Faculty Bibliography

Tay-Sachs disease (TSD) is a fatal neurodegenerative disease caused by a deficiency of the enzyme β-N-acetylhexosaminidase A (HexA). TSD naturally occurs in Jacob sheep is the only experimental model of TSD. TSD in sheep recapitulates neurologic features similar to juvenile onset and late onset TSD patients. Due to the paucity of human literature on pathology of TSD, a better natural history in the sheep TSD brain, which is on the same order of magnitude as a child's, is necessary for evaluating therapy and characterizing the pathological events that occur. To provide clinicians and researchers with a clearer understanding of longitudinal pathology in patients, we compare spectrum of clinical signs and brain pathology in mildly symptomatic (3-months), moderately symptomatic (6-months), or severely affected TSD sheep (humane endpoint at ~9-months of age). Increased GM2 ganglioside in the CSF of TSD sheep and a TSD specific biomarker on MRS (taurine) correlate with disease severity. Microglial activation and reactive astrocytes were observed globally on histopathology in TSD sheep with a widespread reduction in oligodendrocyte density. Myelination is reduced primarily in the forebrain illustrated by loss of white matter on MRI. GM2 and GM3 ganglioside were increased and distributed differently in various tissues. The study of TSD in the sheep model provides a natural history to shed light on the pathophysiology of TSD, which is of utmost importance due to novel therapeutics being assessed in human patients.

SMN is a ubiquitously expressed protein and is essential for life. SMN deficiency causes the neurodegenerative disease spinal muscular atrophy (SMA), the leading genetic cause of infant mortality. SMN interacts with itself and other proteins to form a complex that functions in the assembly of ribonucleoproteins. SMN is modified by SUMO (Small Ubiquitin-like Modifier), but whether sumoylation is required for the functions of SMN that are relevant to SMA pathogenesis is not known. Here, we show that inactivation of a SUMO-interacting motif (SIM) alters SMN sub-cellular distribution, the integrity of its complex, and its function in small nuclear ribonucleoproteins biogenesis. Expression of a SIM-inactivated mutant of SMN in a mouse model of SMA slightly extends survival rate with limited and transient correction of motor deficits. Remarkably, although SIM-inactivated SMN attenuates motor neuron loss and improves neuromuscular junction synapses, it fails to prevent the loss of sensory-motor synapses. These findings suggest that sumoylation is important for proper assembly and function of the SMN complex and that loss of this post-translational modification impairs the ability of SMN to correct selective deficits in the sensory-motor circuit of SMA mice.

Interictal epileptiform discharges (IEDs) can impair memory. The properties of IEDs most detrimental to memory, however, are undefined. We studied the impact of temporal and spatial characteristics of IEDs on list learning. Subjects completed a memory task during intracranial EEG recordings including hippocampal depth and temporal neocortical subdural electrodes. Subjects viewed a series of objects, and after a distracting task, recalled the objects from the list. The impacts of IED presence, duration, and propagation to neocortex during encoding of individual stimuli were assessed. The effects of IED total number and duration during maintenance and recall periods on delayed recall performance were also determined. The influence of IEDs during recall was further investigated by comparing the likelihood of IEDs preceding correctly recalled items vs. periods of no verbal response. Across 6 subjects, we analyzed 28 hippocampal and 139 lateral temporal contacts. Recall performance was poor, with a median of 17.2% correct responses (range 10.4-21.9%). Interictal epileptiform discharges during encoding, maintenance, and recall did not significantly impact task performance, and there was no significant difference between the likelihood of IEDs during correct recall vs. periods of no response. No significant effects of discharge duration during encoding, maintenance, or recall were observed. Interictal epileptiform discharges with spread to lateral temporal cortex during encoding did not adversely impact recall. A post hoc analysis refining model assumptions indicated a negative impact of IED count during the maintenance period, but otherwise confirmed the above results. Our findings suggest no major effect of hippocampal IEDs on list learning, but study limitations, such as baseline hippocampal dysfunction, should be considered. The impact of IEDs during the maintenance period may be a focus of future research.

OBJECTIVE:To report two cases of hemicrania continua (HC) in a mother and daughter. BACKGROUND:HC is a rare primary headache disorder belonging to the family of trigeminal autonomic cephalalgias (TACs). Unlike migraine, familial cases of TACs are rare, and we know relatively little of their inheritance pattern and genetic mechanisms. METHODS:We present a mother and daughter with HC. We compare the similarities and differences between this family and the first report of familial HC and discuss the implications for future studies. RESULTS:Both the mother and daughter presented with a constant, side-locked headache of moderate intensity, with episodic exacerbations of more severe pain that are associated with ipsilateral cranial autonomic activation. After negative workup, both patients were started on indomethacin and achieved absolute response at different doses, confirming HC. CONCLUSIONS:Our report further corroborates other reports of familial TACs that TACs are primary headaches possibly attributable to genetic factors, albeit detailed mechanisms remain elusive. Nevertheless, whether clinical presentation and treatment responses would be substantially different between sporadic and familial HCs remain unclear.

BACKGROUND:Epidemiological studies link vascular disease risk factors such as atherosclerosis, hypertension, and diabetes mellitus with Alzheimer's disease (AD). Whether there are direct links between these conditions to β-amyloid (Aβ) aggregation and tau pathology is uncertain. METHODS:To investigate the possible link between atherosclerosis and AD pathology, we subjected triple transgenic (3 × Tg) AD mice to a high-fat diet (HFD) at 3 months of age, which corresponds to early adulthood in humans. RESULTS:and clusterin. At 9 months and older, platelet-associated fibrillar Aβ aggregates were observed to obstruct the cerebral blood vessels in HFD-treated 3 × Tg mice. HFD-treated 3 × Tg mice exhibited a greater cerebral amyloid angiopathy (CAA) burden and increased cerebral vascular permeability, as well as more extensive neuroinflammation, tau hyperphosphorylation, and neuron loss. Disaggregation of preexisting platelet micro-clots with humanized GPIIIa49-66 scFv Ab (A11) significantly reduced platelet-associated fibrillar Aβ aggregates in vitro and improved vascular permeability in vivo. CONCLUSIONS:These findings suggest that a major contribution of atherosclerosis to AD pathology is via its effects on blood coagulation and the formation of platelet-mediated Aβ aggregates that compromise cerebral blood flow and therefore neuronal function. This leads to cognitive decline.

BACKGROUND AND PURPOSE/OBJECTIVE:We systematically evaluated the impact of the coronavirus 2019 (COVID-19) pandemic on stroke care across the world. METHODS:Observational studies comparing characteristics, acute treatment delivery, or hospitalization outcomes between patients with stroke admitted during the COVID-19 pandemic and those admitted before the pandemic were identified by Medline, Scopus, and Embase databases search. Random-effects meta-analyses were conducted for all outcomes. RESULTS: CONCLUSIONS:The present systematic review and meta-analysis indicates an increased prevalence of younger patients, more severe strokes attributed to large vessel occlusion, and higher endovascular treatment rates during the COVID-19 pandemic. Patients admitted with stroke during the COVID-19 pandemic had higher in-hospital mortality. These findings need to be interpreted with caution in view of discrepant reports and heterogeneity being present across studies.

BACKGROUND:Patients with bipolar spectrum disorders (BSDs) exhibit an increased risk of Parkinson's disease (PD). OBJECTIVE:The aim is to investigate whether a previous diagnosis of BSDs influences the phenotype of PD. METHODS:Of 2660 PD patients followed for at least 6 years (6-27), 250 (BSD-PD) had BSDs, 6-20 years before PD diagnosis; 48%-43% had a PD or BSD family history, and 34 carried glucocerebrosidase (GBA) and Parkin (PRKN) mutations. The cohort was split into a subset of 213 BSD-PD patients, compared with 426 matched PD patients without BSDs, and a subset of 34 BSD-PD and 79 PD patients carrying GBA or PRKN mutations. Carriers of mutations absent in BSD-PD patients and of synuclein triplication were excluded. Structured clinical interviews and mood disorder questionnaires assessed BSDs. Linear mixed models evaluated the assessment scales over time. Thirteen BSD-PD patients underwent subthalamic nucleus deep brain stimulation (STN-DBS) and were compared with 27 matched STN-DBS-treated PD patients. RESULTS:Compared to PD patients, BSD-PD showed (1) higher frequency of family history of PD (odds ratio [OR] 3.31; 2.32-4.71) and BSDs (OR 6.20; 4.11-9.35) 5); (2) higher incidence of impulse control disorders (hazard ratio [HR] 5.95, 3.89-9.09); (3) higher frequency of functional disorders occurring before PD therapy (HR, 5.67, 3.95-8.15); (4) earlier occurrence of delusions or mild dementia (HR, 7.70, 5.55-10.69; HR, 1.43, 1.16-1.75); and (5) earlier mortality (1.48; 1.11-1.97). Genetic BSD-PD subjects exhibited clinical features indistinguishable from nongenetic BSD-PD subjects. STN-DBS-treated BSD-PD patients showed no improvements in quality of life compared to the control group. CONCLUSIONS:BSDs as a prodrome to PD unfavorably shape their course and are associated with detrimental neuropsychiatric features and treatment outcomes. © 2021 International Parkinson and Movement Disorder Society.

BACKGROUND:There is an increased effort to better understand neuropsychiatric symptoms of Alzheimer's disease (AD) as an important feature of symptomatic burden as well as potential modi- fiable factors of the disease process. Anxiety is one of the most common neuropsychiatric symptoms in Alzheimer's disease (AD). A growing body of work has emerged that addresses the epidemiology and biological correlations of anxiety in AD. OBJECTIVE AND METHODS/OBJECTIVE:Here, we review human studies in research and clinical cohorts that examined anxiety in AD. We focused on work related to prevalence across AD stages, correlation with established biomarkers, relationship with AD neuropathology and genetic risk factors, and impact on progression. RESULTS:Anxiety is prominent in the early stages and increases across the spectrum of functional stages. Biomarker relationships are strongest at the level of FDG-PET and amyloid measured via PET or cerebrospinal fluid analysis. Neuropathologically, anxiety emerges with early Braak stage tau pathology. The presence of the apolipoprotein E e4 allele is associated with increased anxiety at all stages, most notably at mild cognitive impairment. Anxiety portended a faster progression at all pre-dementia stages. CONCLUSION/CONCLUSIONS:This body of work suggests a close biological relationship between anxiety and AD that begins in early stages and influences functional decline. As such, we discuss future work that would improve our understanding of this relationship and test the validity of anxiolytic treatment as disease modifying therapy for AD.

Objective: We sought to identify novel genes and to establish the contribution of known genes in a large cohort of patients with nonsyndromic sporadic polymicrogyria and epilepsy.
Method(s): We enrolled participants with polymicrogyria and their parents through the Epilepsy Phenome/Genome Project. We performed phenotyping and whole exome sequencing (WES), trio analysis, and gene-level collapsing analysis to identify de novo or inherited variants, including germline or mosaic (postzygotic) single nucleotide variants, small insertion-deletion (indel) variants, and copy number variants present in leukocyte-derived DNA.
Result(s): Across the cohort of 86 individuals with polymicrogyria and epilepsy, we identified seven with pathogenic or likely pathogenic variants in PIK3R2, including four germline and three mosaic variants. PIK3R2 was the only gene harboring more than expected de novo variants across the entire cohort, and likewise the only gene that passed the genome-wide threshold of significance in the gene-level rare variant collapsing analysis. Consistent with previous reports, the PIK3R2 phenotype consisted of bilateral polymicrogyria concentrated in the perisylvian region with macrocephaly. Beyond PIK3R2, we also identified one case each with likely causal de novo variants in CCND2 and DYNC1H1 and biallelic variants in WDR62, all genes previously associated with polymicrogyria. Candidate genetic explanations in this cohort included single nucleotide de novo variants in other epilepsy-associated and neurodevelopmental disease-associated genes (SCN2A in two individuals, GRIA3, CACNA1C) and a 597-kb deletion at 15q25, a neurodevelopmental disease susceptibility locus.
Significance: This study confirms germline and postzygotically acquired de novo variants in PIK3R2 as an important cause of bilateral perisylvian polymicrogyria, notably with macrocephaly. In total, trio-based WES identified a genetic diagnosis in 12% and a candidate diagnosis in 6% of our polymicrogyria cohort. Our results suggest possible roles for SCN2A, GRIA3, CACNA1C, and 15q25 deletion in polymicrogyria, each already associated with epilepsy or other neurodevelopmental conditions without brain malformations. The role of these genes in polymicrogyria will be further understood as more patients with polymicrogyria undergo genetic evaluation.
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Mutations of PTEN-induced kinase I (PINK1) cause early-onset Parkinson's disease (PD) with selective neurodegeneration in humans. However, current PINK1 knockout mouse and pig models are unable to recapitulate the typical neurodegenerative phenotypes observed in PD patients. This suggests that generating PINK1 disease models in non-human primates (NHPs) that are close to humans is essential to investigate the unique function of PINK1 in primate brains. Paired single guide RNA (sgRNA)/Cas9-D10A nickases and truncated sgRNA/Cas9, both of which can reduce off-target effects without compromising on-target editing, are two optimized strategies in the CRISPR/Cas9 system for establishing disease animal models. Here, we combined the two strategies and injected Cas9-D10A mRNA and two truncated sgRNAs into one-cell-stage cynomolgus zygotes to target the PINK1 gene. We achieved precise and efficient gene editing of the target site in three newborn cynomolgus monkeys. The frame shift mutations of PINK1 in mutant fibroblasts led to a reduction in mRNA. However, western blotting and immunofluorescence staining confirmed the PINK1 protein levels were comparable to that in wild-type fibroblasts. We further reprogramed mutant fibroblasts into induced pluripotent stem cells (iPSCs), which showed similar ability to differentiate into dopamine (DA) neurons. Taken together, our results showed that co-injection of Cas9-D10A nickase mRNA and sgRNA into one-cell-stage cynomolgus embryos enabled the generation of human disease models in NHPs and target editing by pair truncated sgRNA/Cas9-D10A in PINK1 gene exon 2 did not impact protein expression.