Investigating diagnostic sequencing techniques for CADASIL diagnosis

Headache and NOTCH3 Gene Variants in Patients with CADASIL

Autosomal dominant cerebral arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited vascular disease characterized by recurrent strokes, cognitive impairment, psychiatric symptoms, apathy, and migraine. Approximately 40% of patients with CADASIL experience migraine with aura (MA). In addition to MA, CADASIL patients are described in the literature as having migraine without aura (MO) and other types of headaches. Mutations in the NOTCH3 gene cause CADASIL. This study investigated NOTCH3 genetic variants in CADASIL patients and their potential association with headache types. Genetic tests were performed on 30 patients with CADASIL (20 women aged 43.6 ± 11.5 and 10 men aged 39.6 ± 15.8). PCR-HRM and sequencing methods were used in the genetic study. We described three variants as pathogenic/likely pathogenic (p.Tyr189Cys, p.Arg153Cys, p.Cys144Arg) and two benign variants (p.Ala202=, p.Thr101=) in the NOTCH3 gene and also presented the NOTCH3 gene variant (chr19:15192258 G>T), which has not been previously described in the literature. Patients with pathogenic/likely pathogenic variants had similar headache courses. People with benign variants showed a more diverse clinical picture. It seems that different NOTCH3 variants may contribute to the differential presentation of a CADASIL headache, highlighting the diagnostic and prognostic value of headache characteristics in this disease.

Exonic mutations in cell-cell adhesion may contribute to CADASIL-related CSVD pathology

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a condition caused by mutations in NOTCH3 and results in a phenotype characterised by recurrent strokes, vascular dementia and migraines. Whilst a genetic basis for the disease is known, the molecular mechanisms underpinning the pathology of CADASIL are still yet to be determined. Studies conducted at the Genomics Research Centre (GRC) have also identified that only 15-23% of individuals clinically suspected of CADASIL have mutations in NOTCH3. Based on this, whole exome sequencing was used to identify novel genetic variants for CADASIL-like cerebral small-vessel disease (CSVD). Analysis of functionally important variants in 50 individuals was investigated using overrepresentation tests in Gene ontology software to identify biological processes that are potentially affected in this group of patients. Further investigation of the genes in these processes was completed using the TRAPD software to identify if there is an increased number (burden) of mutations that are associated with CADASIL-like pathology. Results from this study identified that cell-cell adhesion genes were positively overrepresented in the PANTHER GO-slim database. TRAPD burden testing identified n = 15 genes that had a higher number of rare (MAF < 0.001) and predicted functionally relevant (SIFT < 0.05, PolyPhen > 0.8) mutations compared to the gnomAD v2.1.1 exome control dataset. Furthermore, these results identified ARVCF, GPR17, PTPRS, and CELSR1 as novel candidate genes in CADASIL-related pathology. This study identified a novel process that may be playing a role in the vascular damage related to CADASIL-related CSVD and implicated n = 15 genes in playing a role in the disease.

Genetic Causes of Cerebral Small Vessel Diseases: A Practical Guide for Neurologists

Cerebral small vessel disease (CSVD) includes various entities affecting the brain and, often, systemic small arteries, arterioles, venules, and capillaries. The underlying causes of CSVD are different, and some of them are genetic. Monogenic CSVDs are responsible for 1%-5% of all strokes and for several other disturbances. Despite many genes being involved, the phenotypes of monogenic CSVD partly overlap. Given that the genetic testing for different diseases can be challenging and time-consuming, the practicing neurologist should be adequately informed of the genetic background of CSVD and should be able to select patients to undergo genetic assessment and the genes to be analyzed. The purpose of this review was to summarize clinical, neurologic and non-neurologic, and neuroimaging features of monogenic CSVD and to provide a flowchart to be used in clinical practice to guide neurologists in this field. The proposed flowchart and the relative tables can be applied to 3 different settings, depending on the presentation: (1) ischemic stroke and/or transient ischemic attack, (2) cerebral hemorrhage, and (3) other neurologic, non-neurologic, and/or neuroimaging features of monogenic CSVD, in the absence of stroke syndromes because of infarction or hemorrhage.

The potential value of Notch1 and DLL1 in the diagnosis and prognosis of patients with active TB

Objectives

The Notch signaling pathway has been implicated in the pathogenesis of active tuberculosis (TB), and Th1-type cell-mediated immunity is essential for effective control of mycobacterial infection. However, it remains unclear whether Notch signaling molecules (Notch1, DLL1, and Hes1) and Th1-type factors (T-bet and IFN-γ) can serve as biomarkers for tracking the progression of active TB at different stages along with peripheral blood white blood cell (WBC) parameters.

Methods

A total of 60 participants were enrolled in the study, including 37 confirmed TB patients (mild (n=17), moderate/severe (n=20)) and 23 healthy controls. The mRNA expression of Notch1, DLL1, Hes1, T-bet and IFN-γ in the peripheral blood mononuclear cells (PBMCs) of the subjects was measured by RT-qPCR, then analyzed for differences. Receiver Operating Characteristic curve (ROC) was used to assess the effectiveness of each factor as a biomarker in identifying lung injury.

Results

We found that mRNA expression levels of Notch1, DLL1, and Hes1 were upregulated in active TB patients, with higher levels observed in those with moderate/severe TB than those with mild TB or without TB. In contrast, mRNA levels of T-bet and IFN-γ were downregulated and significantly lower in mild and moderate/severe cases. Furthermore, the combiROC analysis of IFN-γ and the percentage of lymphocytes (L%) among WBC parameters showed superior discriminatory ability compared to other factors for identifying individuals with active TB versus healthy individuals. Notably, Notch pathway molecules were more effective than Th1-type factors and WBC parameters in differentiating mild and moderate/severe cases of active TB, particularly in the combiROC model that included Notch1 and Hes1.

Conclusions

Our study demonstrated that Notch1, Hes1, IFN-γ, and L% can be used as biomarkers to identify different stages of active TB patients and to monitor the effectiveness of treatment.

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.

PSEN2 Thr421Met Mutation in a Patient with Early Onset Alzheimer’s Disease

Presenilin-2 (PSEN2) mutation Thr421Met was identified from a 57-years old patient with early onset Alzheimer’s disease (EOAD) for the first time in Korea. Previously, this mutation was discovered in an EOAD patient in Japan without a change on amyloid production from the cellular study. Both Korean and Japanese patients developed the disease in their 50s. Memory loss was prominent in both cases, but no additional clinical information was available on the Japanese patient. Magnetic resonance imaging (MRI) images of the Korean patient revealed asymmetric atrophies in both temporo-parietal lobes. In addition, amyloid positron emission tomography (PET) also revealed amyloid deposits in the gray matter of the temporo-parietal lobes asymmetrically. PSEN2 Thr421 was conserved among a majority of vertebrates (such as zebras, elephants, and giant pandas); hence, Thr421 could play an important role in its functions and any mutations could cause detrimental ramifications in its interactions. Interestingly, PSEN2 Thr421 could have homology with PSEN1 Thr440, as PSEN1 T440del mutations were reported from patients with AD or dementia with Lewy bodies. Hence, the changed amino acid from threonine to methionine of PSEN2 Thr421 could cause significant structural alterations in causing local protein dynamics, leading to its pathogenicity in EOAD. Lastly, PSEN2 Thr421Met may interact with other mutations in neurodegenerative disease related genes, which were found in the proband patient, such as ATP binding cassette subfamily A member 7 (ABCA7), Notch Receptor 3 (NOTCH3), or Leucine-rich repeat kinase 2 (LRRK2). These interactions of pathway networks among PSEN2 and other disease risk factors could be responsible for the disease phenotype through other pathways. For example, PSEN2 and ABCA7 may impact amyloid processing and reduce amyloid clearance. Interaction between PSEN2 and NOTCH3 variants may be associated with abnormal NOTCH signaling and a lower degree of neuroprotection. Along with LRRK2 variants, PSEN2 Thr421Met may impact neurodegeneration through Wnt related pathways. In the future, cellular studies of more than one mutation by CRISPR-Cas9 method along with biomarker profiles could be helpful to understand the complicated pathways.

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.

Exploring the Hereditary Nature of Migraine

Migraine is a common neurological disorder which affects 15-20% of the population; it has a high socioeconomic impact through treatment and loss of productivity. Current forms of diagnosis are primarily clinical and can be difficult owing to comorbidity and symptom overlap with other neurological disorders. As such, there is a need for better diagnostic tools in the form of genetic testing. Migraine is a complex disorder, encompassing various subtypes, and has a large genetic component. Genetic studies conducted on rare monogenic subtypes, including familial hemiplegic migraine, have led to insights into its pathogenesis via identification of causal mutations in three genes (CACNA1A, ATP1A2 and SCN1A) that are involved in transport of ions at synapses and glutamatergic transmission. Study of familial migraine with aura pedigrees has also revealed other causal genes for monogenic forms of migraine. With respect to the more common polygenic form of migraine, large genome-wide association studies have increased our understanding of the genes, pathways and mechanisms involved in susceptibility, which are largely involved in neuronal and vascular functions. Given the preponderance of female migraineurs (3:1), there is evidence to suggest that hormonal or X-linked components can also contribute to migraine, and the role of genetic variants in mitochondrial DNA in migraine has been another avenue of exploration. Epigenetic studies of migraine have shown links between hormonal variation and alterations in DNA methylation and gene expression. While there is an abundance of preliminary studies identifying many potentially causative migraine genes and pathways, more comprehensive genomic and functional analysis to better understand mechanisms may aid in better diagnostic and treatment outcomes.

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.