Congruence between NOTCH3 mutations and GOM in 131 CADASIL patients

Association Between Vascular NOTCH3 Aggregation and Disease Severity in a CADASIL Cohort - Implications for NOTCH3 Variant-Specific Disease Prediction

OBJECTIVE

Vascular NOTCH3 protein ectodomain aggregation is a pathological hallmark of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a monogenic small vessel disease typically caused by cysteine-altering variants in NOTCH3. Given their high population frequency, these NOTCH3 variants are an important genetic contributor to stroke and vascular dementia worldwide. Disease severity in CADASIL is highly variable and is mainly determined by the position of the pathogenic NOTCH3 variant in the NOTCH3 ectodomain. Here, we aimed to investigate the association between NOTCH3 aggregation load in skin vessels, cysteine-altering NOTCH3 variants, and disease severity in a prospective cohort study of 212 patients with CADASIL with 39 distinct cysteine-altering NOTCH3 variants.

METHODS

NOTCH3 aggregation load in skin vessels was determined by calculating the NOTCH3 score; the fraction of skin vessel wall area positive for NOTCH3 staining. Variant-specific NOTCH3 scores were calculated for variants present in 10 or more participants, by averaging the NOTCH3 scores of individuals with that distinct variant. The associations between the NOTCH3 score, NOTCH3 variants, and neuroimaging and clinical outcomes were investigated using multivariable linear mixed models, Cox regression, and mediation analyses.

RESULTS

The NOTCH3 score was significantly associated with lifetime stroke probability and small vessel disease neuroimaging outcomes, but not with age. Variant-specific NOTCH3 scores reflected differences in disease severity associated with distinct NOTCH3 variants.

INTERPRETATION

These findings suggest that differences in NOTCH3 aggregation propensity underlie the differences in disease severity associated with NOTCH3 cysteine-altering variants, and show that NOTCH3-variant specific NOTCH3 scores can contribute to improved individualized disease prediction in CADASIL. ANN NEUROL 2025.

Exome sequencing of a Portuguese cohort of early-onset Alzheimer's disease implicates the X-linked lysosomal gene GLA

Cerebrovascular disease is a common comorbidity in patients with Alzheimer's disease (AD) and other dementias. Accumulating evidence suggests that dysfunction of the cerebral vasculature and AD neuropathology interact in multiple ways. Additionally, common variants in COL4A1 and rare variants in HTRA1, NOTCH3, COL4A1, and CST3 have been associated with AD pathogenesis. We aimed to search for rare genetic variants in genes associated with monogenic small vessel disease in a cohort of Portuguese early-onset AD patients. We performed whole-exome sequencing in 104 thoroughly studied patients with early-onset AD who lacked known pathogenic variants in the genes associated with AD or frontotemporal dementia. We searched for rare (minor allele frequency < 0.001) non-synonymous variants in genes associated with small vessel disease: NOTCH3, HTRA1, COL4A1, COL4A2, CSTA, GLA, and TREX1. We identified 12 rare variants in 18 patients (17.3% of the cohort). Three male AD patients carried a pathogenic GLA variant (p.Arg118Cys). One of these patients had a definite neuropathological study, confirming the diagnosis of AD and showing concomitant Fabry pathology in CA1-CA4 and the subiculum. We also found several rare variants in other genes associated with cSVD (NOTCH3, COL4A2 and HTRA1), corroborating previous studies and providing further support for the possibility that cSVD genes may play a role in AD pathogenesis. The presence of the same GLA variant in 3 early-onset AD patients, with no other genetic cause for the disease, together with the colocalization of Fabry disease pathology in areas relevant for AD pathogenesis, suggest GLA may have a role in its pathophysiology, possibly parallel to that of GBA in Parkinson's disease, meriting further studies.

NOTCH3 Variant Position Affects the Phenotype at the Pluripotent Stem Cell Level in CADASIL

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common genetic form of stroke. It is caused by a cysteine-altering variant in one of the 34 epidermal growth factor-like repeat (EGFr) domains of Notch3. NOTCH3 pathogenic variants in EGFr 1-6 are associated with high disease severity, whereas those in EGFr 7-34 are associated with late stroke onset and increased survival. However, whether and how the position of the NOTCH3 variant directly affects the disease severity remains unclear. In this study, we aimed to generate human-induced pluripotent stem cells (hiPSCs) from patients with CADASIL with EGFr 1-6 and 7-34 pathogenic variants to evaluate whether the NOTCH3 position affects the cell phenotype and protein profile of the generated hiPSCs lines. Six hiPSCs lines were generated: two from patients with CADASIL with EGFr 1-6 pathogenic variants, two from patients with EGFr 7-34 variants, and two from controls. Notch3 aggregation and protein profiles were tested in the established six hiPSCs lines. Cell analysis revealed that the NOTCH3 variants did not limit the cell reprogramming efficiency. However, EGFr 1-6 variant position was associated with increased accumulation of Notch3 protein in pluripotent stem cells and proteomic changes related with cytoplasmic reorganization mechanisms. In conclusion, our analysis of hiPSCs derived from patients with CADASIL support the clinical association between the NOTCH3 variant position and severity of CADASIL.

Synergistic effects of mutation and glycosylation on disease progression

Glycosylation, a post-translational modification, plays a crucial role in proper localization and function of proteins. It is regulated by multiple glycosyltransferases and can be influenced by various factors. Inherited missense mutations in glycosylated proteins such as NOTCH3, Low-density lipoprotein receptor (LDLR), and Amyloid precursor protein (APP) could affect their glycosylation states, leading to cerebral small vessel disease, hypercholesterolemia, and Alzheimer's disease, respectively. Additionally, physiological states and aging-related conditions can affect the expression levels of glycosyltransferases. However, the interplay between mutations in glycosylated proteins and changes in their glycosylation levels remains poorly understood. This mini-review summarizes the effects of glycosylation on transmembrane proteins with pathogenic mutations, including NOTCH3, LDLR, and APP. We highlight the synergistic contributions of missense amino acids in the mutant proteins and alterations in their glycosylation states to their molecular pathogenesis.

Novel NOTCH3 mutation c.1564 T > A (p.Cys522Ser) presenting with early-onset Parkinsonism and white matter lesions

CADASIL (Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy) is a hereditary small vessel disease caused by mutations in the NOTCH3 gene, characterized by recurrent strokes, cognitive decline, and psychiatric symptoms. This report presents a novel NOTCH3 c.1564 T > A (p.Cys522Ser) mutation associated with early-onset parkinsonism and significant white matter lesions. We describe a patient who presented with early-onset parkinsonism, characterized by bradykinesia and rigidity, alongside extensive white matter lesions observed through neuroimaging. Genetic testing revealed a novel c.1564 T > A (p.Cys522Ser) mutation in the NOTCH3 gene, contributing to the clinical diagnosis of CADASIL. This case underscores the phenotypic variability of CADASIL and the potential for atypical presentations, including parkinsonism. Early identification of genetic mutations can facilitate appropriate management and counseling for affected individuals and their families. Further research is warranted to explore the mechanisms underlying the association between NOTCH3 mutations and parkinsonism. Our findings contribute to the understanding of CADASIL, suggesting that clinicians should consider CADASIL in differential diagnoses of early-onset parkinsonism, especially in patients with concurrent white matter lesions.

A Chinese CADASIL family with a rare heterozygous mutation in exon 2 of NOTCH3: A case report

RATIONALE

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited cerebrovascular disease caused by the neurogenic locus notch homolog protein 3 (NOTCH3) gene mutation. In recent years, most of the newly reported mutations of CADASIL patients mainly occur in exon 3 to 24, while the cases related to exon 2 mutation are rare, and clinical research data are relatively insufficient. In this study, we have reported a case of a rare heterozygous mutation c.128G>A (p.Cys43Tyr) in exon 2 of NOTCH3 in a 41-year-old Chinese man in the light of relevant literatures.

PATIENT CONCERNS

A 41-year-old man who suffered slurred speech for 5 days and right lower limb weakness for 4 days was admitted to our hospital.

DIAGNOSES

Magnetic resonance imaging of the head revealed diffuse white matter lesions involving the outer capsular area and bilateral temporal poles. The rare heterozygous mutation c.128G>A (p.Cys43Tyr) in exon 2 of NOTCH3 was identified through molecular genetic testing. The proband was diagnosed as having CADASIL. Meanwhile, the same mutation was detected in 2 other family members III5 and IV9.

INTERVENTIONS

Atorvastatin calcium tablet (20 mg qd) and aspirin enteric-coated tablet (100 mg qd).

OUTCOMES

The patient was hospitalized for 3 weeks and discharged after his symptoms improved.

LESSONS

The heterozygous Cys43Tyr mutation in exon 2 of NOTCH3 is rare. Thus, our case report complements the rare mutation of exon 2 and offers additional clinical data for CADASIL patients.

The N-acetylglucosaminyltransferase Radical fringe contributes to defects in JAG1-dependent turnover and signaling of NOTCH3 CADASIL mutants

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a genetic vascular dementia characterized by age-related degeneration of vascular mural cells and accumulation of a NOTCH3 mutant protein. NOTCH3 functions as a signaling receptor, activating downstream gene expression in response to ligands like JAG1 and DLL4, which regulate the development and survival of mural cells. This signal transduction process is thought to be connected with NOTCH3 endocytic degradation. However, the specific cellular circumstances that modulate turnover and signaling efficacy of NOTCH3 mutant protein remain largely unknown. Here, we found elevated NOTCH3 and Radical fringe (RFNG) expression in senescent human pericyte cells. We then investigated impacts of RFNG on glycosylation, degradation, and signal activity of three NOTCH3 CADASIL mutants (R90C, R141C, and C185R) in EGF-like repeat-2, 3, and 4, respectively. Liquid chromatography with tandem mass spectrometry analysis showed that RFNG modified NOTCH3 WT and C185R to different degrees. Additionally, coculture experiments demonstrated that RFNG significantly promoted JAG1-dependent degradation of NOTCH3 WT but not that of R141C and C185R mutants. Furthermore, RFNG exhibited a greater inhibitory effect on JAG1-mediated activity of NOTCH3 R141C and C185R compared to that of NOTCH3 WT and R90C. In summary, our findings suggest that NOTCH3 R141C and C185R mutant proteins are relatively susceptible to accumulation and signaling impairment under cellular conditions of RFNG and JAG1 coexistence.

Most common NOTCH3 mutations causing CADASIL or CADASIL-like cerebral small vessel disease: A systematic review

Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL) is a monogenic disorder caused by mutations in the NOTCH3 gene. The main aim of our survey was to determine if there is an association between phenotypes and genotypes across the most common NOTCH3 mutations found in CADASIL patients. We systematically searched clinical studies and genomic databases from 1996 to 2023 to first identify the most common mutations responsible for CADASIL. We found the six most common NOTCH3 missense mutations globally were the p.R75P, p.R133C, p.R141C, p.R169C, p.R182C, and p.R544C, of which p.R133C was described to occur most often. Focusing on studies with comprehensive clinical records, our analysis further suggested that the p.R75P, p.R141C, p.R182C and p.R544C genotypes were highly congruent with the presence of white matter hyperintensities on magnetic resonance imaging (MRI), which was the most common phenotypic characteristic across all four mutations. We found the p.R141C mutation was associated with increased severity of disease. We also found the average age of onset in p.R544C carriers was more than a decade later compared to the p.R141C carriers. However, statistical analysis showed there were no overall differences between the phenotypic characteristics of the two common mutations, p.R141C and p.R544C. Geographically, China and Japan were the only two countries to report all the four common mutations vis a vis p.R75P, p.R141C, p.R182C and p.R544C. There is a possibility that this is due to a combination of a founder effect, but there also could be sampling biases.

Pro-Hemorrhagic Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy Associated with NOTCH3 p.R75P Mutation with Low Vascular NOTCH3 Aggregation Property

OBJECTIVES

Intracerebral hemorrhage (ICH) and cerebral microbleeds (CMB) in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy are more common in East Asian populations than in people of white European ancestry. We hypothesized that the ethnic difference is explained by the East Asian-specific NOTCH3 p.R75P mutation.

METHODS

This retrospective observational study included 118 patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy in Japanese and Korean cohorts. We investigated whether the p.R75P mutation is associated with symptomatic ICH and multiple CMB (>5) using quasi-Poisson regression models. We predicted the NOTCH3 extracellular domain protein structures in silico and graded NOTCH3 extracellular domain immunostaining in skin vessels of some patients, with subsequent comparisons between p.R75P and other conventional mutations.

RESULTS

Among 63 Japanese patients (median age 55 years; 56% men), 15 had a p.R75P mutation, significantly associated with symptomatic ICH (adjusted relative risk 9.56, 95% CI 2.45-37.31), multiple CMB (3.00, 1.34-6.71), and absence of temporopolar lesions (4.91, 2.29-10.52) after adjustment for age, sex, hypertension, and antithrombotics. In the Korean cohort (n = 55; median age 55 years; 51% men), the p.R75P mutation (n = 13) was also associated with symptomatic ICH (8.11, 1.83-35.89), multiple CMB (1.90, 1.01-3.56), and absence of temporopolar lesions (2.32, 1.08-4.97). Structural analysis revealed solvent-exposed free cysteine thiols in conventional mutations, directly causing aggregation, whereas a stereochemically incompatible proline residue structure in p.R75P lowers correct disulfide bond formation probability, indirectly causing aggregation. Pathologically, the p.R75P mutation resulted in less vascular NOTCH3 extracellular domain accumulation than the other conventional mutations.

INTERPRETATION

NOTCH3 p.R75P mutation is associated with hemorrhagic presentations, milder temporopolar lesions, and distinct mutant protein structure properties. ANN NEUROL 2024;95:1040-1054.

Detecting a Novel NOTCH3 Variant in Patients with Suspected CADASIL: A Single Center Study

Introduction

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common form of familial cerebral small vessel disease in adults and is caused by NOTCH3 variants. Clinical manifestations of CADASIL include recurrent ischemic strokes, dementia, migraine or migraineous headaches, epileptic seizures, and psychiatric disorders. The clinical-radiological phenotype of the disease is also highly variable. In this study, we investigated the variability of clinical, radiological, and genetic data in patients analyzed for NOTCH3 variant in our clinic.

Methods

We performed clinical and neuropsychological examination, cerebral magnetic resonance imaging (MRI) and Doppler sonography of cerebral arteries in all patients. Next-generation sequencing test was used for detect variants in NOTCH3 gene from all CADASIL patients.

Results

By using the next-generation sequencing method, heterozygous c.380C>T pathogenic variant was detected in the 4th exon of the NOTCH3 gene in 3 patients. This is a previously unreported novel variant and resulted in the replacement of the amino acid Proline at 127th position with Leucine.

Discussion and Conclusion

The discovery of this novel pathogenic variant region may contribute to the expansion of the clinical and genetic spectrum of diseases associated with NOTCH3, leading to further research and treatment options for this disease in the future.

Cerebral Autosomal Dominant Arteriopathy With Subcortical Infarcts and Leukoencephalopathy (CADASIL) Syndrome: A Case Report and Review of Literature

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an autosomal dominant genetic disorder of the small arteries that causes ischemic vascular events, subcortical dementia, behavioral changes, and migraine-like headaches. It is caused by a mutation in the NOTCH3 gene; this disease was first described in 1955 by van Bogaert. We present a 29-year-old woman who presented to the neurology department. She has no history of chronic degenerative diseases. She has been complaining of migraine-like headaches for the past six months. She has cognitive impairment with arithmetic and executive function deficits on neurological examination. Blood biometry and blood chemistry are within normal parameters in her laboratory studies. A viral panel and immunological profile were also performed and were not reactive. A lumbar puncture was performed, and the composition of the cerebrospinal fluid was within normal limits. An MRI was performed, which showed bilateral and symmetric white matter hyperintensities consistent with CADASIL syndrome. There is no specific treatment. Management of these patients is based on symptom control. Neurological sequelae have an important impact on the quality of life and mortality of these patients. For this reason, pharmacological preventive therapies have been sought with controversial evidence.

Progress to Clarify How NOTCH3 Mutations Lead to CADASIL, a Hereditary Cerebral Small Vessel Disease

Notch signaling is conserved in C. elegans, Drosophila, and mammals. Among the four NOTCH genes in humans, NOTCH1, NOTCH2, and NOTCH3 are known to cause monogenic hereditary disorders. Most NOTCH-related disorders are congenital and caused by a gain or loss of Notch signaling activity. In contrast, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) caused by NOTCH3 is adult-onset and considered to be caused by accumulation of the mutant NOTCH3 extracellular domain (N3ECD) and, possibly, by an impairment in Notch signaling. Pathophysiological processes following mutant N3ECD accumulation have been intensively investigated; however, the process leading to N3ECD accumulation and its association with canonical NOTCH3 signaling remain unknown. We reviewed the progress in clarifying the pathophysiological process involving mutant NOTCH3.

Monogenic causes of cerebral small vessel disease and stroke

Cerebral small vessel disease (cSVDs) account for 25% of stroke and are a frequent cause of cognitive or motor disability in adults. In a small number of patients, cSVDs result from monogenic diseases, the most frequent being cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). An early disease onset, a suggestive family history, and a low vascular risk profile contrasting with a high load of cSVD imaging markers represent red flags that must trigger molecular screening. To date, a dozen of genes is involved in Mendelian cSVDs, most of them are responsible for autosomal dominant conditions of variable penetrance. Some of these mendelian cSVDs (CADASIL, HTRA1-related cSVD, pontine autosomal dominant microangiopathy and leukoencephalopathy (PADMAL), cathepsin-A related arteriopathy with strokes and leukoencephalopathy (CARASAL), and cSVD related to LAMB1 mutations) are causing ischemic stroke. Others (COL4A1/COL4A2-related angiopathy and hereditary cerebral amyloid angiopathy) preferentially lead to intracerebral hemorrhages. The clinical features of different Mendelian cSVDs can overlap. Therefore, the current approach is based on simultaneous screening of all genes involved in these conditions through a panel-targeted sequencing gene or exome sequencing. Nevertheless, a pathogenic variant is identified in less than 15% of patients with a suspected genetic cerebrovascular disease, suggesting that many additional genes remain to be identified.

Impaired cerebral interstitial fluid dynamics in cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy, caused by cysteine-altering variants in NOTCH3, is the most prevalent inherited cerebral small vessel disease. Impaired cerebral interstitial fluid dynamics has been proposed as one of the potential culprits of neurodegeneration and may play a critical role in the initiation and progression of cerebral small vessel disease. In the present study, we aimed to explore the cerebral interstitial fluid dynamics in patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy and to evaluate its association with clinical features, imaging biomarkers and disease severity of cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy. Eighty-one participants carrying a cysteine-altering variant in NOTCH3, including 44 symptomatic cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy patients and 37 preclinical carriers, and 21 age- and sex-matched healthy control individuals were recruited. All participants underwent brain MRI studies and neuropsychological evaluations. Cerebral interstitial fluid dynamics was investigated by using the non-invasive diffusion tensor image analysis along the perivascular space method. We found that cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy patients exhibited significantly lower values of diffusion tensor image analysis along the perivascular space index comparing to preclinical carriers and healthy controls. For the 81 subjects carrying NOTCH3 variants, older age and presence of hypertension were independently associated with decreased diffusion tensor image analysis along the perivascular space index. The degree of cerebral interstitial fluid dynamics was strongly related to the severity of cerebral small vessel disease imaging markers, with a positive correlation between diffusion tensor image analysis along the perivascular space index and brain parenchymal fraction and negative correlations between diffusion tensor image analysis along the perivascular space index and total volume of white matter hyperintensity, peak width of skeletonized mean diffusivity, lacune numbers and cerebral microbleed counts. In addition, diffusion tensor image analysis along the perivascular space index was a significant risk factor associated with the development of clinical symptoms of stroke or cognitive dysfunction in individuals carrying NOTCH3 variants. In cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy patients, diffusion tensor image analysis along the perivascular space index was significantly associated with Mini-Mental State Examination scores. Mediation analysis showed that compromised cerebral interstitial fluid dynamics was not only directly associated with cognitive dysfunction but also had an indirect effect on cognition by influencing brain atrophy, white matter disruption, lacunar lesions and cerebral microbleeds. In conclusion, cerebral interstitial fluid dynamics is impaired in cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy and its disruption may play an important role in the pathogenesis of cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy. Diffusion tensor image analysis along the perivascular space index may serve as a biomarker of disease severity for cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy.

Deep learning based on susceptibility-weighted MR sequence for detecting cerebral microbleeds and classifying cerebral small vessel disease

BACKGROUND

Cerebral microbleeds (CMBs) serve as neuroimaging biomarkers to assess risk of intracerebral hemorrhage and diagnose cerebral small vessel disease (CSVD). Therefore, detecting CMBs can evaluate the risk of intracerebral hemorrhage and use its presence to support CSVD classification, both are conducive to optimizing CSVD management. This study aimed to develop and test a deep learning (DL) model based on susceptibility-weighted MR sequence (SWS) to detect CMBs and classify CSVD to assist neurologists in optimizing CSVD management. Patients with arteriolosclerosis (aSVD), cerebral amyloid angiopathy (CAA), and cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) treated at three centers were enrolled between January 2017 and May 2022 in this retrospective study. The SWSs of patients from two centers were used as the development set, and the SWSs of patients from the remaining center were used as the external test set. The DL model contains a Mask R-CNN for detecting CMBs and a multi-instance learning (MIL) network for classifying CSVD. The metrics for model performance included intersection over union (IoU), Dice score, recall, confusion matrices, receiver operating characteristic curve (ROC) analysis, accuracy, precision, and F1-score.

RESULTS

A total of 364 SWS were recruited, including 336 in the development set and 28 in the external test set. IoU for the model was 0.523 ± 0.319, Dice score 0.627 ± 0.296, and recall 0.706 ± 0.365 for CMBs detection in the external test set. For CSVD classification, the model achieved a weighted-average AUC of 0.908 (95% CI 0.895-0.921), accuracy of 0.819 (95% CI 0.768-0.870), weighted-average precision of 0.864 (95% CI 0.831-0.897), and weighted-average F1-score of 0.829 (95% CI 0.782-0.876) in the external set, outperforming the performance of the neurologist group.

CONCLUSION

The DL model based on SWS can detect CMBs and classify CSVD, thereby assisting neurologists in optimizing CSVD management.

Four Novel Disease-Causing Variants in the NOTCH3 Gene in Russian Patients with CADASIL

BACKGROUND

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited disease with unknown mechanisms and a broad phenotypic spectrum. It is caused by pathogenic variants in the NOTCH3 gene. The symptoms of the disease mainly include recurrent strokes with vascular risk factors, migraine with aura, dementia, and mood disturbances.

CASE PRESENTATION

Peripheral blood samples were collected from five patients from four unrelated families to extract genomic DNA. In four patients, analysis of exons 2, 3, 4, 5, 6 and adjacent intronic regions of the NOTCH3 gene was made via Sanger sequencing. Two previously undescribed nucleotide variants were identified in two patients: missense variant c.208G>T, (p.Gly70Cys) in exon 1 and splice-site variant c.341-1G>C in intron 3. Further DNA of two other patients were analyzed using a next-generation sequencing-based custom AmpliSeq™ panel for 59 genes associated with leukodystrophies. Two novel missense variants in the NOTCH3 gene were identified, c.1136G>A, (p.Cys379Tyr) in exon 7 and c.1547G>A, (p.Cys516Tyr) in exon 10. The pathogenic variant c.1547G>A, (p.Cys516Tyr) was confirmed in the fifth patient (family case) by Sanger sequencing. All patients had a history of headaches, transient ischemic attacks, memory impairment, and characteristics of MRI results. Three patients had strokes and two patients had psychiatric symptoms.

CONCLUSION

We found four previously undescribed pathogenic variants in the NOTCH3 gene in five patients with CADASIL and described their clinical and genetic characteristics. These results expand the mutational spectrum of CADASIL.

Cerebral Autosomal Dominant Arteriopathy With Subcortical Infarcts and Leukoencephalopathy Presenting During the Postpartum Period as Postpartum Depression and Postpartum Psychosis

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a rare inherited disease that presents with neurologic manifestations such as stroke, psychiatric disturbances, migraine, and cognitive decline. We report a case of a previously well 27-year-old lady presenting with new onset confusion four weeks postpartum. On examination, there was right-sided weakness and tremors. A thorough history revealed existing diagnoses of CADASIL in 1^st and 2^nd-degree relatives. The diagnosis in this patient was confirmed by MRI of the brain and genetic testing for NOTCH 3 mutation. The patient was admitted to the stroke ward, treated with a single antiplatelet agent for stroke, and supported by speech and language therapy. There was a significant symptomatic improvement in her speech at the time of discharge. The mainstay of treatment for CADASIL remains symptomatic at this stage. This case report shows that the first presentation of CADASIL can mimic postpartum psychiatric disorders in a puerperal woman.

Case report: Mild leukoencephalopathy caused by a new mutation of NOTCH3 gene

BACKGROUND

Cerebral autosomal dominant arteriosis with subcortical infarction and leukoencephalopathy (CADASIL) is a single-gene small-vessel disease of the brain characterized by migraine, recurrent ischemic stroke, psychiatric disorders, progressive cognitive decline, and occasional intracerebral hemorrhage.[1]NOTCH3 was identified as a pathogenic gene for CADASIL.[2] The NOTCH3 gene encodes a membrane-bound receptor protein, and to date, several different NOTCH3 gene mutations have been identified.[3] Here, we report a case of CADASIL with a heterozygous mutation c.931T > G (thymine > guanine) on the exon region of the NOTCH3 gene, resulting in an amino acid change p.C311G (cysteine > glycine).

CASE REPORT

We report a case of a female patient with CADASIL whose genetic sequencing revealed a mutation in the NOTCH3 gene. However, this patient did not exhibit any of the typical clinical findings of CADASIL but the patient's cerebral magnetic resonance imaging was consistent with the characteristic findings of CADASIL.

CONCLUSIONS

This case reminds us that mutations caused by different mutation sites present different clinical symptoms.

[Neuropathology II: diseases of the central and peripheral nervous systems : Outlook on new techniques in electron microscopy]

In the diagnosis of diseases of the central and peripheral nervous systems, the use of electron microscopic analyses has become rare these days. However, there are questions in which the method is helpful in confirming the etiopathogenesis of the disease. Hereditary neurodegenerative and metabolic diseases, such as the lysosomal storage disease neuronal ceroid lipofuscinosis, are associated with pathognomonic storage products not only in the central nervous system (CNS) but also in extracerebral tissues such as sweat glands and lymphocytes. These tissues are easily accessible and thus function as "windows to the CNS". In addition, there are new methods that overcome limitations of conventional electron microscopy and may improve ultrastructural diagnostics. This is particularly important for the correct classification of viral particles such as SARS-CoV‑2, leading to a better understanding of COVID19-associated diseases in the CNS and peripheral nervous system.

Update on the Epidemiology, Pathogenesis, and Biomarkers of Cerebral Autosomal Dominant Arteriopathy With Subcortical Infarcts and Leukoencephalopathy

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common monogenic disorder of the cerebral small blood vessels. It is caused by mutations in the NOTCH3 gene on chromosome 19, and more than 280 distinct pathogenic mutations have been reported to date. CADASIL was once considered a very rare disease with an estimated prevalence of 1.3-4.1 per 100,000 adults. However, recent large-scale genomic studies have revealed a high prevalence of pathogenic NOTCH3 variants among the general population, with the highest risk being among Asians. The disease severity and age at onset vary significantly even among individuals who carry the same NOTCH3 mutations. It is still unclear whether a significant genotype-phenotype correlation is present in CADASIL. The accumulation of granular osmiophilic material in the vasculature is a characteristic feature of CADASIL. However, the exact pathogenesis of CADASIL remains largely unclear despite various laboratory and clinical observations being made. Major hypotheses proposed so far have included aberrant NOTCH3 signaling, toxic aggregation, and abnormal matrisomes. Several characteristic features have been observed in the brain magnetic resonance images of patients with CADASIL, including subcortical lacunar lesions and white matter hyperintensities in the anterior temporal lobe or external capsule, which were useful in differentiating CADASIL from sporadic stroke in patients. The number of lacunes and the degree of brain atrophy were useful in predicting the clinical outcomes of patients with CADASIL. Several promising blood biomarkers have also recently been discovered for CADASIL, which require further research for validation.

Small Fiber Pathology in CADASIL: Clinical Correlation With Cognitive Impairment

BACKGROUND AND OBJECTIVES

This study investigated the cutaneous small fiber pathology of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) and its clinical significance, that is, the NOTCH3 deposition in cutaneous vasculatures and CNS neurodegeneration focusing on cognitive impairment.

METHODS

Thirty-seven patients with CADASIL and 59 age-matched healthy controls were enrolled to evaluate cutaneous small fiber pathology by quantitative measures of intraepidermal nerve fiber density (IENFD), sweat gland innervation, and vascular innervation. Cognitive performance of patients with CADASIL was evaluated by a comprehensive neuropsychological assessment, and its association with small fiber pathology was tested using multivariable linear regression analysis adjusted for age and diabetes mellitus. We further assessed the relationships of IENFD with cutaneous vascular NOTCH3 ectodomain (NOTCH3ECD) deposition and biomarkers of neurodegeneration including structural brain MRI measures, serum neurofilament light chain (NfL), glial fibrillary acidic protein (GFAP), tau, and ubiquitin carboxy-terminal hydrolase L1.

RESULTS

Patients with CADASIL showed reduced IENFD (5.22 ± 2.42 vs 7.88 ± 2.89 fibers/mm, p = 0.0001) and reduced sweat gland (p < 0.0001) and vascular (p < 0.0001) innervations compared with age-matched controls. Reduced IENFD was associated with impaired global cognition measured by Mini-Mental State Examination (B = 1.062, 95% CI = 0.370-1.753, p = 0.004), and this association remained after adjustment for age and diabetes mellitus (p = 0.043). In addition, IENFD in patients with CADASIL was associated with mean cortical thickness (Pearson r = 0.565, p = 0.0023) but not white matter hyperintensity volume, total lacune count, or total microbleed count. Reduced IENFD was associated with cutaneous vascular NOTCH3ECD deposition amount among patients harboring pathogenic variants in exon 11 (mainly p.R544C) (B = -0.092, 95% CI = -0.175 to -0.009, p = 0.031). Compared with those with normal cognition, patients with CADASIL with cognitive impairment had an elevated plasma NfL level regardless of concurrent small fiber denervation, whereas only patients with both cognitive impairment and small fiber denervation showed an elevated plasma GFAP level.

DISCUSSION

Cutaneous small fiber pathology correlates with cognitive impairment and CNS neurodegeneration in patients with CADASIL, indicating a peripheral neurodegenerative process related to NOTCH3ECD aggregation.

Detection of Vascular Notch3 Deposits in Unfixed Frozen Skin Biopsy Sample in CADASIL

This study aimed to evaluate the utility of immunohistochemical staining of vascular Notch3 deposits in biopsied unfixed frozen skin samples from patients with suspected cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). We analyzed vascular Notch3 deposits in unfixed frozen skin biopsy samples obtained from 43 patients with suspected CADASIL by immunohistochemistry using antibodies against the extracellular domain (ECD) of Notch3. We also sequenced the NOTCH3 gene in all patients, as well as evaluated their symptoms and neuroimages. We found granular Notch3 ECD deposits in the vessel walls of unfixed frozen skin biopsy samples in 10 of the 43 suspected patients with CADASIL. All 10 cases with skin Notch3 ECD deposits also carried reported pathogenic variants in the NOTCH3 gene associated with CADASIL. NOTCH3 variants of unknown significance were found in the other four patients without vascular Notch3 ECD or granular osmiophilic material deposits in biopsied skin samples. The remaining 29 cases without vascular Notch3 ECD deposits did not have variants in the NOTCH3 gene. Immunohistochemical evaluation of vascular Notch3 ECD deposits in unfixed frozen biopsied skin samples may be useful for detecting Notch3 deposits in CADASIL.

Cerebral Autosomal Dominant Arteriopathy With Subcortical Infarcts and Leukoencephalopathy Family Members With a Pathogenic NOTCH3 Variant Can Have a Normal Brain Magnetic Resonance Imaging and Skin Biopsy Beyond Age 50 Years

BACKGROUND

To determine whether extremely mild small vessel disease (SVD) phenotypes can occur in NOTCH3 variant carriers from Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL) pedigrees using clinical, genetic, neuroimaging, and skin biopsy findings.

METHODS

Individuals from CADASIL pedigrees fulfilling criteria for extremely mild NOTCH3-associated SVD (mSVDNOTCH3) were selected from the cross-sectional Dutch CADASIL cohort (n=200), enrolled between 2017 and 2020. Brain magnetic resonance imaging were quantitatively assessed for SVD imaging markers. Immunohistochemistry and electron microscopy was used to quantitatively assess and compare NOTCH3 ectodomain (NOTCH3ECD) aggregation and granular osmiophilic material deposits in the skin vasculature of mSVDNOTCH3 cases and symptomatic CADASIL patients.

RESULTS

Seven cases were identified that fulfilled the mSVDNOTCH3 criteria, with a mean age of 56.6 years (range, 50-72). All of these individuals harbored a NOTCH3 variant located in one of EGFr domains 7-34 and had a normal brain magnetic resonance imaging, except the oldest individual, aged 72, who had beginning confluence of WMH (Fazekas score 2) and 1 cerebral microbleed. mSVDNOTCH3 cases had very low levels of NOTCH3ECD aggregation in skin vasculature, which was significantly less than in symptomatic EGFr 7-34 CADASIL patients (P=0.01). Six mSVDNOTCH3 cases had absence of granular osmiophilic material deposits.

CONCLUSIONS

Our findings demonstrate that extremely mild SVD phenotypes can occur in individuals from CADASIL pedigrees harboring NOTCH3 EGFr 7-34 variants with normal brain magnetic resonance imaging up to age 58 years. Our study has important implications for CADASIL diagnosis, disease prediction, and the counseling of individuals from EGFr 7-34 CADASIL pedigrees.

Adult Hereditary White Matter Diseases With Psychiatric Presentation: Clinical Pointers and MRI Algorithm to Guide the Diagnostic Process

OBJECTIVE

The investigators aimed to provide clinical and MRI guidelines for determining when genetic workup should be considered in order to exclude hereditary leukoencephalopathies in affected patients with a psychiatric presentation.

METHODS

A systematic literature review was conducted, and clinical cases are provided. Given the central role of MRI pattern recognition in the diagnosis of white matter disorders, the investigators adapted an MRI algorithm that guides the interpretation of MRI findings and thus directs further investigations, such as genetic testing.

RESULTS

Twelve genetic leukoencephalopathies that can present with psychiatric symptoms were identified. As examples of presentations that can occur in clinical practice, five clinical vignettes from patients assessed at a referral center for adult genetic leukoencephalopathies are provided.

CONCLUSIONS

Features such as drug-resistant symptoms, presence of long-standing somatic features, trigger events, consanguinity, and positive family history should orient the clinician toward diagnostic workup to exclude the presence of a genetic white matter disorder. The identification of MRI white matter abnormalities, especially when presenting a specific pattern of involvement, should prompt genetic testing for known forms of genetic leukoencephalopathies.

The pericyte: A critical cell in the pathogenesis of CADASIL

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CADASIL is the most common hereditary small vessel disease presenting with strokes and subcortical vascular dementia caused by mutations in the NOTCH3 gene.

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CADASIL is a vasculopathy primarily involving vascular smooth-muscle cells.

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Arteriolar and capillary pericyte damage or deficiency is a key feature in disease pathogenesis.

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Pericyte-mediated cerebral venous insufficiency may explain white matter lesions and increased perivascular spaces.

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Central role of the pericyte offers novel approaches to the treatment of CADASIL.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a hereditary small vessel disease presenting with migraine, mood and cognitive disorders, focal neurological deficits, recurrent ischemic attacks, lacunar infarcts and brain white matter changes. As they age, CADASIL patients invariably develop cognitive impairment and subcortical dementia. CADASIL is caused by missense mutations in the NOTCH3 gene resulting in a profound cerebral vasculopathy affecting primarily arterial vascular smooth muscle cells, which target the microcirculation and perfusion. Based on a thorough review of morphological lesions in arteries, veins, and capillaries in CADASIL, we surmise that arteriolar and capillary pericyte damage or deficiency appears a key feature in the pathogenesis of the disease. This may affect critical pericyte-endothelial interactions causing stroke injury and vasomotor disturbances. Changes in microvascular permeability due to perhaps localized blood-brain barrier alterations and pericyte secretory dysfunction likely contribute to delayed neuronal as well as glial cell death. Moreover, pericyte-mediated cerebral venous insufficiency may explain white matter lesions and the dilatation of Virchow-Robin perivascular spaces typical of CADASIL. The postulated central role of the pericyte offers some novel approaches to the study and treatment of CADASIL and enable elucidation of other forms of cerebral small vessel diseases and subcortical vascular dementia.

NOTCH3 mutations in a cohort of Portuguese patients within CADASIL spectrum phenotype

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common inherited cerebral small vessel disease. It is caused by mutations in the NOTCH3 gene, which encodes a membranebound receptor protein with three main distinct functional domains. Thus far, several different NOTCH3 mutations, most of them cysteine altering variants, have been described and although they tend to cluster in certain exons, their distribution varies in different geographically populations. Therefore, in this study, we describe the mutation analysis of NOTCH3 gene in 24 Portuguese families with small vessel disease suspected to have CADASIL from the central region of Portugal. The genetic analysis revealed 15 different heterozygous variants, eight pathogenic cysteine altering variants, six cysteine sparing variants and one nonsense variant, located mainly in the exons 4, 8 and 11. Thus, in our population, the genetic testing should initially be focused on these exons. In addition, the genetic findings broaden the mutational and clinical spectrum of CADASIL related phenotype and provide additional evidences for genetic counseling and clinical management.

Notch3 Signaling and Aggregation as Targets for the Treatment of CADASIL and Other NOTCH3-Associated Small-Vessel Diseases

Mutations in the NOTCH3 gene can lead to small-vessel disease in humans, including the well-characterized cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a condition caused by NOTCH3 mutations altering the number of cysteine residues in the extracellular domain of Notch3. Growing evidence indicates that other types of mutations in NOTCH3, including cysteine-sparing missense mutations or frameshift and premature stop codons, can lead to small-vessel disease phenotypes of variable severity or penetrance. There are currently no disease-modifying therapies for small-vessel disease, including those associated with NOTCH3 mutations. A deeper understanding of underlying molecular mechanisms and clearly defined targets are needed to promote the development of therapies. This review discusses two key pathophysiological mechanisms believed to contribute to the emergence and progression of small-vessel disease associated with NOTCH3 mutations: abnormal Notch3 aggregation and aberrant Notch3 signaling. This review offers a summary of the literature supporting and challenging the relevance of these mechanisms, together with an overview of available preclinical experiments derived from these mechanisms. It highlights knowledge gaps and future research directions. In view of recent evidence demonstrating the relatively high frequency of NOTCH3 mutations in the population, and their potential role in promoting small-vessel disease, progress in the development of therapies for NOTCH3-associated small-vessel disease is urgently needed.

Heterozygous Cysteine-sparing NOTCH3 Variant p.Val237Met in a Japanese Patient with Suspected Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy

A 64-year-old Japanese man with recurrent cerebral ischemic events and cognitive impairment was suspected of having cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) because of a family history and brain magnetic resonance imaging findings of cerebral white matter hyperintensities. The cysteine-sparing variation p.Val237Met was identified in NOTCH3. An intensive skin biopsy showed negative results (no granular osmiophilic material or positive NOTCH3 immunostaining), suggesting that the patient's definite diagnosis and pathogenicity of p.Val237Met were uncertain. We additionally reviewed previous reports of two Japanese families with p.Val237Met.

NOTCH3 variant position is associated with NOTCH3 aggregation load in CADASIL vasculature

Aims

CADASIL, the most prevalent hereditary cerebral small vessel disease, is caused by cysteine‐altering NOTCH3 variants (NOTCH3^cys) leading to vascular NOTCH3 protein aggregation. It has recently been shown that variants located in one of NOTCH3 protein epidermal growth‐factor like repeat (EGFr) domains 1–6, are associated with a more severe phenotype than variants located in one of the EGFr domains 7–34. The underlying mechanism for this genotype–phenotype correlation is unknown. The aim of this study was to analyse whether NOTCH3^cys variant position is associated with NOTCH3 protein aggregation load.

Methods

We quantified vascular NOTCH3 aggregation in skin biopsies (n = 25) and brain tissue (n = 7) of CADASIL patients with a NOTCH3^cys EGFr 1–6 variant or a EGFr 7–34 variant, using NOTCH3 immunohistochemistry (NOTCH3 score) and ultrastructural analysis of granular osmiophilic material (GOM count). Disease severity was assessed by neuroimaging (lacune count and white matter hyperintensity volume) and disability (modified Rankin scale).

Results

Patients with NOTCH3^cys EGFr 7–34 variants had lower NOTCH3 scores (P = 1.3·10⁻⁵) and lower GOM counts (P = 8.2·10⁻⁵) than patients with NOTCH3^cys EGFr 1–6 variants in skin vessels. A similar trend was observed in brain vasculature. In the EGFr 7–34 group, NOTCH3 aggregation levels were associated with lacune count (P = 0.03) and white matter hyperintensity volume (P = 0.02), but not with disability.

Conclusions

CADASIL patients with an EGFr 7–34 variant have significantly less vascular NOTCH3 aggregation than patients with an EGFr 1–6 variant. This may be one of the factors underlying the difference in disease severity between NOTCH3^cys EGFr 7–34 and EGFr 1–6 variants.

Genetic Counselling Improves the Molecular Characterisation of Dementing Disorders

Dementing disorders are a complex group of neurodegenerative diseases characterised by different, but often overlapping, pathological pathways. Genetics have been largely associated with the development or the risk to develop dementing diseases. Recent advances in molecular technologies permit analyzing of several genes in a small time, but the interpretation analysis is complicated by several factors: the clinical complexity of neurodegenerative disorders, the frequency of co-morbidities, and the high phenotypic heterogeneity of genetic diseases. Genetic counselling supports the diagnostic path, providing an accurate familial and phenotypic characterisation of patients. In this review, we summarise neurodegenerative dementing disorders and their genetic determinants. Genetic variants and associated phenotypes will be divided into high and low impact, in order to reflect the pathologic continuum between multifactorial and mendelian genetic factors. Moreover, we report a molecular characterisation of genes associated with neurodegenerative disorders with cognitive impairment. In particular, the high frequency of rare coding genetic variants in dementing genes strongly supports the role of geneticists in both, clinical phenotype characterisation and interpretation of genotypic data. The smart application of exome analysis to dementia patients, with a pre-analytical selection on familial, clinical, and instrumental features, improves the diagnostic yield of genetic test, reduces time for diagnosis, and allows a rapid and personalised management of disease.

Loss of cholinergic innervation differentially affects eNOS-mediated blood flow, drainage of Aβ and cerebral amyloid angiopathy in the cortex and hippocampus of adult mice

Vascular dysregulation and cholinergic basal forebrain degeneration are both early pathological events in the development of Alzheimer’s disease (AD). Acetylcholine contributes to localised arterial dilatation and increased cerebral blood flow (CBF) during neurovascular coupling via activation of endothelial nitric oxide synthase (eNOS). Decreased vascular reactivity is suggested to contribute to impaired clearance of β-amyloid (Aβ) along intramural periarterial drainage (IPAD) pathways of the brain, leading to the development of cerebral amyloid angiopathy (CAA). However, the possible relationship between loss of cholinergic innervation, impaired vasoreactivity and reduced clearance of Aβ from the brain has not been previously investigated. In the present study, intracerebroventricular administration of mu-saporin resulted in significant death of cholinergic neurons and fibres in the medial septum, cortex and hippocampus of C57BL/6 mice. Arterial spin labelling MRI revealed a loss of CBF response to stimulation of eNOS by the Rho-kinase inhibitor fasudil hydrochloride in the cortex of denervated mice. By contrast, the hippocampus remained responsive to drug treatment, in association with altered eNOS expression. Fasudil hydrochloride significantly increased IPAD in the hippocampus of both control and saporin-treated mice, while increased clearance from the cortex was only observed in control animals. Administration of mu-saporin in the TetOAPPSweInd mouse model of AD was associated with a significant and selective increase in Aβ40-positive CAA. These findings support the importance of the interrelationship between cholinergic innervation and vascular function in the aetiology and/or progression of CAA and suggest that combined eNOS/cholinergic therapies may improve the efficiency of Aβ removal from the brain and reduce its deposition as CAA.

SQSTM1 gene as a potential genetic modifier of CADASIL phenotype

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common inherited cerebral small vessel disease and is caused by mutations in the NOTCH3 gene. Interestingly, CADASIL patients present a large phenotypic variability even harboring the same pathogenic variant. We describe two CADASIL siblings with a particularly aggressive clinical phenotype characterized by early-onset stroke, gait disturbances and/or dementia, severe emotional dysregulation, and dysexecutive syndrome together with a severe white matter burden on MRI. The genetic analysis revealed the co-occurrence of NOTCH3 (p.Gly420Cys) and SQSTM1 (p.Ser275Phefs*17) pathogenic variants which might worsen the aggressiveness of disease progression in both siblings. Interestingly, to the best of our knowledge, mutations in SQSTM1 gene have never been described in CADASIL patients before. Curiously, both Notch3 and p62 encoded proteins have a key role in the autophagy-lysosomal pathway which is impaired in CADASIL patients. Thus, the contribution of SQSTM1 gene to the clinical heterogeneity of CADASIL patients, in particular for those who develop cognitive impairment or dementia at an early age, is certainly overlooked. Therefore, we advocate expanding the genetic analysis to other genes associated with the phenotype spectrum of CADASIL patients using NGS-customized gene panel.

Combined Transcriptomic and Proteomic Analyses of Cerebral Frontal Lobe Tissue Identified RNA Metabolism Dysregulation as One Potential Pathogenic Mechanism in Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL)

BACKGROUND

Cerebral small vessel disease (SVD) is an important cause of stroke and vascular cognitive impairment (VCI), leading to subcortical ischemic vascular dementia. As a hereditary form of SVD with early onset, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) represents a pure form of SVD and may thus serve as a model disease for SVD. To date, underlying molecular mechanisms linking vascular pathology and subsequent neuronal damage in SVD are incompletely understood.

OBJECTIVE

We performed comparative transcriptional profiling microarray and proteomic analyses on post-mortem frontal lobe specimen from 2 CADASIL patients and 5 non neurologically diseased controls in order to identify dysregulated pathways potentially involved in the development of tissue damage in CADASIL.

METHODS

Transcriptional microarray analysis of material extracted from frontal grey and white matter (WM) identified subsets of up- or down-regulated genes enriched into biological pathways mostly in WM areas. Proteomic analysis of these regions also highlighted cellular processes identified by dysregulated proteins.

RESULTS

Discrepancies between proteomic and transcriptomic data were observed, but a number of pathways were commonly associated with genes and corresponding proteins, such as: "ribosome" identified by upregulated genes and proteins in frontal cortex or "spliceosome" associated with down-regulated genes and proteins in frontal WM.

CONCLUSION

This latter finding suggests that defective expression of spliceosomal components may alter widespread splicing profile, potentially inducing expression abnormalities that could contribute to cerebral WM damage in CADASIL.

Optical Coherence Tomography Angiography in Neurodegenerative Diseases: A Review

Background

Optical coherence tomography angiography (OCT-A) has emerged as a novel, fast, safe and non-invasive imaging technique of analyzing the retinal and choroidal microvasculature in vivo. OCT-A captures multiple sequential B-scans performed repeatedly over a specific retinal area at high speed, thus enabling the composition of a vascular map with areas of contrast change (high flow zones) and areas of steady contrast (slow or no flow zones). It therefore provides unique insight into the exact retinal or choroidal layer and location at which abnormal blood flow develops. OCTA has evolved into a useful tool for understanding a number of retinal pathologies such as diabetic retinopathy, age-related macular degeneration, central serous chorioretinopathy, vascular occlusions, macular telangiectasia and choroidal neovascular membranes of other causes. OCT-A technology is also increasingly being used in the evaluation of optic disc perfusion and has been suggested as a valuable tool in the early detection of glaucomatous damage and monitoring progression.

Objective

To review the existing literature on the applications of optical coherence tomography angiography in neurodegenerative diseases.

Summary

A meticulous literature was performed until the present day. Google Scholar, PubMed, Mendeley search engines were used for this purpose. We used 123 published manuscripts as our references. OCT-A has been utilized so far to describe abnormalities in multiple sclerosis (MS), Alzheimer’s disease, arteritic and non-arteritic optic neuropathy (AION and NAION), Leber’s hereditary optic neuropathy (LHON) papilloedema, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis (ALS), Wolfram syndrome, migraines, lesions of the visual pathway and cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). It appears that OCT-A findings correlate quite well with the severity of the aforementioned diseases. However, OCT-A has its own limitations, namely its lack of wide-field view of the peripheral retina and the inaccurate interpretation due to motion artifacts in uncooperative groups of patients (e.g. children). Larger prospective longitudinal studies will need to be conducted in order to eliminate the aforementioned limitations.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy revisited: Genotype-phenotype correlations of all published cases

Objective

The aim of this study was to evaluate the correlation between the various NOTCH3 mutations and their clinical and genetic profile, along with the presentation of a novel mutation in a patient.

Methods

Here, we describe the phenotype of a patient with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) harboring a novel mutation. We also performed an extensive literature research for NOTCH3 mutations published since the identification of the gene and performed a systematic review of all published cases with NOTCH3 mutations. We evaluated the mutation pathogenicity in a great number of patients with detailed clinical and genetic evaluation and investigated the possible phenotype-genotype correlations.

Results

Our patient harbored a novel mutation in the NOTCH3 gene, the c.3084 G > C, corresponding to the aminoacidic substitution p.Trp1028Cys, presenting with seizures as the first neurologic manifestation. We managed to find a correlation between the pathogenicity of mutations, severity of the phenotype, and age at onset of CADASIL. Significant differences were also identified between men and women regarding the phenotype severity.

Conclusions

The collection and analysis of these scarce data published since the identification of NOTCH3 qualitatively by means of a systematic review and quantitatively regarding genetic profile and pathogenicity scores, highlight the significance of the ongoing trend of investigating phenotypic genotypic correlations.

Clinical and Genetic Aspects of CADASIL

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a hereditary cerebral small vessel disease caused by mutations in NOTCH3, is characterized by recurrent stroke without vascular risk factors, mood disturbances, and dementia. MRI imaging shows cerebral white matter (WM) hyperintensity, particularly in the external capsule and temporal pole. Missense mutations related to a cysteine residue in the 34 EGFr on the NOTCH3 extracellular domain (N3ECD) are a typical mutation of CADASIL. On the other hand, atypical mutations including cysteine sparing mutation, null mutation, homozygous mutation, and other associate genes are also reported. From the viewpoint of gain of function apart from Notch signaling or loss of function of Notch signaling, we review the research article about CADASIL and summarized the pathogenesis of small vessel, stroke, and dementia in this disease.

Multiple Border-Zone Infarcts Triggered by Influenza A Virus Infection in a Patient With Cerebral Autosomal Dominant Arteriopathy Presenting With Subcortical Infarcts and Leukoencephalopathy

Patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) can develop multiple border-zone infarcts due to hypotension, hypovolemia, or surgery. We report the case of a 41-year-old woman with CADASIL who developed multiple border-zone infarcts due to influenza A virus infection. The patient had no apparent history or episode of stroke or altered consciousness following the onset of respiratory symptoms, which were due to the influenza A infection. Diffusion-weighted magnetic resonance images of the brain showed multiple acute-phase infarcts in border-zone areas of both cerebral hemispheres and the corpus callosum; fluid-attenuated inversion-recovery magnetic resonance images showed increased signal in the subcortical areas of both temporal poles. Gene analysis identified a heterozygous mutation c.160C>T in exon 2 of the NOTCH3 gene (p.Arg54Cys). A diagnosis of CADASIL was established. Our case demonstrates that infectious conditions such as influenza A can trigger multiple border-zone infarctions in patients with CADASIL.

George-Hyslop P, Londos E, Zetterberg H, Morgan K, Troakes C, Al-Sarraj S, Lashley T, Holton J, Compta Y, Van Deerlin V, Trojanowski JQ, Serrano GE, Beach TG, Lesage S, Galasko D, Masliah E, Santana I, Pastor P, Tienari PJ, Myllykangas L, Oinas M, Revesz T, Lees A, Boeve BF, Petersen RC, Ferman TJ, Escott-Price V, Graff-Radford N, Cairns NJ, Morris JC, Pickering-Brown S, Mann D, Halliday G, Stone DJ, Dickson DW, Hardy J, Singleton A, Guerreiro R, Bras J. Analysis of neurodegenerative disease-causing genes in dementia with Lewy bodies

Dementia with Lewy bodies (DLB) is a clinically heterogeneous disorder with a substantial burden on healthcare. Despite this, the genetic basis of the disorder is not well defined and its boundaries with other neurodegenerative diseases are unclear. Here, we performed whole exome sequencing of a cohort of 1118 Caucasian DLB patients, and focused on genes causative of monogenic neurodegenerative diseases. We analyzed variants in 60 genes implicated in DLB, Alzheimer’s disease, Parkinson’s disease, frontotemporal dementia, and atypical parkinsonian or dementia disorders, in order to determine their frequency in DLB. We focused on variants that have previously been reported as pathogenic, and also describe variants reported as pathogenic which remain of unknown clinical significance, as well as variants associated with strong risk. Rare missense variants of unknown significance were found in APP, CHCHD2, DCTN1, GRN, MAPT, NOTCH3, SQSTM1, TBK1 and TIA1. Additionally, we identified a pathogenic GRN p.Arg493* mutation, potentially adding to the diversity of phenotypes associated with this mutation. The rarity of previously reported pathogenic mutations in this cohort suggests that the genetic overlap of other neurodegenerative diseases with DLB is not substantial. Since it is now clear that genetics plays a role in DLB, these data suggest that other genetic loci play a role in this disease.

Investigating diagnostic sequencing techniques for CADASIL diagnosis

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a cerebral small vessel disease caused by mutations in the NOTCH3 gene. Our laboratory has been undertaking genetic diagnostic testing for CADASIL since 1997. Work originally utilised Sanger sequencing methods targeting specific NOTCH3 exons. More recently, next-generation sequencing (NGS)-based technologies such as a targeted gene panel and whole exome sequencing (WES) have been used for improved genetic diagnostic testing. In this study, data from 680 patient samples was analysed for 764 tests utilising 3 different sequencing technologies. Sanger sequencing was performed for 407 tests, a targeted NGS gene panel which includes NOTCH3 exonic regions accounted for 354 tests, and WES with targeted analysis was performed for 3 tests. In total, 14.7% of patient samples (n = 100/680) were determined to have a mutation. Testing efficacy varied by method, with 10.8% (n = 44/407) of tests using Sanger sequencing able to identify mutations, with 15.8% (n = 56/354) of tests performed using the NGS custom panel successfully identifying mutations and a likely non-NOTCH3 pathogenic variant (n = 1/3) identified through WES. Further analysis was then performed through stratification of the number of mutations detected at our facility based on the number of exons, level of pathogenicity and the classification of mutations as known or novel. A systematic review of NOTCH3 mutation testing data from 1997 to 2017 determined the diagnostic rate of pathogenic findings and found the NGS-customised panel increases our ability to identify disease-causing mutations in NOTCH3.

Progression and Classification of Granular Osmiophilic Material (GOM) Deposits in Functionally Characterized Human NOTCH3 Transgenic Mice

CADASIL is a NOTCH3-associated cerebral small vessel disease. A pathological ultrastructural disease hallmark is the presence of NOTCH3-protein containing deposits called granular osmiophilic material (GOM), in small arteries. How these GOM deposits develop over time and what their role is in disease progression is largely unknown. Here, we studied the progression of GOM deposits in humanized transgenic NOTCH3^Arg182Cys mice, compared them to GOM deposits in patient material, and determined whether GOM deposits in mice are associated with a functional CADASIL phenotype. We found that GOM deposits are not static, but rather progress in ageing mice, both in terms of size and aspect. We devised a GOM classification system, reflecting size, morphology and electron density. Six-month-old mice showed mostly early stage GOM, whereas older mice and patient vessels showed predominantly advanced stage GOM, but also early stage GOM. Mutant mice did not develop the most severe GOM stage seen in patient material. This absence of end-stage GOM in mice was associated with an overall lack of histological vascular pathology, which may explain why the mice did not reveal functional deficits in cerebral blood flow, cognition and motor function. Taken together, our data indicate that GOM progress over time, and that new GOM deposits are continuously being formed. The GOM staging system we introduce here allows for uniform GOM deposit classification in future mouse and human studies, which may lead to more insight into a potential association between GOM stage and CADASIL disease severity, and the role of GOM in disease progression.

Clinical Features of 4 Novel NOTCH3 Mutations of Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy in China

Background

This study aimed to identify NOTCH3 mutations and describe the genetic and clinical features and magnetic resonance imaging results in 11 unrelated patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) from Henan province in China.

Material/Methods

NOTCH3 was directly sequenced in 11 unrelated patients of Chinese descent. The clinical presentations and magnetic resonance imaging features were retrospectively analyzed in the 11 index patients with a definite diagnosis.

Results

Seven different mutations were identified in 11 unrelated patients, including 4 novel mutations (p.P167S, p.P652S, p.C709R, and p.R1100H) in China and 3 reported mutations (p.C117R, p.R578C, and p.R607C). Four novel mutations (p.P167S, p.P652S, p.C709R, and p.R1100H) were predicted to be probably pathogenic using an online pathogenicity prediction program through comprehensive analysis. Clinical presentations in symptomatic patients included stroke, cognitive decline, psychiatric disturbances, and migraine. Multiple lacunars infarcts and leukoaraiosis were detected on MRI in most symptomatic patients, while white-matter lesions were identified in the temporal pole or the external capsule in all affected patients.

Conclusions

The mutation spectrum of CADASIL patients from Henan province in China displayed some differences from that of those reported previously. DNA sequencing was used to diagnose all 11 patients as having CADASIL, and we found 4 novel mutations. The present results further contribute to the enrichment of NOTCH3 mutation databases.

Genetic Factors of Cerebral Small Vessel Disease and Their Potential Clinical Outcome

Cerebral small vessel diseases (SVD) have been causally correlated with ischemic strokes, leading to cognitive decline and vascular dementia. Neuroimaging and molecular genetic tests could improve diagnostic accuracy in patients with potential SVD. Several types of monogenic, hereditary cerebral SVD have been identified: cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL), cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), cathepsin A-related arteriopathy with strokes and leukoencephalopathy (CARASAL), hereditary diffuse leukoencephalopathy with spheroids (HDLS), COL4A1/2-related disorders, and Fabry disease. These disorders can be distinguished based on their genetics, pathological and imaging findings, clinical manifestation, and diagnosis. Genetic studies of sporadic cerebral SVD have demonstrated a high degree of heritability, particularly among patients with young-onset stroke. Common genetic variants in monogenic disease may contribute to pathological progress in several cerebral SVD subtypes, revealing distinct genetic mechanisms in different subtype of SVD. Hence, genetic molecular analysis should be used as the final gold standard of diagnosis. The purpose of this review was to summarize the recent discoveries made surrounding the genetics of cerebral SVD and their clinical significance, to provide new insights into the pathogenesis of cerebral SVD, and to highlight the possible convergence of disease mechanisms in monogenic and sporadic cerebral SVD.

Lenticulostriate Arteries and Basal Ganglia Changes in Cerebral Autosomal Dominant Arteriopathy With Subcortical Infarcts and Leukoencephalopathy, a High-Field MRI Study

Background and Purpose: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) mainly affects the cerebral small arteries. We aimed to analyze changes in the lenticulostriate arteries (LSAs) and the basal ganglia in patients with CADASIL using high-field magnetic resonance imaging (7.0-T MRI).

Methods: We examined 46 patients with CADASIL and 46 sex- and age-matched healthy individuals using 7.0-T MRI. The number and length of the LSAs, and the proportion of discontinuous LSAs were compared between the two groups. The Mini-Mental State Examination score, the modified Rankin Scale, the Barthel Index, and the MRI lesion load of the basal ganglia were also examined in patients with CADASIL. We analyzed the association between LSA measurements and the basal ganglia lesion load, as well as the association between LSA measurements and clinical phenotypes in this patient group.

Results: We observed a decrease in the number of LSA branches (t = −2.591, P = 0.011), and an increase in the proportion of discontinuous LSAs (z = −1.991, P = 0.047) in patients with CADASIL when compared with healthy controls. However, there was no significant difference in the total length of LSAs between CADASIL patients and healthy individuals (t = −0.412, P = 0.682). There was a positive association between the number of LSA branches and the Mini-Mental State Examination scores of CADASIL patients after adjusting for age and educational level (β = 0.438; 95% CI: 0.093, 0.782; P = 0.014). However, there was no association between LSA measurements and the basal ganglia lesion load among CADASIL patients.

Conclusions: 7.0-T MRI provides a promising and non-invasive method for the study of small artery damage in CADASIL. The abnormalities of small arteries may be related to some clinical symptoms of CADASIL patients such as cognitive impairment. The lack of association between LSA measurements and the basal ganglia lesion load among the patients suggests that changes in the basal ganglia due to CADASIL are caused by mechanisms other than anatomic narrowing of the vessel lumen.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL) presenting with stroke in a young man

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL) is caused by mutations in the NOTCH3 gene which maps to the short arm of chromosome 19 and encodes the NOTCH3 receptor protein, predominantly expressed in adults by vascular smooth muscle cells and pericytes. The receptor has a large extracellular domain with 34 epidermal growth factor-like repeats encoded by exons 2-24, the site at which CADASIL mutations are most commonly found. Migraine with aura is often the earliest feature of the disease, with an increased susceptibility to cortical spreading depression suggested as a possible aetiological mechanism. Stroke, acute encephalopathy and cognitive impairment can also occur. Hypertension and smoking are associated with early age of onset of stroke. It diffusely affects white matter, with distinct findings on T2- weighted MRI, involving the external capsule, anterior poles of the temporal lobe and superior frontal gyri, displaying a characteristic pattern of leucoencephalopathy. Affected individuals have a reduced life expectancy. An effective treatment for CADASIL is not available. The authors describe a 35-year-old manwith an unremarkable medical history, presenting to the emergency department with slurred speech and increased confusion 3 days following a fall. He was a smoker and consumed 16 units of alcohol weekly. He was hypertensive and tachycardic. Physical examination confirmed increased tone in his lower limbs and dysarthria. His CT head showed severe cerebral atrophy, multiple small old infarcts and moderate background microvascular disease. Further investigation with an MRI head confirmed multiple white matter abnormalities with microhaemorrhages. The possibility of a hereditary vasculopathy was rendered as the appearances were thought consistent with a diagnosis of CADASIL. Genetic testing identified the NOTCH3 gene thus confirming the diagnosis. This paper provides an overview of the aetiology, clinical presentation, pathogenesis, investigations and management of CADASIL.

Novel and Recurring NOTCH3 Mutations in Two Chinese Patients with CADASIL

BACKGROUND

Cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an autosomal-dominant, inherited, systemic, vascular disorder primarily involving the small arteries. It is characterized by migraine, recurrent ischemic strokes, cognitive decline, and dementia. Mutations in the Notch receptor 3 gene (NOTCH3) and the HtrA serine peptidase 1 gene (HTRA1) are 2 genetic causes for CADASIL. The NOTCH3 gene, located on chromosome 19p13.12, is the most common disease-causing gene in CADASIL.

OBJECTIVE

To investigate genetic causes in 2 unrelated Han-Chinese patients with presentations strongly suggestive of CADASIL.

METHODS

Exome sequencing was performed on both patients and potential pathogenic mutations were validated by Sanger sequencing.

RESULTS

This study reports on 2 unrelated Han-Chinese patients with presentations strongly suggestive of CADASIL, identifying that NOTCH3 mutations were the genetic cause. A common mutation, c.268C>T (p.Arg90Cys), and a novel mutation, c.331G>T (p.Gly111Cys) in the NOTCH3 gene, were detected and confirmed in the patients, respectively, and were predicted to be deleterious based on bioinformation analyses.

CONCLUSIONS

We identified 2 NOTCH3 mutations as likely genetic causes for CADASIL in these 2 patients. Our findings broaden the mutational spectrum of the NOTCH3 gene accountable for CADASIL. Clinical manifestations supplemented with molecular genetic analyses are critical for accurate diagnosis, the provision of genetic counseling, and the development of therapies for CADASIL.

NOTCH3 and CADASIL syndrome: a genetic and structural overview

CADASIL syndrome is a rare disease that belongs to a group of disorders called leukodystrophies. It is well established that NOTCH3 gene on chromosome 19 is primarily responsible for the development of the CADASIL syndrome. Herein, an attempt is made to shed light on the actual molecular mechanism underlying CADASIL syndrome, through insights extracted from comprehensive evolutionary studies and in silico modelling on Notch 3 protein. In particular, we suggest the use of optical coherence tomography angiography for the detection of early signs of small vessel diseases, which are the major precursors to a repertoire of neurodegenerative conditions, including CADASIL.

Modeling CADASIL vascular pathologies with patient-derived induced pluripotent stem cells

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a rare hereditary cerebrovascular disease caused by a NOTCH3 mutation. However, the underlying cellular and molecular mechanisms remain unidentified. Here, we generated non-integrative induced pluripotent stem cells (iPSCs) from fibroblasts of a CADASIL patient harboring a heterozygous NOTCH3 mutation (c.3226C>T, p.R1076C). Vascular smooth muscle cells (VSMCs) differentiated from CADASIL-specific iPSCs showed gene expression changes associated with disease phenotypes, including activation of the NOTCH and NF-κB signaling pathway, cytoskeleton disorganization, and excessive cell proliferation. In comparison, these abnormalities were not observed in vascular endothelial cells (VECs) derived from the patient's iPSCs. Importantly, the abnormal upregulation of NF-κB target genes in CADASIL VSMCs was diminished by a NOTCH pathway inhibitor, providing a potential therapeutic strategy for CADASIL. Overall, using this iPSC-based disease model, our study identified clues for studying the pathogenic mechanisms of CADASIL and developing treatment strategies for this disease.