 or 3 hours per day, after one hour of adaptation to the recording cage. Each recording hour is stored in a separate file. For each mouse the two recording hours that were selected for analysis in the paper (no major artifacts or disconnection or other problem) are presented, which could be 001 and 002 or 002 and 003, or 001 and 003.

Mousenumberi We present only the recording from the electrode implanted in the kainate-injected ipsilateral hippocampus (i) as these were used for the analysis in the paper.

.smr All files are stored as .smi files (Spike2 format). Signals were amplified (1000-fold, PGA32, Multichannel Systems/SmartEphys), bandpass filtered (1 Hz-5 kHz) and digitized (sampling rate 20 kHz; Power1401 with Spike2 software, CED, UK). Mice were recorded freely moving with a miniature preamplifier (MPA8i), so recordings might contain any kind of behavior (rest, sleep, exploration, grooming etc.).

Histology