Emerging insights from the genetics of cerebral small-vessel disease

A Search for New Biological Pathways in Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy by Proteomic Research

Background/Objectives: Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL) is a hereditary small vessel disease leading to significant morbidity and mortality. Despite advances in genetic diagnosis, the underlying pathophysiology remains incompletely understood. Proteomic studies offer insights into disease mechanisms by identifying altered protein expression patterns. Here, we conducted a proteomic analysis to elucidate molecular pathways associated with CADASIL. Methods: We enrolled genetically diagnosed CADASIL patients and healthy, genetically related controls. Plasma samples were subjected to proteomic analysis using the Olink platform, measuring 552 proteins across six panels. The data were analyzed from several approaches by using three different statistical methods: Exploratory Principal Component Analysis (PCA) and Partial Least Squares-Discriminant Analysis (PLS-DA), differential expression with moderated t-test, and gene set enrichment analysis (GSEA). In addition, bioinformatics analysis, including volcano plot, heatmap, and Variable Importance on Projection (VIP) scores from the PLS-DA model were drawn. Results: Significant differences in protein expression were observed between CADASIL patients and controls. RSPO1 and FGF-19 exhibited elevated levels (p < 0.05), while PPY showed downregulation (p < 0.05) in CADASIL patients, suggesting their involvement in disease pathogenesis. Furthermore, MIC-A/B expression varied significantly between patients with mutations in exon 4 versus exon 11 of the NOTCH3 gene (p < 0.05), highlighting potential immunological mechanisms underlying CADASIL. We identified altered pathways using GSEA, applied after ranking the study data. Conclusions: Our study provides novel insights into the proteomic profile of CADASIL, identifying dysregulated proteins associated with vascular pathology, metabolic dysregulation, and immune activation. These findings contribute to a deeper understanding of CADASIL pathophysiology and may inform the development of targeted therapeutic strategies. Further research is warranted to validate these biomarkers and elucidate their functional roles in disease progression.

Diagnostic Algorithm to Subclassify Atypical Spitzoid Tumors in Low and High Risk According to Their Methylation Status

Current diagnostic algorithms are insufficient for the optimal clinical and therapeutic management of cutaneous spitzoid tumors, particularly atypical spitzoid tumors (AST). Therefore, it is crucial to identify new markers that allow for reliable and reproducible diagnostic assessment and can also be used as a predictive tool to anticipate the individual malignant potential of each patient, leading to tailored individual therapy. Using Reduced Representation Bisulfite Sequencing (RRBS), we studied genome-wide methylation profiles of a series of Spitz nevi (SN), spitzoid melanoma (SM), and AST. We established a diagnostic algorithm based on the methylation status of seven cg sites located in TETK4P2 (Tektin 4 Pseudogene 2), MYO1D (Myosin ID), and PMF1-BGLAP (PMF1-BGLAP Readthrough), which allows the distinction between SN and SM but is also capable of subclassifying AST according to their similarity to the methylation levels of Spitz nevi or spitzoid melanoma. Thus, our epigenetic algorithm can predict the risk level of AST and predict its potential clinical outcomes.

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.

Ischaemic cerebral small vessel disease caused by adenosine deaminase 2 deficiency syndrome

BACKGROUND AND PURPOSE

Only a small proportion of cerebral small vessel disease (cSVD), a frequent cause of stroke and cognitive or motor disability in adults, is attributable to monogenic conditions. The hereditary nature of a patient's cSVD may be masked by a mild or non-informative phenotype, as single-gene disorders have a variable mode of presentation, penetrance and disease severity.

CASE DESCRIPTION

An adult patient is here described with recurrent acute ischaemic strokes due to cSVD with no other phenotypic manifestation, in whom the pathogenic c.139G>A (p.G47R) missense variant in ADA2 (NM_001282225.2), consistent with the diagnosis of adenosine deaminase 2 deficiency syndrome, was detected by targeted next-generation sequencing.

CONCLUSIONS

Clinical suspicion of adenosine deaminase 2 deficiency syndrome may be overlooked in stroke patients in whom other specific disease features are lacking. This case enlarges the mode of presentation of the syndrome and highlights the diagnostic potential of next-generation sequencing of known cSVD genes in young adults with recurrent small subcortical infarcts presenting with a lacunar syndrome.

Progress on Prevention and Treatment of Cerebral Small Vascular Disease Using Integrative Medicine

Cerebral small vessel disease (CSVD) is a senile brain lesion caused by the abnormal structure and function of arterioles, venules and capillaries in the aging brain. The etiology of CSVD is complex, and disease is often asymptomatic in its early stages. However, as CSVD develops, brain disorders may occur, such as stroke, cognitive dysfunction, dyskinesia and mood disorders, and heart, kidney, eye and systemic disorders. As the population continues to age, the burden of CSVD is increasing. Moreover, there is an urgent need for better screening methods and diagnostic markers for CSVD, in addition to preventive and asymptomatic- and mild-stage treatments. Integrative medicine (IM), which combines the holistic concepts and syndrome differentiations of Chinese medicine with modern medical perspectives, has unique advantages for the prevention and treatment of CSVD. In this review, we summarize the biological markers, ultrasound and imaging features, disease-related genes and risk factors relevant to CSVD diagnosis and screening. Furthermore, we discuss IM-based CSVD prevention and treatment strategies to stimulate further research in this field.

Report of two pedigrees with heterozygous HTRA1 variants-related cerebral small vessel disease and literature review

BACKGROUND

Biallelic HTRA1 pathogenic variants are associated with autosomal recessive cerebral arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL). Recent studies have indicated that heterozygous HTRA1 variants are related to autosomal dominant hereditary cerebral small vessel disease (CSVD). However, few studies have assessed heterozygous HTRA1 carriers or the genotype-phenotype correlation.

METHODS

The clinical data of two unrelated Chinese Han families with CSVD were collected. Panel sequencing was used to search for pathogenic genes, Sanger sequencing was used for verification, three-dimensional protein models were constructed, and pathogenicity was analyzed. Published HTRA1-related phenotypes included in PubMed up to September 2021 were extensively reviewed, and the patients' genetic and clinical characteristics were summarized.

RESULTS

We report a novel heterozygous variant c.920T>C p.L307P in the HTRA1, whose main clinical and neuroimaging phenotypes are stroke and gait disturbance. We report another patient with the previously reported pathogenic variant HTRA1 c.589C>T p.R197X characterized by early cognitive decline. A literature review indicated that compared with CARASIL, HTRA1-related autosomal dominant hereditary CSVD has a later onset age, milder clinical symptoms, fewer extraneurological symptoms, and slower progression, indicating a milder CARASIL phenotype. In addition, HTRA1 heterozygous variants were related to a higher proportion of vascular risk factors (p < .001) and male sex (p = .022).

CONCLUSION

These findings broaden the known mutational spectrum and possible clinical phenotype of HTRA1. Considering the semidominant characteristics of HTRA1-related phenotypes, we recommend that all members of HTRA1 variant families undergo genetic screening and clinical follow-up if carrying pathogenic variants.

Correlation of Serum C-Peptide, Soluble Intercellular Adhesion Molecule-1, and NLRP3 Inflammasome-Related Inflammatory Factor Interleukin-1β after Brain Magnetic Resonance Imaging Examination with Cerebral Small Vessel Disease

Objective. To explore the correlation of serum c-peptide, soluble intercellular adhesion molecule-1 (sICAM-1), and NLRP3 inflammasome-related inflammatory factor interleukin-1β (IL-1β) after brain magnetic resonance imaging (MRI) examination with cerebral small vessel disease (CSVD). Methods. A total of 72 CSVD patients treated in our hospital from December 2018 to December 2019 were selected as the case group and another 72 patients who presented cerebrovascular risk factors but obtained normal brain MRI examination result in the same period were selected as the control group. The serum specimen of patients in the two groups were collected, their serum c-peptide levels were measured by radio immunoassay, and their serum sICAM-1 and NLRP3 inflammasome-related inflammatory factor IL-1β were measured by enzyme-linked immunosorbent assay (ELISA), so as to analyze the correlation between these indicators and CSVD. Results. Compared with the control group, the level values of serum c-peptide, sICAM-1, and IL-1β were significantly higher in the case group ( $P<0.001$ ), with CSVD being the dependent variable, and age, smoking, uric acid, history of stroke, serum c-peptide, sICAM-1, and IL-1β being the independent variables. A logistic regression analysis was conducted, and the result showed that age, smoking, serum c-peptide, sICAM-1, and IL-1β were the risk factors for CSVD, and by drawing the ROC curves, it could be concluded that the area under sICAM-1 curve was larger than that of other single indicator. Conclusion. Elevation of level values of serum c-peptide, sICAM-1, and NLRP3 inflammasome-related inflammatory factor IL-1β is correlative with CSVD, and age, smoking, serum c-peptide, sICAM-1, and IL-1β are the independent risk factors for CSVD.

End-Truncated LAMB1 Causes a Hippocampal Memory Defect and a Leukoencephalopathy

OBJECTIVE

The majority of patients with a familial cerebral small vessel disease (CSVD) referred for molecular screening do not show pathogenic variants in known genes. In this study, we aimed to identify novel CSVD causal genes.

METHODS

We performed a gene-based collapsing test of rare protein-truncating variants identified in exome data of 258 unrelated CSVD patients of an ethnically matched control cohort and of 2 publicly available large-scale databases, gnomAD and TOPMed. Western blotting was used to investigate the functional consequences of variants. Clinical and magnetic resonance imaging features of mutated patients were characterized.

RESULTS

We showed that LAMB1 truncating variants escaping nonsense-mediated messenger RNA decay are strongly overrepresented in CSVD patients, reaching genome-wide significance (p < 5 × 10^-8 ). Using 2 antibodies recognizing the N- and C-terminal parts of LAMB1, we showed that truncated forms of LAMB1 are expressed in the endogenous fibroblasts of patients and trapped in the cytosol. These variants are associated with a novel phenotype characterized by the association of a hippocampal type episodic memory defect and a diffuse vascular leukoencephalopathy.

INTERPRETATION

These findings are important for diagnosis and clinical care, to avoid unnecessary and sometimes invasive investigations, and also from a mechanistic point of view to understand the role of extracellular matrix proteins in neuronal homeostasis. ANN NEUROL 2021;90:962-975.

Cerebral small vessel disease and vascular cognitive impairment: from diagnosis to management

PURPOSE OF REVIEW

We present recent developments in the field of small vessel disease (SVD)-related vascular cognitive impairment, including pathological mechanisms, updated diagnostic criteria, cognitive profile, neuroimaging markers and risk factors. We further address available management and therapeutic strategies.

RECENT FINDINGS

Vascular and neurodegenerative pathologies often co-occur and share similar risk factors. The updated consensus criteria aim to standardize vascular cognitive impairment (VCI) diagnosis, relying strongly on cognitive profile and MRI findings. Aggressive blood pressure control and multidomain lifestyle interventions are associated with decreased risk of cognitive impairment, but disease-modifying treatments are still lacking. Recent research has led to a better understanding of mechanisms leading to SVD-related cognitive decline, such as blood-brain barrier dysfunction, reduced cerebrovascular reactivity and impaired perivascular clearance.

SUMMARY

SVD is the leading cause of VCI and is associated with substantial morbidity. Tackling cardiovascular risk factors is currently the most effective approach to prevent cognitive decline in the elderly. Advanced imaging techniques provide tools for early diagnosis and may play an important role as surrogate markers for cognitive endpoints in clinical trials. Designing and testing disease-modifying interventions for VCI remains a key priority in healthcare.

Taohong Siwu Decoction Ameliorates Ischemic Stroke Injury Via Suppressing Pyroptosis

Objective: Taohong Siwu decoction (THSWD) is one of the classic prescriptions for promoting blood circulation and removing blood stasis, and it has a good therapeutic effect on ischemic stroke. We sought to explore the therapeutic effects of THSWD on pyroptosis in rats with middle cerebral artery occlusion-reperfusion (MCAO/R). Methods: MCAO/R model of rats were established by suture-occluded method. MCAO/R rats were randomly divided into five groups, which were model group, nimodipine group, THSWD high, medium and low dose group (18, 9, and 4.5 g/kg, respectively), rats of sham group without thread embolus. All rats were treated by intragastric administration for 7 days. We detected the level of inflammatory factors. NLRP3 and Caspase-1 were detected by immunofluorescence. Western blot was used to detect NLRP3, Caspase-1, ASC, and GSDMD in penumbra. Also, the expression of TXNIP, HMGB1, toll-like receptors (TLR4), NF-κB, and MAPK were detected. Results: THSWD treatment improved the behavioral function and brain pathological damage. These results showed that the levels of TNF-α, TGF-β, IL-2, IL-6, IL-1β, and IL-18 were significantly reduced in THSWD treatment groups. THSWD could significantly decrease the expression levels of NLRP3, Caspase-1, Caspase-1 p10, ASC, TXNIP, GSDMD, HMGB1, TLR4/NFκB, p38 MAPK, and JNK in penumbra. Conclusion: Our results showed that THSWD could reduce the activation level of NLRP3 inflammatory corpuscle, down-regulate GSDMD, and inhibit pyroptosis in MCAO/R rats. These may be affected by inhibiting HMGB1/TLR4/NFκB, MAPK signaling pathways.

A novel heterozygous HTRA1 mutation is associated with autosomal dominant hereditary cerebral small vessel disease

BACKGROUND

We investigated whether a heterozygous mutation that we newly identified in HTRA1 (high-temperature requirement serine protease A1 gene) in a pedigree with autosomal dominant hereditary cerebral small vessel disease (SVD) reduces the function of HTRA1 and affects the transforming growth factor-β1 (TGF-β1)/Smad signaling.

METHODS

Whole-exome sequence from the proband and her two sisters was examined using whole-exome enrichment and sequencing. Expression of HTRA1 and TGF-β1/Smad and HTRA1 activity were assayed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and western blotting analyses after transfecting wild-type and mutant HTRA1 genes into HEK293 cells.

RESULTS

A new heterozygous mutation (c.614C>G:p.Ser205Cys) in HTRA1 was identified in the sequence encoding the trypsin-like serine protease domain. The mutation was predicted to be deleterious by in silico tools. Moreover, in vitro activity and protein analyses revealed a loss-of-function effect of the mutation: the proteolytic activity of mutant HTRA1 was decreased, and, notably, this was accompanied by an increase in TGF-β1/Smad protein levels.

CONCLUSIONS

The heterozygous mutation HTRA1 S205C causing diminished protease activity is associated with-and could represent a cause of-autosomal dominant hereditary cerebral SVD. Our results also indicate a relationship between HTRA1 and TGF-β1/Smad signaling.

Association between Intracranial Arterial Dolichoectasia and Cerebral Small Vessel Disease and Its Underlying Mechanisms

Intracranial arterial dolichoectasia (IADE), also known as dilatative arteriopathy of the brain vessels, refers to an increase in the length and diameter of at least one intracranial artery, and accounts for approximately 12% of all patients with stroke. However, the association of IADE with stroke is usually unclear. Cerebral small vessel disease (CSVD) is characterized by pathological changes in the small vessels. Clinically, patients with CSVD can be asymptomatic or present with stroke or cognitive decline. In the past 20 years, a series of studies have strongly promoted an understanding of the association between IADE and CSVD from clinical and pathological perspectives. It has been proposed that IADE and CSVD may be attributed to abnormal vascular remodeling driven by an abnormal matrix metalloproteinase/tissue inhibitor of metalloproteinase pathway. Also, IAD-Erelated hemodynamic changes may result in initiation or progression of CSVD. Additionally, genetic factors are implicated in the pathogenesis of IADE and CSVD. Patients with Fabry’s disease and late-onset Pompe’s disease are prone to developing concomitant IADE and CSVD, and patients with collagen IV alpha 1 or 2 gene (COL4A1/COL4A2) and forkhead box C1 (FOXC1) variants present with IADE and CSVD. Race, strain, familial status, and vascular risk factors may be involved in the pathogenesis of IADE and CSVD. As well, experiments in mice have pointed to genetic strain as a predisposing factor for IADE and CSVD. However, there have been few direct genetic studies aimed towards determining the association between IADE and CSVD. In the future, more clinical and basic research studies are needed to elucidate the causal relationship between IADE and CSVD and the related molecular and genetic mechanisms.