Glioma genetic profiles associated with electrophysiologic hyperexcitability.

BACKGROUND: Distinct genetic alterations determine glioma aggressiveness, however, the diversity of somatic mutations contributing to peritumoral hyperexcitability and seizures over the course of the disease is uncertain. This study aimed to identify tumor somatic mutation profiles associated with clinically significant hyperexcitability. METHODS: A single center cohort of adults with WHO grades 1-4 glioma and targeted exome sequencing (n = 1716) was analyzed and cross-referenced with a validated EEG database to identify the subset of individuals who underwent continuous EEG monitoring (n = 206). Hyperexcitability was defined by the presence of lateralized periodic discharges and/or electrographic seizures. Cross-validated discriminant analysis models trained exclusively on recurrent somatic mutations were used to identify variants associated with hyperexcitability. RESULTS: The distribution of WHO grades and tumor mutational burdens were similar between patients with and without hyperexcitability. Discriminant analysis models classified the presence or absence of EEG hyperexcitability with an overall accuracy of 70.9%, regardless of IDH1 R132H inclusion. Predictive variants included nonsense mutations in ATRX and TP53, indel mutations in RBBP8 and CREBBP, and nonsynonymous missense mutations with predicted damaging consequences in EGFR, KRAS, PIK3CA, TP53, and USP28. This profile improved estimates of hyperexcitability in a multivariate analysis controlling for age, sex, tumor location, integrated pathologic diagnosis, recurrence status, and preoperative epilepsy. Predicted somatic mutation variants were over-represented in patients with hyperexcitability compared to individuals without hyperexcitability and those who did not undergo continuous EEG. CONCLUSION: These findings implicate diverse glioma somatic mutations in cancer genes associated with peritumoral hyperexcitability. Tumor genetic profiling may facilitate glioma-related epilepsy prognostication and management.

Follow-up ASPECTS improves prediction of potentially lethal malignant edema in patients with large middle cerebral artery stroke.

BACKGROUND: Recent studies have shown that follow-up head CT is a strong predictor of functional outcomes in patients with middle cerebral artery stroke and mechanical thrombectomy. We sought to determine whether total and/or regional follow-up Alberta Stroke Program Early CT Score (ASPECTSfu) are associated with important clinical outcomes during hospitalization and improve the performance of clinical prediction models of potentially lethal malignant edema (PLME). METHODS: We conducted a retrospective study of patients at three medical centers in a major North American metropolitan area with baseline and follow-up head CTs after large middle cerebral artery stroke between 2006 and 2022. We used multivariable logistic regression to test the association of total and regional ASPECTSfu with PLME (cerebral edema related death or surgery), adjusting for total baseline ASPECTS, age, sex, admission glucose, tissue plasminogen activator, and mechanical thrombectomy. We compared existing clinical risk models with and without total or regional ASPECTSfu using area under the curve. RESULTS: In our 560 patient cohort, lower total ASPECTSfu was significantly associated with higher odds of PLME when adjusting for confounders (OR 1.69, 95% CI 1.49 to 2.0), and improved model discrimination compared with existing models and models using baseline ASPECTS. Deep territory involvement (OR 2.46, 95% CI 1.53 to 4.01) and anterior territory involvement (OR 3.23, 95% CI 1.88 to 5.71) were significantly associated with PLME. CONCLUSIONS: Lower ASPECTSfu and certain locations on regional ASPECTSfu, including deep and anterior areas, were significantly associated with PLME. Including ASPECTSfu information improved discrimination of established edema prediction models and could be used immediately to help facilitate clinical management decisions and prognostication.

Glioma genetic profiles associated with electrophysiologic hyperexcitability.

Distinct genetic alterations determine glioma aggressiveness, however the diversity of somatic mutations contributing to peritumoral hyperexcitability and seizures is uncertain. In a large cohort of patients with sequenced gliomas (n=1716), we used discriminant analysis models to identify somatic mutation variants associated with electrographic hyperexcitability in a subset with continuous EEG recording (n=206). Overall tumor mutational burdens were similar between patients with and without hyperexcitability. A cross-validated model trained exclusively on somatic mutations classified the presence or absence of hyperexcitability with an overall accuracy of 70.9%, and improved estimates of hyperexcitability and anti-seizure medication failure in multivariate analysis incorporating traditional demographic factors and tumor molecular classifications. Somatic mutation variants of interest were also over-represented in patients with hyperexcitability compared to internal and external reference cohorts. These findings implicate diverse mutations in cancer genes associated with the development of hyperexcitability and response to treatment.

Target receptor identification and subsequent treatment of resected brain tumors with encapsulated and engineered allogeneic stem cells.

Cellular therapies offer a promising therapeutic strategy for the highly malignant brain tumor, glioblastoma (GBM). However, their clinical translation is limited by the lack of effective target identification and stringent testing in pre-clinical models that replicate standard treatment in GBM patients. In this study, we show the detection of cell surface death receptor (DR) target on CD146-enriched circulating tumor cells (CTC) captured from the blood of mice bearing GBM and patients diagnosed with GBM. Next, we developed allogeneic "off-the-shelf" clinical-grade bifunctional mesenchymal stem cells (MSCBif) expressing DR-targeted ligand and a safety kill switch. We show that biodegradable hydrogel encapsulated MSCBif (EnMSCBif) has a profound therapeutic efficacy in mice bearing patient-derived invasive, primary and recurrent GBM tumors following surgical resection. Activation of the kill switch enhances the efficacy of MSCBif and results in their elimination post-tumor treatment which can be tracked by positron emission tomography (PET) imaging. This study establishes a foundation towards a clinical trial of EnMSCBif in primary and recurrent GBM patients.

Fatal Powassan Encephalitis (Deer Tick Virus, Lineage II) in a Patient With Fever and Orchitis Receiving Rituximab.

Importance: Powassan virus is a rare but increasingly recognized cause of severe neurological disease. Objective: To highlight the diagnostic challenges and neuropathological findings in a fatal case of Powassan encephalitis caused by deer tick virus (lineage II) in a patient with follicular lymphoma receiving rituximab, with nonspecific anti-GAD65 antibodies, who was initially seen with fever and orchiepididymitis. Design, Setting, and Participants: Comparison of clinical, radiological, histological, and laboratory findings, including immunohistochemistry, real-time polymerase chain reaction, antibody detection, and unbiased sequencing assays, in a single case report (first seen in December 2016) at an academic medical center. Exposure: Infection with Powassan virus. Main Outcomes and Measures: Results of individual assays compared retrospectively. Results: In a 63-year-old man with fatal Powassan encephalitis, serum and cerebrospinal fluid IgM antibodies were not detected via standard methods, likely because of rituximab exposure. Neuropathological findings were extensive, including diffuse leptomeningeal and parenchymal lymphohistiocytic infiltration, microglial proliferation, marked neuronal loss, and white matter microinfarctions most severely involving the cerebellum, thalamus, and basal ganglia. Diagnosis was made after death by 3 independent methods, including demonstration of Powassan virus antigen in brain biopsy and autopsy tissue, detection of viral RNA in serum and cerebrospinal fluid by targeted real-time polymerase chain reaction, and detection of viral RNA in cerebrospinal fluid by unbiased sequencing. Extensive testing for other etiologies yielded negative results, including mumps virus owing to prodromal orchiepididymitis. Low-titer anti-GAD65 antibodies identified in serum, suggestive of limbic encephalitis, were not detected in cerebrospinal fluid. Conclusions and Relevance: Owing to the rarity of Powassan encephalitis, a high degree of suspicion is required to make the diagnosis, particularly in an immunocompromised patient, in whom antibody-based assays may be falsely negative. Unbiased sequencing assays have the potential to detect uncommon infectious agents and may prove useful in similar scenarios.

Dynamic control of excitatory synapse development by a Rac1 GEF/GAP regulatory complex.

The small GTPase Rac1 orchestrates actin-dependent remodeling essential for numerous cellular processes including synapse development. While precise spatiotemporal regulation of Rac1 is necessary for its function, little is known about the mechanisms that enable Rac1 activators (GEFs) and inhibitors (GAPs) to act in concert to regulate Rac1 signaling. Here, we identify a regulatory complex composed of a Rac-GEF (Tiam1) and a Rac-GAP (Bcr) that cooperate to control excitatory synapse development. Disruption of Bcr function within this complex increases Rac1 activity and dendritic spine remodeling, resulting in excessive synaptic growth that is rescued by Tiam1 inhibition. Notably, EphB receptors utilize the Tiam1-Bcr complex to control synaptogenesis. Following EphB activation, Tiam1 induces Rac1-dependent spine formation, whereas Bcr prevents Rac1-mediated receptor internalization, promoting spine growth over retraction. The finding that a Rac-specific GEF/GAP complex is required to maintain optimal levels of Rac1 signaling provides an important insight into the regulation of small GTPases.

Viral transduction of the neonatal brain delivers controllable genetic mosaicism for visualising and manipulating neuronal circuits in vivo.

The neonatal intraventricular injection of adeno-associated virus has been shown to transduce neurons widely throughout the brain, but its full potential for experimental neuroscience has not been adequately explored. We report a detailed analysis of the method's versatility with an emphasis on experimental applications where tools for genetic manipulation are currently lacking. Viral injection into the neonatal mouse brain is fast, easy, and accesses regions of the brain including the cerebellum and brainstem that have been difficult to target with other techniques such as electroporation. We show that viral transduction produces an inherently mosaic expression pattern that can be exploited by varying the titer to transduce isolated neurons or densely-packed populations. We demonstrate that the expression of virally-encoded proteins is active much sooner than previously believed, allowing genetic perturbation during critical periods of neuronal plasticity, but is also long-lasting and stable, allowing chronic studies of aging. We harness these features to visualise and manipulate neurons in the hindbrain that have been recalcitrant to approaches commonly applied in the cortex. We show that viral labeling aids the analysis of postnatal dendritic maturation in cerebellar Purkinje neurons by allowing individual cells to be readily distinguished, and then demonstrate that the same sparse labeling allows live in vivo imaging of mature Purkinje neurons at a resolution sufficient for complete analytical reconstruction. Given the rising availability of viral constructs, packaging services, and genetically modified animals, these techniques should facilitate a wide range of experiments into brain development, function, and degeneration.