New mutations in the Notch3 gene in patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL)

Signaling pathways and molecular mechanisms involved in the onset and progression of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL); a focus on Notch3 signaling

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an autosomal-dominantly inherited cerebral small-vessel disease (SVD). CADASIL has diverse clinical features such as migraine with aura, dementia, and recurrent strokes, and is caused by a pathogenic mutation in the NOTCH3 gene which encodes a transmembrane receptor found in smooth muscle cells of small arteries and pericytes of brain capillaries. Pathogenic mutations alter the number of cysteine residues in the extracellular domain of NOTCH3, leading to the abnormal accumulation of granular osmiophilic material in the vessels of affected individuals. In addition, potential signaling pathways, such as transforming growth factor beta (TGF-β), may be involved in pathogenesis of the disease. This review aims to elucidate these mechanisms, particularly NOTCH3, in the context of CADASIL pathogenesis, providing insight into the role of NOTCH3 signaling and discussing the significance of these pathways for potential future therapeutic interventions in CADASIL patients.

Uncovering genetic mimics in multiple sclerosis: A single-center clinical exome sequencing study

Background

Multiple sclerosis (MS) shares clinical/radiological features with several monogenic diseases that can mimic MS.

Objective

We aimed to determine if exome sequencing can identify monogenic diseases in patients diagnosed with MS according to the McDonald criteria thus uncovering them as being misdiagnosed.

Methods

We performed whole exome sequencing in a cohort of 278 patients with MS, clinically or radiologically isolated syndrome without cerebrospinal fluid-specific oligoclonal bands (CSF-OCBs) (n = 228), a positive family history of MS (n = 44), or both (n = 6), thereby focusing on individuals potentially more likely to have underlying monogenic conditions mimicking MS. We prioritized 495 genes associated with monogenic diseases sharing features with MS.

Results

A disease-causing variant in NOTCH3 was identified in one patient without CSF-OCBs, no spinal lesions, with non-response to immunotherapy, and a family history of dementia, thereby converting the diagnosis to cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). Moreover, 18 patients (6.5% of total) carried variants of unclear significance.

Conclusion

Monogenic diseases being misdiagnosed as MS seem rare in patients diagnosed with MS according to the McDonald criteria, even in CSF-OCB negative cases. The detected pathogenic NOTCH3 variant emphasizes CADASIL as a rare differential diagnosis and highlights the relevance of genetic testing in selected MS cases with atypical presentations.

NOTCH3 Variants in Patients with Suspected CADASIL

Background

Cerebral autosomal dominant arteriopathy with subcortical infarctions and leukoencephalopathy (CADASIL) is the most common hereditary form of cerebral small vessel disease. It is clinically, radiologically, and genetically heterogeneous and is caused by NOTCH3 mutations.

Methods

In this study, we analyzed NOTCH3 in 368 patients with suspected CADASIL using next-generation sequencing. The significant variants detected were reported along with the clinical and radiological features of the patients.

Results

Heterozygous NOTCH3 changes, mostly missense mutations, were detected in 44 of the 368 patients (~12%).

Conclusions

In this single-center study conducted on a large patient group, 30 different variants were detected, 17 of which were novel. CADASIL, which can result in mortality, has a heterogeneous phenotype among individuals in terms of clinical, demographic, and radiological findings regardless of the NOTCH3 variant.

Influence of different spectra of NOTCH3 variants on the clinical phenotype of CADASIL - experience from Slovakia

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common hereditary vascular disorder causing ischaemic attacks and strokes in middle-aged adults. Though the clinical spectrum includes some typical symptoms, recognition of the disease, especially at an earlier stage, is very difficult because of the highly variable manifestation and incomplete clinical picture. Characteristic brain MRI findings and the presence of pathogenic variants in the NOTCH3 gene are fundamental for CADASIL diagnosis. In this paper, we provide the first comprehensive report on CADASIL patients from Slovakia. Altogether, we identified 23 different pathogenic variants in 35 unrelated families. In our cohort of patients with clinical suspicion of CADASIL, we found a causal genetic defect and confirmed the diagnosis in 10.2% of cases. We present the case reports with up-to-date unpublished NOTCH3 variants and describe their phenotype-genotype correlation: p.(Cys65Phe), p.(Pro86Leu/Ser502Phe), p.(Arg156*), p.(Cys408Arg), p.(Tyr423Cys), p.(Asp1720His), and p.(Asp1893Thrfs*13). The most frequently described location for pathogenic variants was in exon 4, whereas the most common single variant was p.Arg1076Cys in exon 20. Based on the results of our study, we propose a re-evaluation of the criteria for the selection of patients suitable for NOTCH3 gene analysis. We hereby state that the currently used protocol of a high score requirement is not ideal for assessing molecular analysis, and it will be desirable to be less strict in criteria for genetic testing.

Association between NOTCH3 gene and Parkinson's disease based on whole-exome sequencing

Objective

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a hereditary cerebral small vessel disease caused by mutations in the NOTCH3 gene. Previous studies have established a link between NOTCH3 variants and Parkinson's disease (PD) in terms of neuropathology and clinical characteristics. In this study, we aimed to explore the role of NOTCH3 gene in PD in a large Chinese cohort.

Methods

A total of 1,917 patients with early-onset or familial PD and 1,652 matched controls were included. All variants were divided into common or rare types by minor allele frequency (MAF) at a threshold of 0.01 (MAF > 0.01 into common variants and others into rare variants). Common variants were subjected to single-variant tests by PLINK, then gene-based analyses were used for rare variants with the optimized sequence kernel association test (SKAT-O). For genotype-phenotype correlation assessment, regression models were conducted to compare clinical features between the studied groups.

Results

Three common variants (rs1044006, rs1043997, and rs1043994) showed a nominal protective effect against PD. However, none of these SNPs survived Bonferroni correction. The results in the validation cohort revealed a significant but opposite association between these variants and PD. The gene-based analyses of rare variants showed no significant associations of NOTCH3 with PD. Although we did not find significant associations in the following genotype-phenotype analysis, the higher clinical scores of motor symptoms in NOTCH3-variant carriers were of interest.

Conclusion

Our results indicated that NOTCH3 gene may not play an important role in the early-onset or familial PD of Chinese population.

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.

How understudied populations have contributed to our understanding of Alzheimer's disease genetics

The majority of genome-wide association studies have been conducted using samples with a broadly European genetic background. As a field, we acknowledge this limitation and the need to increase the diversity of populations studied. A major challenge when designing and conducting such studies is to assimilate large samples sizes so that we attain enough statistical power to detect variants associated with disease, particularly when trying to identify variants with low and rare minor allele frequencies. In this review, we aimed to illustrate the benefits to genetic characterization of Alzheimer's disease, in researching currently understudied populations. This is important for both fair representation of world populations and the translatability of findings. To that end, we conducted a literature search to understand the contributions of studies, on different populations, to Alzheimer's disease genetics. Using both PubMed and Alzforum Mutation Database, we systematically quantified the number of studies reporting variants in known disease-causing genes, in a worldwide manner, and discuss the contributions of research in understudied populations to the identification of novel genetic factors in this disease. Additionally, we compared the effects of genome-wide significant single nucleotide polymorphisms across populations by focusing on loci that show different association profiles between populations (a key example being APOE). Reports of variants in APP, PSEN1 and PSEN2 can initially determine whether patients from a country have been studied for Alzheimer's disease genetics. Most genome-wide significant associations in non-Hispanic white genome-wide association studies do not reach genome-wide significance in such studies of other populations, with some suggesting an opposite effect direction; this is likely due to much smaller sample sizes attained. There are, however, genome-wide significant associations first identified in understudied populations which have yet to be replicated. Familial studies in understudied populations have identified rare, high effect variants, which have been replicated in other populations. This work functions to both highlight how understudied populations have furthered our understanding of Alzheimer's disease genetics, and to help us gauge our progress in understanding the genetic architecture of this disease in all populations.

A Novel Heterozygous Variant in Exon 19 of NOTCH3 in a Saudi Family with Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy

Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL; OMIM #125310) is the most common cause of monogenic familial cerebral small vessel disease. It typically manifests at middle adulthood with highly variable clinical features including migraine with aura, recurrent transient ischemic attacks or ischemic strokes, mood disorders, and progressive cognitive decline. It is caused by mutations in the NOTCH3 gene, which maps to the short arm of chromosome 19 and encode for epidermal growth factor-like repeats. In this article, we report a 40-year-old male patient who presented with a two-year history of progressive cognitive decline including impaired attention, memory, executive functions, and processing speed whose family history was strongly positive for young-onset ischemic stroke and memory impairment. His father, uncle, and grandfather died due to ischemic strokes and cognitive impairment (similar condition). A whole exome sequencing to the patient (proband II-1) revealed a novel heterozygous missense variant c.3009G>T, p.(Trp1003Cys) (chr19;15291625; hg19) in exon 19 of the NOTCH3 gene. Sanger sequencing was used to confirm the variant in other family members. This variant has not been described in the literature so far. The novel mutation described in the present study widened the genetic spectrum of NOTCH3-associated diseases, which will benefit studies addressing this disease in the future. CADASIL remains a disabling disorder leading to medical retirement in our patient due to late clinical presentation, lack of family history taking prior to joining the military, and lack of curative therapy. Further research for therapeutic options is needed including stem cell therapy .

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.

Vascular cognitive impairment associated with NOTCH3 Exon 33 mutation: A case report

RATIONALE

Vascular cognitive impairment (VCI) is a common cause of dementia. Research suggests that hereditary factors (gene mutations) play an important role in the pathogenesis of VCI, and a mutation of the NOTCH3 locus is frequently identified in affected patients. Herein, we report the case of a patient with confirmed VCI associated with a NOTCH3 exon 33 gene mutation and review the relevant VCI literature.

PATIENT CONCERNS

A 48-year-old man presented to our neurology clinic with gradually progressive cognitive impairment.

DIAGNOSES

Brain magnetic resonance imaging revealed multiple punctate hyperintensities in the patient's periventricular white matter. Genetic analysis showed a c.6744C > T, p. Ala2223Val substitution in exon 33 of the NOTCH3 gene. We diagnosed thepatient with VCI secondary to a NOTCH3 gene mutation.

INTERVENTIONS

Donepezil (5 mg) and memantine (5 mg) daily.

OUTCOMES

The patient showed symptom improvement at his 3-month and 6-month follow-up appointments.

LESSONS

This patient may have a new type of mutation that is different from the one seen in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, although it involves a NOTCH3 defect. We propose that the entire NOTCH3 gene should be sequenced in patients with suspected hereditary VCI. This practice could facilitate the discovery of newpathogenic mutations and diseases.

A Study of Congenital Protein C Deficiency With Infancy Onset of CADASIL in a Chinese Baby

OBJECTIVE

The main objectives of this article were to study a severe congenital protein C deficiency (PCD) in a patient with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) and analyze the cause of this case.

MATERIALS AND METHODS

We had recorded clinical manifestations of the patient, laboratory tests, imaging studies, and gene sequencing of the PROC gene and NOTCH3 gene to study the disease in this family. We checked the change of NOTCH3 protein by immunohistochemistry.

RESULTS

Laboratory studies of the patient had revealed that his PC activity was 3%. Magnetic resonance imaging results showed hyperintense lesions in the cerebral white matter of the patient. PROC gene and NOTCH3 gene sequencing was performed among the family members. The patient was confirmed as homozygous for the (A-G)-12 at the transcription initiation site in the promoter region of the PROC gene and heterozygous mutation of the NOTCH3 gene. Immunohistochemical results showed that NOTCH3 protein was positive in the skin vascular smooth muscle of the patient.

CONCLUSIONS

We studied a rare case of an infat boy diagnosed with both congenital PCD and CADASIL; congenital PCD was attributable to a compound that was homozygous for (A-G)-12 at the transcription initiation site in the promoter region of the PROC gene, and CADASIL was caused by missense mutation in exon 24 of NOTCH3. He was a sporadic patient with congenital PCD and CADASIL; it maybe that the deficiency of protein C led to early onset of CADASIL. The gene sequencing of PROC gene and NOTCH3 gene may have important value for fertility guidance and prenatal diagnosis.

Clinical and research applications of magnetic resonance imaging in the study of CADASIL

Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL) is an inherited small vessel disease that leads to early cerebrovascular events and functional disability. It is the most common single-gene disorder leading to stroke. Magnetic resonance imaging (MRI) is a central component of the diagnosis and monitoring of CADASIL. Here we provide a descriptive review of the literature on three important aspects pertaining to the use of MRI in CADASIL. First, we review past research exploring MRI markers for this disease. Secondly, we describe results from studies investigating associations between neuroimaging abnormalities and neuropathology in CADASIL. Finally, we discuss previous findings relating MRI markers to clinical symptoms. This review thus provides a summary of the current state of knowledge regarding the use of MRI in CADASIL as well as suggestions for future research.

CADASIL

Cerebral small-vessel disease is a prevalent condition that is strongly associated with ischemic stroke and dementia. The most prevalent inherited cause of cerebral small-vessel disease is CADASIL, cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy, a disorder linked to mutations in NOTCH3. The most common symptoms of CADASIL are small ischemic strokes and/or transient ischemic attacks and cognitive impairment, appearing in middle age, that may progress to frank vascular dementia. However, it is increasingly recognized that individual symptom types, onset, and disease severity span a wide spectrum, even among individuals in the same family. Magnetic resonance imaging in CADASIL reveals severe white-matter hyperintensities, evidence of prior subcortical strokes, and, in some cases, microhemorrhages. Several hundred mutations in NOTCH3 have been described worldwide in CADASIL, and virtually all of these mutations alter the cysteine content of the extracellular NOTCH3 gene product. This molecular genetic signature of CADASIL has led to the hypothesis that structural abnormalities in the vascular smooth-muscle protein NOTCH3 trigger arterial degeneration, vascular protein accumulation, and cerebrovascular failure.

Systematic Review of Cysteine-Sparing NOTCH3 Missense Mutations in Patients with Clinical Suspicion of CADASIL

CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy) is caused by mutations in the NOTCH3 gene, affecting the number of cysteines in the extracellular domain of the receptor, causing protein misfolding and receptor aggregation. The pathogenic role of cysteine-sparing NOTCH3 missense mutations in patients with typical clinical CADASIL syndrome is unknown. The aim of this article is to describe these mutations to clarify if any could be potentially pathogenic. Articles on cysteine-sparing NOTCH3 missense mutations in patients with clinical suspicion of CADASIL were reviewed. Mutations were considered potentially pathogenic if patients had: (a) typical clinical CADASIL syndrome; (b) diffuse white matter hyperintensities; (c) the 33 NOTCH3 exons analyzed; (d) mutations that were not polymorphisms; and (e) Granular osmiophilic material (GOM) deposits in the skin biopsy. Twenty-five different mutations were listed. Four fulfill the above criteria: p.R61W; p.R75P; p.D80G; and p.R213K. Patients carrying these mutations had typical clinical CADASIL syndrome and diffuse white matter hyperintensities, mostly without anterior temporal pole involvement. Cysteine-sparing NOTCH3 missense mutations are associated with typical clinical CADASIL syndrome and typical magnetic resonance imaging (MRI) findings, although with less involvement of the anterior temporal lobe. Hence, these mutations should be further studied to confirm their pathological role in CADASIL.

[Differential diagnosis of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy]

Cerebral autosomal dominant arteriopathy with subcortical infarctions and leucoencephalopathy (CADASIL) is an inherited CNS disease, which is caused by mutations in the NOTCH3 gene. Selective disorders of small vessels underlie the disease pathogenesis. Clinically CADASIL is characterized by headaches, multiple stroke-like disorders (in most cases transient ischemic attacks and lacunar strokes), and different focal neurological symptoms and dementia. There are specific MRI signs of the disease: multiple lacunar infarctions located in the basal ganglia, brain steam and cerebellum, focal lesions of temporal poles, capsula externa, periventricular and subcortical areas; diffuse white matter changes and leukoaraiosis can be observed as well. The differential diagnosis of CADASIL is made with many diseases, which are manifested by multiple brain matter lesions, including demyelinating disorders. It should be taken into account that CADASIL is characterized by headaches as one of the initial symptoms, multiple lacunar and diffuse brain matter lesions based on MRI data with an absence of atherosclerosis and arterial hypertension. Family history and autosomal dominant mode of inheritance is also typical of CADASIL. Detection of the NOTCH3 gene mutation is necessary for the definite diagnosis of CADASIL.

Targeted next generation sequencing identifies novel NOTCH3 gene mutations in CADASIL diagnostics patients

BACKGROUND

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a monogenic, hereditary, small vessel disease of the brain causing stroke and vascular dementia in adults. CADASIL has previously been shown to be caused by varying mutations in the NOTCH3 gene. The disorder is often misdiagnosed due to its significant clinical heterogeneic manifestation with familial hemiplegic migraine and several ataxia disorders as well as the location of the currently identified causative mutations. The aim of this study was to develop a new, comprehensive and efficient single assay strategy for complete molecular diagnosis of NOTCH3 mutations through the use of a custom next-generation sequencing (NGS) panel for improved routine clinical molecular diagnostic testing.

RESULTS

Our custom NGS panel identified nine genetic variants in NOTCH3 (p.D139V, p.C183R, p.R332C, p.Y465C, p.C597W, p.R607H, p.E813E, p.C977G and p.Y1106C). Six mutations were stereotypical CADASIL mutations leading to an odd number of cysteine residues in one of the 34 NOTCH3 gene epidermal growth factor (EGF)-like repeats, including three new typical cysteine mutations identified in exon 11 (p.C597W; c.1791C>G); exon 18 (p.C977G; c.2929T>G) and exon 20 (p.Y1106C; c.3317A>G). Interestingly, a novel missense mutation in the CACNA1A gene was also identified in one CADASIL patient. All variants identified (novel and known) were further investigated using in silico bioinformatic analyses and confirmed through Sanger sequencing.

CONCLUSIONS

NGS provides an improved and effective methodology for the diagnosis of CADASIL. The NGS approach reduced time and cost for comprehensive genetic diagnosis, placing genetic diagnostic testing within reach of more patients.