Heterozygous mutations of HTRA1 gene in patients with familial cerebral small vessel disease

HTRA1-related cerebral small-vessel disease causes cerebral microbleeds on the brainstem surface

BACKGROUND AND OBJECTIVES

Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) has recently been known as HTRA1-related cerebral small-vessel disease (CSVD), it is caused by variants in HTRA1. Recently, it has been reported to develop in heterozygotes with some variants of the gene. Multiple prospective studies have reported that the frequency of heterozygous HTRA1 variants developing CSVD is 2 - 6.5 % in CARASIL. Heterozygous variant cases lack unique clinical features, have an older age of onset, and are difficult to detect. Characteristic findings are required to identify such cases.

METHOD

Magnetic resonance imaging (MRI) images of cases that experienced cerebral infarction and carried heterozygous variants in HTRA1 were reviewed.

RESULTS

Four cases of heterozygous HTRA1-related CSVD in two families (Family 1: c.754G > A, p.A252T; three males. Family 2: c.497G > T, p.R166L, one female). In all cases, white matter lesions with lacunar infarcts were observed in the periventricular and basal ganglia, external capsule, and brainstem. Moreover, T2 star weighted image (T2*WI) low presented dot-like lesions were present along the surface of the brainstem, which have only been reported in one homozygous case. Susceptibility-weighted imaging (SWI) was performed in two cases, and the dot-like lesions on T2*WI resembled a pearly tiara along the surface of the brainstem.

CONCLUSION

Brainstem surface on T2*WI low showed dot-like lesions, which are not generally observed in patients with stroke and can be characteristic of HTRA1-CSVD associated with heterozygous variant. The pathology requires further investigation for diagnosis.

Progress in the Study of the Role and Mechanism of HTRA1 in Diseases Related to Vascular Abnormalities

High temperature requirement A1 (HTRA1) is a member of the serine protease family, comprising four structural domains: IGFBP domain, Kazal domain, protease domain and PDZ domain. HTRA1 encodes a serine protease, a secreted protein that is widely expressed in the vasculature. HTRA1 regulates a wide range of physiological processes through its proteolytic activity, and is also involved in a variety of vascular abnormalities-related diseases. This article reviews the role of HTRA1 in the development of vascular abnormalities-related hereditary cerebral small vessel disease (CSVD), age-related macular degeneration (AMD), tumors and other diseases. Through relevant research advances to understand the role of HTRA1 in regulating signaling pathways or refolding, translocation, degradation of extracellular matrix (ECM) proteins, thus directly or indirectly regulating angiogenesis, vascular remodeling, and playing an important role in vascular homeostasis, further understanding the mechanism of HTRA1's role in vascular abnormality-related diseases is important for HTRA1 to be used as a therapeutic target in related diseases.

CADASIL: A NOTCH3-associated cerebral small vessel disease

BACKGROUND

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common hereditary cerebral small vessel disease (CSVD), pathologically characterized by a non-atherosclerotic and non-amyloid diffuse angiopathy primarily involving small to medium-sized penetrating arteries and leptomeningeal arteries. In 1996, mutation in the notch receptor 3 gene (NOTCH3) was identified as the cause of CADASIL. However, since that time other genetic CSVDs have been described, including the HtrA serine peptidase 1 gene-associated CSVD and the cathepsin A gene-associated CSVD, that clinically mimic the original phenotype. Though NOTCH3-associated CSVD is now a well-recognized hereditary disorder and the number of studies investigating this disease is increasing, the role of NOTCH3 in the pathogenesis of CADASIL remains elusive.

AIM OF REVIEW

This review aims to provide insights into the pathogenesis and the diagnosis of hereditary CSVDs, as well as personalized therapy, predictive approach, and targeted prevention. In this review, we summarize the current progress in CADASIL, including the clinical, neuroimaging, pathological, genetic, diagnostic, and therapeutic aspects, as well as differential diagnosis, in which the role of NOTCH3 mutations is highlighted.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this review, CADASIL is revisited as a NOTCH3-associated CSVD along with other hereditary CSVDs.

Genetically proxied HTRA1 protease activity and circulating levels independently predict risk of ischemic stroke and coronary artery disease

HTRA1 has emerged as a major risk gene for stroke and cerebral small vessel disease with both rare and common variants contributing to disease risk. However, the precise mechanisms mediating this risk remain largely unknown as does the full spectrum of phenotypes associated with genetic variation in HTRA1 in the general population. Using a family-history informed approach, we first show that rare variants in HTRA1 are linked to ischemic stroke in 425,338 European individuals from the UK Biobank with replication in 143,149 individuals from the Biobank Japan. Integrating data from biochemical experiments on 76 mutations occurring in the UK Biobank, we next show that rare variants causing loss of protease function in vitro associate with ischemic stroke, coronary artery disease, and skeletal traits. In addition, a common causal variant (rs2672592) modulating circulating HTRA1 mRNA and protein levels enhances the risk of ischemic stroke, small vessel stroke, and coronary artery disease while lowering the risk of migraine and age-related macular dystrophy in GWAS and UK Biobank data from > 2,000,000 individuals. There was no evidence of an interaction between genetically proxied HTRA1 activity and levels. Our findings demonstrate a central role of HTRA1 for human disease including stroke and coronary artery disease and identify two independent mechanisms that might qualify as targets for future therapeutic interventions.

Exploring the contribution of ARMS2 and HTRA1 genetic risk factors in age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of severe irreversible central vision loss in individuals over 65 years old. Genome-wide association studies (GWASs) have shown that the region at chromosome 10q26, where the age-related maculopathy susceptibility (ARMS2/LOC387715) and HtrA serine peptidase 1 (HTRA1) genes are located, represents one of the strongest associated loci for AMD. However, the underlying biological mechanism of this genetic association has remained elusive. In this article, we extensively review the literature by us and others regarding the ARMS2/HTRA1 risk alleles and their functional significance. We also review the literature regarding the presumed function of the ARMS2 protein and the molecular processes of the HTRA1 protein in AMD pathogenesis in vitro and in vivo, including those of transgenic mice overexpressing HtrA1/HTRA1 which developed Bruch's membrane (BM) damage, choroidal neovascularization (CNV), and polypoidal choroidal vasculopathy (PCV), similar to human AMD patients. The elucidation of the molecular mechanisms of the ARMS2 and HTRA1 susceptibility loci has begun to untangle the complex biological pathways underlying AMD pathophysiology, pointing to new testable paradigms for treatment.

Dualistic roles and mechanistic insights of macrophage migration inhibitory factor in brain injury and neurodegenerative diseases

Macrophage migration inhibitory factor (MIF) is involved in various immune-mediated pathologies and regulates both innate and adaptive immune reactions, thus being related to several acute and chronic inflammatory diseases such as rheumatoid arthritis, septic shock, and atherosclerosis. Its role in acute and chronic brain pathologies, such as stroke and neurodegenerative diseases, has attracted increasing attention in recent years. In response to stimuli like hypoxia, inflammation or infection, different cell types can rapidly release MIF, including immune cells, endothelial cells, and neuron cells. Notably, clinical data from past decades also suggested a possible link between serum MIF levels and the severity of stroke and the evolving of neurodegenerative diseases. In this review, we summarize the major and recent findings focusing on the mechanisms of MIF modulating functions in brain injury and neurodegenerative diseases, which may provide important therapeutic targets meriting further investigation.

Heterozygous Pathogenic and Likely Pathogenic Symptomatic HTRA1 Variant Carriers in Cerebral Small Vessel Disease

High temperature requirement serine peptidase A1 (HTRA1) related cerebral small vessel disease (CSVD) includes both symptomatic heterozygous HTRA1 variant carrier and cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) patients. Presently, most reported symptomatic heterozygous HTRA1 variant carrier cases are sporadic family reports with a lack of specific characteristics. Additionally, the molecular mechanism of heterozygous HTRA1 gene variants is unclear. We conducted this review to collect symptomatic carriers of heterozygous HTRA1 gene variants reported as of 2022, analyzed all pathogenicity according to American College of Medical Genetics and Genomics (ACMG) variant classification, and summarized the cases with pathogenic and likely pathogenic HTRA1 variants gender characteristics, age of onset, geographical distribution, initial symptoms, clinical manifestations, imaging signs, HTRA1 gene variant information and to speculate its underlying pathogenic mechanisms. In this review, we summarized the following characteristics of pathogenic and likely pathogenic symptomatic HTRA1 variant carriers: to date, the majority of reported symptomatic HTRA1 carriers are in European and Asian countries, particularly in China which was found to have the highest number of reported cases. The age of first onset is mostly concentrated in the fourth and fifth decades. The heterozygous HTRA1 gene variants were mostly missense variants. The two variant sites, 166-182 aa and 274-302 aa, were the most concentrated. Clinicians need to pay attention to de novo data and functional data, which may affect the pathogenicity analysis. The decrease in HtrA1 protease activity is currently the most important explanation for the genetic pathogenesis.

Clinical features and pathogenicity assessment in patients with HTRA1-autosomal dominant disease

BACKGROUND

Heterozygous mutations in HTRA1 were recently found to cause autosomal dominant cerebral small vessel disease (CSVD), and it was named HTRA1-autosomal dominant disease (AD-HTRA1) in the consensus recommendations of the European Academy of Neurology. This study aimed to investigate the clinical features of a mutation in HTRA1 and the effect of HTRA1 mutation on white matter hyperintensity (WMH).

METHODS

A proband's brain magnetic resonance imaging (MRI) showed multiple lacunar infarctions and multiple WMH in the lateral ventricle, external capsule, frontal lobe and corpus callosum. The proband and family members were tested for CSVD-related genes by next-generation sequencing and the clinical data of the patients were collected. The published literature on AD-HTRA1 was collected, and the clinical characteristics and pathogenicity of the patients were summarized. Combined Annotation Dependent Depletion (CADD) is a tool for scoring the deleteriousness of single-nucleotide variants and insertion/deletion variants in the human genome. The relationship between the degree of WMH and the pathogenicity of the mutation was further analyzed.

RESULT

It was found that the proband and her family members had a heterozygous missense mutation of c.854C > T (p.P285L) in the 4 exon of HTRA1 gene. A retrospective analysis of 5 families with c.854C > T mutation found that the patients had an early age of onset, cognitive impairment was more common, and alopecia and spondylosis could be combined at the same time. By univariate analysis, the severity of WMH was found to be significantly associated with the mutated CADD score (p < 0.05, Spearman's rho = 0.266).

CONCLUSION

The clinical manifestations of AD-HTRA1 with mutation site c.854C > T (p.P285L) are similar to CARASIL, and brain MRI are mainly moderate or severe WMH and lacunar infarction (LI). WMH are affected by mutation sites. Therefore, our pathogenicity score for mutations can predict the severity of WMH.

Case report: Two unique nonsense mutations in HTRA1-related cerebral small vessel disease in a Chinese population and literature review

Background

Homozygous or compound heterozygous mutations in the high-temperature requirement A serine protease 1 gene (HTRA1) elicits cerebral autosomal recessive arteriopathy with subcortical infarcts and white matter lesions (CARASIL). The relationship between some heterozygous mutations, most of which are missense ones, and the occurrence of cerebral small vessel diseases (CSVD) has been reported. Recently, heterozygous HTRA1 nonsense mutations have been recognized to be pathogenic.

Case presentation

We described two Chinese patients diagnosed with HTRA1-CSVD accompanied by heterozygous nonsense mutations. Their first clinical manifestations were symptoms due to ischemic stroke, and brain Magnetic Resonance Imaging (MRI) showed diffuse white matter lesions (WMLs) and microbleeds in both of them. Genetic sequencing revealed two novel heterozygous nonsense mutations: c.1096G>T (p.E366X) and c.151G>T (p.E51X).

Conclusion

This case report expands the clinical, radiographic, and genetic spectrum of HTRA1-CSVD. Attention should be paid to young patients with ischemic stroke as the first clinical manifestation. Genetic screening for such sporadic CSVD is recommended, even if the symptoms are atypical.

HeterozygousHTRA1Mutations Cause Cerebral Small Vessel Diseases

Background and Objectives

Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is a rare hereditary cerebrovascular disease caused by homozygous or compound heterozygous variations in the high-temperature requirement A serine peptidase 1 (HTRA1) gene. However, several studies in recent years have found that some heterozygousHTRA1mutations also cause cerebral small vessel disease (CSVD). The current study aims to report the novel genotypes, phenotypes, and histopathologic results of 3 pedigrees of CSVD with heterozygousHTRA1mutation.

Methods

Three pedigrees of familiar CSVD, including 11 symptomatic patients and 3 asymptomatic carriers, were enrolled. Whole-exome sequencing was conducted in the probands for identifying rare variants, which were then evaluated for pathogenicity according to the American College of Medical Genetics and Genomics guidelines. Sanger sequencing was performed for validation of mutations in the probands and other family members. The protease activity was assayed for the novel mutations. All the participants received detailed clinical and imaging examinations and the corresponding results were concluded. Hematoma evacuation was performed for an intracerebral hemorrhage patient with the p.Q318H mutation, and the postoperative pathology including hematoma and cerebral small vessels were examined.

Results

Three novel heterozygousHTRA1mutations (p.Q318H, p.V279M, and p.R274W) were detected in the 3 pedigrees. The protease activity was largely lost for all the mutations, confirming that they were loss-of-function mutations. The patients in each pedigree presented with typical clinical and imaging features of CVSD, and some of them displayed several new phenotypes including color blindness, hydrocephalus, and multiple arachnoid cysts. In addition, family 1 is the largest pedigree with heterozygousHTRA1mutation so far and includes homozygous twins, displaying some variation in clinical phenotypes. More importantly, pathologic study of a patient with p.Q318H mutation showed hyalinization, luminal stenosis, loss of smooth muscle cells, splitting of the internal elastic lamina, and intramural hemorrhage/dissection-like structures.

Discussion

These findings broaden the mutational and clinical spectrum of heterozygousHTRA1-related CSVD. Pathologic features were similar with the previous heterozygous and homozygous cases. Moreover, clinical heterogeneity was revealed within the largest single family, and the mechanisms of the phenotypic heterogenetic remain unclear. Overall, heterozygous HTRA1-related CSVD should not be simply taken as a mild type of CARASIL as previously considered.

Novel mutations in HTRA1-related cerebral small vessel disease and comparison with CADASIL

Objective

There is evidence showing both heterozygous HTRA1 and homozygous HTRA1 mutations as causal for familial cerebral small vessel disease (CSVD). The clinical and neuroimaging signs of heterozygous HTRA1‐related CSVD can mimic cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). We aimed to characterize the genotypic and phenotypic features of HTRA1‐related CSVD, and we compared the features of heterozygous HTRA1‐related CSVD and CADASIL.

Methods

We carried out genetic sequencing in a series of unrelated patients with suspected familial CSVD from China. Clinical and imaging characteristics of heterozygous HTRA1‐related CSVD and CADASIL were compared.

Results

We identified nine heterozygous HTRA1 mutations and one homozygous HTRA1 mutation, seven of which are novel. Compared with CADASIL, patients with heterozygous HTRA1‐related CSVD had a higher proportion of spine disorders and a lower proportion of white matter hyperintensities involving the anterior temporal lobe (p < 0.001).

Interpretation

This study shows that most HTRA1‐related CSVD patients in China carry heterozygous HTRA1 mutations. The specific extra‐neurological features and neuroimaging features reveal informative differences between heterozygous HTRA1‐related CSVD and CADASIL. We expand the mutational spectrum of HTRA1.

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.

Identified novel heterozygous HTRA1 pathogenic variants in Chinese patients with HTRA1-associated dominant cerebral small vessel disease

Background: Homozygous and compound heterozygous mutations in HTRA1 cause cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL). Recently, heterozygous pathogenic variants in HTRA1 were described in patients with autosomal dominant cerebral small vessel disease (CSVD). Here, we investigated the genetic variants in a cohort of Chinese patients with CSVD.

Methods: A total of 95 Chinese index patients with typical characteristics of CSVD were collected. Whole exome sequencing was performed in the probands, followed by Sanger sequencing. Pathogenicity prediction software was applied to evaluate the pathogenicity of the identified variants.

Results: We detected five heterozygous HTRA1 pathogenic variants in five index patients. These pathogenic variants included four known variants (c.543delT, c.854C&gt;T, c.889G&gt;A, and c.824C&gt;T) and one novel variant (c.472 + 1G&gt;A). Among them, c.854C&gt;T, c.824C&gt;T, and c.472 + 1G&gt;A have never been reported in China and c.889G&gt;A was once reported in homozygous but never in heterozygous. Three of them were distributed in exon 4, one in exon 2, and another splicing variant in intron 1. Four out of five probands presented typical features of CARASIL but less severe. The common clinical features included lacunar infarction, cognitive decline, alopecia, and spondylosis. All of them showed leukoencephalopathy, and the main involved cerebral area include periventricular and frontal area, centrum semiovale, thalamus, and corpus callosum. Anterior temporal lobes and external capsule involvement were also observed. Three probands had intracranial microbleeds.

Conclusion: Our study expanded the mutation spectrum of HTRA1, especially in Chinese populations, and provided further evidence for “hot regions” in exon 1–4, especially in exon 4, in heterozygous HTRA1 pathogenic variants. Our work further supported that patients with heterozygous HTRA1 pathogenic variants presented with similar but less-severe features than CARASIL but in an autosomal dominantly inherited pattern.

Clinically reversible ustekinumab-induced encephalopathy: case report and review of the literature

Ustekinumab, a monoclonal antibody against interleukin (IL)-12 and IL-23 approved for the treatment of Crohn’s disease, has shown to be an effective therapy with a favourable safety profile. Clinical trials and real-world studies have reported very few neurological adverse events, including posterior reversible encephalopathy syndrome, idiopathic intracranial hypertension and headache. We describe the case of a 48-year-old man with Crohn’s disease who initiated treatment with ustekinumab on top of ongoing treatment with methotrexate 25 mg/week who presented with an acute-onset encephalopathy that rapidly evolved to severe tetraparesis and akinetic mutism, associated with extensive leukoencephalopathy and restricted diffusion on brain magnetic resonance imaging (MRI), 1 month after the second dose of ustekinumab. Comprehensive in-patient diagnostic testing ruled out vascular, demyelinating, metabolic, tumoral and infectious etiologies. Brain biopsy showed patchy infiltrates of foamy histiocytes with perivascular distribution, associated with edema, diffuse astrocytic gliosis and focal perivascular axonal destruction without demyelination, and ustekinumab-induced neurotoxicity was suspected. After drug discontinuation, the patient presented a complete clinical recovery despite the persistence of leukoencephalopathy. In conclusion, in an era in which biological therapies are continually evolving and expanding, knowledge about the potential neurotoxicity of these new therapies and their management becomes crucial. Although ustekinumab-induced encephalopathy is uncommon, the recognition of this potentially serious side effect is important because prompt withdrawal is associated with a favourable outcome. Whether methotrexate played an additional contributing role is currently unknown, but it is a factor that should be considered.

A novel heterozygous HTRA1 mutation in an Asian family with CADASIL-like disease

BACKGROUND

HTRA1 gene mutations are related to the pathogenesis of cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL). However, heterozygous HTRA1 mutations at specific sites can also lead to rare autosomal dominant cerebral artery disease (CADASIL-like disease). To date, 28 heterozygous mutations in the HTRA1 gene have been reported to be related to CADASIL-like diseases. Only one case of this disease was caused by a heterozygous mutation of c.497G>T in exon 2 of the HTRA1 gene.

METHODS

In this case, we report on an Asian family with CADASIL-like disease caused by a heterozygous mutation of c.497G>T in exon 2 of the HTRA1 gene. The clinical and imaging characteristics of the proband were summarized, and gene mutations were verified by whole-exome sequencing (WES) and direct Sanger sequencing.

RESULTS

The result of the gene sequencing showed a heterozygous missense mutation at the c.497G>T locus of the HTRA1 gene in the proband of one sick family member, resulting in a change in amino acid (p.arg166leu).

CONCLUSION

This is the first reported pathogenic mutation at the c.497G>T locus of the HTRA1 gene in an Asian population. It provides an important theoretical basis for the specific gene-based diagnosis and treatment of CADASIL-like diseases.

Novel In-Frame Deletion in HTRA1 Gene, Responsible for Stroke at a Young Age and Dementia-A Case Study

Biallelic mutations in the high-temperature requirement A serine peptidase 1 (HTRA1) gene are known to cause an extremely rare cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL), which belongs to the group of hereditary cerebral small vessel diseases and is mainly observed in the Japanese population. Even though this pathology is inherited in an autosomal recessive manner, recent studies have described symptomatic carriers with heterozygous HTRA1 mutations who have milder symptoms than patients with biallelic HTRA1 mutations. We present the case of a Lithuanian male patient who had a stroke at the age of 36, experienced several transient ischemic attacks, and developed an early onset, progressing dementia. These clinical symptoms were associated with extensive leukoencephalopathy, lacunar infarcts, and microbleeds based on brain magnetic resonance imaging (MRI). A novel heterozygous in-frame HTRA1 gene deletion (NM_002775.5:c.533_535del; NP_002766.1:p.(Lys178del)) was identified by next generation sequencing. The variant was consistent with the patient's phenotype, which could not be explained by alternative causes, appeared highly deleterious after in silico analysis, and was not reported in the medical literature or population databases to date.

Two Unique Mutations in HTRA1-Related Cerebral Small Vessel Disease in North America and Africa and Literature Review

OBJECTIVE

To describe and compare two cases of North American and African patients who were diagnosed with HTRA1-related cerebral small vessel disease (CSVD) with homozygous and heterozygous mutations, respectively, in the linker domain of the HTRA1 gene.

MATERIALS AND METHODS

Case reports and literature review.

RESULTS

A 49-year-old man from Mexico presented with recurrent lacunar strokes and memory loss. A 46-year-old woman from Eritrea presented with progressive memory loss. Neither patient had alopecia. MRI of the brain and spine in both patients showed leukoencephalopathy, microbleeds and spondylosis. Microbleeds along the subpial surfaces of the brainstem were only seen in the Mexican man. Genetic sequencing of HTRA1 gene revealed a novel homozygous mutation of p.A173S in the Mexican man supporting cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL). A heterozygous mutation of p.V175M was detected in the African woman, which has not been reported in patients of African ethnicity. In reviewing literature, CARASIL patients with mutation in the linker domain are older at neurological symptom onset and more frequently presented with stroke compared to patients with non-linker domain mutations. In patients of HTRA1-CSVD from heterozygous mutations, male is more common.

CONCLUSIONS

HTRA1-related CSVD may be seen in patients of non-Asian ethnicity without alopecia. These case reports extend the clinical and radiographic spectrum of HTRA1-related CSVD.

Clinicoradiographic and genetic features of cerebral small vessel disease indicate variability in mode of inheritance for monoallelic HTRA1 variants

BACKGROUND

Biallelic pathogenic variants in HTRA1 cause CARASIL. More recently, monoallelic variants have been associated with the autosomal dominant disorder CADASIL2 but not all carriers develop disease manifestations. We describe the clinicoradiologic and mutation spectrum of four new CADASIL2 individuals.

METHODS

Medical records at Mayo Clinic between 2013 and 2020 were retrospectively reviewed to identify patients with cerebral small vessel disease related to monoallelic HTRA1 variants.

RESULTS

Four patients met the study inclusion criteria for cerebral small vessel disease related to HTRA1 monoallelic variants. The mean age at onset of first clinical stroke was 51.25 years (range 41-64 years). The mean disease duration was 6.5 years (range 4-12). All individuals had recurrent strokes within the duration of follow-up with a mean number of strokes per patient being 5.5 (range 2-12). Three individuals had leukoencephalopathy with brain stem involvement. Microhemorrhages were seen on brain MRI in three patients. HTRA1 monoallelic variants identified in our cohort were missense variants in three patients and a novel frameshift variation in one patient. Interestingly, two of these missense variants were previously reported in an autosomal recessive pattern of inheritance and here are associated with a dominant effect.

CONCLUSIONS

Clinicoradiologic characteristics of heterozygous HTRA1-related CSVD may overlap with sporadic CSVD. Heterozygous HTRA1 variants can contribute to dominant or recessive disease mechanisms.

The role of genetics in neurodegenerative dementia: a large cohort study in South China

Neurodegenerative dementias are a group of diseases with highly heterogeneous pathology and complicated etiology. There exist potential genetic component overlaps between different neurodegenerative dementias. Here, 1795 patients with neurodegenerative dementias from South China were enrolled, including 1592 with Alzheimer's disease (AD), 110 with frontotemporal dementia (FTD), and 93 with dementia with Lewy bodies (DLB). Genes targeted sequencing analysis were performed. According to the American College of Medical Genetics (ACMG) guidelines, 39 pathogenic/likely pathogenic (P/LP) variants were identified in 47 unrelated patients in 14 different genes, including PSEN1, PSEN2, APP, MAPT, GRN, CHCHD10, TBK1, VCP, HTRA1, OPTN, SQSTM1, SIGMAR1, and abnormal repeat expansions in C9orf72 and HTT. Overall, 33.3% (13/39) of the variants were novel, the identified P/LP variants were seen in 2.2% (35/1592) and 10.9% (12/110) of AD and FTD cases, respectively. The overall molecular diagnostic rate was 2.6%. Among them, PSEN1 was the most frequently mutated gene (46.8%, 22/47), followed by PSEN2 and APP. Additionally, the age at onset of patients with P/LP variants (51.4 years), ranging from 30 to 83 years, was ~10 years earlier than those without P/LP variants (p < 0.05). This study sheds insight into the genetic spectrum and clinical manifestations of neurodegenerative dementias in South China, further expands the existing repertoire of P/LP variants involved in known dementia-associated genes. It provides a new perspective for basic research on genetic pathogenesis and novel guiding for clinical practice of neurodegenerative dementia.

Brain MRI in Monogenic Cerebral Small Vessel Diseases: A Practical Handbook

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Monogenic cerebral small vessel diseases are a topic of growing interest, as several genes responsible have been recently described and new sequencing techniques such as Next generation sequencing are available. Brain imaging is a key exam in these diseases. First, since it is often the first exam performed, an MRI is key in selecting patients for genetic testing and for interpreting Next generation sequencing reports. In addition, neuroimaging can be helpful in describing the underlying pathological mechanisms involved in cerebral small vessel disease. With this review, we aim to provide Neurologists and Stroke physicians with an up-to date overview of the current neuroimaging knowledge on monogenic small vessel diseases.

High Diagnostic Utility Incorporating a Targeted Neurodegeneration Gene Panel With MRI Brain Diagnostic Algorithms in Patients With Young-Onset Cognitive Impairment With Leukodystrophy

Leukodystrophies are a diverse group of genetic disorders that selectively involve the white matter of the brain and are a frequent cause of young-onset cognitive impairment. Genetic diagnosis is challenging. Data on the utility of incorporating brain magnetic resonance imaging (MRI) diagnostic algorithms with next-generation sequencing (NGS) for diagnosis in a real-life clinical setting is limited. We performed sequencing using a custom-designed panel of 200 neurodegeneration-associated genes on 45 patients with young-onset cognitive impairment with leukodystrophy, and classified them based on van der Knaap et al.'s MRI diagnostic algorithm. We found that 20/45 (44.4%) patients carried pathogenic variants or novel variants predicted to be pathogenic (one in CSF1R, two in HTRA1 and 17 in NOTCH3). All patients with an established genetic diagnosis had an MRI brain pattern consistent with a specific genetic condition/s. More than half (19/37, 51.4%) of patients with MRI changes consistent with vascular cognitive impairment secondary to small vessel disease (VCI-SVD) had pathogenic variants, including all patients with pathogenic NOTCH3 (17/19, 89.5%) and HTRA1 variants (2/19, 11.5%). Amongst patients harboring pathogenic NOTCH3 variants, 13/17 (76.5%) carried the p.R544C variant seen predominantly in East Asians. Anterior temporal white matter involvement was seen only in patients with pathogenic NOTCH3 variants (6/17, 35.3%). Overall, we demonstrated a high diagnostic utility incorporating a targeted neurodegeneration gene panel and MRI-based diagnostic algorithms in young-onset cognitive impairment patients with leukodystrophy.

HTRA1-related autosomal dominant cerebral small vessel disease

BACKGROUND

Homozygous or compound heterozygous mutations in high temperature requirement serine peptidase A1 (HTRA1) gene are responsible for cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL). Recently, increasing evidence has shown that heterozygous HTRA1 mutations are also associated with cerebral small vessel disease (CSVD) with an autosomal dominant pattern of inheritance. This study was aimed to analyze the genetic and clinical characteristics of HTRA1-related autosomal dominant CSVD.

METHODS

We presented three new Chinese cases of familial CSVD with heterozygous HTRA1 mutations and reviewed all clinical case reports and articles on HTRA1-related autosomal dominant CSVD included in PUBMED by the end of March 1, 2020. CARASIL probands with genetic diagnosis reported to date were also reviewed. The genetic and clinical characteristics of HTRA1-related autosomal dominant CSVD were summarized and analyzed by comparing with CARASIL.

RESULTS

Forty-four HTRA1-related autosomal dominant CSVD probands and 22 CARASIL probands were included. Compared with typical CARASIL, HTRA1-related autosomal dominant probands has a higher proportion of vascular risk factors (P < 0.001), a later onset age (P < 0.001), and a relatively slower clinical progression. Alopecia and spondylosis can be observed, but less than those in the typical CARASIL. Thirty-five heterozygous mutations in HTRA1 were reported, most of which were missense mutations. Amino acids located close to amino acids 250-300 were most frequently affected, followed by these located near 150∼200. While amino acids 250∼300 were also the most frequently affected region in CARASIL patients, fewer mutations precede the 200th amino acids were detected, especially in the Kazal-type serine protease domain.

CONCLUSIONS

HTRA1-related autosomal dominant CSVD is present as a mild phenotype of CARASIL. The trend of regional concentration of mutation sites may be related to the concentration of key sites in these regions which are responsible for pathogenesis of HTRA1-related autosomal dominant CSVD.

HTRA1 expression profile and activity on TGF-β signaling in HTRA1 mutation carriers

High temperature requirement A1 (HTRA1) is a serine protease playing a modulatory role in various cell processes, particularly in the regulation of transforming growth factor-β (TGF-β) signaling. A deleterious role in late-onset cerebral small vessel diseases (CSVDs) of heterozygous HTRA1 mutations, otherwise causative in homozygosity of cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy, was recently suggested. However, the pathomechanism of these heterozygous mutations is still undefined. Our aim is to evaluate the expression profile and activity of HTRA1 on TGF-β signaling in fibroblasts from four subjects carrying the HTRA1 heterozygous mutations-p.E42Dfs*173, p.A321T, p.G295R, and p.Q151K. We found a 50% reduction of HTRA1 expression in HTRA1 mutation carriers compared to the control. Moreover, we showed no changes in TGF-β signaling pathway downstream intermediate, Phospho Smad2/3. However, we found overexpression of genes involved in the extracellular matrix formation in two heterozygous HTRA1 carriers. Our results suggest that each heterozygous HTRA1 missense mutation displays a different and peculiar HTRA1 expression pattern and that CSVD phenotype may also result from 50% of HTRA1 expression.

HTRA1-Related Cerebral Small Vessel Disease: A Review of the Literature

Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is clinically characterized by early-onset dementia, stroke, spondylosis deformans, and alopecia. In CARASIL cases, brain magnetic resonance imaging reveals severe white matter hyperintensities (WMHs), lacunar infarctions, and microbleeds. CARASIL is caused by a homozygous mutation in high-temperature requirement A serine peptidase 1 (HTRA1). Recently, it was reported that several heterozygous mutations in HTRA1 also cause cerebral small vessel disease (CSVD). Although patients with heterozygous HTRA1-related CSVD (symptomatic carriers) are reported to have a milder form of CARASIL, little is known about the clinical and genetic differences between the two diseases. Given this gap in the literature, we collected clinical information on HTRA1-related CSVD from a review of the literature to help clarify the differences between symptomatic carriers and CARASIL and the features of both diseases. Forty-six symptomatic carriers and 28 patients with CARASIL were investigated. Twenty-eight mutations in symptomatic carriers and 22 mutations in CARASIL were identified. Missense mutations in symptomatic carriers are more frequently identified in the linker or loop 3 (L3)/loop D (LD) domains, which are critical sites in activating protease activity. The ages at onset of neurological symptoms/signs were significantly higher in symptomatic carriers than in CARASIL, and the frequency of characteristic extraneurological findings and confluent WMHs were significantly higher in CARASIL than in symptomatic carriers. As previously reported, heterozygous HTRA1-related CSVD has a milder clinical presentation of CARASIL. It seems that haploinsufficiency can cause CSVD among symptomatic carriers according to the several patients with heterozygous nonsense/frameshift mutations. However, the differing locations of mutations found in the two diseases indicate that distinct molecular mechanisms influence the development of CSVD in patients with HTRA1-related CSVD. These findings further support continued careful examination of the pathogenicity of mutations located outside the linker or LD/L3 domain in symptomatic carriers.

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.

How common are single gene mutations as a cause for lacunar stroke? A targeted gene panel study

OBJECTIVES

To determine the frequency of rare and pertinent disease-causing variants in small vessel disease (SVD)-associated genes (such as NOTCH3, HTRA1, COL4A1, COL4A2, FOXC1, TREX1, and GLA) in cerebral SVD, we performed targeted gene sequencing in 950 patients with younger-onset apparently sporadic SVD stroke using a targeted sequencing panel.

METHODS

We designed a high-throughput sequencing panel to identify variants in 15 genes (7 known SVD genes, 8 SVD-related disorder genes). The panel was used to screen a population of 950 patients with younger-onset (≤70 years) MRI-confirmed SVD stroke, recruited from stroke centers across the United Kingdom. Variants were filtered according to their frequency in control databases, predicted effect, presence in curated variant lists, and combined annotation dependent depletion scores. Whole genome sequencing and genotyping were performed on a subset of patients to provide a direct comparison of techniques. The frequency of known disease-causing and pertinent variants of uncertain significance was calculated.

RESULTS

We identified previously reported variants in 14 patients (8 cysteine-changing NOTCH3 variants in 11 patients, 2 HTRA1 variants in 2 patients, and 1 missense COL4A1 variant in 1 patient). In addition, we identified 29 variants of uncertain significance in 32 patients.

CONCLUSION

Rare monogenic variants account for about 1.5% of younger onset lacunar stroke. Most are cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy variants, but the second most common gene affected is HTRA1. A high-throughput sequencing technology platform is an efficient, reliable method to screen for such mutations.

Genetic Factors of Cerebral Small Vessel Disease and Their Potential Clinical Outcome

Cerebral small vessel diseases (SVD) have been causally correlated with ischemic strokes, leading to cognitive decline and vascular dementia. Neuroimaging and molecular genetic tests could improve diagnostic accuracy in patients with potential SVD. Several types of monogenic, hereditary cerebral SVD have been identified: cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL), cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), cathepsin A-related arteriopathy with strokes and leukoencephalopathy (CARASAL), hereditary diffuse leukoencephalopathy with spheroids (HDLS), COL4A1/2-related disorders, and Fabry disease. These disorders can be distinguished based on their genetics, pathological and imaging findings, clinical manifestation, and diagnosis. Genetic studies of sporadic cerebral SVD have demonstrated a high degree of heritability, particularly among patients with young-onset stroke. Common genetic variants in monogenic disease may contribute to pathological progress in several cerebral SVD subtypes, revealing distinct genetic mechanisms in different subtype of SVD. Hence, genetic molecular analysis should be used as the final gold standard of diagnosis. The purpose of this review was to summarize the recent discoveries made surrounding the genetics of cerebral SVD and their clinical significance, to provide new insights into the pathogenesis of cerebral SVD, and to highlight the possible convergence of disease mechanisms in monogenic and sporadic cerebral SVD.

HTRA1 Mutations Identified in Symptomatic Carriers Have the Property of Interfering the Trimer-Dependent Activation Cascade

Background: Mutations in the high-temperature requirement A serine peptidase 1 (HTRA1) cause cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL). Most carriers for HTRA1 mutations are asymptomatic, but more than 10 mutations have been reported in symptomatic carriers. The molecular differences between the mutations identified in symptomatic carriers and mutations identified only in CARASIL patients are unclear. HTRA1 is a serine protease that forms homotrimers, with each HTRA1 subunit activating the adjacent HTRA1 via the sensor domain of loop 3 (L3) and the activation domain of loop D (LD). Previously, we analyzed four HTRA1 mutant proteins identified in symptomatic carriers and found that they were unable to form trimers or had mutations in the LD or L3 domain. The mutant HTRA1s with these properties are presumed to inhibit trimer-dependent activation cascade. Indeed, these mutant HTRA1s inhibited wild-type (WT) protease activity. In this study, we further analyzed 15 missense HTRA1s to clarify the molecular character of mutant HTRA1s identified in symptomatic carriers.

Methods: We analyzed 12 missense HTRA1s identified in symptomatic carriers (hetero-HTRA1) and three missense HTRA1s found only in CARASIL (CARASIL-HTRA1). The protease activity of the purified recombinant mutant HTRA1s was measured using fluorescein isothiocyanate-labeled casein as substrate. Oligomeric structure was evaluated by size-exclusion chromatography. The protease activities of mixtures of WT with each mutant HTRA1 were also measured.

Results: Five hetero-HTRA1s had normal protease activity and were excluded from further analysis. Four of the seven hetero-HTRA1s and one of the three CARASIL-HTRA1s were unable to form trimers. The other three hetero-HTRA1s had mutations in the LD domain. Together with our previous work, 10 of 11 hetero-HTRA1s and two of six CARASIL-HTRA1s were either defective in trimerization or had mutations in the LD or L3 domain (P = 0.006). By contrast, eight of 11 hetero-HTRA1s and two of six CARASIL-HTRA1 inhibited WT protease activity (P = 0.162).

Conclusions: HTRA1 mutations identified in symptomatic carriers have the property of interfering the trimer-dependent activation cascade of HTRA1.

Cerebral small vessel disease: classification, clinical manifestations, diagnosis, and features of treatment

The paper considers the relevance of the problem of cerebral small vessel disease (CSVD) that is an important cause of ischemic and hemorrhagic stroke, associated with the development of cognitive impairment and complications of antithrombotic therapy. It presents briefly the current issues of etiology and pathogenesis of the disease. Sporadic non-amyloid microangiopathy, cerebral amyloid angiopathy, and cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) are discussed in detail from the point of view of their clinical presentation, neuroimaging, and features of therapeutic tactics. An algorithm for diagnosing CSVD in patients admitted to hospital for stroke and a differentiated approach to their treatment are proposed. Consideration of the neuroimaging manifestations of CSVD is noted to be necessary for the safe and more effective treatment of patients with cerebrovascular diseases.

Novel and Recurring NOTCH3 Mutations in Two Chinese Patients with CADASIL

BACKGROUND

Cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an autosomal-dominant, inherited, systemic, vascular disorder primarily involving the small arteries. It is characterized by migraine, recurrent ischemic strokes, cognitive decline, and dementia. Mutations in the Notch receptor 3 gene (NOTCH3) and the HtrA serine peptidase 1 gene (HTRA1) are 2 genetic causes for CADASIL. The NOTCH3 gene, located on chromosome 19p13.12, is the most common disease-causing gene in CADASIL.

OBJECTIVE

To investigate genetic causes in 2 unrelated Han-Chinese patients with presentations strongly suggestive of CADASIL.

METHODS

Exome sequencing was performed on both patients and potential pathogenic mutations were validated by Sanger sequencing.

RESULTS

This study reports on 2 unrelated Han-Chinese patients with presentations strongly suggestive of CADASIL, identifying that NOTCH3 mutations were the genetic cause. A common mutation, c.268C>T (p.Arg90Cys), and a novel mutation, c.331G>T (p.Gly111Cys) in the NOTCH3 gene, were detected and confirmed in the patients, respectively, and were predicted to be deleterious based on bioinformation analyses.

CONCLUSIONS

We identified 2 NOTCH3 mutations as likely genetic causes for CADASIL in these 2 patients. Our findings broaden the mutational spectrum of the NOTCH3 gene accountable for CADASIL. Clinical manifestations supplemented with molecular genetic analyses are critical for accurate diagnosis, the provision of genetic counseling, and the development of therapies for CADASIL.

Ultrastructural analysis of submacular choriocapillaris and its transport systems in AMD and aged control eyes

The choriocapillaris is the source of nutrients and oxygen for photoreceptors, which consume more oxygen per gram of tissue than any other cell in the body. The purpose of this study was to evaluate and compare the ultrastructure of the choriocapillaris and its transport systems in patients with and without age-related macular degeneration (AMD). Ultrastructural changes were also evaluated in subjects that were homozygous for polymorphisms in high risk CFH alleles (Pure 1) only or homozygous only for high risk ARMS2/HTRA1 (Pure 10) alleles. Tissue samples were obtained from the macular region of forty male (n = 24) and female (n = 16) donor eyes and prepared for ultrastructural studies with transmission electron microscopy (TEM). The average age of the aged donors was 74 ± 7.2 (n = 30) and the young donors 31.7 ± 11.25 (n = 10). There was no significant difference in average ages between the adult groups. TEM images of the capillaries in the choriocapillaris (CC) were taken at 4,000X and 25,000X and used to measure the area of endothelial cell somas, the number of fenestrations, and area of caveolae within the endothelial cells per length of Bruchs membrane (BrMb). The Student t-test and Wilcoxon sum rank test were used to determine significant differences. There was no significant difference between young subjects and aged controls in any of the morphological criteria assessed. There was a significant decrease in the number of fenestrations/mm of BrMb in atrophic areas of GA eyes (p = 0.007) when compared with aged control eyes. A significant increase was found in the caveolae area as a percent of the endothelial cell soma of capillaries from GA subjects as compared with the controls (p = 0.03). Loss of capillary segments in choriocapillaris was also evident, especially in areas of geographic atrophy and CNV. In eyes from patients with sequence variations, the capillary endothelial cells often appeared degenerative and exhibited atypical fenestrations and pericytes covering the blood vessels. Subjects that were homozygous for polymorphisms in high risk CFH alleles only had more fenestrations/mm of BrMb than subjects that were homozygous only for high risk ARMS2/HTRA1 alleles (p = 0.04), while the latter had greater caveolae area/endothelial cell area than the former (p = 0.007). This study demonstrated an attenuation of CC and a significant decline in the two major transport systems in CC endothelial cells in AMD. This may contribute to drusen deposition, nutrient transport, and vision loss in AMD subjects.

Heterozygous HTRA1 mutations with mimicking symptoms of CARASIL in two families

The term cerebral small vessel disease (SVD) refers to a group of pathological processes with various etiologies that affect the small arteries, arterioles, venules, and capillaries of the brain. SVD occurs in approximately 5% of patients. Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL),a recessive form of heritable SVD, is caused by a mutation in the high temperature requirement A serine peptidase (HTRA1) gene. Recently, heterozygous mutations in HTRA1 were identified in patients with symptomatic SVD. We identified two families harboring HTRA1 (p.S284 N and p.V216 M) heterozygous mutations with symptoms that mimicked common symptoms of CARASIL.

Characterization of Heterozygous HTRA1 Mutations in Taiwanese Patients With Cerebral Small Vessel Disease

BACKGROUND AND PURPOSE

Homozygous and compound heterozygous mutations in the high temperature requirement serine peptidase A1 gene (HTRA1) cause cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy. However, heterozygous HTRA1 mutations were recently identified to be associated with autosomal dominant cerebral small vessel disease (SVD). The present study aims at investigating the clinical features, frequency, and spectrum of HTRA1 mutations in a Taiwanese cohort with SVD.

METHODS

Mutational analyses of HTRA1 were performed by Sanger sequencing in 222 subjects, selected from a cohort of 337 unrelated patients with SVD after excluding those harboring a NOTCH3 mutation. The influence of these mutations on HTRA1 protease activities was characterized.

RESULTS

Seven novel heterozygous mutations in HTRA1 were identified, including p.Gly120Asp, p.Ile179Asn, p.Ala182Profs*33, p.Ile256Thr, p.Gly276Ala, p.Gln289Ter, and p.Asn324Thr, and each was identified in 1 single index patient. All mutations significantly compromise the HTRA1 protease activities. For the 7 index cases and another 2 affected siblings carrying a heterozygous HTRA1 mutation, the common clinical presentations include lacunar infarction, intracerebral hemorrhage, cognitive decline, and spondylosis at the fifth to sixth decade of life. Among the 9 patients, 4 have psychiatric symptoms as delusion, depression, and compulsive behavior, 3 have leukoencephalopathy in anterior temporal poles, and 2 patients have alopecia.

CONCLUSIONS

Heterozygous HTRA1 mutations account for 2.08% (7 of 337) of SVD in Taiwan. The clinical and neuroradiological features of HTRA1-related SVD and sporadic SVD are similar. These findings broaden the mutational spectrum of HTRA1 and highlight the pathogenic role of heterozygous HTRA1 mutations in SVD.

Two novel heterozygous HTRA1 mutations in two pedigrees with cerebral small vessel disease families

Heterozygous HTRA1 mutations, recently, have been reported as a cause of autosomal dominant hereditary cerebral small vessel disease (CSVD). We herein describe clinical and neuroimaging findings in two familial CSVD with two different heterozygous HTRA1 mutations. Detailed clinical and neuroimaging examination were conducted in probands and their available family members. A next-generation sequencing-based comprehensive gene panel was used to investigate their causative mutations. A novel heterozygous missense variant c.527T>C (p.V176A) and a novel heterozygous nonsense variant c.589C>T (p.R197X) in HTRA1 gene were detected in probands of family 1 and family 2, respectively. Co-segregation analysis in family 1 showed eight family members were mutation carriers. All alive male patients showed typical clinical and neuroimaging features of CSVD. All alive female mutation carriers were clinical or neuroimaging asymptomatic. Screening of HTRA1 should be considered in patients with familial CSVD. A male predominance may exist in patients with heterozygous HTRA1 mutations and need to be further investigated.

Heterozygous mutations of HTRA1 gene in patients with familial cerebral small vessel disease

AIMS

Cerebral small vessel disease (SVD) is the leading cause of vascular dementia. Although the most of cases are sporadic, familial monogenic causes have been identified in a growing minority of patients. CADASIL, due to mutations of NOTCH3 gene, is the most common genetic SVD, and CARASIL, linked to HTRA1 gene mutations, is a rare but well known autosomal recessive SVD. Recently, also heterozygous HTRA1 mutations have been described in patients with familial SVD. To detect a genetic cause of familial SVD, we performed mutational analysis of HTRA1 gene in a large cohort of Italian NOTCH3-negative patients.

METHODS

We recruited 142 NOTCH3-negative patients and 160 healthy age-matched controls. Additional control data were obtained from five pathogenicity prediction software.

RESULTS

Five different HTRA1 heterozygous mutations were detected in nine patients from five unrelated families. Clinical phenotype was typical of SVD, and the onset was presenile. Brain magnetic resonance imaging (MRI) showed a subcortical leukoencephalopathy, with involvement of the external and internal capsule, corpus callosum, and multiple lacunar infarcts. Cerebral microbleeds were also seen, while anterior temporal lobes involvement was not present.

CONCLUSION

Our observation further supports the pathogenic role of the heterozygous HTRA1 mutations in familial SVD.