Serine 421 regulates mutant huntingtin toxicity and clearance in mice

Huntington's disease (HD) is a progressive, adult-onset neurodegenerative disease caused by a polyglutamine (polyQ) expansion in the N-terminal region of the protein huntingtin (HTT). There are no cures or disease-modifying therapies for HD. HTT has a highly conserved Akt phosphorylation site at serine 421, and prior work in HD models found that phosphorylation at S421 (S421-P) diminishes the toxicity of mutant HTT (mHTT) fragments in neuronal cultures. However, whether S421-P affects the toxicity of mHTT in vivo remains unknown. In this work, we used murine models to investigate the role of S421-P in HTT-induced neurodegeneration. Specifically, we mutated the human mHTT gene within a BAC to express either an aspartic acid or an alanine at position 421, mimicking tonic phosphorylation (mHTT-S421D mice) or preventing phosphorylation (mHTT-S421A mice), respectively. Mimicking HTT phosphorylation strongly ameliorated mHTT-induced behavioral dysfunction and striatal neurodegeneration, whereas neuronal dysfunction persisted when S421 phosphorylation was blocked. We found that S421 phosphorylation mitigates neurodegeneration by increasing proteasome-dependent turnover of mHTT and reducing the presence of a toxic mHTT conformer. These data indicate that S421 is a potent modifier of mHTT toxicity and offer in vivo validation for S421 as a therapeutic target in HD.

PolyQ disease: too many Qs, too much function?

The nature of the gain-of-function toxicity found in polyglutamine (polyQ) diseases has been the subject of considerable debate. In this issue of Neuron, Duvick et al. and Nedelsky et al. show that, in two of these diseases, pathology is mediated by normal protein activity.

Targeted neurostimulation reverses a spatiotemporal biomarker of treatment-resistant depression

Major depressive disorder (MDD) is widely hypothesized to result from disordered communication across brain-wide networks. Yet, prior resting-state-functional MRI (rs-fMRI) studies of MDD have studied zero-lag temporal synchrony (functional connectivity) in brain activity absent directional information. We utilize the recent discovery of stereotyped brain-wide directed signaling patterns in humans to investigate the relationship between directed rs-fMRI activity, MDD, and treatment response to FDA-approved neurostimulation paradigm termed Stanford neuromodulation therapy (SNT). We find that SNT over the left dorsolateral prefrontal cortex (DLPFC) induces directed signaling shifts in the left DLPFC and bilateral anterior cingulate cortex (ACC). Directional signaling shifts in the ACC, but not the DLPFC, predict improvement in depression symptoms, and moreover, pretreatment ACC signaling predicts both depression severity and the likelihood of SNT treatment response. Taken together, our findings suggest that ACC-based directed signaling patterns in rs-fMRI are a potential biomarker of MDD.

Anterior Sensorimotor Subthalamic Nucleus Stimulation Is Associated With Improved Voice Function

BACKGROUND

Despite the impact of Parkinson disease (PD) on speech communication, there is no consensus regarding the effect of lead location on voice-related outcomes in subthalamic nucleus (STN) deep brain stimulation (DBS).

OBJECTIVE

To determine the relationship of stimulation location to changes in cepstral analyses of voice following STN DBS.

METHODS

Speech pathology evaluations were obtained from 14 PD subjects, before and after STN DBS, including audio-perceptual voice ratings (overall severity, loudness, hoarseness changes), measured indices of dysphonia (cepstral peak prominence and cepstral spectral index of dysphonia), and phonatory aerodynamics. The contact locations used for active stimulation at the time of postoperative voice evaluations were determined and assessed in relation to voice outcomes.

RESULTS

Voice outcomes remained relatively unchanged on average. Stimulation locations in the anterior portion of the sensorimotor region of the left STN, however, were associated with improvements in voice severity scores, cepstral spectral index of dysphonia, shortness of breath, and phonatory airflow during connected speech. Posterior locations were associated with worsening of these outcomes. Variation in the medial-lateral or dorsal-ventral position on the left, and in any direction on the right, did not correlate with any voice outcome.

CONCLUSION

Active contact placement within the anterior sensorimotor STN was associated with improved perceptual and acoustic-aerodynamic voice-related outcomes. These findings suggest an STN topography for improving airflow for speech, in turn improving how PD patients' voices sound.

Magnesium-ibogaine therapy in veterans with traumatic brain injuries

Traumatic brain injury (TBI) is a leading cause of disability. Sequelae can include functional impairments and psychiatric syndromes such as post-traumatic stress disorder (PTSD), depression and anxiety. Special Operations Forces (SOF) veterans (SOVs) may be at an elevated risk for these complications, leading some to seek underexplored treatment alternatives such as the oneirogen ibogaine, a plant-derived compound known to interact with multiple neurotransmitter systems that has been studied primarily as a treatment for substance use disorders. Ibogaine has been associated with instances of fatal cardiac arrhythmia, but coadministration of magnesium may mitigate this concern. In the present study, we report a prospective observational study of the Magnesium-Ibogaine: the Stanford Traumatic Injury to the CNS protocol (MISTIC), provided together with complementary treatment modalities, in 30 male SOVs with predominantly mild TBI. We assessed changes in the World Health Organization Disability Assessment Schedule from baseline to immediately (primary outcome) and 1 month (secondary outcome) after treatment. Additional secondary outcomes included changes in PTSD (Clinician-Administered PTSD Scale for DSM-5), depression (Montgomery-Åsberg Depression Rating Scale) and anxiety (Hamilton Anxiety Rating Scale). MISTIC resulted in significant improvements in functioning both immediately (Pcorrected < 0.001, Cohen's d = 0.74) and 1 month (Pcorrected < 0.001, d = 2.20) after treatment and in PTSD (Pcorrected < 0.001, d = 2.54), depression (Pcorrected < 0.001, d = 2.80) and anxiety (Pcorrected < 0.001, d = 2.13) at 1 month after treatment. There were no unexpected or serious adverse events. Controlled clinical trials to assess safety and efficacy are needed to validate these initial open-label findings. ClinicalTrials.gov registration: NCT04313712 .

Stereoselective macrocyclization through zirconocene-mediated coupling of achiral dialkynes

1,4-Bis[trimethylsilyl(ethynyl)]naphthalene () and 1,4-bis[trimethylsilyl(ethynyl)]anthracene () undergo diastereoselective coupling with Cp2Zr(py)(Me3SiC[triple bond, length as m-dash]CSiMe3) to give trimeric macrocycles in good yield.

Lateralized Effect of Thalamic Deep Brain Stimulation Location on Verbal Abstraction

BACKGROUND

Regionalized thalamic activity has been implicated in language function, and yet the effect of thalamic deep brain stimulation (DBS) on language-related clinical outcomes is underexplored.

OBJECTIVE

The objective of this study was to determine if the location of stimulation within the thalamus correlates with changes in language-related neuropsychological outcomes following DBS for essential tremor.

METHODS

Thirty patients with essential tremor underwent comprehensive neuropsychological evaluations before and after DBS surgery targeting the ventral intermediate nucleus of the thalamus. Changes in neuropsychological functions were evaluated. The relationships between language-related outcomes and stimulation location were assessed using both categorical and linear methods. Any significant results were further validated using linear discriminant analysis.

RESULTS

Most neuropsychological functions remained unchanged at the group level. However, outcome on a measure of verbal abstraction was significantly dependent on stimulation location along the anterior-posterior axis within the left ventral lateral thalamus, with anterior stimulation associated with reduced verbal abstraction performance. This result was supported by linear discriminant analysis, which showed that stimulation locations with improved and reduced verbal abstraction function were best separated by a vector nearly parallel to the anterior-posterior axis. No stimulation location dependence was found for verbal abstraction outcome in the right thalamus or for outcomes of other language functions in either hemisphere.

CONCLUSION

We demonstrate an effect of thalamic DBS on verbal abstraction as a function of left thalamic topography. This finding provides clinical evidence for the lateralization and regionalization of thalamic language function that may be relevant for understanding nonmotor effects of stimulation. © 2021 International Parkinson and Movement Disorder Society.

Responsive deep brain stimulation guided by ventral striatal electrophysiology of obsession durably ameliorates compulsion

Treatment-resistant obsessive-compulsive disorder (OCD) occurs in approximately one-third of OCD patients. Obsessions may fluctuate over time but often occur or worsen in the presence of internal (emotional state and thoughts) and external (visual and tactile) triggering stimuli. Obsessive thoughts and related compulsive urges fluctuate (are episodic) and so may respond well to a time-locked brain stimulation strategy sensitive and responsive to these symptom fluctuations. Early evidence suggests that neural activity can be captured from ventral striatal regions implicated in OCD to guide such a closed-loop approach. Here, we report on a first-in-human application of responsive deep brain stimulation (rDBS) of the ventral striatum for a treatment-refractory OCD individual who also had comorbid epilepsy. Self-reported obsessive symptoms and provoked OCD-related distress correlated with ventral striatal electrophysiology. rDBS detected the time-domain area-based feature from invasive electroencephalography low-frequency oscillatory power fluctuations that triggered bursts of stimulation to ameliorate OCD symptoms in a closed-loop fashion. rDBS provided rapid, robust, and durable improvement in obsessions and compulsions. These results provide proof of concept for a personalized, physiologically guided DBS strategy for OCD.

Network effects of Stanford Neuromodulation Therapy (SNT) in treatment-resistant major depressive disorder: a randomized, controlled trial

Here, we investigated the brain functional connectivity (FC) changes following a novel accelerated theta burst stimulation protocol known as Stanford Neuromodulation Therapy (SNT) which demonstrated significant antidepressant efficacy in treatment-resistant depression (TRD). In a sample of 24 patients (12 active and 12 sham), active stimulation was associated with significant pre- and post-treatment modulation of three FC pairs, involving the default mode network (DMN), amygdala, salience network (SN) and striatum. The most robust finding was the SNT effect on amygdala-DMN FC (group*time interaction F(1,22) = 14.89, p < 0.001). This FC change correlated with improvement in depressive symptoms (rho (Spearman) = -0.45, df = 22, p = 0.026). The post-treatment FC pattern showed a change in the direction of the healthy control group and was sustained at the one-month follow-up. These results are consistent with amygdala-DMN connectivity dysfunction as an underlying mechanism of TRD and bring us closer to the goal of developing imaging biomarkers for TMS treatment optimization.Trial registration: ClinicalTrials.gov NCT03068715.

Association of Preoperative Visual Hallucinations With Cognitive Decline After Deep Brain Stimulation for Parkinson's Disease

OBJECTIVE

Deep brain stimulation (DBS) is effective for the motor symptoms of Parkinson's disease (PD). Although most patients benefit with minimal cognitive side effects, cognitive decline is a risk, and there is little available evidence to guide preoperative risk assessment. Visual illusions or visual hallucinations (VHs) and impulse-control behaviors (ICBs) are relatively common complications of PD and its treatment and may be a marker of more advanced disease, but their relationship with postoperative cognition has not been established. The authors aimed to determine whether any preoperative history of VHs or ICBs is associated with cognitive change after DBS.

METHODS

Retrospective chart review identified 54 patients with PD who received DBS of the subthalamic nucleus or globus pallidus internus and who completed both pre- and postoperative neuropsychological testing. Linear regression models were used to assess whether any preoperative history of VHs or ICBs was associated with changes in attention, executive function, language, memory, or visuospatial cognitive domains while controlling for surgical target and duration between evaluations.

RESULTS

The investigators found that a history of VHs was associated with declines in attention (b=-4.04, p=0.041) and executive function (b=-4.24, p=0.021). A history of ICBs was not associated with any significant changes.

CONCLUSIONS

These results suggest that a history of VHs may increase risk of cognitive decline after DBS; thus, specific preoperative counseling and targeted remediation strategies for these patients may be indicated. In contrast, a history of ICBs does not appear to be associated with increased cognitive risk.

Depression history modulates effects of subthalamic nucleus topography on neuropsychological outcomes of deep brain stimulation for Parkinson's disease

Patients with psychiatric symptoms, such as depression, anxiety, and visual hallucinations, may be at increased risk for adverse effects following deep brain stimulation of the subthalamic nucleus for Parkinson's disease, but there have been relatively few studies of associations between locations of chronic stimulation and neuropsychological outcomes. We sought to determine whether psychiatric history modulates associations between stimulation location within the subthalamic nucleus and postoperative affective and cognitive changes. We retrospectively identified 42 patients with Parkinson's disease who received bilateral subthalamic nucleus deep brain stimulation and who completed both pre- and postoperative neuropsychological testing. Active stimulation contacts were localized in MNI space using Lead-DBS software. Linear discriminant analysis identified vectors maximizing variance in postoperative neuropsychological changes, and Pearson's correlations were used to assess for linear relationships. Stimulation location was associated with postoperative change for only 3 of the 18 neuropsychological measures. Variation along the superioinferior (z) axis was most influential. Constraining the analysis to patients with a history of depression revealed 10 measures significantly associated with active contact location, primarily related to location along the anterioposterior (y) axis and with worse outcomes associated with more anterior stimulation. Analysis of patients with a history of anxiety revealed 5 measures with location-associated changes without a predominant axis. History of visual hallucinations was not associated with significant findings. Our results suggest that a history of depression may influence the relationship between active contact location and neuropsychological outcomes following subthalamic nucleus deep brain stimulation. These patients may be more sensitive to off-target (nonmotor) stimulation.

Early differences in lassitude predicts outcomes in Stanford Neuromodulation Therapy for difficult to treat depression

Stanford Neuromodulation Therapy (SNT), has recently shown rapid efficacy in difficult to treat (DTT) depression. We conducted an exploratory analysis of individual symptom improvements during treatment, correlated with fMRI, to investigate this rapid improvement in 23 DTT participants from an SNT RCT (12 active, 11 sham). Montgomery-Åsberg Depression Rating Scale item 7 (Lassitude) was the earliest to show improvements between active and sham, as early as treatment day 2. Lassitude score at treatment day 3 was predictive of response at 4 weeks post-treatment and response immediately after treatment. Participants with lower lassitude scores at treatment day 3 had different patterns of sgACC functional connectivity compared to participants with higher scores in both baseline and post-treatment minus baseline analyses. Further work will aim to first replicate these preliminary findings, and then to extend these findings and examine how SNT may affect lassitude and behavioral activation early in treatment.

A Preliminary Investigation Of Repetitive Transcranial Magnetic Stimulation Applied To The Left Dorsolateral Prefrontal Cortex In Treatment Seeking Participants With Cannabis Use Disorder

Background

Cannabis use disorder (CUD) is a common and consequential disorder. When applied to the dorsolateral prefrontal cortex (DLPFC), repetitive transcranial magnetic stimulation (rTMS) reduces craving across substance use disorders and may have a therapeutic clinical effect when applied in serial sessions. The present study sought to preliminarily determine whether serial sessions of rTMS applied to the DLPFC had a therapeutic effect in CUD.

Methods

This study was a two-site, phase-2, double-blind, randomized-controlled-trial. Seventy-two treatment-seeking participants (37.5% Women, mean age 30.2±9.9SD) with ≥moderate-CUD were randomized to active or sham rTMS (Beam-F3, 10Hz, 20-total-sessions, with cannabis cues) while undergoing a three-session motivational enhancement therapy intervention. The primary outcome was the change in craving between pre- and post-treatment (Marijuana Craving Questionnaire Short-Form-MCQ-SF). Secondary outcomes included the number of weeks of abstinence and the number of days-per-week of cannabis use during 4-weeks of follow-up.

Results

There were no significant differences in craving between conditions. Participants who received active rTMS reported numerically, but not significantly, more weeks of abstinence in the follow-up period than those who received sham rTMS (15.5%-Active; 9.3%-Sham; rate ratio = 1.66 [95% CI: 0.84, 3.28]; p=0.14). Participants who received active rTMS reported fewer days-per-week of cannabis use over the final two-weeks of the follow-up period (Active vs. Sham: -0.72; Z=-2.33, p=0.02).

Conclusions

This trial suggests rTMS is safe and feasible in individuals with CUD and may have a therapeutic effect on frequency of cannabis use, though further study is needed with additional rTMS-sessions and a longer follow-up period.

Causal network localization of brain stimulation targets for trait anxiety

Transcranial magnetic stimulation (TMS) and deep brain stimulation (DBS) can treat some neuropsychiatric disorders, but there is no consensus approach for identifying new targets. We localized causal circuit-based targets for anxiety that converged across multiple natural experiments. Lesions (n=451) and TMS sites (n=111) that modify anxiety mapped to a common normative brain circuit (r=0.68, p=0.01). In an independent dataset (n=300), individualized TMS site connectivity to this circuit predicted anxiety change (p=0.02). Subthalamic DBS sites overlapping the circuit caused more anxiety (n=74, p=0.006), thus demonstrating a network-level effect, as the circuit was derived without any subthalamic sites. The circuit was specific to trait versus state anxiety in datasets that measured both (p=0.003). Broadly, this illustrates a pathway for discovering novel circuit-based targets across neuropsychiatric disorders.

Huntingtin contains an ubiquitin-binding domain and regulates lysosomal targeting of mitochondrial and RNA-binding proteins

Understanding the normal function of the Huntingtin (HTT) protein is of significance in the design and implementation of therapeutic strategies for Huntington's disease (HD). Expansion of the CAG repeat in the HTT gene, encoding an expanded polyglutamine (polyQ) repeat within the HTT protein, causes HD and may compromise HTT's normal activity contributing to HD pathology. Here, we investigated the previously defined role of HTT in autophagy specifically through studying HTT's association with ubiquitin. We find that HTT interacts directly with ubiquitin in vitro. Tandem affinity purification was used to identify ubiquitinated and ubiquitin-associated proteins that copurify with a HTT N-terminal fragment under basal conditions. Copurification is enhanced by HTT polyQ expansion and reduced by mimicking HTT serine 421 phosphorylation. The identified HTT-interacting proteins include RNA-binding proteins (RBPs) involved in mRNA translation, proteins enriched in stress granules, the nuclear proteome, the defective ribosomal products (DRiPs) proteome and the brain-derived autophagosomal proteome. To determine whether the proteins interacting with HTT are autophagic targets, HTT knockout (KO) cells and immunoprecipitation of lysosomes were used to investigate autophagy in the absence of HTT. HTT KO was associated with reduced abundance of mitochondrial proteins in the lysosome, indicating a potential compromise in basal mitophagy, and increased lysosomal abundance of RBPs which may result from compensatory up-regulation of starvation-induced macroautophagy. We suggest HTT is critical for appropriate basal clearance of mitochondrial proteins and RBPs, hence reduced HTT proteostatic function with mutation may contribute to the neuropathology of HD.

A preliminary randomized controlled trial of repetitive transcranial magnetic stimulation applied to the left dorsolateral prefrontal cortex in treatment seeking participants with cannabis use disorder

BACKGROUND

Cannabis use disorder (CUD) is a common and consequential disorder. When applied to the dorsolateral prefrontal cortex (DLPFC), repetitive transcranial magnetic stimulation (rTMS) reduces craving across substance use disorders and may have therapeutic clinical effects when applied in serial-sessions. The present study sought to preliminarily determine whether serial-sessions of rTMS applied to the DLPFC had a therapeutic effect in CUD.

METHODS

This study was a two-site, phase-2, double-blind, randomized-controlled-trial. Seventy-two treatment-seeking participants (37.5% Women, mean age 30.2±9.9SD) with ≥moderate-CUD were randomized to active or sham rTMS (Beam-F3, 10Hz, 20-total-sessions, two-sessions-per-visit, two-visits-per-week, with cannabis cues) while undergoing a three-session motivational enhancement therapy intervention. The primary outcome was the change in craving between pre- and post- treatment (Marijuana Craving Questionnaire Short-Form-MCQ-SF). Secondary outcomes included the number of weeks of abstinence and the number of days-per-week of cannabis use during 4-weeks of follow-up.

RESULTS

There were no significant differences in craving between conditions. Participants who received active-rTMS reported numerically, but not significantly, more weeks of abstinence in the follow-up period than those who received sham-rTMS (15.5%-Active; 9.3%-Sham; rate ratio = 1.66 [95% CI: 0.84, 3.28]; p=0.14). Participants who received active-rTMS reported fewer days-per-week of cannabis use over the final two-weeks of the follow-up period than those receiving sham-rTMS (Active vs. Sham: -0.72; Z=-2.33, p=0.02).

CONCLUSIONS

This trial suggests rTMS is safe and feasible in individuals with CUD and may have a therapeutic effect on frequency of cannabis use, though further study is needed with additional rTMS-sessions and a longer follow-up period.

Increased anti-correlation between the left dorsolateral prefrontal cortex and the default mode network following Stanford Neuromodulation Therapy (SNT): analysis of a double-blinded, randomized, sham-controlled trial

SNT is a high-dose accelerated intermittent theta-burst stimulation (iTBS) protocol coupled with functional-connectivity-guided targeting that is an efficacious and rapid-acting therapy for treatment-resistant depression (TRD). We used resting-state functional MRI (fMRI) data from a double-blinded sham-controlled randomized controlled trial1 to reveal the neural correlates of SNT-based symptom improvement. Neurobehavioral data were acquired at baseline, post-treatment, and 1-month follow-up. Our primary analytic objective was to investigate changes in seed-based functional connectivity (FC) following SNT and hypothesized that FC changes between the treatment target and the sgACC, DMN, and CEN would ensue following active SNT but not sham. We also investigated the durability of post-treatment observed FC changes at a 1-month follow-up. Study participants included transcranial magnetic stimulation (TMS)-naive adults with a primary diagnosis of moderate-to-severe TRD. Fifty-four participants were screened, 32 were randomized, and 29 received active or sham SNT. An additional 5 participants were excluded due to imaging artifacts, resulting in 12 participants per group (Sham: 5F; SNT: 5F). Although we did not observe any significant group × time effects on the FC between the individualized stimulation target (L-DLPFC) and the CEN or sgACC, we report an increased magnitude of negative FC between the target site and the DMN post-treatment in the active as compared to sham SNT group. This change in FC was sustained at the 1-month follow-up. Further, the degree of change in FC was correlated with improvements in depressive symptoms. Our results provide initial evidence for the putative changes in the functional organization of the brain post-SNT.