Sporadic cerebral cavernous malformations: report of further mutations of CCM genes in 40 Italian patients

Can Hemorrhagic Stroke Genetics Help Forensic Diagnosis in Pediatric Age (<5 Years Old)?

When stroke occurs in pediatric age, it might be mistakenly interpreted as non-accidental head injury (NAHI). In these situations, a multidisciplinary approach is fundamental, including a thorough personal and familial history, along with accurate physical examination and additional investigations. Especially when the clinical picture is uncertain, it is important to remember that certain genetic conditions can cause bleeding inside the brain, which may resemble NAHI. Pediatric strokes occurring around the time of birth can also be an initial sign of undiagnosed genetic disorders. Hence, it is crucial to conduct a thorough evaluation, including genetic testing, when there is a suspicion of NAHI but the symptoms are unclear. In these cases, a characteristic set of symptoms is often observed. This study aims to summarize some of the genetic causes of hemorrhagic stroke in the pediatric population, thus mimicking non-accidental head injury, considering elements that can be useful in characterizing pathologies. A systematic review of genetic disorders that may cause ICH in children was carried out according to the Preferred Reporting Item for Systematic Review (PRISMA) standards. We selected 10 articles regarding the main genetic diseases in stroke; we additionally selected 11 papers concerning patients with pediatric stroke and genetic diseases, or studies outlining the characteristics of stroke in these patients. The disorders we identified were Moyamoya disease (MMD), COL4A1, COL4A2 pathogenic variant, Ehlers-Danlos syndrome (E-D), neurofibromatosis type 1 (Nf1), sickle cell disease (SCD), cerebral cavernous malformations (CCM), hereditary hemorrhagic telangiectasia (HHT) and Marfan syndrome. In conclusion, this paper provides a comprehensive overview of the genetic disorders that could be tested in children when there is a suspicion of NAHI but an unclear picture.

NOGOB receptor deficiency increases cerebrovascular permeability and hemorrhage via impairing histone acetylation-mediated CCM1/2 expression

The loss function of cerebral cavernous malformation (CCM) genes leads to most CCM lesions characterized by enlarged leaking vascular lesions in the brain. Although we previously showed that NOGOB receptor (NGBR) knockout in endothelial cells (ECs) results in cerebrovascular lesions in the mouse embryo, the molecular mechanism by which NGBR regulates CCM1/2 expression has not been elucidated. Here, we show that genetic depletion of Ngbr in ECs at both postnatal and adult stages results in CCM1/2 expression deficiency and cerebrovascular lesions such as enlarged vessels, blood-brain-barrier hyperpermeability, and cerebral hemorrhage. To reveal the molecular mechanism, we used RNA-sequencing analysis to examine changes in the transcriptome. Surprisingly, we found that the acetyltransferase HBO1 and histone acetylation were downregulated in NGBR-deficient ECs. The mechanistic studies elucidated that NGBR is required for maintaining the expression of CCM1/2 in ECs via HBO1-mediated histone acetylation. ChIP-qPCR data further demonstrated that loss of NGBR impairs the binding of HBO1 and acetylated histone H4K5 and H4K12 on the promotor of the CCM1 and CCM2 genes. Our findings on epigenetic regulation of CCM1 and CCM2 that is modulated by NGBR and HBO1-mediated histone H4 acetylation provide a perspective on the pathogenesis of sporadic CCMs.

Cerebral Cavernous Malformation Pathogenesis: Investigating Lesion Formation and Progression with Animal Models

Cerebral cavernous malformation (CCM) is a cerebromicrovascular disease that affects up to 0.5% of the population. Vessel dilation, decreased endothelial cell-cell contact, and loss of junctional complexes lead to loss of brain endothelial barrier integrity and hemorrhagic lesion formation. Leakage of hemorrhagic lesions results in patient symptoms and complications, including seizures, epilepsy, focal headaches, and hemorrhagic stroke. CCMs are classified as sporadic (sCCM) or familial (fCCM), associated with loss-of-function mutations in KRIT1/CCM1, CCM2, and PDCD10/CCM3. Identifying the CCM proteins has thrust the field forward by (1) revealing cellular processes and signaling pathways underlying fCCM pathogenesis, and (2) facilitating the development of animal models to study CCM protein function. CCM animal models range from various murine models to zebrafish models, with each model providing unique insights into CCM lesion development and progression. Additionally, these animal models serve as preclinical models to study therapeutic options for CCM treatment. This review briefly summarizes CCM disease pathology and the molecular functions of the CCM proteins, followed by an in-depth discussion of animal models used to study CCM pathogenesis and developing therapeutics.

Cerebral cavernous malformations do not fall in the spectrum of PIK3CA-related overgrowth

Somatic gain-of-function (GOF) mutations in phosphatidylinositol-4, 5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), the catalytic subunit of phosphoinositide 3-kinase (PI3K), have been recently discovered in cerebral cavernous malformations (CCMs), raising the possibility that the activation of PI3K pathways is a possible universal regulator of vascular morphogenesis. However, there have been contradicting data presented among various groups and studies. To enhance the current understanding of vascular anomalies, it is essential to explore this possible relationship between altered PI3K signalling pathways and its influence on the pathogenesis of CCMs. GOF PIK3CA-mutants have been linked to overgrowth syndromes, allowing this group of disorders, resulting from somatic activating mutations in PIK3CA, to be collectively named as PIK3CA-related overgrowth spectrum disorders. This paper reviews and attempts to conceptualise the relationships and differences among clinical presentations, genotypic and phenotypic correlations and possible coexistence of PIK3CA and CCM mutations/phenotypes in CCM lesions. Finally, we present a model reflecting our hypothetical understanding of CCM pathogenesis based on a systematic review and conceptualisation of data obtained from other studies.

A novel insight into differential expression profiles of sporadic cerebral cavernous malformation patients with different symptoms

Cerebral cavernous malformation (CCM) is a vascular lesion of the central nervous system that may lead to distinct symptoms among patients including cerebral hemorrhages, epileptic seizures, focal neurologic deficits, and/or headaches. Disease-related mutations were identified previously in one of the three CCM genes: CCM1, CCM2, and CCM3. However, the rate of these mutations in sporadic cases is relatively low, and new studies report that mutations in CCM genes may not be sufficient to initiate the lesions. Despite the growing body of research on CCM, the underlying molecular mechanism has remained largely elusive. In order to provide a novel insight considering the specific manifested symptoms, CCM patients were classified into two groups (as Epilepsy and Hemorrhage). Since the studied patients experience various symptoms, we hypothesized that the underlying cause for the disease may also differ between those groups. To this end, the respective transcriptomes were compared to the transcriptomes of the control brain tissues and among each other. This resulted into the identification of the differentially expressed coding genes and the delineation of the corresponding differential expression profile for each comparison. Notably, some of those differentially expressed genes were previously implicated in epilepsy, cell structure formation, and cell metabolism. However, no CCM1-3 gene deregulation was detected. Interestingly, we observed that when compared to the normal controls, the expression of some identified genes was only significantly altered either in Epilepsy (EGLN1, ELAVL4, and NFE2l2) or Hemorrhage (USP22, EYA1, SIX1, OAS3, SRMS) groups. To the best of our knowledge, this is the first such effort focusing on CCM patients with epileptic and hemorrhagic symptoms with the purpose of uncovering the potential CCM-related genes. It is also the first report that presents a gene expression dataset on Turkish CCM patients. The results suggest that the new candidate genes should be explored to further elucidate the CCM pathology. Overall, this work constitutes a step towards the identification of novel potential genetic targets for the development of possible future therapies.

The exosomal transfer of human bone marrow mesenchymal stem cell-derived miR-1913 inhibits osteosarcoma progression by targeting NRSN2

OBJECTIVE

Osteosarcoma is a malignant bone tumor consisting of mesenchymal cells. This study aimed to investigate the inhibitory effects of human bone marrow mesenchymal stem cell (hBMSC)-derived miR-1913 on osteosarcoma.

METHODS

Cell viability was determined using CCK8 and colony formation assays. The cell migration and invasion abilities were assessed using wound healing and transwell assays. RT-qPCR and western blot were used to measure the miR-1913, Neurensin-2 (NRSN2), N-cadherin, and E-cadherin expression levels. Dual luciferase reporter assays were conducted to identify the target relationship between miR-1913 and NRSN2. The exosomes were extracted and identified using TEM and NTA assays.

RESULTS

In the osteosarcoma tumor tissues and cell lines, the NRSN2 expressions were up-regulated, which correlated with a poor osteosarcoma prognosis. MiR-1913 inhibited the cell viability, proliferation, migration, and invasion by negatively targeting NRSN2. Furthermore, the hBMSC-derived exosomes delivered miR-1913 to inhibit the NRSN2 expression in the osteosarcoma cells.

CONCLUSION

The inhibitory role of hBMSC-derived miR-1913 on osteosarcoma progression was achieved by targeting NRSN2, indicating the potential therapeutic value of hBMSC-derived miR-1913.

Somatic PIK3CA Mutations in Sporadic Cerebral Cavernous Malformations

BACKGROUND

Cerebral cavernous malformations (CCMs) are common sporadic and inherited vascular malformations of the central nervous system. Although familial CCMs are linked to loss-of-function mutations in KRIT1 (CCM1), CCM2, or PDCD10 (CCM3), the genetic cause of sporadic CCMs, representing 80% of cases, remains incompletely understood.

METHODS

We developed two mouse models harboring mutations identified in human meningiomas with the use of the prostaglandin D2 synthase (PGDS) promoter. We performed targeted DNA sequencing of surgically resected CCMs from patients and confirmed our findings by droplet digital polymerase-chain-reaction analysis.

RESULTS

We found that in mice expressing one of two common genetic drivers of meningioma - Pik3ca ^H1047R or AKT1 ^E17K - in PGDS-positive cells, a spectrum of typical CCMs develops (in 22% and 11% of the mice, respectively) instead of meningiomas, which prompted us to analyze tissue samples from sporadic CCMs from 88 patients. We detected somatic activating PIK3CA and AKT1 mutations in 39% and 1%, respectively, of lesion tissue from the patients. Only 10% of lesions harbored mutations in the CCM genes. We analyzed lesions induced by the activating mutations Pik3ca ^H1074R and AKT1 ^E17K in mice and identified the PGDS-expressing pericyte as the probable cell of origin.

CONCLUSIONS

In tissue samples from sporadic CCMs, mutations in PIK3CA were represented to a greater extent than mutations in any other gene. The contribution of somatic mutations in the genes that cause familial CCMs was comparatively small. (Funded by the Fondation ARC pour la Recherche contre le Cancer and others.).

Signalling through cerebral cavernous malformation protein networks

Cerebral cavernous malformations (CCMs) are neurovascular abnormalities characterized by thin, leaky blood vessels resulting in lesions that predispose to haemorrhages, stroke, epilepsy and focal neurological deficits. CCMs arise due to loss-of-function mutations in genes encoding one of three CCM complex proteins, KRIT1, CCM2 or CCM3. These widely expressed, multi-functional adaptor proteins can assemble into a CCM protein complex and (either alone or in complex) modulate signalling pathways that influence cell adhesion, cell contractility, cytoskeletal reorganization and gene expression. Recent advances, including analysis of the structures and interactions of CCM proteins, have allowed substantial progress towards understanding the molecular bases for CCM protein function and how their disruption leads to disease. Here, we review current knowledge of CCM protein signalling with a focus on three pathways which have generated the most interest—the RhoA–ROCK, MEKK3–MEK5–ERK5–KLF2/4 and cell junctional signalling pathways—but also consider ICAP1-β1 integrin and cdc42 signalling. We discuss emerging links between these pathways and the processes that drive disease pathology and highlight important open questions—key among them is the role of subcellular localization in the control of CCM protein activity.

Familial cerebral cavernous malformation presenting with epilepsy caused by mutation in the CCM2 gene: A case report

RATIONALE

Cerebral cavernous malformation (CCM) of the familial type is caused by abnormalities in the CCM1, CCM2, and CCM3 genes. These 3 proteins forming a complex associate with the maintenance of vascular endothelial cell-cell junctions. Dysfunction of these proteins results in the development of hemangiomas and abnormal intercellular junctions.

PATIENT CONCERNS

We report a 68-year-old man with familial cerebral cavernous malformation with initial presentation as convulsions at an advanced age. Brain magnetic resonance imaging revealed multiple cavernous hemangiomas in the right occipital lobe. The convulsions were considered to be induced by hemorrhage from cavernous hemangioma in the right occipital lobe.

DIAGNOSES

Genetic screening of the CCM1, CCM2, and CCM3 genes revealed a novel mutation in the CCM2 gene (exon4 c: 359 T>A, p: V120D). No abnormalities were found in CCM1 or CCM3. Therefore, we diagnosed the patient with familial CCM caused by a CCM2 mutation.

INTERVENTIONS

This patient was treated with the administration of levetiracetam at a dosage of 1000 mg/day.

OUTCOMES

No seizures have been observed since the antiepileptic drug was administered. We performed brain magnetic resonance imaging (MRI) regularly to follow-up on appearance of new cerebral hemorrhages and cavernous hemangiomas.

LESSONS

This report reviews cases of familial cerebral cavernous malformations caused by abnormalities in the CCM2 gene. This mutation site mediates interactions with CCM1 and CCM3. The mutation occurs in the phosphotyrosine binding (PTB) site, which is considered functionally important to CCM2.

A Novel CCM2 Gene Mutation Associated With Cerebral Cavernous Malformation

Cerebral cavernous malformations (CCMs) are the second most prevalent type of vascular malformation within the central nervous system. CCMs occur in two forms—sporadic and familial—the latter of which has an autosomal dominant mode of inheritance with incomplete penetrance and variable clinical expressivity. There are three genes considered to be associated with CCMs,—CCM1, which codes for KRIT1 protein; CCM2, which codes for MGC4607 protein; and CCM3, which codes for PDCD10 protein. To date, more than 74 gene mutations of CCM2 have been reported, and ~45% are deletion mutations. In this article, we disclose a novel CCM2 genetic variant (c.755delC, p.S252fs^*40X) identified in a Chinese family to enrich the database of CCM2 genotypes.

Two Novel KRIT1 and CCM2 Mutations in Patients Affected by Cerebral Cavernous Malformations: New Information on CCM2 Penetrance

Wide comprehension of genetic features of cerebral cavernous malformations (CCM) represents the starting point to better manage patients and risk rating in relatives. The causative mutations spectrum is constantly growing. KRIT1, CCM2, and PDCD10 are the three loci to date linked to familial CCM development, although germline mutations have also been detected in patients affected by sporadic forms. In this context, the main challenge is to draw up criteria to formulate genotype-phenotype correlations. Clearly, genetic factors determining incomplete penetrance of CCM need to be identified. Here, we report two novel intronic variants probably affecting splicing. Molecular screening of CCM genes was performed on DNA purified by peripheral blood. Coding exons and intron-exon boundaries were sequenced by the Sanger method. The first was detected in a sporadic patient and involves KRIT1. The second affects CCM2 and it is harbored by a woman with familial CCM. Interestingly, molecular analysis extended to both healthy and ill relatives allowed to estimate, for the first time, a penetrance for CCM2 lower than 100%, as to date reported. Moreover, heterogeneity of clinical manifestations among those affected carrying the same genotype further confirms involvement of modifier factors in CCM development.

Magnetic Resonance (MR) Imaging of Vascular Malformations

Vascular malformations pose a diagnostic and therapeutic challenge due to the broad differential diagnosis as well as common utilization of inadequate or inaccurate classification systems among healthcare providers. Therapeutic approaches to these lesions vary based on the type, size, and extent of the vascular anomaly, necessitating accurate diagnosis and classification. Magnetic resonance (MR) imaging (MRI) is an effective modality for classifying vascular anomalies due to its ability to delineate the extent and anatomic relationship of the malformation to adjacent structures. In addition to anatomical mapping, the complete evaluation of vascular anomalies includes hemodynamic characterization. Dynamic time-resolved contrast-enhanced MR angiography provides information regarding hemodynamics of vascular anomalies, differentiating high- and low-flow vascular malformations. Radiologists must identify the MRI features of vascular malformations for better diagnosis and classification.

A Novel KRIT1/CCM1 Gene Insertion Mutation Associated with Cerebral Cavernous Malformations in a Chinese Family

Familial cerebral cavernous malformation (FCCM) is a vascular malformation disorder that closely associated with three identified genes: KRIT1/CCM1, MGC4607/CCM2, and PDCD10/CCM3. Here, we present a Chinese family affected by FCCM due to a novel KRIT1/CCM1 insertion mutation. The proband was hospitalized for sudden unconsciousness and underwent surgical treatment. The section of lesions showed classical cavernous-dilated vessels without intervening brain parenchyma, and hemosiderin-laden macrophages were accumulated in the surrounding tissue. In addition, magnetic resonance imaging (MRI) showed severe multiple cerebral cavernous malformation (CCM) lesions in cerebrum, brainstem, and cerebellum in other affected subjects. Especially, for the proband's mother, hundreds of lesions were presented, and a few lesions were found in the expanded lateral ventricle (Evans' index =0.33). Moreover, she showed the similar symptoms of hydrocephalus, including headache, dizziness, and diplopia. It was extremely rare in previous reports. To date, the genetic alterations leading to FCCM in Chinese population remain largely unknown. We investigated genetic defects of this family. Sequence analyses disclosed a novel heterozygous insertion mutation (c.1896_1897insT; p.Pro633SerfsTer22) in KRIT1/CCM1. Moreover, our real-time PCR results revealed that the mRNA level of KRIT1/CCM1 were significantly decreased in FCCM subjects (CCM family =0.42 ± 0.20 vs. healthy control =1.01 ± 0.16, P = 0.004). It indicated that this mutation could cause KRIT1/CCM1 functional mRNA deficiency. It may be closely related with the pathogenesis of FCCM. Our findings provided a new gene mutation profile which will be of great significance in early diagnosis and appropriate clinical surveillance of FCCM patients.

Introduction to cerebral cavernous malformation: a brief review

The disease known as cerebral cavernous malformations mostly occurs in the central nervous system, and their typical histological presentations are multiple lumen formation and vascular leakage at the brain capillary level, resulting in disruption of the blood-brain barrier. These abnormalities result in severe neurological symptoms such as seizures, focal neurological deficits and hemorrhagic strokes. CCM research has identified ‘loss of function’ mutations of three ccm genes responsible for the disease and also complex regulation of multiple signaling pathways including the WNT/β-catenin pathway, TGF-β and Notch signaling by the ccm genes. Although CCM research is a relatively new and small scientific field, as CCM research has the potential to regulate systemic blood vessel permeability and angiogenesis including that of the blood-brain barrier, this field is growing rapidly. In this review, I will provide a brief overview of CCM pathogenesis and function of ccm genes based on recent progress in CCM research. [BMB Reports 2016; 49(5): 255-262]

Genetics of cerebral cavernous malformations: current status and future prospects

Cerebral cavernous malformations (CCM) are vascular lesions which affect up to 0.5% of the general population, predisposing to headaches, seizures, cerebral hemorrhages and focal neurological deficits. CCM occurs in both sporadic and familial forms; familial cases follow an autosomal-dominant mode of inheritance and are caused by mutations in CCM1 (KRIT1), CCM2 (MGC4607), or CCM3 (PDCD10). Somatic mutations within the three CCM genes have been identified in CCM lesions from both sporadic and familial patients. We reviewed articles published in PubMed in English prior to March 2015 and provide an update on CCM mutations and the screening strategies used to identify them. Further, we summarize the specific clinical features related to CCM genotypes. As 5% to 15% of familial CCM cases remain genetically unexplained, we also discuss future approaches to expand understanding of the genetic architecture of CCM. Finally, we discuss possible genetic modifiers of CCM disease severity and progression. Understanding the genetic architecture of CCM is essential for an earlier diagnosis of the disease, predictive testing of at-risk patients, and design of targeted medical therapies of which there are currently none available.