Skin biopsy immunostaining with a Notch3 monoclonal antibody for CADASIL diagnosis

Multimodal retinal vessel analysis in CADASIL patients

PURPOSE

To further elucidate retinal findings and retinal vessel changes in Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) patients by means of high resolution retinal imaging.

METHODS

28 eyes of fourteen CADASIL patients and an equal number of control subjects underwent confocal scanning laser ophthalmoscopy (cSLO), spectral-domain optical coherence tomography (SD-OCT), retinal nerve fibre layer (RNFL) measurements, fluorescein and indocyanine angiography. Three vessel measurement techniques were applied: RNFL thickness, a semiautomatic software tool based on cSLO images and manual vessel outlining based on SD-OCT.

RESULTS

Mean age of patients was 56.2 ± 11.6 years. Arteriovenous nicking was present in 22 (78.6%) eyes and venous dilation in 24 (85.7%) eyes. Retinal volume and choroidal volume were 8.77 ± 0.46 mm(3) and 8.83 ± 2.24 mm(3). RNFL measurements showed a global increase of 105.2 µm (

CONTROL GROUP

98.4 µm; p = 0.015). Based on semi-automatic cSLO measurements, maximum diameters of arteries and veins were 102.5 µm (106.0 µm; p = 0.21) and 128.6 µm (124.4 µm; p = 0.27) respectively. Manual SD-OCT measurements revealed significantly increased mean arterial 138.7 µm (125.4 µm; p<0.001) and venous 160.0 µm (146.9; p = 0.003) outer diameters as well as mean arterial 27.4 µm (19.2 µm; p<0.001) and venous 18.3 µm (15.7 µm; p<0.001) wall thicknesses in CADASIL patients.

CONCLUSIONS

The findings reflect current knowledge on pathophysiologic changes in vessel morphology in CADASIL patients. SD-OCT may serve as a complementary tool to diagnose and follow-up patients suffering from cerebral small-vessel diseases.

CADASIL and CARASIL

CADASIL and CARASIL are hereditary small vessel diseases leading to vascular dementia. CADASIL commonly begins with migraine followed by minor strokes in mid-adulthood. Dominantly inherited CADASIL is caused by mutations (n > 230) in NOTCH3 gene, which encodes Notch3 receptor expressed in vascular smooth muscle cells (VSMC). Notch3 extracellular domain (N3ECD) accumulates in arterial walls followed by VSMC degeneration and subsequent fibrosis and stenosis of arterioles, predominantly in cerebral white matter, where characteristic ischemic MRI changes and lacunar infarcts emerge. The likely pathogenesis of CADASIL is toxic gain of function related to mutation-induced unpaired cysteine in N3ECD. Definite diagnosis is made by molecular genetics but is also possible by electron microscopic demonstration of pathognomonic granular osmiophilic material at VSMCs or by positive immunohistochemistry for N3ECD in dermal arteries. In rare, recessively inherited CARASIL the clinical picture and white matter changes are similar as in CADASIL, but cognitive decline begins earlier. In addition, gait disturbance, low back pain and alopecia are characteristic features. CARASIL is caused by mutations (presently n = 10) in high-temperature requirement. A serine peptidase 1 (HTRA1) gene, which result in reduced function of HTRA1 as repressor of transforming growth factor-β (TGF β) -signaling. Cerebral arteries show loss of VSMCs and marked hyalinosis, but not stenosis.

Identification of a novel nonsense mutation in the rod domain of GFAP that is associated with Alexander disease

Alexander disease (AxD) is an astrogliopathy that primarily affects the white matter of the central nervous system (CNS). AxD is caused by mutations in a gene encoding GFAP (glial fibrillary acidic protein). The GFAP mutations in AxD have been reported to act in a gain-of-function manner partly because the identified mutations generate practically full-length GFAP. We found a novel nonsense mutation (c.1000 G>T, p.(Glu312Ter); also termed p.(E312*)) within a rod domain of GFAP in a 67-year-old Korean man with a history of memory impairment and leukoencephalopathy. This mutation, GFAP p.(E312*), removes part of the 2B rod domain and the whole tail domain from the GFAP. We characterized GFAP p.(E312*) using western blotting, in vitro assembly and sedimentation assay, and transient transfection of human adrenal cortex carcinoma SW13 (Vim(+)) cells with plasmids encoding GFAP p.(E312*). The GFAP p.(E312*) protein, either alone or in combination with wild-type GFAP, elicited self-aggregation. In addition, the assembled GFAP p.(E312*) aggregated into paracrystal-like structures, and GFAP p.(E312*) elicited more GFAP aggregation than wild-type GFAP in the human adrenal cortex carcinoma SW13 (Vim(+)) cells. Our findings are the first report, to the best of our knowledge, on this novel nonsense mutation of GFAP that is associated with AxD and paracrystal formation.

[Normal skin biopsy as a tool for extra-cutaneous disorders]

Biopsies of apparently healthy skin can contribute to the diagnosis of an internal disorder in a patient or in the detection of a potential disease carrier. Herein, we review those diseases for which dermatologists may be asked to perform a biopsy on normal skin where analysis by optical microscopy, immunofluorescence or electronic microscopy may result in diagnosis of an "internal" disease. Diseases for which biopsies are required for cell cultures (e.g. fibroblasts cultures), clonality testing or chromosomal analysis are not discussed here.

Novel pathological features and potential therapeutic approaches for CADASIL: insights obtained from a mouse model of CADASIL

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common condition of hereditary stroke and vascular dementia. CADASIL is caused by Notch3 mutation, leading to progressive degeneration of vascular smooth muscle cells (vSMCs) of the small arteries in the brain. However, the pathogenesis of CADASIL remains largely unknown, and treatment that can stop or delay the progression of CADASIL is not yet available. Using both wild type mice and transgenic mice carrying the human mutant Notch3 gene (CADASIL mice), we have recently characterized the pathological features of CADASIL and determined the therapeutic efficacy of two hematopoietic growth factors, stem cell factor (SCF) and granulocyte colony-stimulating factor (G-CSF) in CADASIL. Our findings have revealed novel pathological changes in the endothelium of cerebral capillaries and in the neural stem cells (NSCs). We have also observed the impairment of cognitive function in CADASIL mice. Moreover, SCF+G-CSF treatment improves cognitive function, inhibits Notch3 mutation-induced vSMC degeneration, cerebral blood bed reduction, cerebral capillary damage, and NSC loss, and increases neurogenesis and angiogenesis. Here we compile an overview of our recently published studies, which provide new insights into understanding the pathogenesis of CADASIL and developing therapeutic strategies for this devastating neurological disease.

Spectrum of NOTCH3 mutations in Korean patients with clinically suspicious cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is caused by mutations in the NOTCH3 gene on chromosome 19. Previous studies showed that NOTCH3 contains mutational hotspots that can vary among individuals of different ethnic backgrounds. In this study, we investigated the spectrum of NOTCH3 mutations in Korean patients with CADASIL. We retrospectively analyzed 156 patients who underwent NOTCH3 gene testing for molecular diagnosis of CADASIL using Sanger sequencing with a tiered approach. First, we screened previously reported mutational hotspots (exons 2-6, 8, 11, 18, 19, and 22). If no mutation was detected and samples were available, we extended our analysis to additional exons (7, 9, 10, 14, 15, 20, 21, 23, and 25). In 45 of 156 patients (28.8%), 29 mutations and 16 novel variants of unknown significance (VUS) were identified. The p.R544C mutation in exon 11 of NOTCH3 was the most frequently observed mutation (n = 8), followed by p.R75P in exon 3 (n = 7), p.R332C in exon 6 (n = 3), p.R54C in exon 2 (n = 2), and p.R90C in exon 3 (n = 2). Among the VUS, p.R1175W in exon 22, p.S414C in exon 8, and p.N1207S in exon 22 were found in 5, 3, and 2 patients, respectively. Other mutations and VUS were observed in 1 patient each. Although this was not a prospective, nationwide cohort study, the results above suggested that the spectrum of NOTCH3 mutations might be different in Koreans than in individuals of Caucasian ethnicity. Therefore, further analysis of Koreans with CADASIL might be necessary to implement a Korean-specific mutation screening paradigm.

Hypomorphic NOTCH3 alleles do not cause CADASIL in humans

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is caused by stereotyped missense mutations in NOTCH3. Whether these mutations lead to the CADASIL phenotype via a neomorphic effect, or rather by a hypomorphic effect, is subject of debate. Here, we report two novel NOTCH3 mutations, both leading to a premature stop codon with predicted loss of NOTCH3 function. The first mutation, c.307C>T, p.Arg103*, was detected in two brothers aged 50 and 55 years, with a brain MRI and skin biopsy incompatible with CADASIL. The other mutation was found in a 40-year-old CADASIL patient compound heterozygous for a pathogenic NOTCH3 mutation (c.2129A>G, p.Tyr710Cys) and an intragenic frameshift deletion. The deletion was inherited from his father, who did not have the skin biopsy abnormalities seen in CADASIL patients. These individuals with rare NOTCH3 mutations indicate that hypomorphic NOTCH3 alleles do not cause CADASIL.

Role of electron microscopy in the diagnosis of cadasil syndrome: a study of 32 patients

Background and Purpose

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is caused by NOTCH3 gene mutations that result in vascular smooth muscle cell (VSMC) degeneration. Its distinctive feature by electron microscopy (EM) is granular osmiophilic material (GOM) detected in VSMC indentations and/or the extracellular space close to VSMCs. Reports of the sensitivity of EM in detecting GOM in biopsies from CADASIL patients are contradictory. We present data from 32 patients clinically suspected to have CADASIL and discuss the role of EM in its diagnosis in this retrospective study.

Methods

Skin, skeletal muscle, kidney and pericardial biopsies were examined by EM; the NOTCH3 gene was screened for mutations. Skin and muscle biopsies from 12 patients without neurological symptoms served as controls.

Results and Discussion

All GOM-positive patients exhibited NOTCH3 mutations and vice versa. This study i) confirms that EM is highly specific and sensitive for CADASIL diagnosis; ii) extends our knowledge of GOM distribution in tissues where it has never been described, e.g. pericardium; iii) documents a novel NOTCH3 mutation in exon 3; and iv) shows that EM analysis is critical to highlight the need for comprehensive NOTCH3 analysis. Our findings also confirm the genetic heterogeneity of CADASIL in a small Italian subpopulation and emphasize the difficulties in designing algorithms for molecular diagnosis.

Abnormal recruitment of extracellular matrix proteins by excess Notch3 ECD: a new pathomechanism in CADASIL

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, or CADASIL, one of the most common inherited small vessel diseases of the brain, is characterized by a progressive loss of vascular smooth muscle cells and extracellular matrix accumulation. The disease is caused by highly stereotyped mutations within the extracellular domain of the NOTCH3 receptor (Notch3(ECD)) that result in an odd number of cysteine residues. While CADASIL-associated NOTCH3 mutations differentially affect NOTCH3 receptor function and activity, they all are associated with early accumulation of Notch3(ECD)-containing aggregates in small vessels. We still lack mechanistic explanation to link NOTCH3 mutations with small vessel pathology. Herein, we hypothesized that excess Notch3(ECD) could recruit and sequester functionally important proteins within small vessels of the brain. We performed biochemical, nano-liquid chromatography-tandem mass spectrometry and immunohistochemical analyses, using cerebral and arterial tissue derived from patients with CADASIL and mouse models of CADASIL that exhibit vascular lesions in the end- and early-stage of the disease, respectively. Biochemical fractionation of brain and artery samples demonstrated that mutant Notch3(ECD) accumulates in disulphide cross-linked detergent-insoluble aggregates in mice and patients with CADASIL. Further proteomic and immunohistochemical analyses identified two functionally important extracellular matrix proteins, tissue inhibitor of metalloproteinases 3 (TIMP3) and vitronectin (VTN) that are sequestered into Notch3(ECD)-containing aggregates. Using cultured cells, we show that increased levels or aggregation of Notch3 enhances the formation of Notch3(ECD)-TIMP3 complex, promoting TIMP3 recruitment and accumulation. In turn, TIMP3 promotes complex formation including NOTCH3 and VTN. In vivo, brain vessels from mice and patients with CADASIL exhibit elevated levels of both insoluble cross-linked and soluble TIMP3 species. Moreover, reverse zymography assays show a significant elevation of TIMP3 activity in the brain vessels from mice and patients with CADASIL. Collectively, our findings lend support to a Notch3(ECD) cascade hypothesis in CADASIL disease pathology, which posits that aggregation/accumulation of Notch3(ECD) in the brain vessels is a central event, promoting the abnormal recruitment of functionally important extracellular matrix proteins that may ultimately cause multifactorial toxicity. Specifically, our results suggest a dysregulation of TIMP3 activity, which could contribute to mutant Notch3(ECD) toxicity by impairing extracellular matrix homeostasis in small vessels.

Skin and sural nerve biopsies: ultrastructural findings in the first genetically confirmed cases of CADASIL in Serbia

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited vascular disorder caused by Notch3 gene mutations. The main histopathological hallmark is granular osmiophilic material (GOM) deposited in the close vicinity of vascular smooth muscle cells (VSMCs). The authors report the first 7 ultrastructurally and genetically confirmed cases of CADASIL in Serbia. Samples of skin and sural nerve were investigated by transmission electron microscopy. GOM deposits were observed around degenerated VSMCs in all the skin biopsies examined. Sural nerve biopsies revealed severe alterations of nerve fibers, endoneurial blood vessels with GOM deposits, endoneurial fibroblasts, and perineurial myofibroblasts. Total genomic DNA was extracted from peripheral blood leukocytes, and exons 2-6 of the Notch3 gene were amplified by PCR and subsequently sequenced. Four different mutations in exons 2 (Cys65Tyr), 3 (Gly89Cys and Arg90Cys), and 6 (Ala319Cys), which determine the CADASIL disease, were detected among all described patients. A novel missense mutation Gly89Cys involving exon 3 was detected. Due to the difficulties in the determination of the Notch3 mutations, these data suggest that electron microscopic analysis for GOMs in dermal vessel wall provides a rapid and reliable screening method for this disease.

Two novel mutations and a previously unreported intronic polymorphism in the NOTCH3 gene

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a hereditary disease of small vessel caused by mutations in the NOTCH3 gene (NCBI Gene ID: 4854) located on chromosome 19p13.1. NOTCH3 consists of 33 exons which encode a protein of 2321 amino acids. Exons 3 and 4 were found to be mutation hotspots, containing more than 65% of all CADASIL mutations. We performed direct sequencing on an ABI 3130 Genetic Analyser to screen for mutations and polymorphisms on 300 patients who were clinically suspected to have CADASIL. First, exons 3 and 4 were screened in NOTCH3 and if there were no variations found, then extended CADASIL testing (exons 2, 11, 18 and 19) was offered to patients. Here we report two novel non-synonymous mutations identified in the NOTCH3 gene. The first mutation, located in exon 4 was found in a 49-year-old female and causes an alanine to valine amino acid change at position 202 (605C>T). The second mutation, located in exon 11, was found in a 66-year-old female and causes a cysteine to arginine amino acid change at position 579 (1735T>C). We also report a 46-year-old male with a known polymorphism Thr101Thr (rs3815188) and an unreported polymorphism NM_000435.2:c.679+60G>A observed in intron 4 of the NOTCH3 gene. Although Ala202Ala (rs1043994) is a common polymorphism in the NOTCH3 gene, our reported novel mutation (Ala202Val) causes an amino acid change at the same locus. Our other reported mutation (Cys579Arg) correlates well with other known mutations in NOTCH3, as the majority of the CADASIL-associated mutations in NOTCH3 generally occur in the EGF-like (epidermal growth factor-like) repeat domain, causing a change in the number of cysteine residues. The intronic polymorphism NM_000435.2:c.679+60G>A lies close to the intron-exon boundary and may affect the splicing mechanism in the NOTCH3 gene.

[Diagnosis, pathomechanism and treatment of CADASIL]

During the past 10 years, our understanding of the pathomechanism and pathophysiology of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) has improved through clinical examination, imaging studies, pathological studies, cell experiments and the development of transgenic mice. Although epidemiological studies of CADASIL in Japan have been limited, more than 100 cases of this condition have been diagnosed in Japan. In our laboratory, we diagnosed 37 CADASIL cases genetically and identified three features common to Japanese cases. One is the wide distribution of onset age for clinical symptoms other than migraine, with the onset of symptoms being later than age 60 in 22% of cases. Second, the majority (65%) of Japanese CADASIL cases have stroke risk factors, such as hypertension, hyperlipidemia, or smoking. Third, in 22% cases there was no definite family history of stroke. However, the previous diagnostic criteria proposed by Dabous excluded several definite cases in our cohort. Therefore, to avoid missing undiagnosed cases of CADASIL, we have generated new diagnostic criteria for Japanese CADASIL based on the knowledge accumulated during the past 10 years, and compared sensitivity of two criteria. In our diagnosed Japanese CADASIL cases, the sensitivity of the new criteria was 19% and 78% for probable and possible cases, respectively, and only one case was (Fig. 3) missed when using the new criteria. In comparison, the sensitivity of Dabous's was 11% and 51% for probable and possible cases, respectively, and 24% cases were excluded due to hypertension, elderly onset or no family history, although these cases showed recurrent strokes, white matter lesions and NOTCH3 mutations. Using our new criteria, diagnosis of CADASIL can be made even in cases with elderly onset, stroke risk factors, and obscure family history.

Vascular dementia: Diagnostic criteria and supplementary exams. Recommendations of the Scientific Department of Cognitive Neurology and Aging of the Brazilian Academy of Neurology. Part I

Vascular dementia (VaD) is the most prevalent form of secondary dementia and the second most common of all dementias. The present paper aims to define guidelines on the basic principles for treating patients with suspected VaD (and vascular cognitive impairment - no dementia) using an evidence-based, systematized approach. The knowledge used to define these guidelines was retrieved from searches of several databases (Medline, Scielo, Lilacs) containing scientific articles, systematic reviews, meta-analyses, largely published within the last 15 years or earlier when pertinent. Information retrieved and selected for relevance was used to analyze diagnostic criteria and to propose a diagnostic system encompassing diagnostic criteria, anamnesis, as well as supplementary and clinical exams (neuroimaging and laboratory). Wherever possible, instruments were selected that had versions previously adapted and validated for use in Brazil that take into account both schooling and age. This task led to proposed protocols for supplementary exams based on degree of priority, for application in clinical practice and research settings.

[A case of CADASIL without characteristic anterior temporal pole lesion diagnosed by skin biopsy]

A 40 year-old man with migraine presented cerebral ischemic attacks several times in one year. He had no risk factors for cerebrovascular disease including hypertension, but had strong family history suggesting autosomal dominant inheritance. A brain MRI on T(2) weighted and FLAIR images revealed patchy and confluent hyper intensity areas in the subcortical white matters and bilateral external capsules, while no anterior temporal pole lesions characteristic of CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy) were detected. His skin biopsy demonstrated granular osmiophilic materials (GOM) on the basement membrane of the vascular smooth muscle cells in dermis as shown by an electron microscope. The following mutational analysis of the Notch3 gene disclosed a missense mutation of p.Arg133Cys in exon 3. Molecular diagnosis of CADASIL may be time consuming because Notch3 is a huge gene and mutations may occur at multiple sites. GOM on skin biopsy is diagnostic especially in cases where anterior temporal pole involvement on MRI is negative.

Notch3 Arg170Cys knock-in mice display pathologic and clinical features of the neurovascular disorder cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy

OBJECTIVE

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an adult-onset neurovascular disorder caused by stereotyped mutations in the NOTCH3 receptor. Elucidation of its pathobiology is still incomplete and remains a challenge, in part because the available preclinical mouse models to date do not reproduce the full spectrum of CADASIL pathology and clinical disease.

METHODS AND RESULTS

Here, we report a novel knock-in mouse with Arg170Cys substitution in murine Notch3, corresponding to the prevalent Arg169Cys substitution in CADASIL. The Notch3(Arg170Cys) mice displayed late-onset, dominant CADASIL arteriopathy with typical granular osmiophilic material deposition and developed brain histopathology including thrombosis, microbleeds, gliosis, and microinfarction. Furthermore, Notch3(Arg170Cys) mice experienced neurological symptoms with motor defects such as staggering gait and limb paresis.

CONCLUSIONS

This model, for the first time, phenocopies the arteriopathy and the histopathologic as well as clinical features of CADASIL and may offer novel opportunities to investigate disease pathogenesis.

Vascular contributions to cognitive impairment and dementia: a statement for healthcare professionals from the american heart association/american stroke association

BACKGROUND AND PURPOSE

This scientific statement provides an overview of the evidence on vascular contributions to cognitive impairment and dementia. Vascular contributions to cognitive impairment and dementia of later life are common. Definitions of vascular cognitive impairment (VCI), neuropathology, basic science and pathophysiological aspects, role of neuroimaging and vascular and other associated risk factors, and potential opportunities for prevention and treatment are reviewed. This statement serves as an overall guide for practitioners to gain a better understanding of VCI and dementia, prevention, and treatment.

METHODS

Writing group members were nominated by the writing group co-chairs on the basis of their previous work in relevant topic areas and were approved by the American Heart Association Stroke Council Scientific Statement Oversight Committee, the Council on Epidemiology and Prevention, and the Manuscript Oversight Committee. The writing group used systematic literature reviews (primarily covering publications from 1990 to May 1, 2010), previously published guidelines, personal files, and expert opinion to summarize existing evidence, indicate gaps in current knowledge, and, when appropriate, formulate recommendations using standard American Heart Association criteria. All members of the writing group had the opportunity to comment on the recommendations and approved the final version of this document. After peer review by the American Heart Association, as well as review by the Stroke Council leadership, Council on Epidemiology and Prevention Council, and Scientific Statements Oversight Committee, the statement was approved by the American Heart Association Science Advisory and Coordinating Committee.

RESULTS

The construct of VCI has been introduced to capture the entire spectrum of cognitive disorders associated with all forms of cerebral vascular brain injury-not solely stroke-ranging from mild cognitive impairment through fully developed dementia. Dysfunction of the neurovascular unit and mechanisms regulating cerebral blood flow are likely to be important components of the pathophysiological processes underlying VCI. Cerebral amyloid angiopathy is emerging as an important marker of risk for Alzheimer disease, microinfarction, microhemorrhage and macrohemorrhage of the brain, and VCI. The neuropathology of cognitive impairment in later life is often a mixture of Alzheimer disease and microvascular brain damage, which may overlap and synergize to heighten the risk of cognitive impairment. In this regard, magnetic resonance imaging and other neuroimaging techniques play an important role in the definition and detection of VCI and provide evidence that subcortical forms of VCI with white matter hyperintensities and small deep infarcts are common. In many cases, risk markers for VCI are the same as traditional risk factors for stroke. These risks may include but are not limited to atrial fibrillation, hypertension, diabetes mellitus, and hypercholesterolemia. Furthermore, these same vascular risk factors may be risk markers for Alzheimer disease. Carotid intimal-medial thickness and arterial stiffness are emerging as markers of arterial aging and may serve as risk markers for VCI. Currently, no specific treatments for VCI have been approved by the US Food and Drug Administration. However, detection and control of the traditional risk factors for stroke and cardiovascular disease may be effective in the prevention of VCI, even in older people.

CONCLUSIONS

Vascular contributions to cognitive impairment and dementia are important. Understanding of VCI has evolved substantially in recent years, based on preclinical, neuropathologic, neuroimaging, physiological, and epidemiological studies. Transdisciplinary, translational, and transactional approaches are recommended to further our understanding of this entity and to better characterize its neuropsychological profile. There is a need for prospective, quantitative, clinical-pathological-neuroimaging studies to improve knowledge of the pathological basis of neuroimaging change and the complex interplay between vascular and Alzheimer disease pathologies in the evolution of clinical VCI and Alzheimer disease. Long-term vascular risk marker interventional studies beginning as early as midlife may be required to prevent or postpone the onset of VCI and Alzheimer disease. Studies of intensive reduction of vascular risk factors in high-risk groups are another important avenue of research.

Genetic susceptibility to ischemic stroke

Clinicians who treat patients with stroke need to be aware of several single-gene disorders that have ischemic stroke as a major feature, including sickle cell disease, Fabry disease, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, and retinal vasculopathy with cerebral leukodystrophy. The reported genome-wide association studies of ischemic stroke and several related phenotypes (for example, ischemic white matter disease) have shown that no single common genetic variant imparts major risk. Larger studies with samples numbering in the thousands are ongoing to identify common variants with smaller effects on risk. Pharmacogenomic studies have uncovered genetic determinants of response to warfarin, statins and clopidogrel. Despite increasing knowledge of stroke genetics, incorporating this new knowledge into clinical practice remains a challenge. The goals of this article are to review common single-gene disorders relevant to ischemic stroke, summarize the status of candidate gene and genome-wide studies aimed at discovering genetic stroke risk factors, and to briefly discuss pharmacogenomics related to stroke treatment.

Stroke-related translational research

Stroke-related translational research is multifaceted. Herein, we highlight genome-wide association studies and genetic studies of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, COL4A1 mutations, and cerebral cavernous malformations; advances in molecular biology and biomarkers; newer brain imaging research; and recovery from stroke emphasizing cell-based and other rehabilitative modalities.

Notch3 is essential for regulation of the renal vascular tone

The Notch3 receptor participates in the development and maturation of vessels. Mutations of Notch3 in humans are associated with defective regulation of cerebral blood flow. To investigate the role of Notch3 in the regulation of renal hemodynamics, we used mice lacking expression of the Notch3 gene (Notch3-/- mice). Bolus injections of norepinephrine and angiotensin II increased renal vascular resistance and decreased renal blood flow in a dose-dependent manner in wild-type mice. In sharp contrast, renal vascular resistance of Notch3-/- mice varied little after boluses of norepinephrine and angiotensin II. Inversely, bradykinin and prostacyclin relaxed renal vasculature in wild-type mice. Both vasodilators had a negligible effect on renal vascular resistance of Notch3-/- mice. Afferent arterioles freshly isolated from Notch3-/- mice displayed decreased thickness of vascular wall compared with wild -type mice and showed a deficient contractile response to angiotensin II. To examine the physiopathological consequences of the above-described deficiency, hypertension was induced by continuous infusion of angiotensin II. Angiotensin II gradually increased blood pressure in both strains, but this increase was lesser in the Notch3-/- mice. Despite this blunted systemic effect, Notch3-/- mice displayed high mortality rates (65%) attributed to heart failure. In the kidney, the surviving Notch3-/- mice showed focal structural alterations characteristic of nephroangiosclerosis. These data show that Notch3 is necessary for the adaptive response of the renal vasculature to vasoactive systems. A deficiency in the expression of Notch3 could have important physiopathological consequences in the adaptation of the cardiac and renal function to chronic increase of blood pressure.

Diagnosis of CADASIL disease in normotensive and non-diabetics with lacunar infarct

BACKGROUND

CADASIL (Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy) is characterized by recurrent cerebral ischemic episodes of the lacunar subtype usually without traditional vascular risk factors. We investigated the frequency of CADASIL among selected patients with cerebral ischemia of the lacunar subtype.

METHODS

we studied patients under 65 years old who presented cerebral ischemia of the lacunar subtype without hypertension, diabetes mellitus or other causes that explained the cerebral ischemia. On the skin biopsies, we performed immunostaining analysis on 5μm frozen sections with monoclonal antibody anti-Notch 3 (1E4). We also performed a genetic analysis of the Notch 3 gene (exons 3,4,5,6,11 and 19).

RESULTS

of 1.519 patients analyzed, only 57 (3.7%) fulfilled the selection criteria, and 30 of them accepted to participated in the study. We studied 30 patients, mean age was 53 years (range 34 to 65), 50% were men and all patients suffered a lacunar stroke. Immunostaining analysis was positive in two patients (6.6%) and the genetic analysis confirmed a mutation characteristic of CADASIL in exon 4 nt 622C/T (Arg 182 Cys) and 694 T/C (Cys206Arg) respectively.

CONCLUSIONS

CADASIL disease was present in 6.6% of patients younger than 65 years with a lacunar stroke and without hypertension or diabetes mellitus. Screening for CADASIL should be considered in these patients.

A cortical form of CADASIL with cerebral Aβ amyloidosis

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) was diagnosed by genetic testing in a 53-year-old patient, 10 years before death. Following two strokes with partial recovery, he developed rapidly progressive cognitive decline 3 years before death. Neuropathology confirmed CADASIL. Characteristic arteriolar changes were associated with subcortical infarcts, and status cribrosus in basal ganglia and the cortico-subcortical junctions. Leukoencephalopathy was very mild. Severe arteriolar changes in the cerebral cortex and leptomeninges were associated with numerous intracortical microinfarcts. There was abundant Abeta deposition throughout the cerebral cortex, mainly as Aβ42 diffuse plaques, frequently periarteriolar. There was no cerebral amyloid angiopathy apart from rare Aβ40 deposits around Notch3-positive deposits. Amyloid plaques were rare. Tau pathology was minimal. Alzheimer disease associated with CADASIL has been described, but the few reported cases had abundant amyloid plaques, amyloid angiopathy, fibrillar plaques and neurofibrillary tangles. Aβ accumulation could result from abnormal Aβ synthesis or impaired elimination due to the arteriolar changes of CADASIL. We did not find Aβ deposits in our other CADASIL cases with milder cortical arteriolar changes. Additional genetic predisposing factors were not identified. This case suggests that besides the classical, purely subcortical form of CADASIL, a "cortical" form with numerous lacunar infarcts and Aβ deposition in the cerebral cortex may occur and may be difficult to differentiate clinically from Alzheimer disease.

CADASIL

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a dominantly inherited small artery disease that leads to dementia and disability in mid-life. The clinical presentation of CADASIL is variable between and within affected families and is characterized by symptoms including migraine with aura, subcortical ischemic events, mood disturbances, apathy, and cognitive impairment. The mean age at onset of symptoms is 45 years, with variable duration of the disease ranging from 10 to 40 years. In 1996, linkage studies mapped and identified mutations in the NOTCH3 gene on chromosome 19 as causative in CADASIL. Head magnetic resonance imaging (MRI) is always abnormal in participants with NOTCH3 mutations after age 35. Magnetic resonance imaging shows on T2-weighted images or fluid attenuation inversion recovery (FLAIR) sequence, widespread areas of increased signal in the white matter associated with focal hyperintensities in basal ganglia, thalamus, and brainstem. The pathologic hallmark of CADASIL is the presence of electron-dense granules in the media of arterioles that can be identified by electron microscopic evaluation of skin biopsies.

Cognitive impairment of vascular origin: neuropathology of cognitive impairment of vascular origin

The term cognitive impairment of vascular origin is used to designate global cognitive deficits as well as focal neurological deficits such as aphasia, apraxia and agnosia of vascular/circulatory origin. It has been useful for identifying early clinical and neuroradiological alterations that might permit therapeutic strategies geared to curbing the progression of cerebrovascular disease. Multi-infarct encephalopathy, infarcts in strategic areas, lacunae and lacunar status, Binswanger's encephalopathy, hippocampal sclerosis, cortical granular atrophy and watershed infarcts are common lesions. Hypertension and vascular diseases such as arteriosclerosis, small blood vessel disease, inflammatory diseases of the blood vessels, Sneddon syndrome, cerebral amyloid angiopathies, cerebral autosomic dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), and Maeda's syndrome are causative of cognitive impairment of vascular origin. Other less common causes are hereditary endotheliopathy with retinopathy, neuropathy and strokes (HERNS), cerebro-retinian vasculopathy (CRV), hereditary vascular retinopathy (HVR) (all three linked to 3p21.1-p21.3), hereditary infantile hemiparesis with arteriolar retinopathy and leukoencephalopathy (HIHRATL) (not linked to 3p21), fibromuscular dysplasia, and moya-moya disease. Lack of uniformity of clinical manifestations, the variety of vascular diseases and circulatory factors, the diverse, but often convergent, neuropathological substrates, and the common association with unrelated neurodegenerative diseases in the elderly, make it hard to assume a single clinical approach in the diagnosis and treatment of cognitive impairment of vascular origin. Rather, environmental and genetic risk factors, underlying vascular diseases, associated systemic, metabolic and neurodegenerative diseases and identification of extent and distribution of lesions with morphological and functional neuroimaging methods should be applied in every individual patient.

Genetics and genomics of stroke: novel approaches

Evidence for a genetic basis for stroke comes from twin and family studies and from the occurrence of a number of uncommon monogenic disorders, but the contribution of genetic factors identified for stroke so far is small. Advances in genetics and genomics may permit new insights. In recent genome-wide association studies, a number of single-nucleotide polymorphisms have been associated with specific stroke subtypes and major stroke risk factors such as diabetes and atrial fibrillation. These await replication. Studies of messenger ribonucleic acid expression have also shown promise for the development of genomic signatures for stroke classification. Stroke and coronary heart disease share some features of pathophysiology, risk, and treatment, and their genetic and genomic bases also appear to overlap.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy: a genetic cause of cerebral small vessel disease

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a single-gene disorder of the cerebral small blood vessels caused by mutations in the Notch3 gene. The exact prevalence of this disorder was unknown currently, and the number of reported CADASIL families is steadily increasing as the clinical picture and diagnostic examinations are becoming more widely known. The main clinical manifestations are recurrent stroke, migraine, psychiatric symptoms, and progressive cognitive impairment. The clinical course of CADASIL is highly variable, even within families. The involvement of the anterior temporal lobe and the external capsule on brain magnetic resonance imaging was found to have high sensitivity and specificity in differentiating CADASIL from the much more common sporadic cerebral small-vessel disease (SVD). The pathologic hallmark of the disease is the presence of granular osmiophilic material in the walls of affected vessels. CADASIL is a prototype single-gene disorder that has evolved as a unique model for studying the mechanisms underlying cerebral SVD. At present, the incidence and prevalence of CADASIL seem to be underestimated due to limitations in clinical, neuroradiological, and genetic diagnoses of this disorder.

Cerebrovascular dysfunction and microcirculation rarefaction precede white matter lesions in a mouse genetic model of cerebral ischemic small vessel disease

Cerebral ischemic small vessel disease (SVD) is the leading cause of vascular dementia and a major contributor to stroke in humans. Dominant mutations in NOTCH3 cause cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a genetic archetype of cerebral ischemic SVD. Progress toward understanding the pathogenesis of this disease and developing effective therapies has been hampered by the lack of a good animal model. Here, we report the development of a mouse model for CADASIL via the introduction of a CADASIL-causing Notch3 point mutation into a large P1-derived artificial chromosome (PAC). In vivo expression of the mutated PAC transgene in the mouse reproduced the endogenous Notch3 expression pattern and main pathological features of CADASIL, including Notch3 extracellular domain aggregates and granular osmiophilic material (GOM) deposits in brain vessels, progressive white matter damage, and reduced cerebral blood flow. Mutant mice displayed attenuated myogenic responses and reduced caliber of brain arteries as well as impaired cerebrovascular autoregulation and functional hyperemia. Further, we identified a substantial reduction of white matter capillary density. These neuropathological changes occurred in the absence of either histologically detectable alterations in cerebral artery structure or blood-brain barrier breakdown. These studies provide in vivo evidence for cerebrovascular dysfunction and microcirculatory failure as key contributors to hypoperfusion and white matter damage in this genetic model of ischemic SVD.

Cadasil

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL) is the most common heritable cause of stroke and vascular dementia in adults. Clinical and neuroimaging features resemble those of sporadic small-artery disease, although patients with CADASIL have an earlier age at onset of stroke events, an increased frequency of migraine with aura, and a slightly variable pattern of ischaemic white-matter lesions on brain MRI. NOTCH3 (Notch homolog 3), the gene involved in CADASIL, encodes a transmembrane receptor primarily expressed in systemic arterial smooth-muscle cells. Pathogenetic mutations alter the number of cysteine residues in the extracellular domain of NOTCH3, which accumulates in small arteries of affected individuals. Functional and imaging studies in cultured cells, genetically engineered mice, and patients with CADASIL have all provided insights into the molecular and vascular mechanisms underlying this disease. A recent multicentre trial in patients with cognitive impairment emphasises the feasibility of randomised trials in patients with CADASIL. In this Review, we summarise the current understanding of CADASIL, a devastating disorder that also serves as a model for the more common forms of subcortical ischaemic strokes and pure vascular dementia.

CADASIL management or what to do when there is little one can do

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a rare disease that leads to migraine, mood disorders, recurrent lacunar strokes and early vascular dementia. This autosomal-dominant condition is caused by mutations in the NOTCH3 gene and is characterized by degeneration of vascular smooth muscle cells. At present, no evidence-based treatment for CADASIL is available and only relief of symptoms can be offered to patients. This review focuses on an update of CADASIL management, based on the recent clinical and basic evidence, and discusses possible new treatment targets for CADASIL.

Distinct phenotypic and functional features of CADASIL mutations in the Notch3 ligand binding domain

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an autosomal dominant small-vessel disease of the brain caused by mutations in the NOTCH3 receptor. The highly stereotyped nature of the mutations, which alter the number of cysteine residues within the epidermal growth factor-like repeats (EGFR), predicts that all mutations share common mechanisms. Prior in vitro assays and genetic studies in the mouse support the hypothesis that common mutations do not compromise canonical Notch3 function but instead convey a non-physiological and deleterious activity to the receptor through the unpaired cysteine residue. Intriguingly, in vitro studies predict that mutations located in the Delta/Serrate/LAG-2 ligand binding domain-(EGFR10-11) may result in a loss of Notch3 receptor function. However, the in vivo relevance and functional significance of this with respect to the pathogenic mechanisms and clinical expression of the disease remain largely unexplored. To ascertain, in vivo, the functional significance of EGFR10-11 mutations, we generated transgenic mice with one representative mutation (C428S) in EGFR10 of Notch3. These mice, like those with a common R90C mutation, developed characteristic arterial accumulation of Notch3 protein and granular osmiophilic material upon aging. By introducing the mutant C428S transgene into a Notch3 null background, we found that, unlike the R90C mutant protein, the C428S mutant protein has lost wild-type Notch3 activity and exhibited mild dominant-negative activity in three different biological settings. From a large prospectively recruited cohort of 176 CADASIL patients, we identified 10 patients, from five distinct pedigrees carrying a mutation in EGFR10 or 11. These mutations were associated with significantly higher Mini-Mental State Examination and Mattis Dementia Rating Scale scores (P < 0.05), when compared with common mutations. Additionally, we found a strong effect of this genotype on the burden of white matter hyperintensities (P < 0.01). Collectively, these results highlight distinctive functional and phenotypic features of EGFR10-11 mutations relative to the common CADASIL mutations. Our findings are compatible with the hypothesis that EGFR10-11 mutations cause the disease through the same gain of novel function as the common mutations, and lead us to propose that reduced Notch3 signalling acts as a modifier of the CADASIL phenotype.

Congruence between NOTCH3 mutations and GOM in 131 CADASIL patients

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common hereditary subcortical vascular dementia. It is caused by mutations in NOTCH3 gene, which encodes a large transmembrane receptor Notch3. The key pathological finding is the accumulation of granular osmiophilic material (GOM), which contains extracellular domains of Notch3, on degenerating vascular smooth muscle cells (VSMCs). GOM has been considered specifically diagnostic for CADASIL, but the reports on the sensitivity of detecting GOM in patients' skin biopsy have been contradictory. To solve this contradiction, we performed a retrospective investigation of 131 Finnish, Swedish and French CADASIL patients, who had been adequately examined for both NOTCH3 mutation and presence of GOM. The patients were examined according to the diagnostic practice in each country. NOTCH3 mutations were assessed by restriction enzyme analysis of specific mutations or by sequence analysis. Presence of GOM was examined by electron microscopy (EM) in skin biopsies. Biopsies of 26 mutation-negative relatives from CADASIL families served as the controls. GOM was detected in all 131 mutation positive patients. Altogether our patients had 34 different pathogenic mutations which included three novel point mutations (p.Cys67Ser, p.Cys251Tyr and p.Tyr1069Cys) and a novel duplication (p.Glu434_Leu436dup). The detection of GOM by EM in skin biopsies was a highly reliable diagnostic method: in this cohort the congruence between NOTCH3 mutations and presence of GOM was 100%. However, due to the retrospective nature of this study, exact figure for sensitivity cannot be determined, but it would require a prospective study to exclude possible selection bias. The identification of a pathogenic NOTCH3 mutation is an indisputable evidence for CADASIL, but demonstration of GOM provides a cost-effective guide for estimating how far one should proceed with the extensive search for a new or an uncommon mutations among the presently known over 170 different NOTCH3 gene defects. The diagnostic skin biopsy should include the border zone between deep dermis and upper subcutis, where small arterial vessels of correct size are located. Detection of GOM requires technically adequate biopsies and distinction of true GOM from fallacious deposits. If GOM is not found in the first vessel or biopsy, other vessels or additional biopsies should be examined.

CADASIL: the most common hereditary subcortical vascular dementia

Cerebral autosomal dominant arteriopathy with subcortical infarct and leukoencephalopathy (CADASIL) is the most common hereditary subcortical vascular dementia. It is caused by the defective NOTCH3 gene, which encodes a transmembrane receptor; over 170 different mutations are known. The main clinical features are migraine with aura (often atypical or isolated), strokes, cognitive decline/dementia and psychiatric symptoms. Executive and organizing cognitive functions are impaired first, memory is affected late. Typical MRI findings are T2 weighted hyperintensities in temporopolar white matter and the capsula externa. Smooth muscle cells in small arteries throughout the body degenerate and vessel walls become fibrotic. In the brain, this results in circulatory disturbances and lacunar infarcts, mainly in cerebral white matter and deep gray matter. The exact pathogenesis is still open: a dominant-negative toxic effect is suggested, possibly related to Notch3 misfolding. Diagnosis is reached either by identifying a pathogenic NOTCH3 mutation or by electron microscopic demonstration of granular osmiophilic material in a (skin) biopsy. Only symptomatic treatment is available at present.

Nephroangiosclerosis in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy: is NOTCH3 mutation the common culprit?

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a systemic arterial disease characterized by impairment of vascular smooth muscle cell structure and function related to NOTCH3 mutations. Pathological findings include pathognomonic granular osmiophilic material (GOM) deposition with nonspecific hyalinization within the artery wall in a variety of tissues. The main clinical presentation is iterative strokes in young adults despite the lack of cardiovascular risk factors, leading to early dementia. Although arteriosclerosis and GOM have been found in kidneys from patients with CADASIL, kidney disease has been described only once up to now, in association with immunoglobulin A nephropathy. We report the case of a 61-year-old patient with a medical history of CADASIL and recent mild hypertension. His mother also showed neuropsychiatric symptoms and end-stage renal disease of unknown cause. The patient had a chronic kidney disease defined by means of estimated glomerular filtration rate using the 4-variable Modification of Diet in Renal Disease Study equation of 58 mL/min/1.73 m(2) associated with mild proteinuria and intermittent microscopic hematuria. Renal histological analysis showed severe arteriosclerosis and mild interstitial fibrosis. Glomeruli did not show mesangial immunoglobulin A deposition or focal segmental proliferation. Electron microscopic analysis showed typical GOM deposition in the vicinity of altered vascular smooth muscle cells in interlobular and juxtaglomerular arteries. The nephroangiosclerosis-like lesions were unusually severe in contrast to the recent mild hypertension. The presence of GOM strongly suggests that renal lesions were related to the NOTCH3 mutation. Here, we describe the first case of familial occurrence of kidney disease with decreased kidney function in the absence of coexisting nephropathy in patients with CADASIL. We discuss the role of NOTCH3 mutation in the pathogenesis of nephroangiosclerosis through functional impairment of renal microcirculation or primary Notch3-related vascular disease.