Mutations within the programmed cell death 10 gene cause cerebral cavernous malformations

Vascular integrity mediated by vascular endothelial cadherin and regulated by sphingosine 1-phosphate and angiopoietin-1

Development of blood vessels is coordinated by angiogenesis and stabilization of vascular endothelial cells (ECs). The vascular network is established during embryogenesis to supply oxygen and nutrients to the tissues and organs. However, after cardiac or peripheral ischemia is caused by occlusion of the vessels, new vessels must be formed to rescue the ischemic tissues. Many angiogenic growth factors and chemokines are produced in the ischemic tissue to induce angiogenic sprouting of preexisting vessels. Branched vessels must be again restabilized to form mature vessels that deliver blood to the tissues. To this end, vascular EC-cell adhesion is tightly regulated by cell-cell adhesion molecules and extracellular stimuli that activate G protein-coupled receptors and receptor tyrosine kinases exclusively expressed on vascular ECs. This review spotlights the recent studies of vascular endothelial cadherin and of sphingosine 1-phosphate signaling and angiopoietin-Tie signaling.

Inherited cavernous malformations of the central nervous system: clinical and genetic features in 19 Swiss families

Cavernous malformations (CCMs) are benign, well-circumscribed, and mulberry-like vascular malformations that may be found in the central nervous system in up to 0.5% of the population. Cavernous malformations can be sporadic or inherited. The common symptoms are epilepsy, hemorrhages, focal neurological deficits, and headaches. However, CCMs are often asymptomatic. The familiar form is associated with three gene loci, namely 7q21-q22 (CCM1), 7p13-p15 (CCM2), and 3q25.2-q27 (CCM3) and is inherited as an autosomal dominant trait with incomplete penetrance. The CCM genes are identified as Krit 1 (CCM1), MGC4607 (CCM2), and PDCD10 (CCM3). Here, we present the clinical and genetic features of CCMs in 19 Swiss families. Furthermore, surgical aspects in such families are also discussed.

Cerebral cavernous malformations: somatic mutations in vascular endothelial cells

OBJECTIVE

Germline mutations in 3 genes have been found in familial cases of cerebral cavernous malformations (CCMs). We previously discovered somatic and germline truncating mutations in the KRIT1 gene, supporting the "2-hit" mechanism of CCM lesion formation in a single lesion. The purpose of this study was to screen for somatic, nonheritable mutations in 3 more lesions from different patients and identify the cell type(s) in which somatic mutations occur.

METHODS

Somatic mutations were sought in DNA from 3 surgically excised, fresh-frozen CCM lesions by cloning and screening polymerase chain reaction products generated from KRIT1 or PDCD10 coding regions. Laser capture microdissection was used on isolated endothelial and nonendothelial cells to determine whether somatic mutations were found in endothelial cells.

RESULTS

CCM lesions harbor somatic and germline KRIT1 mutations on different chromosomes and are therefore biallelic. Both mutations are predicted to truncate the protein. The KRIT1 somatic mutations (novel c.1800delG mutation and previously identified 34 nucleotide deletion) in CCMs from 2 different patients were found only in the vascular endothelial cells lining caverns. No obvious somatic mutations were identified in the 2 other lesions; however, the results were inconclusive, possibly owing to the technical limitations or the fact that these specimens had a small proportion of vascular endothelial cells lining pristine caverns.

CONCLUSION

The "2-hit" mechanism occurs in vascular endothelial cells lining CCM caverns from 2 patients with somatic and Hispanic-American KRIT1 germline mutations. Methods for somatic mutation detection should focus on vascular endothelial cells lining pristine caverns.

c-Myc regulates the coordinated transcription of brain disease-related PDCD10-SERPINI1 bidirectional gene pair

Two brain disease-related genes, one coding for the protease inhibitor SERPINI1 which is down-regulated in brain tumors, and the other for the PDCD10 programmed cell death gene which is often mutated in cerebral cavernous malformation, are closely adjacent in a head-to-head configuration and separated by only 851 bp on human chromosome 3q26. The 851-bp intergenic region contains a GC-rich 175-bp minimal bidirectional promoter which is essential for transcriptional activation of the two flanking genes. The oncogenic c-Myc transcription factor was identified to bind to a non-canonical E-box element (5'-CATGCG-3') of the minimal bidirectional promoter to drive both gene expressions. Methylation at the specific C nucleotide within the E-box sequence (5'-CATG(m)CG-3'), however, would severely interfere with the binding of c-Myc to the E-box. These results suggest that c-Myc plays an important role in regulating the coordinated transcription of the PDCD10-SERPINI1 bidirectional gene pair, and is possibly involved in differential expressions of these two neighboring genes in central nervous system diseases such as brain cancer.

Molecular screening test in familial forms of cerebral cavernous malformation: the impact of the Multiplex Ligation-dependent Probe Amplification approach

Object The purpose of this study was to underline the effectiveness of molecular analysis in cerebral cavernous angioma, with special attention to the familial forms. Methods Multiplex Ligation-dependent Probe Amplification analysis integrates the consecutive sequence analysis of the 3 genes (Krit1/CCM1, MGC4607/CCM2, and PDCD10/CCM3) known to be responsible for cerebral cavernous malformation lesions. Results The Multiplex Ligation-dependent Probe Amplification analysis revealed a new mutation, a heterozygous exon 9/10 deletion of Krit1, in the proband and in all affected family members. Conclusions The identification of the molecular defect allows physicians to screen family members at risk and to identify affected individuals before the onset of clinical symptoms caused by the presence of lesions.

C329X in KRIT1 is a founder mutation among CCM patients in Sardinia

Cerebral cavernous malformations (CCMs) are CNS vascular anomalies associated with seizures, headaches and hemorrhagic strokes and represent 10-20% of cerebral lesions. CCM is present in 0.1-0.5 of the population. This disorder most often occurs sporadically but may also be familial. Familial cases are inherited as a dominant trait with incomplete penetrance and are estimated to account for KRIT1 10-40% of the patients. The identification of the genes involved in such disorders allows to characterize carriers of the mutations without clear symptoms. The first gene involved in CCM1 is KRIT1. In addition to two other genes have been described: MGC4607 (CCM2) and PDCD10 (CCM3). We selected 13 patients belonging to seven Sardinian families on the basis of clinical symptoms and Magnetic Resonance results. In MGC4607 gene an undescribed exon five deletion likely producing a truncated protein was identified in one family. In two patients with clear phenotype and in three asymptomatic relatives a 4 bp deletion in exon 9 of KRIT1 gene, leading to a premature stop codon, was detected. A unique nonsense mutation (C329X) has been found in seven patients and two asymptomatic subjects belonging to four unrelated families. Haplotype analysis revealed a common origin of this mutation. These data suggest a "founder effect" in Sardinia for the C329X mutation, similar to other mutations described in different populations.

Frequency and phenotypes of cutaneous vascular malformations in a consecutive series of 417 patients with familial cerebral cavernous malformations

BACKGROUND

Familial cerebral cavernous malformations (FCCM) are vascular malformations inherited as an autosomal-dominant condition. Three genes (KRIT1/CCM1, MGC4607/CCM2, PDCD10/CCM3) have been identified so far. Extra-neurological manifestations include retinal and cutaneous vascular malformations. The cutaneous vascular malformation, which had been more specifically associated with FCCM, is hyperkeratotic cutaneous capillary venous malformation (HCCVM).

OBJECTIVES

To define the frequency of cutaneous vascular malformations in patients with FCCM, to precise their different phenotypes, and to study the association of each cutaneous vascular malformation subtype with the different three mutated CCM genes.

METHODS

Dermatological inquiry was systematically performed in a large series of consecutive FCCM patients. Cutaneous biopsies were reviewed when available. Cutaneous vascular malformations classification was based on predominant anomalous channels, using the current International Society for the Study of Vascular Anomalies classification. Molecular screening of CCM genes was performed. Results Four hundred seventeen consecutive FCCM patients from 182 unrelated families were included. 38 patients (9%) from 25 different families had cutaneous vascular malformations. In these 38 patients, cutaneous vascular malformations were classified as follows: 13 capillary malformations (CM), 15 HCCVM, 8 venous malformations (VM) and 2 unclassified lesions. All patients (92%), but one with CM had a KRIT1/CCM1 mutation. The last patient had no detectable mutation. All of the 15 patients with HCCVM had a KRIT1/CCM1 mutation; 86.7% of cutaneous vascular malformation patients (33 of 38) had a KRIT1/CCM1 mutation.

CONCLUSION

Cutaneous vascular malformations are seen in 9% of FCCM patients. Three distinct major cutaneous vascular malformations phenotypes were identified: HCCVM (39%), CM (34%) and VM (21%). CCM1 is the most frequently mutated gene in cutaneous vascular malformations-FCCM patients.

From germline towards somatic mutations in the pathophysiology of vascular anomalies

The localized structural abnormalities that arise during vasculogenesis, angiogenesis and lymphangiogenesis, the developmental processes which give rise to the adult vasculature, are collectively termed vascular anomalies. The last 2 years have seen an explosion of studies that underscore paradominant inheritance, the combination of inherited changes with somatic second-hits to the same genes, as underlying rare familial forms. Moreover, local, somatic genetic defects that cause some of the common sporadic forms of these malformations have been unraveled. This highlights the importance of assessing for tissue-based genetic changes, especially acquired genetic changes, as possible pathophysiological causes, which have been largely overlooked except in the area of cancer research. Large-scale somatic screens will therefore be essential in uncovering the nature and prevalence of such changes, and their downstream effects. The identification of disease genes combined with exhaustive, precise clinical delineations of the entire spectra of associated phenotypes guides better management and genetic counseling. Such a synthesis of information on functional and phenotypic effects will enable us to make and use animal models to test less invasive, targeted, perhaps locally administered, biological therapies.

Genetics, epigenetics and pharmaco-(epi)genomics in angiogenesis

Angiogenesis is controlled by a balance between pro- and anti-angiogenic factors. Studies in mice and human beings have shown that this balance, as well as the general sensitivity of the endothelium to these factors, is genetically pre-determined. In an effort to dissect this genetic basis, different types of genetic variability have emerged: mutations and translocations in angiogenic factors have been linked to several vascular malformations and haemangiomas, whereas SNPs have been associated with complex genetic disorders, such as cancer, neurodegeneration and diabetes. In addition, copy number alterations of angiogenic factors have been reported in several tumours. More recently, epigenetic changes caused by aberrant DNA methylation or histone acetylation of anti-angiogenic molecules have been shown to determine angiogenesis as well. Initial studies also revealed a crucial role for microRNAs in stimulating or reducing angiogenesis. So far, most of these genetic studies have focused on tumour angiogenesis, but future research is expected to improve our understanding of how genetic variants determine angiogenesis in other diseases. Importantly, these genetic insights might also be of important clinical relevance for the use of anti-angiogenic strategies in cancer or macular degeneration.

A novel deletion mutation in CCM1 gene (krit1) is detected in a Chinese family with cerebral cavernous malformations

Cerebral Cavernous Malformations (CCM) are vascular malformations that are mostly located in the central nervous system (CNS) and occasionally within the skin and retina, which are classified into three types (CCM1, CCM2 and CCM3) by being located at different loci on chromosomes. At present, CCM1 (7q21), CCM2 (7p13-p15) and CCM3 (3q25.2-q27) are respectively linked to krit1 (Krev interaction trapped gene 1), MGC4607 and PDCD10 (programmed cell death 10). In this work, we identified a novel "GTA" deletion mutation at the acceptor splicing site of intron9/exon10 on krit1. The mutation results in an abnormally spliced protein by creating a premature termination code at the 23rd amino acid downstream from the sequence alteration. Our results are consistent with previous research on krit1 mutations and confirm the conclusion that KRIT1 haploinsufficiency may be the underlying mechanism of CCM1.

Apoptotic functions of PDCD10/CCM3, the gene mutated in cerebral cavernous malformation 3

BACKGROUND AND PURPOSE

Mutations in the Programmed Cell Death 10 (PDCD10) gene cause autosomal dominant familial cerebral cavernous malformations (CCM3). To date, little is known about the function of this gene and its role in disease pathogenesis.

METHODS

We examined the effects of overexpression of wild-type and 2 human disease-causing variants of PDCD10 on cell death using 3 different methods (TUNEL and MTT assays and caspase-3 activation). We analyzed expression of CCM3, activated caspase-3, and p38 in endothelial cell lines using the serum deprivation model of apoptosis induction. Finally, we assayed the effects of siRNA-mediated inhibition of endogenous PDCD10 expression on cell death in endothelial cell cultures.

RESULTS

Overexpression of wild-type CCM3, but not disease-linked mutant forms, induced apoptosis as confirmed by TUNEL and increased levels of activated caspase-3. Serum starvation of endothelial cells, an inducer of apoptosis, led to increased expression of CCM3 and activation of p38 and ultimately activated caspase-3. siRNA-mediated inhibition of CCM3 expression resulted in decreased levels of p38 and activated caspase-3, and decreased cell death.

CONCLUSIONS

CCM3 is both necessary and sufficient to induce apoptosis in vitro in well-defined cell culture systems. Even though it is currently unclear whether this effect on apoptosis is direct or indirect through modulation of cell cycle, these results led to the novel hypothesis that CCM lesions may form as a consequence of aberrant apoptosis, potentially altering the balance between the endothelium and neural cells within the neurovascular unit.

De novo formation of cerebral cavernous malformation in a patient with intractable epilepsy: case report and review

AIM

The exact origin and process of development of cerebral cavernous malformations (CCMs) is currently unknown. In this article, the authors present de novo CCM formation in a patient with intractable epilepsy and discuss the pathogenesis of CCM in light of several current theories.

CASE DESCRIPTION

A 34-year-old man presented with a 10-year history of intractable seizures. His neurological examination was normal, and the initial magnetic resonance imaging (MRI) was suggestive of right mesial temporal sclerosis (MTS). Follow-up MRI study showed development of CCM in the right frontal region. Subsequently, invasive monitoring revealed right temporal seizure source, prompting right temporal lobectomy that resulted in abolition of epilepsy. Histological diagnosis of CCM was confirmed after the lesion was removed in a separate surgery. The patient recovered to normal lifestyle without any complications.

CONCLUSION

This appears to be a first documented case of de novo CCM formation in the setting of intractable epilepsy with ipsilateral MTS. Since the possibility of lesion development cannot be ruled out based on clinical examination, updated imaging and thorough neurophysiological workup are needed for successful treatment of patients with intractable epilepsy.

Tissue-specific conditional CCM2 knockout mice establish the essential role of endothelial CCM2 in angiogenesis: implications for human cerebral cavernous malformations

Cerebral cavernous malformations (CCM) are vascular malformations of the brain that lead to cerebral hemorrhages. In 20% of CCM patients, this results from an autosomal dominant condition caused by loss-of-function mutations in one of the three CCM genes. High expression levels of the CCM genes in the neuroepithelium indicate that CCM lesions might be caused by a loss of function of these genes in neural cells rather than in vascular cells. However, their in vivo function, particularly during cerebral angiogenesis, is totally unknown. We developed mice with constitutive and tissue-specific CCM2 deletions to investigate CCM2 function in vivo. Constitutive deletion of CCM2 leads to early embryonic death. Deletion of CCM2 from neuroglial precursor cells does not lead to cerebrovascular defects, whereas CCM2 is required in endothelial cells for proper vascular development. Deletion of CCM2 from endothelial cells severely affects angiogenesis, leading to morphogenic defects in the major arterial and venous blood vessels and in the heart, and results in embryonic lethality at mid-gestation. These findings establish the essential role of endothelial CCM2 for proper vascular development and strongly suggest that the endothelial cell is the primary target in the cascade of events leading from CCM2 mutations to CCM cerebrovascular lesions.

Cutaneous venous malformations in familial cerebral cavernomatosis caused by KRIT1 gene mutations

BACKGROUND

Cerebral cavernous malformations (CCMs) are vascular lesions characterized by abnormally enlarged capillary cavities without intervening brain parenchyma. Although often asymptomatic, seizures, cerebral haemorrhages and focal neurological deficits are well-documented complications. Mutations in the CCM1 (7q21-22), CCM2 (7p13-15) and CCM3 (3q25.2-27) genes have been identified in familial CCM. In rare instances, the association of congenital hyperkeratotic cutaneous capillary-venous malformations (HCCVMs) with CCM1 has been reported.

OBSERVATIONS

We studied 6 members of a family with CCMs. Four members of the family developed late-onset multiple, tiny, bluish, soft, cutaneous papules, mainly located on the face, arm and abdominal area, corresponding histologically to venous malformations. A splice donor site mutation in intron 4 (c. 1146 + 1 G-->A) in the CCM1 gene was identified.

CONCLUSIONS

Our findings suggest that mutations in the KRIT1 gene may cause phenotypically heterogeneous cutaneous vascular lesions other than those previously described as HCCVMs.

Endogenous endothelial cell signaling systems maintain vascular stability

The function of the endothelium is to provide a network to allow delivery of oxygen and nutrients to tissues throughout the body. This network comprises adjacent endothelial cells that utilize adherens junction proteins such as vascular endothelial cadherin (VE-cadherin) to maintain the appropriate level of vascular permeability. The disruption of VE-cadherin interactions during pathologic settings can lead to excessive vascular leak with adverse effects. Endogenous cell signaling systems have been defined, which help to maintain the proper level of vascular stability. Perhaps the best described system is Angiopoietin-1 (Ang-1). Ang-1 acting through its receptor Tie2 generates a well-described set of signaling events ultimately leading to enhanced vascular stability. In this review, we will focus on what is known about additional endogenous cell signaling systems that stabilize the vasculature, and using Ang-1/Tie2 as a model, we will address where our understanding of these additional systems is lacking.

The cerebral cavernous malformation signaling pathway promotes vascular integrity via Rho GTPases

Cerebral cavernous malformation (CCM) is a common vascular dysplasia that affects both systemic and CNS blood vessels. Loss of function mutations in the CCM2 gene cause CCM. Here we show that targeted disruption of Ccm2 in mice results in failed lumen formation and early embryonic death through an endothelial cell autonomous mechanism. We demonstrate that CCM2 regulates endothelial cytoskeletal architecture, cell-cell interactions and lumen formation. Heterozygosity at Ccm2, a genotype equivalent to human CCM, results in impaired endothelial barrier function. Because our biochemical studies indicate that loss of CCM2 results in activation of RHOA GTPase, we rescued the cellular phenotype and barrier function in heterozygous mice using simvastatin, a drug known to inhibit Rho GTPases. These data offer the prospect for pharmacologic treatment of a human vascular dysplasia using a widely available and safe drug.

Regulation of cardiovascular development and integrity by the heart of glass-cerebral cavernous malformation protein pathway

Cerebral cavernous malformations (CCMs) are human vascular malformations caused by mutations in three genes of unknown function, KRIT1, CCM2 and PDCD10. Here we show that the HEG1 receptor, linked to CCM genes in zebrafish, is selectively expressed in endothelial cells and that Heg1^-/- mice exhibit defective integrity of the heart, blood vessels and lymphatic vessels. In contrast, Heg1^-/-;Ccm2^+/lacZ and Ccm2^lacZ/lacZ mice die early in development due to a failure of nascent endothelial cells to associate into patent vessels, a phenotype shared by deficient zebrafish embryos and reproduced by deficient endothelial cells ex vivo. These cardiovascular defects are associated with abnormal endothelial junctions like those observed in human CCMs, and biochemical and cellular imaging studies identify a cell autonomous pathway in which HEG1 receptors couple to KRIT1 at cell junctions. These studies identify HEG1-CCM signaling as a critical regulator of cardiovascular organ formation and integrity.

A PP2A phosphatase high density interaction network identifies a novel striatin-interacting phosphatase and kinase complex linked to the cerebral cavernous malformation 3 (CCM3) protein

The serine/threonine protein phosphatases are targeted to specific subcellular locations and substrates in part via interactions with a wide variety of regulatory proteins. Understanding these interactions is thus critical to understanding phosphatase function. Using an iterative affinity purification/mass spectrometry approach, we generated a high density interaction map surrounding the protein phosphatase 2A catalytic subunit. This approach recapitulated the assembly of the PP2A catalytic subunit into many different trimeric complexes but also revealed several new protein-protein interactions. Here we define a novel large multiprotein assembly, referred to as the striatin-interacting phosphatase and kinase (STRIPAK) complex. STRIPAK contains the PP2A catalytic (PP2Ac) and scaffolding (PP2A A) subunits, the striatins (PP2A regulatory B''' subunits), the striatin-associated protein Mob3, the novel proteins STRIP1 and STRIP2 (formerly FAM40A and FAM40B), the cerebral cavernous malformation 3 (CCM3) protein, and members of the germinal center kinase III family of Ste20 kinases. Although the function of the CCM3 protein is unknown, the CCM3 gene is mutated in familial cerebral cavernous malformations, a condition associated with seizures and strokes. Our proteomics survey indicates that a large portion of the CCM3 protein resides within the STRIPAK complex, opening the way for further studies of CCM3 biology. The STRIPAK assembly establishes mutually exclusive interactions with either the CTTNBP2 proteins (which interact with the cytoskeletal protein cortactin) or a second subcomplex consisting of the sarcolemmal membrane-associated protein (SLMAP) and the related coiled-coil proteins suppressor of IKKepsilon (SIKE) and FGFR1OP2. We have thus identified several novel PP2A-containing protein complexes, including a large assembly linking kinases and phosphatases to a gene mutated in human disease.

Biallelic somatic and germline mutations in cerebral cavernous malformations (CCMs): evidence for a two-hit mechanism of CCM pathogenesis

Cerebral cavernous malformations (CCMs) are vascular anomalies of the central nervous system, comprising dilated blood-filled capillaries lacking structural support. The lesions are prone to rupture, resulting in seizures or hemorrhagic stroke. CCM can occur sporadically, manifesting as solitary lesions, but also in families, where multiple lesions generally occur. Familial cases follow autosomal-dominant inheritance due to mutations in one of three genes, CCM1/KRIT1, CCM2/malcavernin or CCM3/PDCD10. The difference in lesion burden between familial and sporadic CCM, combined with limited molecular data, suggests that CCM pathogenesis may follow a two-hit molecular mechanism, similar to that seen for tumor suppressor genes. In this study, we investigate the two-hit hypothesis for CCM pathogenesis. Through repeated cycles of amplification, subcloning and sequencing of multiple clones per amplicon, we identify somatic mutations that are otherwise invisible by direct sequencing of the bulk amplicon. Biallelic germline and somatic mutations were identified in CCM lesions from all three forms of inherited CCMs. The somatic mutations are found only in a subset of the endothelial cells lining the cavernous vessels and not in interstitial lesion cells. These data suggest that CCM lesion genesis requires complete loss of function for one of the CCM genes. Although widely expressed in the different cell types of the brain, these data also suggest a unique role for the CCM proteins in endothelial cell biology.

Combinatorial interaction between CCM pathway genes precipitates hemorrhagic stroke

Intracranial hemorrhage (ICH) is a particularly severe form of stroke whose etiology remains poorly understood, with a highly variable appearance and onset of the disease (Felbor et al., 2006; Frizzell, 2005; Lucas et al., 2003). In humans, mutations in any one of three CCM genes causes an autosomal dominant genetic ICH disorder characterized by cerebral cavernous malformations (CCM). Recent evidence highlighting multiple interactions between the three CCM gene products and other proteins regulating endothelial junctional integrity suggests that minor deficits in these other proteins could potentially predispose to, or help to initiate, CCM, and that combinations of otherwise silent genetic deficits in both the CCM and interacting proteins might explain some of the variability in penetrance and expressivity of human ICH disorders. Here, we test this idea by combined knockdown of CCM pathway genes in zebrafish. Reducing the function of rap1b, which encodes a Ras GTPase effector protein for CCM1/Krit1, disrupts endothelial junctions in vivo and in vitro, showing it is a crucial player in the CCM pathway. Importantly, a minor reduction of Rap1b in combination with similar reductions in the products of other CCM pathway genes results in a high incidence of ICH. These findings support the idea that minor polygenic deficits in the CCM pathway can strongly synergize to initiate ICH.

Ancestry and evolution of a secretory pathway serpin

BACKGROUND

The serpin (serine protease inhibitor) superfamily constitutes a class of functionally highly diverse proteins usually encompassing several dozens of paralogs in mammals. Though phylogenetic classification of vertebrate serpins into six groups based on gene organisation is well established, the evolutionary roots beyond the fish/tetrapod split are unresolved. The aim of this study was to elucidate the phylogenetic relationships of serpins involved in surveying the secretory pathway routes against uncontrolled proteolytic activity.

RESULTS

Here, rare genomic characters are used to show that orthologs of neuroserpin, a prominent representative of vertebrate group 3 serpin genes, exist in early diverging deuterostomes and probably also in cnidarians, indicating that the origin of a mammalian serpin can be traced back far in the history of eumetazoans. A C-terminal address code assigning association with secretory pathway organelles is present in all neuroserpin orthologs, suggesting that supervision of cellular export/import routes by antiproteolytic serpins is an ancient trait, though subtle functional and compartmental specialisations have developed during their evolution. The results also suggest that massive changes in the exon-intron organisation of serpin genes have occurred along the lineage leading to vertebrate neuroserpin, in contrast with the immediately adjacent PDCD10 gene that is linked to its neighbour at least since divergence of echinoderms. The intron distribution pattern of closely adjacent and co-regulated genes thus may experience quite different fates during evolution of metazoans.

CONCLUSION

This study demonstrates that the analysis of microsynteny and other rare characters can provide insight into the intricate family history of metazoan serpins. Serpins with the capacity to defend the main cellular export/import routes against uncontrolled endogenous and/or foreign proteolytic activity represent an ancient trait in eukaryotes that has been maintained continuously in metazoans though subtle changes affecting function and subcellular location have evolved. It is shown that the intron distribution pattern of neuroserpin gene orthologs has undergone substantial rearrangements during metazoan evolution.

Novel CCM1, CCM2, and CCM3 mutations in patients with cerebral cavernous malformations: in-frame deletion in CCM2 prevents formation of a CCM1/CCM2/CCM3 protein complex

Cerebral cavernous malformations (CCM) are prevalent cerebrovascular lesions predisposing to chronic headaches, epilepsy, and hemorrhagic stroke. Using a combination of direct sequencing and MLPA analyses, we identified 15 novel and eight previously published CCM1 (KRIT1), CCM2, and CCM3 (PDCD10) mutations. The mutation detection rate was >90% for familial cases and >60% for isolated cases with multiple malformations. Splice site mutations constituted almost 20% of all CCM mutations identified. One of these proved to be a de novo mutation of the most 3' acceptor splice site of the CCM1 gene resulting in retention of intron 19. A further mutation affected the 3' splice site of CCM2 intron 2 leading to cryptic splice site utilization in both CCM2 and its transcript variant lacking exon 2. With the exception of one in-frame deletion of CCM2 exon 2, which corresponds to the naturally occurring splice variant of CCM2 on the RNA level and is predicted to result in the omission of 58 amino acids (CCM2:p.P11_K68del), all mutations lead to the introduction of premature stop codons. To gain insight into the likely mechanisms underlying the only known CCM2 in-frame deletion, we analyzed the functional consequences of loss of CCM2 exon 2. The CCM2:p.P11_K68del protein could be expressed in cell culture and complexed with CCM3. However, its ability to interact with CCM1 and to form a CCM1/CCM2/CCM3 complex was lost. These data are in agreement with a loss-of-function mechanism for CCM mutations, uncover an N-terminal CCM2 domain required for CCM1 binding, and demonstrate full-length CCM2 as the essential core protein in the CCM1/CCM2/CCM3 complex.

A novel syndrome of cerebral cavernous malformation and Greig cephalopolysyndactyly. Laboratory investigation

OBJECT

Greig cephalopolysyndactyly syndrome (GCPS) is one of a spectrum of overlapping clinical syndromes resulting from mutations in the gene GLI3 on chromosome 7p. Cerebral cavernous malformation (CCM) is caused by mutations in three distinct genes, including Malcavernin (CCM2), which also maps to chromosome 7p and is located 2.8 Mbp from GLI3. The authors describe a new syndrome that combines the vascular lesions characteristic of CCM with the hallmarks of GCPS, including polydactyly, hypertelorism, and developmental delay.

METHODS

The authors used high-resolution array-based comparative genome hybridization (CGH) analysis to characterize the 3 million-bp deletion on chromosome 7 that accounts for this novel clinical presentation. A 4-year-old girl presented with polydactyly, hypertelorism, and developmental delay and was also found to have multiple CCMs after suffering a seizure. RESULTS. Genetic analysis using array-based CGH revealed a deletion affecting multiple genes in the 7p14-13 locus, the interval that includes both CCM2 and GLI3. Quantitative real-time polymerase chain reaction (RT-PCR) on genomic DNA confirmed this genomic lesion.

CONCLUSIONS

A novel syndrome, combining features of CCM and GCPS, can be added to the group of entities that result from deleterious genetic variants involving GLI3, including GCPS, acrocallosal syndrome, Pallister-Hall syndrome, and contiguous gene syndrome. The deletion responsible for this new entity can be easily detected using either array-based chromosomal analysis or quantitative RT-PCR.

Different spectra of genomic deletions within the CCM genes between Italian and American CCM patient cohorts

Cerebral cavernous malformations (CCMs) are vascular abnormalities of the brain that can result in hemorrhagic stroke and seizures. Familial forms of CCM are inherited in an autosomal-dominant fashion, and three CCM genes have been identified. We recently determined that large genomic deletions in the CCM2 gene represent 22% of mutations in a large CCM cohort from the USA. In particular, a 77.6 kb deletion spanning CCM2 exons 2-10 displays an identical recombination event in eight CCM probands/families and appears to be common in the US population. In the current study, we report the identification of six additional probands/families from the USA with this same large deletion. Haplotype analysis strongly suggests that this common deletion derives from an ancestral founder. We also examined an Italian CCM cohort consisting of 24 probands/families who tested negative for mutations in the CCM1, CCM2, and CCM3 genes by DNA sequence analysis. Surprisingly, the common CCM2 deletion spanning exons 2-10 is not present in this population. Further analysis of the Italian cohort by multiplex ligation-dependent probe analysis identified a total of ten deletions and one duplication. The overall spectrum of genomic rearrangements in the Italian cohort is thus quite different than that seen in a US cohort. These results suggest that there are elements within all three of the CCM genes that predispose them to large deletion/duplication events but that the common deletion spanning CCM2 exons 2-10 appears to be specific to the US population due to a founder effect.

Identification of an Arg35X mutation in the PDCD10 gene in a patient with cerebral and multiple spinal cavernous malformations

Although cerebral cavernous malformations (CCMs) are not uncommon, the concurrent finding of cavernous malformations (CMs) both in the brain and spinal cord is quite rare. Furthermore, multiple spinal cord CMs are extremely rare with only a few cases being reported thus far. Recently, we encountered a 33-year-old Korean male with both CCM and multiple spinal intramedullary CMs. The patient complained of seizure and right chest paresthesia. The lesions were located throughout the neuraxis including the cerebral hemisphere, brain stem, and cervical and thoracic spinal cords. Molecular analysis of the KRIT1 (CCM1), CCM2, and PDCD10 (CCM3) genes identified a heterozygous nonsense mutation (c.103C>T; Arg35X) in the PDCD10 gene, which was reported previously in a CCM family. The patient denied a family history, however, his daughter had an identical mutation, but was asymptomatic. Three months later, after identifying the mutation in the father and the daughter, the daughter presented with seizure. To the best of our knowledge, this is the first report of an association between a mutation in the PDCD10 gene and spinal CMs.

Susceptibility-weighted imaging for the evaluation of patients with familial cerebral cavernous malformations: a comparison with t2-weighted fast spin-echo and gradient-echo sequences

BACKGROUND AND PURPOSE

The T2-weighted gradient-echo (GRE) imaging is currently the gold standard MR imaging sequence for the evaluation of patients with cerebral cavernous malformation (CCM) lesions. We aimed to compare the sensitivity of susceptibility-weighted imaging (SWI) with T2-weighted fast spin-echo (FSE) and GRE imaging in assigning the number of CCM lesions in patients with the familial form of the disease.

MATERIALS AND METHODS

We studied 15 patients (8 men, 7 women; mean age, 34 years) with familial CCM. All patients underwent MR imaging with the following sequences: T1-weighted spin echo, T2-weighted FSE, T2-weighted GRE, and SWI. Two neuroradiologists read the images regarding the number of lesions seen on each sequence. The final decisions were reached by consensus. The number of lesions on the different sequences was compared with analysis of variance, followed by a nonparametric Wilcoxon matched-pairs signed rank test.

RESULTS

The number of lesions was higher on T2-weighted GRE than on T2-weighted FSE (P = .001). In addition, more lesions were seen on SWI than on T2-weighted GRE (P = .001) and FSE (P = .001) sequences.

CONCLUSION

The sensitivity of SWI in assigning the number of CCM lesions in patients with the familial form of the disease is significantly higher than that of T2-weighted FSE and GRE sequences.

[Familial forms of central nervous system cavernomas: from recognition to gene therapy]

Ten percent of all cavernomas are familial forms. 300 independent families have been identified in France since 1995. Clinical manifestations are more frequent in familial (50%) than in sporadic forms (5%). The symptoms are the same in both forms: epilepsy, hemorrhages, neurological focal deficits and headache, but hemorrhages are more frequent and the age of revelation is younger, before 30 years. It is also frequent to observe extraneural location, cutaneous and retinal. On MRI, four types of lesional aspects were described and lesions are multiple in all cases with numerous "de novo" cavernomas. The prognostic does not depend on the number of lesions, but on their topography, especially in the brain stem. Familial forms may be considered not only as a neurological but as a systemic disease for which global management with a genetic counseling should be considered. Gene therapy is not today available, but perhaps in the future.

[Contribution of molecular genetics in cavernous angiomas]

In 20% of cases, central nervous system cavernomas are an autosomal dominant familial disease. In these cases, lesions are multiple and one or more parents suffer of the same affection. Three genes (CCM 1, 2 and 3) have been identified since 1999, two on chromosome 7 (one on each arm) and one on the short arm of chromosome 3. The role of these genes in normal cerebral angiogenesis is unknown today. In clinical practice, molecular tests may be useful in some situations: 1) in sporadic cases with a unique lesion, molecular test should not be performed since these cases are not genetic; 2) in patients with multiple lesions who have an affected relative, the genetic nature of the disease is obvious and molecular tests are useful only for genetic counseling; 3) in sporadic cases with multiple lesions and no known affected relative, molecular tests can establish the genetic nature of the disease and be useful for genetic counseling.

Proteomic identification of the cerebral cavernous malformation signaling complex

Cerebral cavernous malformations (CCM) are sporadic or inherited vascular lesions of the central nervous system characterized by dilated, thin-walled, leaky vessels. Linkage studies have mapped autosomal dominant mutations to three loci: ccm1 (KRIT1), ccm2 (OSM), and ccm3 (PDCD10). All three proteins appear to be scaffolds or adaptor proteins, as no enzymatic function can be attributed to them. Our previous results demonstrated that OSM is a scaffold for the assembly of the GTPase Rac and the MAPK kinase kinase MEKK3, for the hyperosmotic stress-dependent activation of p38 MAPK. Herein, we show that the three CCM proteins are members of a larger signaling complex. To define this complex, epitope-tagged wild type OSM or OSM harboring the mutation of F217-->A, which renders the OSM phosphotyrosine binding (PTB) domain unable to bind KRIT1, were stably introduced into RAW264.7 mouse macrophages. FLAG-OSM or FLAG-OSMF217A and the associated complex members were purified by immunoprecipitation using anti-FLAG antibody. OSM binding partners were identified by gel-based methods combined with electrospray ionization-MS or by multidimensional protein identification technology (MudPIT). Previously identified proteins that associate with OSM including KRIT1, MEKK3, Rac, and the KRIT1-binding protein ICAP-1 were found in the immunoprecipitates. In addition, we show for the first time that PDCD10 binds to OSM and is found in cellular CCM complexes. Other prominent proteins that bound the CCM complex include EF1A1, RIN2, and tubulin, with each interaction disrupted with the OSMF217A mutant protein. We further show that PDCD10 binds phosphatidylinositol di- and triphosphates and OSM binds phosphatidylinositol monophosphates. The findings define the targeting of the CCM complex to membranes and to proteins regulating trafficking and the cytoskeleton.

A Marfan syndrome gene expression phenotype in cultured skin fibroblasts

BACKGROUND

Marfan syndrome (MFS) is a heritable connective tissue disorder caused by mutations in the fibrillin-1 gene. This syndrome constitutes a significant identifiable subtype of aortic aneurysmal disease, accounting for over 5% of ascending and thoracic aortic aneurysms.

RESULTS

We used spotted membrane DNA macroarrays to identify genes whose altered expression levels may contribute to the phenotype of the disease. Our analysis of 4132 genes identified a subset with significant expression differences between skin fibroblast cultures from unaffected controls versus cultures from affected individuals with known fibrillin-1 mutations. Subsequently, 10 genes were chosen for validation by quantitative RT-PCR.

CONCLUSION

Differential expression of many of the validated genes was associated with MFS samples when an additional group of unaffected and MFS affected subjects were analyzed (p-value < 3 x 10-6 under the null hypothesis that expression levels in cultured fibroblasts are unaffected by MFS status). An unexpected observation was the range of individual gene expression. In unaffected control subjects, expression ranges exceeding 10 fold were seen in many of the genes selected for qRT-PCR validation. The variation in expression in the MFS affected subjects was even greater.

pak2a mutations cause cerebral hemorrhage in redhead zebrafish

The zebrafish is a powerful model for studying vascular development, demonstrating remarkable conservation of this process with mammals. Here, we identify a zebrafish mutant, redhead (rhd(mi149)), that exhibits embryonic CNS hemorrhage with intact gross development of the vasculature and normal hemostatic function. We show that the rhd phenotype is caused by a hypomorphic mutation in p21-activated kinase 2a (pak2a). PAK2 is a kinase that acts downstream of the Rho-family GTPases CDC42 and RAC and has been implicated in angiogenesis, regulation of cytoskeletal structure, and endothelial cell migration and contractility among other functions. Correction of the Pak2a-deficient phenotype by Pak2a overexpression depends on kinase activity, implicating Pak2 signaling in the maintenance of vascular integrity. Rescue by an endothelial-specific transgene further suggests that the hemorrhage seen in Pak2a deficiency is the result of an autonomous endothelial cell defect. Reduced expression of another PAK2 ortholog, pak2b, in Pak2a-deficient embryos results in a more severe hemorrhagic phenotype, consistent with partially overlapping functions for these two orthologs. These data provide in vivo evidence for a critical function of Pak2 in vascular integrity and demonstrate a severe disease phenotype resulting from loss of Pak2 function.

CCM3 interacts with CCM2 indicating common pathogenesis for cerebral cavernous malformations

Individuals carrying a mutation in one of the three cerebral cavernous malformation genes (CCM1/KRIT1, CCM2, CCM3) cannot be clinically distinguished, raising the possibility that they act within common molecular pathways. In this study, we demonstrate that CCM3 (PDCD10) coprecipitates and colocalizes with CCM2. We also show that CCM3 directly binds to serine/threonine kinase 25 (STK25, YSK1, SOK1) and the phosphatase domain of Fas-associated phosphatase-1 (FAP-1, PTPN13, PTP-Bas, PTP-BL). CCM3 is phosphorylated by STK25 but not by its other Yeast-Two hybrid interactor STK24, whereas the C-terminal catalytic domain of FAP-1 dephosphorylates CCM3. Finally, our experiments reveal that STK25 forms a protein complex with CCM2. Thus, our data link two proteins of unknown function, CCM3 and STK25, with CCM2, which is part of signaling pathways essential for vascular development and CCM pathogenesis.

The natural history of conservatively managed symptomatic intramedullary spinal cord cavernomas

OBJECTIVE

The presentation and natural history of untreated, symptomatic intramedullary spinal cavernomas at our institution were analyzed. The objective is to provide additional information regarding the natural history of conservatively managed, symptomatic, intramedullary spinal cord cavernous malformations.

METHODS

The medical records of patients treated in our institution between 1989 and 2002 were reviewed to identify those with intramedullary cavernomas. The medical, radiological, surgical, and pathological records from these patients were retrospectively reviewed and analyzed.

RESULTS

Fourteen patients were included in the study. The mean age at presentation was 42 years. Four lesions (29%) were located in the cervical region and 10 lesions (71%) were present in the thoracolumbar spinal cord. All patients were symptomatic at the time of presentation. In this cohort of 14 patients, 10 patients (71%) were conservatively managed. For these patients, the mean duration of symptoms before presentation was 10 months. The mean duration of follow-up from the time of presentation was 80 months. The median McCormick grade for conservatively treated patients at presentation was II. During this period, none of the conservatively managed patients had an acute intramedullary bleed. In nine patients, the McCormick grade at the last follow-up evaluation was the same as or better than their score at presentation. Four patients (29%) were treated surgically. The mean duration of symptoms before presentation was 33 months. The mean duration of follow-up from the time of presentation was 42 months. In two surgical patients, the McCormick grade at the last follow-up evaluation remained unchanged compared with their score at presentation, whereas the McCormick grade improved in one patient and deteriorated in another patient.

CONCLUSION

This cohort of conservatively managed patients with symptomatic, intramedullary spinal cord cavernomas was clinically stable throughout the follow-up period. In this series, patients harboring symptomatic spinal cord cavernous malformation did not have significant, permanent neurological decline during the follow-up period when treated with the conservative approach of observation. This data provides additional information for determining the appropriate treatment strategy for patients with intramedullary spinal cavernomas.

Anatomie pathologique des cavernomes du système nerveux central

Central nervous system cavernomas are vascular malformations, which occur in two circumstances: sporadic forms and familial autosomal dominant forms. The lesion consists of enlarged, closely packed vessels without interposition of brain parenchyma, surrounded by hemosiderin and gliosis, calcified in few cases. In 80% of sporadic forms the lesion is unique, multiple lesions are rare (median: 4). In familial forms the lesions are always multiple. Cavernomas are often associated with other vascular malformations, especially with venous developmental anomalies. The size of cavernomas is variable from 1 mm to several centimeters. About 70% of cases are supratentorial and 30% in the posterior fossa, particularly in the brain stem. Macroscopic and histopathological findings are typical and the diagnostic is generally easy.

PDCD10 interacts with Ste20-related kinase MST4 to promote cell growth and transformation via modulation of the ERK pathway

PDCD10 (programmed cell death 10, TFAR15), a novel protein associated with cell apoptosis has been recently implicated in mutations associated with Cerebral Cavernous Malformations (CCM). Yeast two-hybrid screening revealed that PDCD10 interacts with MST4, a member of Ste20-related kinases. This interaction was confirmed by coimmunoprecipitation and colocalization assays in mammalian cells. Furthermore, the co-overexpression of PDCD10 and MST4 promoted cell proliferation and transformation via modulation of the extracellular signal-regulated kinase (ERK) pathway. Potent short interfering RNAs (siRNAs) against PDCD10 (siPDCD10) and MST4 (siMST4) were designed to specifically inhibit the expression of PDCD10 and MST4 mRNA, respectively. The induction of siPDCD10 or siMST4 resulted in decreased expression of endogenous PDCD10 or MST4, which was accompanied by reduced ERK activity and attenuated cell growth and anchorage-independent growth. On the other hand, siMST4 had similar effects in PDCD10-overexpressed cells. And more importantly, we confirmed that either overexpressing or endogenous PDCD10 can increase the MST4 kinase activity in vitro. Our results demonstrated that PDCD10 modulation of ERK signaling was mediated by MST4, and PDCD10 could be a regulatory adaptor necessary for MST4 function, suggesting a link between cerebral cavernous malformation pathogenesis and the ERK-MAPK cascade via PDCD10/MST4.

Genetics of cavernous angiomas

Cerebral cavernous malformations (CCM) are vascular malformations that can occur as a sporadic or a familial autosomal dominant disorder. Clinical and cerebral MRI data on large series of patients with a genetic form of the disease are now available. In addition, three CCM genes have been identified: CCM1/KRIT1, CCM2/MGC4607, and CCM3/PDCD10. These recent developments in clinical and molecular genetics have given us useful information about clinical care and genetic counselling and have broadened our understanding of the mechanisms of this disorder.

Study of cerebral cavernous malformation in Spain and Portugal: high prevalence of a 14 bp deletion in exon 5 of MGC4607 (CCM2 gene)

OBJECTIVE

We aimed to study clinical, radiological and molecular genetic features of patients with cerebral cavernous malformations (CCMs) from the Iberian Peninsula.

METHODS

We screened Krit1(CCM1), MGC4607(CCM2), and PDCD10(CCM3) by systematic SSCP and direct sequencing of coding exons in 48 nuclear families and 30 sporadic cases of CCM from Spain and Portugal.

RESULTS

Screening of CCM patients detected nine different mutations in 19 families. We found four new mutations in Krit1. Three of them were caused by either a small insertion or deletion, which lead to frameshift and premature termination codons. We also found a missense L308H mutation located in a highly conserved sequence within the ankyrin domain of Krit1. In CCM2, we found a redundant 14 bp deletion in exon 5 of MGC4607 which predicts a truncated protein at residue 230. We did not find mutations in CCM3.

CONCLUSIONS

Finding that the 14 bp deletion was present in eleven families from the Iberian Peninsula indicates a high prevalence of this mutation. This redundant CCM2 mutation is worth considering in molecular diagnosis and genetic counselling of cerebral cavernous malformations.

Spectrum of genotype and clinical manifestations in cerebral cavernous malformations

OBJECTIVE

Cerebral cavernous malformations (CCMs) are focal dysmorphic blood vessel anomalies predisposing individuals to hemorrhagic stroke and epilepsy. CCMs are sporadic or inherited as autosomal dominant disease with three known genes. The hypothesis that genetic heterogeneity would account for the remarkable variability in CCM manifestations was tested.

METHODS

CCM cases were prospectively enrolled. Germline CCM1 gene mutations were sought in 89 CCM samples. Associations with clinical manifestations and lesion characteristics were made among 41 symptomatic familial cases, including one cohort of 26 cases with CCM1 mutations and a second cohort of 15 cases without identifiable CCM1 mutations. The 15 cases were screened for CCM2 and CCM3 mutations.

RESULTS

CCM1 mutations were found in 34 out of 50 subjects with familial disease and in none of 39 sporadic CCM cases. CCM2 and CCM3 mutations were found in three out of 10 families screened without CCM1 mutations. Clinical manifestations in 22 Hispanic-American cases with identical CCM1 mutations were highly variable. Fewer CCM1 patients experienced hemorrhage than others with familial disease (P = 0.0139 for all cases and P = 0.0442 for symptomatic cases). Adjusting for sex and age improved the logistic regression model, suggesting decreased numbers of patients with hemorrhage in CCM1 familial disease (P = 0.003 for all cases and P = 0.014 for symptomatic cases). Hemorrhage differences were not related to size or number of lesions.

CONCLUSION

Factors in addition to CCM1 germline mutation contribute to CCM clinical manifestations. However, this evidence suggests that familial cases with CCM1 mutations may have less severe clinical manifestations than other familial cases.