Detection of granular osmiophilic material of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy by light microscopy in frozen sections

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

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

Contribution of "Omic" Studies to the Understanding of Cadasil. A Systematic Review

CADASIL (Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy) is a small vessel disease caused by mutations in NOTCH3 that lead to an odd number of cysteines in the epidermal growth factor (EGF)-like repeat domain, causing protein misfolding and aggregation. The main symptoms are migraines, psychiatric disorders, recurrent strokes, and dementia. Omic technologies allow the massive study of different molecules for understanding diseases in a non-biased manner or even for discovering targets and their possible treatments. We analyzed the progress in understanding CADASIL that has been made possible by omics sciences. For this purpose, we included studies that focused on CADASIL and used omics techniques, searching bibliographic resources, such as PubMed. We excluded studies with other phenotypes, such as migraine or leukodystrophies. A total of 18 articles were reviewed. Due to the high prevalence of NOTCH3 mutations considered pathogenic to date in genomic repositories, one can ask whether all of them produce CADASIL, different degrees of the disease, or whether they are just a risk factor for small vessel disease. Besides, proteomics and transcriptomics studies found that the molecules that are significantly altered in CADASIL are mainly related to cell adhesion, the cytoskeleton or extracellular matrix components, misfolding control, autophagia, angiogenesis, or the transforming growth factor β (TGFβ) signaling pathway. The omics studies performed on CADASIL have been useful for understanding the biological mechanisms and could be key factors for finding potential drug targets.

Novel dot-blot assay for detection of vascular Notch3 aggregates in patients with CADASIL

To detect vascular Notch3 extracellular domain aggregates in CADASIL, we developed a novel dot-blot assay with both autopsy and biopsy skin samples. We obtained samples from 11 patients with CADASIL and 12 control patients, and we performed dot-blot analyses by using sequential biochemical tissue extractions with three different antibodies against specific regions of the Notch3 extracellular domain. We also analyzed clinical features and vascular accumulations of Notch3 by immunohistochemistry. Via the dot-blot assay with the antibody against the C-terminal region of the Notch3 extracellular domain, we successfully detected Notch3 extracellular domain aggregates in skin tissue homogenates obtained from patients with CADASIL. Our novel method may therefore aid the diagnosis of CADASIL.

Serum amyloid P component: A novel potential player in vessel degeneration in CADASIL

In cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), granular osmiophilic material (GOM) may play some roles in inducing cerebrovascular events. To elucidate the pathogenesis of CADASIL, we used laser microdissection and liquid chromatography-tandem mass spectrometry to analyze cerebrovascular lesions of patients with CADASIL for GOM. The analyses detected serum amyloid P component (SAP), annexin A2, and periostin as the proteins with the largest increase in the samples, which also demonstrated NOTCH3. For the three proteins, anti-human SAP antibody had the strongest reaction in the lesions where the anti-human NOTCH3 antibody showed positive staining. Moreover, immunofluorescence staining with the two antibodies clearly showed co-localization of SAP and NOTCH3. mRNA analyses indicated no positive SAP expression in the brain materials, which suggested that the source of SAP found in the GOM was only the liver. A solid phase enzyme-linked immunosorbent assay confirmed the binding of SAP with NOTCH3. Serum SAP concentrations were neither up-regulated nor down-regulated in CADASIL patients, when compared with those in control subjects. SAP may play an important role in GOM formation although precise mechanisms remain to be elucidated.

Genotypic and phenotypic spectrum of CADASIL in Japan: the experience at a referral center in Kumamoto University from 1997 to 2014

This study elucidates the genotypic and phenotypic spectrum and histopathological findings related to cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) in Japan. For this single-center retrospective observational study, we enrolled 215 patients who were clinically suspected of having CADASIL and were examined at Kumamoto University from 1997 to 2014, and we diagnosed CADASIL in 70 patients. We found 19 different NOTCH3 mutations in the patients, with the NOTCH3 Arg133Cys mutation being found most frequently. We also found the Arg75Pro mutation, a cysteine-sparing NOTCH3 mutation. CADASIL patients with this Arg75Pro mutation were frequently found throughout Japan, and fewer patients with the Arg75Pro mutation showed MRI hyperintensity in the anterior temporal pole compared with patients with other NOTCH3 mutations. Significantly more CADASIL patients with the NOTCH3 Arg133Cys mutation had hyperintensity in the external capsule compared with CADASIL patients with the other mutations not including the NOTCH3 Arg75Pro mutation. We also showed postmortem pathological findings of the first Japanese CADASIL case with the NOTCH3 Arg133Cys mutation, and histopathological findings of fresh frozen skin biopsy specimens of CADASIL patients. In conclusions, the spectrum of NOTCH3 mutations in Japanese CADASIL patients may be partially explained by founder effects. Genotype-phenotype correlations may exist in CADASIL, which should be considered so as to make an accurate diagnosis of CADASIL in each population. Fresh frozen skin biopsy specimens may aid detection of Notch3 deposits on vascular walls for an improved diagnosis of CADASIL.

[The new diagnostic methods of CADASIL as differential diagnosis of HDLS]

Both hereditary diffuse leukoencephalopathy with axonal spheroids (HDLS) and cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) are autosomal dominant white matter diseases. First symptoms of HDLS are cognitive decline or dementia, while those of CADASIL are migraine or ischemic infarcts. Family histories of young patients with stroke are important, because most of patients with CADASIL have these family histories. Temporal pole lesions are specific for CADASIL. However, some of the patients have no such lesions. We should differ CADASIL from non-CADASIL by evaluation of family history or the other MRI findings such as confluent external capsular lesions or multiple white matter medullary infarcts. Coronal views of MRI are useful for differentiating ischemic lesions from demyelinated lesions, even if horizontal views of MRI give little information. In addition, evaluation of immunohistochemical staining of Notch3 by frozen skin samples is useful for diagnosis. We discovered the methods of detecting light microscopic findings of GOM in frozen section. To reveal the pathogenesis of CADASIL, it is indispensable to analyze the chemical nature of GOM by histochemical stainings. We are going to analyze coexist proteins or materials in small arterial granular degeneration by proteomics of LC/ MS/ MS.

[The pathomechanism and treatment of CADASIL]

CADASIL has been reported notably in Europe, has recently been found to occur in Japan and, with the increase in the number of reported cases, has been attracting attention. Currently, the diagnosis of CADASIL is established clinically if the patient: (1) develops the condition at a relatively young age (40-50 years), (2) is not at risk for stroke, (3) has repeated attacks of lacunar infarction with gradual progression to pseudobulbar paralysis and dementia, and (4) has other family members with similar symptoms. The diagnosis is also established by imaging and laboratory studies if: (1) MRI reveals leukoaraiosis and multiple small infarcts in the deep white matter, basal ganglia, thalamus, and pons, with hyperintensities of the temporal pole and external capsule bilaterally; (2) electron microscopy demonstrates granular osmiophilic material (GOM) around vascular smooth muscles in the brain, skeletal muscle, and skin; and (3) DNA analysis shows notch3 mutations. The mechanism of development of CADASIL due to notch3 mutations is still unknown. However, a recent study revealed that Notch3 ectodomain is a major component of GOM. On binding to the ligand, Notch3 normally undergoes proteolytic cleavage, with the resulting clearance of the extracellular domain. However, in CADASIL, it accumulates as GOM and potentially inhibits normal metabolism in smooth muscle cells. It is necessary to suppress the production of GOM for fundamental therapy of CADASIL.

Leukoencephalopathies and leukodystrophies

The leukoencephalopathies encompass a heterogeneous group of disorders that involve the brain white matter. The cause may be acquired or inherited; in the latter case, mutations have been found in genes that encode protein components of the myelin membrane or enzymes implicated in the turnover of myelin. In patients with cognitive dysfunction and white matter lesions evident on MRI, analysis of the type, pattern, and distribution of lesions can enable a presumptive diagnosis, which can be confirmed by biochemical and/or molecular testing. The presence or absence of peripheral neuropathy and/or autonomic dysfunction can be a helpful clue in differentiating individual diagnoses. Often, patients may be suspected of having and being initially treated inappropriately for a case of primary or secondary progressive multiple sclerosis. In a significant number of patients, the diagnosis may not be made, even after an extensive search. Establishing the cause enables counseling regarding prognosis, family planning, monitoring for disease-related complications, and introducing therapy, when available.