Periventricular heterotopia: new insights into Ehlers-Danlos syndrome

A gain-of-function filamin A mutation in mouse platelets induces thrombus instability

BACKGROUND

Filaminopathies A are rare disorders affecting the brain, intestine, or skeleton, characterized by dominant X-linked filamin A (FLNA) gene mutations. Macrothrombocytopenia with functionally defective platelets is frequent. We have described a filaminopathy A male patient, exhibiting a C-terminal frame-shift FLNa mutation (Berrou et al., Arterioscler Thromb Vasc Biol. 2017;37:1087-1097). Contrasting with female patients, this male patient exhibited gain of platelet functions, including increased platelet aggregation, integrin αIIbβ3 activation, and secretion at low agonist concentration, raising the issue of thrombosis risk.

OBJECTIVES

Our goal is to assess the thrombotic potential of the patient FLNa mutation in an in vivo model.

METHODS

We have established a mutant FlnA knock-in mouse model.

RESULTS

The mutant FlnA mouse platelets phenocopied patient platelets, showing normal platelet count, lower expression level of mutant FlnA, and gain of platelet functions: increased platelet aggregation, secretion, and αIIbβ3 activation, as well as increased spreading and clot retraction. Surprisingly, mutant FlnA mice exhibited a normal bleeding time, but with increased re-bleeding (77%) compared to wild type (WT) FlnA mice (27%), reflecting hemostatic plug instability. Again, in an in vivo thrombosis model, the occlusion time was not altered by the FlnA mutation, but arteriolar embolies were increased (7-fold more frequent in mutant FlnA mice versus WT mice), confirming thrombus instability.

CONCLUSIONS

This study shows that the FlnA mutation found in the male patient induced gain of platelet functions in vitro, but thrombus instability in vivo. Implications for the role of FLNa in physiology of thrombus formation are discussed.

Asymmetrical aortic root aneurism in patient with Filamin A mutation

We report the case of a 28 years old woman with periventricular nodular heterotopia, due to Filamin A mutation. She had an asymmetrical aneurysm of the aortic root, involving, above all, noncoronary Valsalva sinus. She was asymptomatic and she had moderate aortic regurgitation. Reimplantation of the aortic valve with replacement of the aortic root was successfully accomplished. Filamin A is a protein that is encoded by the FLNA gene, which shows X-linked dominant inheritance. This protein is involved in neuronal migration, angiogenesis, cytoskeleton regulation, and cell signaling. Therefore, mutations of FLNA gene might result in brain, blood vessels, heart, and connective tissue disorders. A miscellany of cardiovascular abnormalities could be present in this subset of patients; cardiac symptoms may precede neurological manifestations. Aorta seems to be frequently affected. Consequently, in presence of FLNA gene mutations, cardiovascular evaluation should include vascular magnetic resonance imaging or computed tomography scan.

Gray matter heterotopia: clinical and neuroimaging report on 22 children

OBJECTIVE

To investigate the clinical characteristics and neuroimaging features of childhood presenting with gray matter heterotopia observed in a single tertiary Pediatric Department in Catania and compare the data with those reported in the literature.

METHODS

A retrospectively review of the history, clinical findings, electrophysiological features and magnetic resonance images of 22 children presenting with gray matter heterotopia observed from January 2010 to January 2020.

RESULTS

Among the 22 children included in the study, 17 presented with periventricular heterotopia (PVNH), two with Subcortical Band Heterotopia (SBH), and three with other subcortical heterotopia (SUBH). In the affected children, the ages at first diagnosis ranged from 3 months to 16 years with a mean age of 8.2 years (± 5.4); twelve (54.5%) suffered by developmental delay and intellectual deficit; eleven children (50%) complained of epileptic seizures, mostly focal to bilateral tonic-clonic seizure. In addition, in the periventricular heterotopia group (PVNH), cerebral and systemic malformations were reported in twelve (70%) and in ten (58%) children, respectively, out of seventeen. In the SBH plus SUBH group, epileptic seizures were recorded in 3 (60%) out of 5 children, cerebral malformations in one child and systemic malformations in two children.

CONCLUSIONS

Heterotopic gray matter malformations include a group of disorders that manifest with a variety of neurological implications, such as cognitive impairment and epilepsy, and often related with epilepsy, other cerebral malformations and systemic anomalies.

Cardiovascular and connective tissue disorder features in FLNA-related PVNH patients: progress towards a refined delineation of this syndrome

BACKGROUND

FLNA Loss-of-Function (LoF) causes periventricular nodular heterotopia type 1 (PVNH1), an acknowledged cause of seizures of various types. Neurological symptoms are inconstant, and cardiovascular (CV) defects or connective tissue disorders (CTD) have regularly been associated. We aimed at refining the description of CV and CTD features in patients with FLNA LoF and depicting the multisystemic nature of this condition.

METHODS

We retrospectively evaluated FLNA variants and clinical presentations in FLNA LoF patient with at least one CV or CTD feature, from three cohorts: ten patients from the French Reference Center for Rare Vascular Diseases, 23 patients from the national reference diagnostic lab for filaminopathies-A, and 59 patients from literature review.

RESULTS

Half of patients did not present neurological symptoms. Most patients presented a syndromic association combining CV and CTD features. CV anomalies, mostly aortic aneurysm and/or dilation were present in 75% of patients. CTD features were present in 75%. Variants analysis demonstrated an enrichment of coding variants in the CH1 domain of FLNA protein.

CONCLUSION

In FLNA LoF patients, the absence of seizures should not be overlooked. When considering a diagnosis of PVNH1, the assessment for CV and CTD anomalies is of major interest as they represent interlinked features. We recommend systematic study of FLNA within CTD genes panels, regardless of the presence of neurological symptoms.

Neurodevelopmental atypisms in the context of joint hypermobility, hypermobility spectrum disorders, and Ehlers-Danlos syndromes

Joint hypermobility (JHM), defined as an increased range of joint motion, is a frequent somatic trait in the general population but also the hallmark of many of the hereditary disorders of connective tissue. Ehlers-Danlos syndromes (EDS) belong to this group of diseases and are characterized by tissue fragility, skin abnormalities, and JHM. Between JHM and EDS, there are the so-called hypermobility spectrum disorders (HSD), which is an umbrella term referring to people with symptomatic JHM who do not fulfill criteria for a syndromic connective tissue disorder such as EDS. Among the variety of clinical correlates of JHM/HSD/EDS, neurodevelopmental atypisms are common although often not screened for and identified in the clinical setting. This article reviews the pertinent literature concerning neurodevelopmental conditions for which there is some evidence of an association with JHM/HSD/EDS. These include hyperactivity and attention deficit, learning, communication, and motor problems including tic disorders such as Tourette syndrome and autism spectrum disorders. Underlying mechanism hypotheses for such interconnections are also reviewed. The coexistence of connective tissue-altered conditions and neurodevelopmental atypisms increases disability in patients from an early age. Thus, increased awareness among clinicians and researchers is necessary to promote assessment, diagnosis, and develop management strategies to meet the specific needs of those affected.

Septo-optic dysplasia caused by a novel FLNA splice site mutation: a case report

Background

Septo-optic dysplasia (SOD), also known as de-Morsier syndrome, is a rare disorder characterized by any combination of optic nerve hypoplasia, pituitary gland hypoplasia, and midline abnormalities of the brain including absence of the septum pellucidum and corpus callosum dysgenesis. The variable presentation of SOD includes visual, neurologic, and/or hypothalamic-pituitary endocrine defects. The unclear aetiology of a large proportion of SOD cases underscores the importance of identifying novel SOD-associated genes.

Case presentation

To identify the disease-causing gene in a male infant with neonatal hypoglycaemia, dysmorphic features, and hypoplasia of the optic nerve and corpus callosum, we designed a targeted next-generation sequencing panel for brain morphogenesis defects. We identified a novel hemizygous deletion, c.6355 + 4_6355 + 5delAG, in intron 38 of the FLNA gene that the patient had inherited from his mother. cDNA studies showed that this variant results in the production of 3 aberrant FLNA transcripts, the most abundant of which results in retention of intron 38 of FLNA.

Conclusions

We report for the first time a case of early-onset SOD associated with a mutation in the FLNA gene. This finding broadens the spectrum of genetic causes of this rare disorder and expands the phenotypic spectrum of the FLNA gene.

Linking Cell Polarity to Cortical Development and Malformations

Cell polarity refers to the asymmetric distribution of signaling molecules, cellular organelles, and cytoskeleton in a cell. Neural progenitors and neurons are highly polarized cells in which the cell membrane and cytoplasmic components are compartmentalized into distinct functional domains in response to internal and external cues that coordinate polarity and behavior during development and disease. In neural progenitor cells, polarity has a prominent impact on cell shape and coordinate several processes such as adhesion, division, and fate determination. Polarity also accompanies a neuron from the beginning until the end of its life. It is essential for development and later functionality of neuronal circuitries. During development, polarity governs transitions between multipolar and bipolar during migration of postmitotic neurons, and directs the specification and directional growth of axons. Once reaching final positions in cortical layers, neurons form dendrites which become compartmentalized to ensure proper establishment of neuronal connections and signaling. Changes in neuronal polarity induce signaling cascades that regulate cytoskeletal changes, as well as mRNA, protein, and vesicle trafficking, required for synapses to form and function. Hence, defects in establishing and maintaining cell polarity are associated with several neural disorders such as microcephaly, lissencephaly, schizophrenia, autism, and epilepsy. In this review we summarize the role of polarity genes in cortical development and emphasize the relationship between polarity dysfunctions and cortical malformations.

Normal and Disordered Formation of the Cerebral Cortex : Normal Embryology, Related Molecules, Types of Migration, Migration Disorders

The expansion and folding of the cerebral cortex occur during brain development and are critical factors that influence cognitive ability and sensorimotor skills. The disruption of cortical growth and folding may cause neurological disorders, resulting in severe intellectual disability and intractable epilepsy in humans. Therefore, understanding the mechanism that regulates cortical growth and folding will be crucial in deciphering the key steps of brain development and finding new therapeutic targets for the congenital anomalies of the cerebral cortex. This review will start with a brief introduction describing the anatomy of the brain cortex, followed by a description of our understanding of the proliferation, differentiation, and migration of neural progenitors and important genes and molecules that are involved in these processes. Finally, various types of disorders that develop due to malformation of the cerebral cortex will be discussed.

Prevalence of neuropsychiatric symptoms associated with malformations of cortical development

PURPOSE

Malformations of cortical development (MCD) are structural abnormality of the cortex or brain parenchyma with diverse clinical manifestations. Little is known about the association of psychiatric and behavioral problems in MCD. We aimed to determine prevalence and risk factors of neuropsychiatric symptoms in a cohort of adult patients with MCD.

METHODS

We conducted a retrospective medical records review of 86 adult patients followed at the epilepsy clinic of the Montreal Neurological Hospital. Information on diagnosis of medical and psychiatric disorders, family history, intellectual disability, and psychiatric symptoms was obtained from their medical records.

RESULTS

The cohort (n = 86) had a mean age of 39 ± 14.07 (range: 18-74) years. The three most common MCD subtypes were focal cortical dysplasia (47.7%), periventricular nodular heterotopia (29.1%), and polymicrogyria (16.3%). Overall, prevalence of formally diagnosed psychiatric disorders and psychiatric symptoms were respectively 15.1% and 31.4%. The most frequently described symptoms were anxiety-related (59.3%), followed by irritability (40.7%) and agitation (37.0%). Patients with family psychiatric history (OR: 8.168, 95% CI: 1.44-46.48) and intellectual disability (OR: 5.824, 95% CI: 1.30-26.10) were significantly more likely to have psychiatric symptoms than those without. The prevalence of psychiatric symptoms did not defer between major groups of MCD.

CONCLUSIONS

Neuropsychiatric symptoms are commonly associated with MCD, but psychiatric disorders may be underrecognized given that only half of the patients with psychiatric symptoms were referred for a specialized consultation. The presence of intellectual disability and family psychiatric history may help identify and predict risk of psychiatric manifestations in MCD.

Autism, Joint Hypermobility-Related Disorders and Pain

Autism Spectrum Disorder (ASD) and Joint Hypermobility-Related Disorders are blanket terms for two etiologically and clinically heterogeneous groups of pathologies that usually appears in childhood. These conditions are seen by different medical fields, such as psychiatry in the case of ASD, and musculoskeletal disciplines and genetics in the case of hypermobility-related disorders. Thus, a link between them is rarely established in clinical setting, despite a scarce but growing body of research suggesting that both conditions co-occur more often than expected by chance. Hypermobility is a frequent sign of hereditary disorders of connective tissue (e.g., Ehlers-Danlos syndromes, Marfan syndrome), in which the main characteristic is the multisystem fragility that prone to proprioceptive and motor coordination dysfunction and hence to trauma and chronic pain. Considering the high probability that pain remains disregarded and untreated in people with ASD due to communication and methodological difficulties, increasing awareness about the interconnection between ASD and hypermobility-related disorders is relevant, since it may help identify those ASD patients susceptible to chronic pain.

Prenatally diagnosed periventricular nodular heterotopia: Further delineation of the imaging phenotype and outcome

OBJECTIVES

Periventricular nodular heterotopia (PNH) is a malformation of cortical development which presents with heterogeneous imaging, neurological phenotype and outcome. There is a paucity of comprehensive description detailing the prenatal diagnosis of PNH. The aim of this study is to report neuroimaging features and correlated outcomes in order to delineate the spectrum of prenatally diagnosed PNH.

METHODS

It was a retrospective study over 15 years in five tertiary centers. All fetuses with prenatally diagnosed PNH were collected. Fetal ultrasound and MRI were reviewed and genetic screening collected. Prenatal findings were analyzed in correlation to fetopathological analyses and post-natal follow up.

RESULTS

Thirty fetuses (22 females and 8 males) with PNH were identified. The two major ultrasound signs were ventriculomegaly associated with dysmorphic frontal horns (60%) and posterior fossa anomalies (73.3%). On MRI, two groups of PNH were identified: the contiguous and diffuse PNH (n = 15, 50%), often associated with megacisterna magna, and the non-diffuse, either anterior, posterior or unilateral PNH. FLNA mutations were found in 6/11 cases with diffuse PNH. Additional cortical malformations were exclusively observed in non diffuse PNH (9/15; 60%). Twenty-four pregnancies (80%) were terminated. Six children aged 6 months to 5 years are alive. Five have normal neurodevelopment (all had diffuse PNH) whereas one case with non diffuse PNH has developmental delay and epilepsy.

CONCLUSION

PNH is heterogeneous but patients with diffuse PNH are a common subgroup with specific findings on prenatal imaging and implications for prenatal counseling.

Remitting long-standing major depression in a multiple sclerosis patient with several concurrent conditions

In this report, we discuss the case of an multiple sclerosis (MS) patient, age 62, who learned to attain and sustain euthymia despite his ailments. He has Ehlers Danlos Syndrome (EDS), asthma, MS, urticaria, and major depression (MD). Despite thriving limitations, the patient is an accomplished scientist, who struggled for > twelve years to emerge from being confined to bed and wheel chair with MS, to walking with crutches, scuba diving, writing manuscripts, and living a positive life. Through former educators, he reacquired problem-solving habits to study the literature on his illnesses; keep records; try new therapies; and use pharmaceutical, nutritional, physical, and psychological methods to attain euthymia. With this inculcation, years later, he discovered that dimethyl fumarate (DMF) suppressed inflammation, cramping, urticaria, and asthma; and the combination of bupropion, S-adenosylmethionine (SAMe), vitamin-D3 (vit-D3), yoga, and self-hypnosis relieved MD. Then, after a 14-month respite, the patient, discovered that he had adult onset craniopharyngioma: a benign, recurring, epithelial tumor that grows from vestigial embryonic tissue (Rathke's pouch) which formed the anterior pituitary. The tumor grows aggressively and causes surrounding tissue and function losses. It caused headaches, disorientation, bitemporal vision loss, among other problems. To emerge from this conundrum, the patient employed his relearned habits; the above antidepressant cocktail (bupropion, SAMe, and vit-D3); and with 30 fractionated stereotactic radiation treatments shrank his tumor and gained relief. This is a single case, and methods we discovered serendipitously may not work for other chronically ill patients. Consequently, we want to encourage such patients and their physicians to discuss their experiences in peer-reviewed domains so readers may acquire new perspectives that help individualize their care, and have productive contented lives.

Cerebral cortex expansion and folding: what have we learned?

One of the most prominent features of the human brain is the fabulous size of the cerebral cortex and its intricate folding. Cortical folding takes place during embryonic development and is important to optimize the functional organization and wiring of the brain, as well as to allow fitting a large cortex in a limited cranial volume. Pathological alterations in size or folding of the human cortex lead to severe intellectual disability and intractable epilepsy. Hence, cortical expansion and folding are viewed as key processes in mammalian brain development and evolution, ultimately leading to increased intellectual performance and, eventually, to the emergence of human cognition. Here, we provide an overview and discuss some of the most significant advances in our understanding of cortical expansion and folding over the last decades. These include discoveries in multiple and diverse disciplines, from cellular and molecular mechanisms regulating cortical development and neurogenesis, genetic mechanisms defining the patterns of cortical folds, the biomechanics of cortical growth and buckling, lessons from human disease, and how genetic evolution steered cortical size and folding during mammalian evolution.

Juvenile muscular atrophy of the distal upper extremities associated with x-linked periventricular heterotopia with features of Ehlers-Danlos syndrome

INTRODUCTION

Juvenile muscular atrophy of the distal upper extremities (JMADUE) is a rare, sporadic disorder that affects adolescent males and is characterized by progressive but self-limited weakness of the distal upper extremities. The etiology is unknown, but cervical hyperflexion has been hypothesized.

METHODS

We report a case of an adolescent male who presented with typical JMADUE but also had joint hypermobility and multiple congenital anomalies, including periventricular heterotopias, suggesting a multisystem syndrome.

RESULTS

Subsequent diagnostic testing confirmed a diagnosis of JMADUE, and sequencing of the filamin-A gene showed a novel, pathogenic mutation that confirmed an additional diagnosis of X-linked periventricular heterotopias with features of Ehlers-Danlos syndrome (XLPH-EDS).

CONCLUSIONS

The concurrent diagnosis of these 2 rare conditions suggests a pathogenic connection. It is likely that the joint hypermobility from XLPH-EDS predisposed this patient to developing JMADUE. This supports the cervical hyperflexion theory of pathogenesis. This case also expands the phenotype associated with FLNA mutations. Muscle Nerve 54: 794-797, 2016.

Structure of the Elastin-Contractile Units in the Thoracic Aorta and How Genes That Cause Thoracic Aortic Aneurysms and Dissections Disrupt This Structure

The medial layer of the aorta confers elasticity and strength to the aortic wall and is composed of alternating layers of smooth muscle cells (SMCs) and elastic fibres. The SMC elastin-contractile unit is a structural unit that links the elastin fibres to the SMCs and is characterized by the following: (1) layers of elastin fibres that are surrounded by microfibrils; (2) microfibrils that bind to the integrin receptors in focal adhesions on the cell surface of the SMCs; and (3) SMC contractile filaments that are linked to the focal adhesions on the inner side of the membrane. The genes that are altered to cause thoracic aortic aneurysms and aortic dissections encode proteins involved in the structure or function of the SMC elastin-contractile unit. Included in this gene list are the genes encoding protein that are structural components of elastin fibres and microfibrils, FBN1, MFAP5, ELN, and FBLN4. Also included are genes that encode structural proteins in the SMC contractile unit, including ACTA2, which encodes SMC-specific α-actin and MYH11, which encodes SMC-specific myosin heavy chain, along with MYLK and PRKG1, which encode kinases that control SMC contraction. Finally, mutations in the gene encoding the protein linking integrin receptors to the contractile filaments, FLNA, also predispose to thoracic aortic disease. Thus, these data suggest that functional SMC elastin-contractile units are important for maintaining the structural integrity of the aorta.

Unilateral periventricular heterotopia and epilepsy in a girl with Ehlers-Danlos syndrome

Purpose

Ehlers–Danlos syndrome (EDS), comprising a variety of inherited connective tissue disorders, has already been described in association with various neurological features, particularly with epilepsy and periventricular heterotopia (PH). Until now, there are reports of only bilateral periventricular heterotopia associated with Ehlers–Danlos syndrome.

Methods and results

Here we describe a 1-year, 4-month-old female who came under our care in the Pediatric Emergency Room because of prolonged afebrile generalized seizures, whose clinical picture allowed us to suspect a diagnosis of Ehlers–Danlos syndrome. Neuroradiological investigations showed unilateral periventricular heterotopias, and genetic analyses confirmed the hypothesized diagnosis, identifying in particular a mutation in the COL5A1 gene. After starting anticonvulsant therapy, her seizures showed a good response with seizure control and she had a favorable long-term course.

Conclusion

To our knowledge, this is the first report of unilateral periventricular heterotopia associated with Ehlers–Danlos syndrome. We first hypothesized a mosaicism as the cause of both, a unilateral localization of the heterotopias and a favorable long-term course with good response to anticonvulsant therapy; however, intriguingly, we could not demonstrate a mosaicism as the genetic condition in our patient and the neuroradiological findings and the favorable clinical outcome still remain unexplained.

Role of mechanotransduction in vascular biology: focus on thoracic aortic aneurysms and dissections

Thoracic aortic diseases that involve progressive enlargement, acute dissection, or rupture are influenced by the hemodynamic loads and mechanical properties of the wall. We have only limited understanding, however, of the mechanobiological processes that lead to these potentially lethal conditions. Homeostasis requires that intramural cells sense their local chemomechanical environment and establish, maintain, remodel, or repair the extracellular matrix to provide suitable compliance and yet sufficient strength. Proper sensing, in turn, necessitates both receptors that connect the extracellular matrix to intracellular actomyosin filaments and signaling molecules that transmit the related information to the nucleus. Thoracic aortic aneurysms and dissections are associated with poorly controlled hypertension and mutations in genes for extracellular matrix constituents, membrane receptors, contractile proteins, and associated signaling molecules. This grouping of factors suggests that these thoracic diseases result, in part, from dysfunctional mechanosensing and mechanoregulation of the extracellular matrix by the intramural cells, which leads to a compromised structural integrity of the wall. Thus, improved understanding of the mechanobiology of aortic cells could lead to new therapeutic strategies for thoracic aortic aneurysms and dissections.

Ehlers-Danlos syndrome: a cause of epilepsy and periventricular heterotopia

PURPOSE

Ehlers-Danlos syndrome (EDS) comprises a variety of inherited connective tissue disorders that have been described in association with various neurological features. Until now the neurological symptoms have not been studied in detail; therefore, the aim of this review is to analyze the possible association between EDS, epilepsy and periventricular heterotopia (PH).

METHODS

We have carried out a critical review of all cases of epilepsy in EDS patients with and without PH.

RESULTS

Epilepsy is a frequent neurological manifestation of EDS; generally, it is characterized by focal seizures with temporo-parieto-occipital auras and the most common EEG findings epileptiform discharges and slow intermittent rhythm with delta-theta waves. Epilepsy in EDS patients is usually responsive to common antiepileptic therapy; very few cases of drug resistant focal epilepsy requested surgical treatment, with favorable results in terms of outcome. Epilepsy is the most common presenting neurological manifestation associated with PH in EDS patients. Abnormal anatomic circuitries (including heterotopic nodules) could generate epilepsy in patients with PH.

CONCLUSION

Among the principal neurological manifestations, epilepsy and PH have a considerable importance and can influence the long-term evolution of these patients. We hypothesize that PH may determine the epileptic manifestations in patients with EDS; much remains to be learnt about the relationships between nodules and the epileptic manifestations in EDS syndrome.

Autism as a sequence: from heterochronic germinal cell divisions to abnormalities of cell migration and cortical dysplasias

The considerable heterogeneity in the number and severity of symptoms observed in autism spectrum disorders (ASD) has been regarded as an obstacle to any future research. Some authors believe that clinical heterogeneity results from the complex interplay of the many genetic and environmental factors that themselves define a condition as multifactorial. However, it is important to note that neuropathological findings in both idiopathic and syndromic autism suggests a single pathophysiological mechanism acting during brain development: the heterochronic division of germinal cells and subsequent migrational abnormalities of daughter cells to their target fields. Multiple exogenous (e.g., viruses, drugs) and endogenous (e.g., genetic mutations) factors are known to disrupt the division of germinal cells and provide for an autism phenotype. The variety of endogenous and exogenous factors, their timing of action during brain development, and the genetic susceptibility of affected individuals (a Triple Hit hypothesis) may all account for the clinical heterogeneity of ASD.

Obligatory roles of filamin A in E-cadherin-mediated cell-cell adhesion in epidermal keratinocytes

BACKGROUND

Extracellular Ca(2+) (Cao(2+))-induced E-cadherin-mediated cell-cell adhesion plays a critical role in promoting differentiation in epidermal keratinocytes. Our previous studies show that the calcium-sensing receptor (CaR) regulates keratinocyte cell-cell adhesion and differentiation via Rho A-mediated signaling. CaR forms a protein complex with Rho A, guanine nucleotide exchange factor Trio, and a cytoskeletal actin-binding protein, filamin A, at the cell-cell junctions in response to elevated Cao(2+) levels. Filamin A has the ability to interact directly with CaR, Trio, and Rho and mediate CaR-dependent signaling events.

OBJECTIVE

This study was conducted to investigate the roles of filamin A and Trio in regulating Cao(2+)-induced Rho activation and intercellular adhesion.

METHODS

Expression of filamin A and Trio in keratinocytes was inhibited by siRNA. Its effects on Cao(2+)-dependent junction formation and adhesion complex formation were evaluated by fluorescence immunostaining and immunoprecipitation. Endogenous Rho activity and expression of keratinocyte differentiation markers were also examined. The significance of the physical interactions of filamin A with Trio and Rho was assessed in dominant-negative inhibition studies.

RESULTS

Inhibiting filamin A expression blocked the formation of CaR-Rho A-Trio-E-cadherin protein complex. Knockdown of filamin A or Trio inhibited Cao(2+)-induced membrane localization and activation of Rho A, formation of the E-cadherin-catenin adhesion complex, and keratinocyte terminal differentiation. Expressing dominant-negative peptides disruptive to the endogenous filamin-Trio, filamin-Rho, and CaR-filamin interactions suppressed the formation of adherens junctions.

CONCLUSION

Through physical interactions with CaR, Trio and Rho, filamin A generates a scaffold for organizing a signaling complex that promotes E-cadherin-mediated cell-cell adhesion and keratinocyte differentiation.

Complex roles of filamin-A mediated cytoskeleton network in cancer progression

Filamin-A (FLNA), also called actin-binding protein 280 (ABP-280), was originally identified as a non-muscle actin binding protein, which organizes filamentous actin into orthogonal networks and stress fibers. Filamin-A also anchors various transmembrane proteins to the actin cytoskeleton and provides a scaffold for a wide range of cytoplasmic and nuclear signaling proteins. Intriguingly, several studies have revealed that filamin-A associates with multiple non-cytoskeletal proteins of diverse function and is involved in several unrelated pathways. Mutations and aberrant expression of filamin-A have been reported in human genetic diseases and several types of cancer. In this review, we discuss the implications of filamin-A in cancer progression, including metastasis and DNA damage response.

Vascular and connective tissue anomalies associated with X-linked periventricular heterotopia due to mutations in Filamin A

Mutations conferring loss of function at the FLNA (encoding filamin A) locus lead to X-linked periventricular nodular heterotopia (XL-PH), with seizures constituting the most common clinical manifestation of this disorder in female heterozygotes. Vascular dilatation (mainly the aorta), joint hypermobility and variable skin findings are also associated anomalies, with some reports suggesting that this might represents a separate syndrome allelic to XL-PH, termed as Ehlers-Danlos syndrome-periventricular heterotopia variant (EDS-PH). Here, we report a cohort of 11 males and females with both hypomorphic and null mutations in FLNA that manifest a wide spectrum of connective tissue and vascular anomalies. The spectrum of cutaneous defects was broader than previously described and is inconsistent with a specific type of EDS. We also extend the range of vascular anomalies associated with XL-PH to included peripheral arterial dilatation and atresia. Based on these observations, we suggest that there is little molecular or clinical justification for considering EDS-PH as a separate entity from XL-PH, but instead propose that there is a spectrum of vascular and connective tissues anomalies associated with this condition for which all individuals with loss-of-function mutations in FLNA should be evaluated. In addition, since some patients with XL-PH can present primarily with a joint hypermobility syndrome, we propose that screening for cardiovascular manifestations should be offered to those patients when there are associated seizures or an X-linked pattern of inheritance.

Peritrigonal and temporo-occipital heterotopia with corpus callosum and cerebellar dysgenesis

OBJECTIVE

To describe a homogeneous subtype of periventricular nodular heterotopia (PNH) as part of a newly defined malformation complex.

METHODS

Observational study including review of brain MRI and clinical findings of a cohort of 50 patients with PNH in the temporo-occipital horns and trigones, mutation analysis of the FLNA gene, and anatomopathologic study of a fetal brain.

RESULTS

There were 28 females and 22 males. All were sporadic with the exception of an affected mother and son. Epilepsy occurred in 62%, cerebellar signs in 56%, cognitive impairment in 56%, and autism in 12%. Seventy percent were referred within the 3rd year of life. Imaging revealed a normal cerebral cortex in 76% and abnormal cortical folding in 24%. In all patients the hippocampi were under-rotated and in 10% they merged with the heterotopia. Cerebellar dysgenesis was observed in 84% and a hypoplastic corpus callosum in 60%. There was no gender bias or uneven gender distribution of clinical and anatomic severity. No mutations of FLNA occurred in 33 individuals examined. Heterotopia in the fetal brain revealed cytoarchitectonic characteristics similar to those associated with FLNA mutations; cortical pathology was not typical of polymicrogyria. Cerebellar involvement was more severe and the hippocampi appeared simple and under-rotated.

CONCLUSIONS

This series delineates a malformation complex in which PNH in the trigones and occipito-temporal horns is associated with hippocampal, corpus callosum, and cerebellar dysgenesis. This subtype of PNH is distinct from classic PNH caused by FLNA mutations.

Clinical and genetic aspects of Ehlers-Danlos syndrome, classic type

Classic Ehlers-Danlos syndrome is a heritable connective tissue disorder characterized by skin hyperextensibility, fragile and soft skin, delayed wound healing with formation of atrophic scars, easy bruising, and generalized joint hypermobility. It comprises Ehlers-Danlos syndrome type I and Ehlers-Danlos syndrome type II, but it is now apparent that these form a continuum of clinical findings and differ only in phenotypic severity. It is currently estimated that approximately 50% of patients with a clinical diagnosis of classic Ehlers-Danlos syndrome harbor mutations in the COL5A1 and the COL5A2 gene, encoding the α1 and the α2-chain of type V collagen, respectively. However, because no prospective molecular studies of COL5A1 and COL5A2 have been performed in a clinically well-defined patient group, this number may underestimate the real proportion of patients with classic Ehlers-Danlos syndrome harboring a mutation in one of these genes. In the majority of patients with molecularly characterized classic Ehlers-Danlos syndrome, the disease is caused by a mutation leading to a nonfunctional COL5A1 allele and resulting in haploinsufficiency of type V collagen. A smaller proportion of patients harbor a structural mutation in COL5A1 or COL5A2, causing the production of a functionally defective type V collagen protein. Most mutations identified so far result in a reduced amount of type V collagen in the connective tissues available for collagen fibrillogenesis. Inter- and intrafamilial phenotypic variability is observed, but no genotype-phenotype correlations have been observed. No treatment for the underlying defect is presently available for Ehlers-Danlos syndrome. However, a series of preventive guidelines are applicable.

De novo ACTA2 mutation causes a novel syndrome of multisystemic smooth muscle dysfunction

Smooth muscle cells (SMCs) contract to perform many physiological functions, including regulation of blood flow and pressure in arteries, contraction of the pupils, peristalsis of the gut, and voiding of the bladder. SMC lineage in these organs is characterized by cellular expression of the SMC isoform of α-actin, encoded by the ACTA2 gene. We report here on a unique and de novo mutation in ACTA2, R179H, that causes a syndrome characterized by dysfunction of SMCs throughout the body, leading to aortic and cerebrovascular disease, fixed dilated pupils, hypotonic bladder, malrotation, and hypoperistalsis of the gut and pulmonary hypertension.

Bilateral Posterior Periventricular Nodular Heterotopia with Cerebellar Hypoplasia, Communicating Hydrocephalus and Bilateral Hippocampal Sclerosis

Heterotopias are foci of grey matter in abnormal locations in the brain and are secondary to arrest of neuronal migration. Bilateral periventricular nodular heterotopias (BPVNH) are a rare form of heterotopic disorders. Many varieties of BPVNH with various associations have been reported in the literature, the commonest being the classical X-linked variety usually associated with filamin A gene (FLNA) mutations. The relationship of other types of BPVNH to this gene is variable. We report a rare variety of this entity – BPVNH with cerebellar hypoplasia, communicating hydrocephalus and bilateral hippocampal sclerosis. An exostosis arising from the left petrous temporal bone was an added finding in our patient.

Novel localization of tenascin-X in adult mouse leptomeninges and choroid plexus

Tenascin-X (Tn-X) belongs to the tenascin family of glycoproteins and is clearly associated with the human connective tissue disorder Ehlers-Danlos syndrome. Recently, human single nucleotide polymorphism analyses showed that Tn-X is associated with schizophrenia. Tn-X-related central nervous system (CNS) disorder has been reported in recent years. However, details of Tn-X localization are not clear in the adult cerebral cortex and its meninges. Using immunohistochemical techniques, we found novel localizations of Tn-X in the leptomeningeal trabecula (TB) of adult mice and in the connective tissue of the choroid plexus (CP) in the brains of mice. Subsequent immunohistochemical studies showed complementary localization of Tn-X in the leptomeninges and CP. Localization of tenascin-C was not detected in the leptomeningeal TB or in the connective tissue of the CP. These results might provide insight into the role of Tn-X in the pathogenesis of disorders in the CNS.