Genetic Factors, Brain Atrophy, and Response to Rehabilitation Therapy After Stroke

Objective Patients show substantial differences in response to rehabilitation therapy after stroke. We hypothesized that specific genetic profiles might explain some of this variance and, secondarily, that genetic factors are related to cerebral atrophy post-stroke. Methods The phase 3 ICARE study examined response to motor rehabilitation therapies. In 216 ICARE enrollees, DNA was analyzed for presence of the BDNF val66met and the ApoE ε4 polymorphism. The relationship of polymorphism status to 12-month change in motor status (Wolf Motor Function Test, WMFT) was examined. Neuroimaging data were also evaluated (n=127). Results Subjects were 61±13 years old (mean±SD) and enrolled 43±22 days post-stroke; 19.7% were BDNF val66met carriers and 29.8% ApoE ε4 carriers. Carrier status for each polymorphism was not associated with WMFT, either at baseline or over 12 months of follow-up. Neuroimaging, acquired 5±11 days post-stroke, showed that BDNF val66met polymorphism carriers had a 1.34-greater degree of cerebral atrophy compared to non-carriers (P=.01). Post hoc analysis found that age of stroke onset was 4.6 years younger in subjects with the ApoE ε4 polymorphism (P=.02). Conclusion Neither the val66met BDNF nor ApoE ε4 polymorphism explained inter-subject differences in response to rehabilitation therapy. The BDNF val66met polymorphism was associated with cerebral atrophy at baseline, echoing findings in healthy subjects, and suggesting an endophenotype. The ApoE ε4 polymorphism was associated with younger age at stroke onset, echoing findings in Alzheimer’s disease and suggesting a common biology. Genetic associations provide insights useful to understanding the biology of outcomes after stroke.

DTYMK is essential for genome integrity and neuronal survival

Nucleotide metabolism is a complex pathway regulating crucial cellular processes such as nucleic acid synthesis, DNA repair and proliferation. This study shows that impairment of the biosynthesis of one of the building blocks of DNA, dTTP, causes a severe, early-onset neurodegenerative disease. Here, we describe two unrelated children with bi-allelic variants in DTYMK, encoding dTMPK, which catalyzes the penultimate step in dTTP biosynthesis. The affected children show severe microcephaly and growth retardation with minimal neurodevelopment. Brain imaging revealed severe cerebral atrophy and disappearance of the basal ganglia. In cells of affected individuals, dTMPK enzyme activity was minimal, along with impaired DNA replication. In addition, we generated dtymk mutant zebrafish that replicate this phenotype of microcephaly, neuronal cell death and early lethality. An increase of ribonucleotide incorporation in the genome as well as impaired responses to DNA damage were observed in dtymk mutant zebrafish, providing novel pathophysiological insights. It is highly remarkable that this deficiency is viable as an essential component for DNA cannot be generated, since the metabolic pathway for dTTP synthesis is completely blocked. In summary, by combining genetic and biochemical approaches in multiple models we identified loss-of-function of DTYMK as the cause of a severe postnatal neurodegenerative disease and highlight the essential nature of dTTP synthesis in the maintenance of genome stability and neuronal survival.

Human Genetic Disorders Resulting in Systemic Selenoprotein Deficiency

Selenium, a trace element fundamental to human health, is incorporated as the amino acid selenocysteine (Sec) into more than 25 proteins, referred to as selenoproteins. Human mutations in SECISBP2, SEPSECS and TRU-TCA1-1, three genes essential in the selenocysteine incorporation pathway, affect the expression of most if not all selenoproteins. Systemic selenoprotein deficiency results in a complex, multifactorial disorder, reflecting loss of selenoprotein function in specific tissues and/or long-term impaired selenoenzyme-mediated defence against oxidative and endoplasmic reticulum stress. SEPSECS mutations are associated with a predominantly neurological phenotype with progressive cerebello-cerebral atrophy. Selenoprotein deficiency due to SECISBP2 and TRU-TCA1-1 defects are characterized by abnormal circulating thyroid hormones due to lack of Sec-containing deiodinases, low serum selenium levels (low SELENOP, GPX3), with additional features (myopathy due to low SELENON; photosensitivity, hearing loss, increased adipose mass and function due to reduced antioxidant and endoplasmic reticulum stress defence) in SECISBP2 cases. Antioxidant therapy ameliorates oxidative damage in cells and tissues of patients, but its longer term benefits remain undefined. Ongoing surveillance of patients enables ascertainment of additional phenotypes which may provide further insights into the role of selenoproteins in human biological processes.

Interferon-driven brain phenotype in a mouse model of RNaseT2 deficient leukoencephalopathy

Infantile-onset RNaseT2 deficient leukoencephalopathy is characterised by cystic brain lesions, multifocal white matter alterations, cerebral atrophy, and severe psychomotor impairment. The phenotype is similar to congenital cytomegalovirus brain infection and overlaps with type I interferonopathies, suggesting a role for innate immunity in its pathophysiology. To date, pathophysiological studies have been hindered by the lack of mouse models recapitulating the neuroinflammatory encephalopathy found in patients. In this study, we generated Rnaset2−/− mice using CRISPR/Cas9-mediated genome editing. Rnaset2−/− mice demonstrate upregulation of interferon-stimulated genes and concurrent IFNAR1-dependent neuroinflammation, with infiltration of CD8+ effector memory T cells and inflammatory monocytes into the grey and white matter. Single nuclei RNA sequencing reveals homeostatic dysfunctions in glial cells and neurons and provide important insights into the mechanisms of hippocampal-accentuated brain atrophy and cognitive impairment. The Rnaset2−/− mice may allow the study of CNS damage associated with RNaseT2 deficiency and may be used for the investigation of potential therapies.

Cortical Thinning and White Matter Loss in Sickle Cell Anemia Despite Chronic Exchange Transfusion Therapy

Neurovascular complications are a common and major cause of morbidity and mortality in patients with sickle cell disease (SCD). Prior studies have demonstrated cortical thinness (Kim et al. 2016) as well as reduced cerebral volume in children with SCD (Kawadler et al. 2013) when compared to age-matched controls. There is very limited data regarding cerebral volume in adults with SCD. Recently, our group showed that adults with SCD have reduced cerebral volumes when compared to race and age-matched controls (Santini et al. 2021a). A prior prospective study by Nitkunan et al. 2011. demonstrated brain atrophy rate of −0.914%±0.8% in older adults (mean 68 years old) with Small Vessels Disease, which is about twice the rate of healthy controls. Transfusion therapy has been effective in the primary and secondary prevention of strokes and silent infarcts in SCD. Automated erythrocytapheresis (exchange transfusion), in particular, is the most aggressive disease modifying-treatment in SCD, by rapidly diluting sickle hemoglobin and replacing it with normal hemoglobin. We hereby present a case of a 42 -year-old woman with sickle cell anemia (HbSS) who developed accelerated loss of cerebral volume within a three-year period despite chronic exchange transfusion therapy. The patient underwent brain MRI in 2016 and 2019 as part of an NIH-funded, prospective, longitudinal study of the neuroradiological correlates of cognitive dysfunction in SCD. Past medical history is notable for prior right hemispheric stroke for which she was placed on chronic exchange transfusion monthly with the goal of reducing HbS to <30%. T1-weighted images were acquired at 7T MRI using a customized RF coil (Santini et al. 2021b) and with the following parameters: 3D MPRAGE, TE/TI/TR = 2.17/1200/3000 ms, resolution 0.75 mm isotropic, total acquisition time = 5 min. The extent of atrophy was estimated using the longitudinal analysis as part of the Freesurfer package (version 7.1.1) and ITK-snap (version 3.8.0). The pre-exchange HbS was reliably maintained <30% throughout the observation period, during which the patient did not develop new strokes or neurological complications. Unfortunately, in spite of the patient's excellent adherence with the treatment and the achievement of the target HbS values, we observed progression of cerebral atrophy of 2.47% in volume in the hemisphere contralateral to the stroke between the two time points. The differences are also visible in the raw data (Figure 1). Chronic exchange transfusion is the most aggressive preventive treatment for the neurological sequelae of sickle cell disease. This case demonstrates an accelerated brain atrophy, suggesting that this treatment may not be fully protective against progressive cerebral atrophy. Unfortunately, the mechanism of brain atrophy in SCD is not fully understood. More longitudinal studies are needed to assess cortical changes and cerebral volume changes as this can lead to further understanding of their pathophysiology and to the development of therapeutic options to arrest the progression of cerebrovascular disease in this population. Figure 1 Figure 1. Disclosures Novelli: Novartis Pharmaceuticals: Consultancy.

265. Rocky Mountain Spotted Fever Encephalopathy

Background Rocky mountain spotted fever (RMSF) is a rickettsial disease with incidence of 11 per million and is rarely associated with encephalopathy. Here we discuss a patient with RMSF encephalopathy, highlighting the natural course. Methods A 54 year old man with history of hypertension and chronic progressive external ophthalmoplegia, presented with waxing and waning confusion, headache, slurred speech, agitation and difficulty swallowing. He was afebrile and hemodynamically stable. Investigations showed leukocytosis of 15400 and mild transaminitis. Computed-tomography (CT) head was unremarkable. Lumbar puncture revealed normal pressure. Cerebrosopinal fluid (CSF) analysis was notable for WBC 7, glucose 76 and moderately elevated total protein 114. Urine drug screen was negative. Blood, fungal, and CSF cultures were sent and empiric therapy with vancomycin, ceftriaxone, ampicillin and acyclovir commenced, for suspected encephalitis. High dose solumedrol 1gm/day was given due to suspicion of autoimmune encephalitis. MRI brain showed cerebral atrophy. There was slight abnormal FLAIR/T2 signal within the medial aspect of the temporal lobes, right more than left. Results Occupational history revealed that he was a logger by profession, which steered our focus on tick borne diseases. Extensive serologic evaluation was requested and RMSF IgG titres came back positive at 1:512. Doxycycline was added, while ampicillin and ceftriaxone were discontinued. With doxycycline, patient made remarkable recovery and was discharged home well. However, he returned within 48 hours with recurring encephalopathy. His clinical presentation remained convincing for RMSF encephalitis, with the natural course of the illness spanning over weeks, with waxing and waning symptoms. Patient was managed with IV doxycycline for 72 hours following which he returned to his baseline mental status. Figure 1. MRI findings Figure 2. Serological investigations Figure 3. CSF studies Conclusion Patient’s occupation played a pivotal role in establishing diagnosis. In RMSF, IgM and IgG antibodies appear 7 to 10 days after the onset of the illness, and a fourfold rise in IgG is diagnostic of seroconversion and recent illness. Patient’s waxing and waning symptoms, persisting for weeks and remarkable response to doxycycline, are typical features of RMSF encephalitis. Disclosures All Authors: No reported disclosures

Recovery from Severe Neurological Sequelae due to Anti-N-methyl D-aspartate Receptor Encephalitis after Three Infusions of Allogeneic Umbilical Cord-derived Mesenchymal Stem Cells: A First Case Report

PurposeAnti-N-methyl D-aspartate (NMDA) receptor encephalitis is caused by altered patients’ immune reactions. This study reports the first patient with severe neurologic sequelae after NMDA receptor encephalitis treated with allogeneic umbilical cord-derived mesenchymal stem/stromal cells (UC-MSCs) via intrathecal route.MethodsUC-MSCs were obtained from a healthy donor and expanded under a xeno- and serum-free condition. The patient received three intrathecal UC-MSC infusions at the dose of 106 cells/Kg. The outcome was accessed using the German Coma Recovery Scale (CRS), the Gross Motor Function Classification System (GMFCS), the Gross Motor Function Measure–88 (GMFM-88), Manual Ability Classification System (MACS), Modified Ashworth Scale, and the Denver II test.ResultsA 5-year-old girl suffered from a permanent vegetative state with diffuse cerebral atrophy due to NMDA receptor encephalitis despite intensive treatment of immunosuppressive medicaments and IVIG. After three UC-MSC infusions, her cognition and motoric functions improved progressively. In the last visits, she could walk, practice writing, and count numbers. Urinary and bowel functions were completely controlled. Cerebral atrophy reduced on brain MRI.ConclusionsThe outcomes of this patient suggest a potential cell therapy for autoimmune encephalitis and its neurological consequences.

Transmission of amyloid-beta and tau pathologies is associated with cognitive impairments in a primate

Amyloid-β (Aβ) pathology transmission has been described in patients following iatrogenic exposure to compounds contaminated with Aβ proteins. It can induce cerebral Aβ angiopathy resulting in brain hemorrhages and devastating clinical impacts. Iatrogenic transmission of tau pathology is also suspected but not experimentally proven. In both scenarios, lesions were detected several decades after the putatively triggering medico-surgical act. There is however little information regarding the cognitive repercussions in individuals who do not develop cerebral hemorrhages. In the current study, we inoculated the posterior cingulate cortex and underlying corpus callosum of young adult primates (Microcebus murinus) with either Alzheimer’s disease or control brain extracts. This led to widespread Aβ and tau pathologies in all of the Alzheimer-inoculated animals following a 21-month-long incubation period (n = 12) whereas none of the control brain extract-inoculated animals developed such lesions (n = 6). Aβ deposition affected almost all cortical regions. Tau pathology was also detected in Aβ-deposit-free regions distant from the inoculation sites (e.g. in the entorhinal cortex), while some regions adjacent, but not connected, to the inoculation sites were spared (e.g. the occipital cortex). Alzheimer-inoculated animals developed cognitive deficits and cerebral atrophy compared to controls. These pathologies were induced using two different batches of Alzheimer brain extracts. This is the first experimental demonstration that tau can be transmitted by human brain extracts inoculations in a primate. We also showed for the first time that the transmission of widespread Aβ and tau pathologies can be associated with cognitive decline. Our results thus reinforce the need to organize a systematic monitoring of individuals who underwent procedures associated with a risk of Aβ and tau iatrogenic transmission. They also provide support for Alzheimer brain-inoculated primates as relevant models of Alzheimer pathology.

microRNA-150-5p: A Novel Blood-Based Biomarker for Alzheimer’s Dementia with Good Correlation to Cognition, Cerebrospinal Fluid Amyloid-β, and Cerebral Atrophy

Background: There is an urgent need for non-invasive, cost-effective biomarkers for Alzheimer’s disease (AD), such as blood-based biomarkers. It is not only to support clinical diagnosis of dementia, but also to allow for timely pharmacological and non-pharmacological interventions evaluation. The aim of this study is to identify and validate a novel blood-based microRNA (miRNA) biomarker for dementia of Alzheimer’s disease type (DAT). The miRNA correlations with AD pathology and AD clinical-radiological imaging were conducted.Methods: We conducted miRNA-sequencing (miRNA-Seq) using peripheral blood mononuclear cells (PBMCs) isolated from a discovery cohort comprising DAT, mild cognitive impairment (MCI), and healthy subject (HS). Identified miRNA was validated in an independent cohort. Correlation analysis evaluated the relationships between miRNA expression and DAT clinical measures, including Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) scores, CSF Aβ1-42 and tau levels, and AD pattern cerebral atrophy. Furthermore, we conducted bioinformatics analysis and cell-based assay to identify miRNA target genes. Results: MiRNA-seq identified a distinct miRNA (miR-328-3p, miR-7706, and miR-150-5p) expression signature differentiating DAT from MCI and HS. qPCR analysis reveals that miR-150-5p was consistent with the miRNA-seq data and was further validated. Specifically, we found that miR-150-5p expression was significantly upregulated in DAT compared to MCI and HS, and discriminated DAT from MCI and HS with a high accuracy with AUC of 0.86 and 0.86, respectively. We further found that higher miR-150-5p levels correlated with clinical measures of DAT, including lower global cognitive scores of MMSE and MoCA, lower CSF Aβ1-42, and higher CSF tau. Interestingly, we observed that higher miR-150-5p levels is associated with the lower grey matter volumes in the medial temporal lobe, posterior cingulate cortex and precuneus. These regions implicated default mood network and executive control network regions that are important for AD brain atrophy. Furthermore, pathway analysis identified the targets of miR-150-5p to be enriched in the Wnt signalling pathway, including programmed cell death 4 (PDCD4). We further found that PDCD4 was downregulated in DAT blood and was downregulated by miR-150-5p at both transcriptional and protein levels.Conclusions: Our findings demonstrated that miR-150-5p is a reliable clinical blood-based biomarker for DAT.