Mutations in the X-linked filamin 1 gene cause periventricular nodular heterotopia in males as well as in females

Filamin A in triple negative breast cancer

Triple-negative breast cancer is a rare but highly heterogeneous breast cancer subtype with a limited choice of specific treatments. Chemotherapy remains the only efficient treatment, but its side effects and the development of resistance consolidate the urgent need to discover new targets. In TNBC, filamin A expression correlates to grade and TNM stage. Accordingly, this protein could constitute a new target for this BC subtype. Even if most of the data indicates its direct involvement in cancer progression, some contrasting results underline the need to deepen the studies. To elucidate a possible function of this protein as a TNBC marker, we summarized the main characteristic of filamin A and its involvement in physiological and pathological processes such as cancer. Lastly, we scrutinized its actions in triple-negative breast cancer and highlighted the need to increase the number of studies useful to better clarify the role of this versatile protein as a marker and target in TNBC, alone or in "collaboration" with other proteins with a relevant role in this BC subgroup.

X-linked neuronal migration disorders: Gender differences and insights for genetic screening

Cortical development depends on neuronal migration of both excitatory and inhibitory interneurons. Neuronal migration disorders (NMDs) are conditions characterised by anatomical cortical defects leading to varying degrees of neurocognitive impairment, developmental delay and seizures. Refractory epilepsy affects 15 million people worldwide, and it is thought that cortical developmental disorders are responsible for 25% of childhood cases. However, little is known about the epidemiology of these disorders, nor are their aetiologies fully understood, though many are associated with sporadic genetic mutations. In this review, we aim to highlight X-linked NMDs including lissencephaly, periventricular nodular heterotopia and polymicrogyria because of their mostly familial inheritance pattern. We focus on the most prominent genes responsible: including DCX, ARX, FLNA, FMR1, L1CAM, SRPX2, DDX3X, NSHDL, CUL4B and OFD1, outlining what is known about their prevalence among NMDs, and the underlying pathophysiology. X-linked disorders are important to recognise clinically, as females often have milder phenotypes. Consequently, there is a greater chance they survive to reproductive age and risk passing the mutations down. Effective genetic screening is important to prevent and treat these conditions, and for this, we need to know gene mutations and have a clear understanding of the function of the genes involved. This review summarises the knowledge base and provides clear direction for future work by both scientists and clinicians alike.

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.

Computational analysis of missense filamin-A variants, including the novel p.Arg484Gln variant of two brothers with periventricular nodular heterotopia

Background

Periventricular nodular heterotopia (PNH) is a cell migration disorder associated with mutations in Filamin-A (FLNA) gene on chromosome X. Majority of the individuals with PNH-associated FLNA mutations are female whereas liveborn males with FLNA mutations are very rare. Fetal viability of the males seems to depend on the severity of the variant. Splicing or severe truncations presumed loss of function of the protein product, lead to male lethality and only partial-loss-of-function variants are reported in surviving males. Those variants mostly manifest milder clinical phenotypes in females and thus avoid detection of the disease in females.

Methods

We describe a novel p.Arg484Gln variant in the FLNA gene by performing whole exome analysis on the index case, his one affected brother and his healthy non-consanguineous parents. The transmission of PNH from a clinically asymptomatic mother to two sons is reported in a fully penetrant classical X-linked dominant mode. The variant was verified via Sanger sequencing. Additionally, we investigated the impact of missense mutations reported in affected males on the FLNa protein structure, dynamics and interactions by performing molecular dynamics (MD) simulations to examine the disease etiology and possible compensative mechanisms allowing survival of the males.

Results

We observed that p.Arg484Gln disrupts the FLNa by altering its structural and dynamical properties including the flexibility of certain regions, interactions within the protein, and conformational landscape of FLNa. However, these impacts existed for only a part the MD trajectories and highly similar patterns observed in the other 12 mutations reported in the liveborn males validated this mechanism.

Conclusion

It is concluded that the variants seen in the liveborn males result in transient pathogenic effects, rather than persistent impairments. By this way, the protein could retain its function occasionally and results in the survival of the males besides causing the disease.

Cardiovascular, Brain, and Lung Involvement in a Newborn With a Novel FLNA Mutation: A Case Report and Literature Review

BACKGROUND

Filamin A (FLNA) is an intracellular actin-binding protein, encoded by the FLNA gene, with a wide tissue expression. It is involved in several cellular functions, and extracellular matrix structuring. FLNA gene alterations lead to diseases with a wide phenotypic spectrum, such as brain periventricular nodular heterotopia (PVNH), cardiovascular abnormalities, skeletal dysplasia, and lung involvement.

CLINICAL FINDINGS

We present the case of a female infant who showed at birth aortic valve stenosis and PVNH, and subsequently developed interstitial lung disease with severe pulmonary hypertension.

PRIMARY DIAGNOSIS

The association of aortic valve dysplasia, left ventricular outflow obstruction, persistent patent ductus arteriosus, and brain heterotopic gray matter suggested a possible FLNA gene alteration. A novel heterozygous intronic variant in the FLNA gene (NM_001110556.1), c.4304-1G >A, was detected.

INTERVENTIONS

In consideration of valve morphology and severity of stenosis, the neonate was scheduled for a transcatheter aortic valvuloplasty. At 3 months of life, she developed hypoxemic respiratory failure with evidence of severe pulmonary hypertension. Inhaled nitric oxide (iNO) and milrinone on continuous infusion were started. Because of a partial response to iNO, an intravenous continuous infusion of sildenafil was introduced.

OUTCOMES

In consideration of severe clinical course and fatal outcome, the new FLNA gene mutation described in our patient seems to be associated with a loss of function of FLNA.

PRACTICE RECOMMENDATIONS

Lung and brain involvement, in association with left ventricular outflow obstruction and persistent patency of ductus arteriosus, should be considered highly suggestive of FLNA gene alterations, in a female newborn.

Control of Synapse Structure and Function by Actin and Its Regulators

Neurons transmit and receive information at specialized junctions called synapses. Excitatory synapses form at the junction between a presynaptic axon terminal and a postsynaptic dendritic spine. Supporting the shape and function of these junctions is a complex network of actin filaments and its regulators. Advances in microscopic techniques have enabled studies of the organization of actin at synapses and its dynamic regulation. In addition to highlighting recent advances in the field, we will provide a brief historical perspective of the understanding of synaptic actin at the synapse. We will also highlight key neuronal functions regulated by actin, including organization of proteins in the pre- and post- synaptic compartments and endocytosis of ion channels. We review the evidence that synapses contain distinct actin pools that differ in their localization and dynamic behaviors and discuss key functions for these actin pools. Finally, whole exome sequencing of humans with neurodevelopmental and psychiatric disorders has identified synaptic actin regulators as key disease risk genes. We briefly summarize how genetic variants in these genes impact neurotransmission via their impact on synaptic actin.

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.

Developmental malformations in Huntington disease: neuropathologic evidence of focal neuronal migration defects in a subset of adult brains

Neuropathologic hallmarks of Huntington Disease (HD) include the progressive neurodegeneration of the striatum and the presence of Huntingtin (HTT) aggregates that result from abnormal polyQ expansion of the HTT gene. Whether the pathogenic trinucleotide repeat expansion of the HTT gene causes neurodevelopmental abnormalities has garnered attention in both murine and human studies; however, documentation of discrete malformations in autopsy brains of HD individuals has yet to be described. We retrospectively searched the New York Brain Bank (discovery cohort) and an independent cohort (validation cohort) to determine whether developmental malformations are more frequently detected in HD versus non-HD brains and to document their neuropathologic features. One-hundred and thirty HD and 1600 non-HD whole brains were included in the discovery cohort and 720 HD and 1989 non-HD half brains were assessed in the validation cohort. Cases with developmental malformations were found at 6.4–8.2 times greater frequency in HD than in non-HD brains (discovery cohort: OR 8.68, 95% CI 3.48–21.63, P=4.8 × 10^-5; validation cohort: OR 6.50, 95% CI 1.83–23.17, P=0.0050). Periventricular nodular heterotopias (PNH) were the most frequent malformations and contained HTT and p62 aggregates analogous to the cortex, whereas cortical malformations with immature neuronal populations did not harbor such inclusions. HD individuals with malformations had heterozygous HTT CAG expansions between 40 and 52 repeats, were more frequently women, and all were asymmetric and focal, aside from one midline hypothalamic hamartoma. Using two independent brain bank cohorts, this large neuropathologic series demonstrates an increased occurrence of developmental malformations in HD brains. Since pathogenic HTT gene expansion is associated with genomic instability, one possible explanation is that neuronal precursors are more susceptible to somatic mutation of genes involved in cortical migration. Our findings further support emerging evidence that pathogenic trinucleotide repeat expansions of the HTT gene may impact neurodevelopment.

A Case of Prenatally Diagnosed Periventricular Nodular Heterotopia in a Surviving Male Patient with FLNA Mutation

FLNA is a gene on the X chromosome that encodes Filamin A, a widely expressed protein crucial for forming the cell cytoskeleton and mediating cell signaling. Loss-of-function mutations have been associated with periventricular nodular heterotopia (PVNH) with associated epilepsy and intellectual deficits, as well as cardiovascular disease, connective tissue disorders, pulmonary disease, bleeding diathesis, and gastrointestinal disease. Alternatively, gain-of-function mutations have been described with otopalatodigital spectrum disorders.

The loss-of-function variants of FLNA associated with PVNH have historically been considered lethal in males, often prenatally or by the first year of life. However, more surviving males with FLNA variants are being described. Most of the surviving males have missense or distal truncating mutations or a degree of mosaicism. Others are thought to have splice site mutations or in-frame exon skipping leading to production of some degree of functional Filamin A as possible mechanisms of survival.

Here, we presented a case of a 20-month-old small but developmentally appropriate and healthy male infant who was prenatally diagnosed with PVNH, and postnatally found to have a nonsense variant of the FLNA gene. This mutation has not been previously clinically described or published to our knowledge.

Treatment of Epilepsy Associated with Periventricular Nodular Heterotopia

PURPOSE OF REVIEW

Epilepsy associated with periventricular nodular heterotopia (PNH), a developmental malformation, is frequently drug-resistant and requires focal therapeutic intervention. Invasive EEG study is usually necessary to delineate the epileptogenic zone, but constructing an accurate hypothesis to define an appropriate electrode implantation scheme and the treatment is challenging. This article reviews recent studies that help understanding the epileptogenicity and potential therapeutic options in PNH.

RECENT FINDINGS

New noninvasive diagnostic and intracerebral EEG analytic tools demonstrated that cortical hyperexcitability and aberrant connectivity (between nodules and cortices and among nodules) are likely mechanisms causing epilepsy in most patients. The deeply seated PNH, if epileptogenic, are ideal target for stereotactic ablative techniques, which offer concomitant ablation of multiple regions with relatively satisfactory seizure outcome. Advance in diagnostic and analytic tools have enhanced our understanding of the complex epileptogenicity in PNH. Development in stereotactic ablative techniques now offers promising therapeutic options for these patients.

International consensus recommendations on the diagnostic work-up for malformations of cortical development

Malformations of cortical development (MCDs) are neurodevelopmental disorders that result from abnormal development of the cerebral cortex in utero. MCDs place a substantial burden on affected individuals, their families and societies worldwide, as these individuals can experience lifelong drug-resistant epilepsy, cerebral palsy, feeding difficulties, intellectual disability and other neurological and behavioural anomalies. The diagnostic pathway for MCDs is complex owing to wide variations in presentation and aetiology, thereby hampering timely and adequate management. In this article, the international MCD network Neuro-MIG provides consensus recommendations to aid both expert and non-expert clinicians in the diagnostic work-up of MCDs with the aim of improving patient management worldwide. We reviewed the literature on clinical presentation, aetiology and diagnostic approaches for the main MCD subtypes and collected data on current practices and recommendations from clinicians and diagnostic laboratories within Neuro-MIG. We reached consensus by 42 professionals from 20 countries, using expert discussions and a Delphi consensus process. We present a diagnostic workflow that can be applied to any individual with MCD and a comprehensive list of MCD-related genes with their associated phenotypes. The workflow is designed to maximize the diagnostic yield and increase the number of patients receiving personalized care and counselling on prognosis and recurrence risk.

Prune belly syndrome in surviving males can be caused by Hemizygous missense mutations in the X-linked Filamin A gene

Background

Prune belly syndrome (PBS) is a rare, multi-system congenital myopathy primarily affecting males that is poorly described genetically. Phenotypically, its morbidity spans from mild to lethal, however, all isolated PBS cases manifest three cardinal pathological features: 1) wrinkled flaccid ventral abdominal wall with skeletal muscle deficiency, 2) urinary tract dilation with poorly contractile smooth muscle, and 3) intra-abdominal undescended testes. Despite evidence for a genetic basis, previously reported PBS autosomal candidate genes only account for one consanguineous family and single cases.

Methods

We performed whole exome sequencing (WES) of two maternal adult half-brothers with syndromic PBS (PBS + Otopalatodigital spectrum disorder [OPDSD]) and two unrelated sporadic individuals with isolated PBS and further functionally validated the identified mutations.

Results

We identified three unreported hemizygous missense point mutations in the X-chromosome gene Filamin A (FLNA) (c.4952 C > T (p.A1448V), c.6727C > T (p.C2160R), c.5966 G > A (p.G2236E)) in two related cases and two unrelated sporadic individuals. Two of the three PBS mutations map to the highly regulatory, stretch-sensing Ig19–21 region of FLNA and enhance binding to intracellular tails of the transmembrane receptor β-integrin 1 (ITGβ1).

Conclusions

FLNA is a regulatory actin-crosslinking protein that functions in smooth muscle cells as a mechanosensing molecular scaffold, transmitting force signals from the actin-myosin motor units and cytoskeleton via binding partners to the extracellular matrix. This is the first evidence for an X-linked cause of PBS in multiple unrelated individuals and expands the phenotypic spectrum associated with FLNA in males surviving even into adulthood.

Filamin A: key actor in platelet biology

Filamins (FLNs) are large dimeric actin-binding proteins that regulate actin cytoskeleton remodeling. In addition, FLNs serve as scaffolds for signaling proteins, such as tyrosine kinases, GTPases, or phosphatases, as well as for adhesive receptors, such as integrins. Thus, they connect adhesive receptors to signaling pathways and to cytoskeleton. There are 3 isoforms of FLN (filamin a [FLNa], FLNb, FLNc) that originate from 3 homologous genes. FLNa has been the recent focus of attention because its mutations are responsible for a wide spectrum of defects called filaminopathies A, affecting brain (peri-ventricular nodular heterotopia), heart (valve defect), skeleton, gastrointestinal tract, and, more recently, the megakaryocytic lineage. This review will focus on the physiological and pathological roles of FLNa in platelets. Indeed, FLNa mutations alter platelet production from their bone marrow precursors, the megakaryocytes, yielding giant platelets in reduced numbers (macrothrombocytopenia). In platelets per se, FLNa mutations may lead to impaired αIIbβ3 integrin activation or in contrast, increased αIIbβ3 activation, potentially enhancing the risk of thrombosis. Experimental work delineating the interaction of FLNa with its platelet partners, including αIIbβ3, the von Willebrand factor receptor GPIb-IX-V, the tyrosine kinase Syk, and the signaling pathway of the collagen receptor GPVI, will also be reviewed.

A Primate-Specific Isoform of PLEKHG6 Regulates Neurogenesis and Neuronal Migration

The mammalian neocortex has undergone remarkable changes through evolution. A consequence of such rapid evolutionary events could be a trade-off that has rendered the brain susceptible to certain neurodevelopmental and neuropsychiatric conditions. We analyzed the exomes of 65 patients with the structural brain malformation periventricular nodular heterotopia (PH). De novo coding variants were observed in excess in genes defining a transcriptomic signature of basal radial glia, a cell type linked to brain evolution. In addition, we located two variants in human isoforms of two genes that have no ortholog in mice. Modulating the levels of one of these isoforms for the gene PLEKHG6 demonstrated its role in regulating neuroprogenitor differentiation and neuronal migration via RhoA, with phenotypic recapitulation of PH in human cerebral organoids. This suggests that this PLEKHG6 isoform is an example of a primate-specific genomic element supporting brain development.

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.

Disorders of neurogenesis and cortical development

The development of the cerebral cortex requires complex sequential processes that have to be precisely orchestrated. The localization and timing of neuronal progenitor proliferation and of neuronal migration define the identity, laminar positioning, and specific connectivity of each single cortical neuron. Alterations at any step of this organized series of events—due to genetic mutations or environmental factors—lead to defined brain pathologies collectively known as malformations of cortical development (MCDs), which are now recognized as a leading cause of drug-resistant epilepsy and intellectual disability. In this heterogeneous group of disorders, macroscopic alterations of brain structure (eg, heterotopic nodules, small or absent gyri, double cortex) can be recognized and probably subtend a general reorganization of neuronal circuits. In this review, we provide an overview of the molecular mechanisms that are implicated in the generation of genetic MCDs associated with aberrations at various steps of neurogenesis and cortical development.

Congenital emphysematous lung disease associated with a novel Filamin A mutation. Case report and literature review

BACKGROUND

Progressive lung involvement in Filamin A (FLNA)-related cerebral periventricular nodular heterotopia (PVNH) has been reported in a limited number of cases.

CASE PRESENTATION

We report a new pathogenic FLNA gene variant (c.7391_7403del; p.Val2464Alafs*5) in a male infant who developed progressive lung disease with emphysematous lesions and interstitial involvement. Following lobar resection, chronic respiratory failure ensued necessitating continuous mechanical ventilation and tracheostomy. Cerebral periventricular nodular heterotopia was also present.

CONCLUSIONS

We report a novel variant of the FLNA gene, associated with a severe lung disorder and PNVH. The lung disorder led to respiratory failure during infancy and these pulmonary complications may be the first sign of this disorder. Early recognition with thoracic imaging is important to guide genetic testing, neuroimaging and to define optimal timing of potential therapies, such as lung transplant in progressive lung disease.

Thoracic aortic aneurysm in patients with loss of function Filamin A mutations: Clinical characterization, genetics, and recommendations

The frequency and gender distribution of thoracic aortic aneurysm as a cardiovascular manifestation of loss-of-function (LOF) X-linked FilaminA (FLNA) mutations are not known. Furthermore, there is very limited cardiovascular morbidity or mortality data in children and adults. We analyzed cardiac data on the largest series of 114 patients with LOF FLNA mutations, both children and adults, with periventricular nodular heterotopia (PVNH), including 48 study patients and 66 literature patients, median age of 22.0 years (88 F, 26 M, range: 0-71 years), with 75 FLNA mutations observed in 80 families. Most (64.9%) subjects had a cardiac anomaly or vascular abnormality (80.8% of males and 60.2% of females). Thoracic aortic aneurysms or dilatation (TAA) were found in 18.4% (n = 21), and were associated with other structural cardiac malformations in 57.1% of patients, most commonly patent ductus arteriosus (PDA) and valvular abnormalities. TAA most frequently involved the aortic root and ascending aorta, and sinus of Valsalva aneurysms were present in one third of TAA patients. Six TAA patients (28.5%) required surgery (median age 37 yrs, range 13-41 yrs). TAA with its associated complications was also the only recorded cause of premature, non-accidental mortality in adults (2 M, 2 F). Two adult patients (1 F, 1 M, median 38.5 yrs), died of spontaneous aortic rupture at aortic dimensions smaller than current recommendations for surgery for other aortopathies. Data from this largest series of LOF FLNA mutation patients underscore the importance of serial follow-up to identify and manage these potentially devastating cardiovascular complications.

A review of filamin A mutations and associated interstitial lung disease

The filamin A gene (FLNA) on Xq28 encodes the filamin A protein. Mutation in FLNA causes a wide spectrum of disease including skeletal dysplasia, neuronal migration abnormality, cardiovascular malformation, intellectual disability and intestinal obstruction. Recently, childhood-onset interstitial lung disease associated with a range of FLNA mutations has been recognised and reported. We document our personal experience of this emerging disorder and compile a comprehensive overview of clinical features and molecular changes in all identifiable published cases. Reviewing the emerging dataset, we underline this unanticipated phenotypic consequence of pathogenic FLNA mutation-associated pulmonary disease.Conclusion: From the emerging data, we suggest that while reviewing complex cases with a sustained oxygen requirement against a clincial background of cardiac concerns or intestinal obstruction to have a high index of suspicion for FLNA related pathology and to instigate early MRI brain scan and FLNA mutation analysis. What is Known: • FLNA gene on Xq28 encodes the filamin A protein and mutation therein is associated with variable phenotypes depending on its nature of mutation. • Loss-of-function mutation of filamin A is associated with X-linked inherited form of periventricular nodular heterotopia with or without epilepsy with most individuals affected being female. There is a recently recognised associated respiratory phenotype. What is New: • The respiratory phenotype in the form of childhood interstitial lung disease is a recently recognised clinical consequence of loss-of-function FLNA mutation. • Rare male patients with loss-of-function FLNA mutation-associated lung disease with residual protein function can survive into infancy with a severe form of the phenotype.

Multiple genomic copy number variants associated with periventricular nodular heterotopia indicate extreme genetic heterogeneity

Periventricular nodular heterotopia (PNH) is a brain malformation in which nodules of neurons are ectopically retained along the lateral ventricles. Genetic causes include FLNA abnormalities (classical X-linked PNH), rare variants in ARFGEF2, DCHS1, ERMARD, FAT4, INTS8, MAP1B, MCPH1, and NEDD4L, as well as several chromosomal abnormalities. We performed array-CGH in 106 patients with different malformations of cortical development (MCD) and looked for common pathways possibly involved in PNH. Forty-two patients, including two parent/proband couples, exhibited PNH associated or not with other brain abnormalities, 44 had polymicrogyria and 20 had rarer MCDs. We found an enrichment of either large rearrangements or cryptic copy number variants (CNVs) in PNH (15/42, 35.7%) vs polymicrogyria (4/44, 9.1%) (i.e., 5.6 times increased risk for PNH of carrying a pathogenic CNV). CNVs in seven genomic regions (2p11.2q12.1, 4p15, 14q11.2q12, 16p13.3, 19q13.33, 20q13.33, 22q11) represented novel, potentially causative, associations with PNH. Through in silico analysis of genes included in imbalances whose breakpoints were clearly detailed, we detected in 9/12 unrelated patients in our series and in 15/24 previously published patients, a significant (P < 0.05) overrepresentation of genes involved in vesicle-mediated transport. Rare genomic imbalances, either small CNVs or large rearrangements, are cumulatively a frequent cause of PNH. Dysregulation of specific cellular mechanisms might play a key pathogenic role in PNH but it remains to be determined whether this is exerted through single genes or the cumulative dosage effect of more genes. Array-CGH should be considered as a first-line diagnostic test in PNH, especially if sporadic and non-classical.

Fetal and neonatal neurogenetics

Disorders of the developing nervous system may be of genetic origin, comprising congenital malformations of spine and brain as well as metabolic or vascular disorders that affect normal brain development. Acquired causes include congenital infections, hypoxic-ischemic or traumatic brain injury, and a number of rare neoplasms. This chapter focuses on the clinical presentation and workup of neurogenetic disorders presenting in the fetal or neonatal period. After a summary of the most frequent clinical presentations, clues from history taking and clinical examination are illustrated with short case reports. This is followed by a discussion of the different tools available for the workup of neurogenetic disorders, including the various genetic techniques with their advantages and disadvantages. The implications of a molecular genetic diagnosis for the patient and family are addressed in the section on counseling. The chapter concludes with a proposed workflow that may help the clinician when confronted with a potential neurogenetic disorder in the fetal or neonatal period.

A case report on filamin A gene mutation and progressive pulmonary disease in an infant: A lung tissued derived mesenchymal stem cell study

RATIONALE

Mesenchymal stem cells (MSC) play a crucial role in both the maintenance of pulmonary integrity and the pathogenesis of lung disease. Lung involvement has been reported in patients with the filamin A (FLNA) gene mutation. Considering FLNA's role in the intrinsic mechanical properties of MSC, we characterized MSCs isolated from FLNA-defective lung tissue, in order to define their pathogenetic role in pulmonary damage.

PATIENT CONCERNS

A male infant developed significant lung disease resulting in emphysematous lesions and perivascular and interstitial fibrosis. He also exhibited general muscular hypotonia, bilateral inguinal hernia, and deformities of the lower limbs (pes tortus congenitalis and hip dysplasia). Following lobar resection, chronic respiratory failure occurred.

DIAGNOSIS

Genetic testing was performed during the course of his clinical care and revealed a new pathogenic variant of the FLNA gene c.7391_7403del; (p.Val2464AlafsTer5). Brain magnetic resonance imaging revealed periventricular nodular heterotopia.

INTERVENTIONS AND OUTCOMES

Surgical thoracoscopic lung biopsy was performed in order to obtain additional data on the pathological pulmonary features. A small portion of the pulmonary tissue was used for MSC expansion. Morphology, immunophenotype, differentiation capacity, and proliferative growth were evaluated. Bone marrow-derived mesenchymal stem cells (BM-MSC) were employed as a control. MSCs presented the typical MSC morphology and phenotype while exhibiting higher proliferative capacity (P <.001) and lower migration potential (P=.02) compared to control BM-MSC.

LESSONS

The genetic profile and altered features of the MSCs isolated from FLNA-related pediatric lung tissue could be directly related to defects in cell migration during embryonic lung development and pulmonary damage described in FLNA-defective patients.

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.

Somatic mosaicism and neurodevelopmental disease

Traditionally, we have considered genetic mutations that cause neurodevelopmental diseases to be inherited or de novo germline mutations. Recently, we have come to appreciate the importance of de novo somatic mutations, which occur postzygotically and are thus present in only a subset of the cells of an affected individual. The advent of next-generation sequencing and single-cell sequencing technologies has shown that somatic mutations contribute to normal and abnormal human brain development. Somatic mutations are one important cause of neuronal migration and brain overgrowth disorders, as suggested by visible focal lesions. In addition, somatic mutations contribute to neurodevelopmental diseases without visible lesions, including epileptic encephalopathies, intellectual disability, and autism spectrum disorder, and may contribute to a broad range of neuropsychiatric diseases. Studying somatic mutations provides insight into the mechanisms underlying human brain development and neurodevelopmental diseases and has important implications for diagnosis and treatment.

Structural basis of the filamin A actin-binding domain interaction with F-actin

Actin-cross-linking proteins assemble actin filaments into higher-order structures essential for orchestrating cell shape, adhesion, and motility. Missense mutations in the tandem calponin homology domains of their actin-binding domains (ABDs) underlie numerous genetic diseases, but a molecular understanding of these pathologies is hampered by the lack of high-resolution structures of any actin-cross-linking protein bound to F-actin. Here, taking advantage of a high-affinity, disease-associated mutant of the human filamin A (FLNa) ABD, we combine cryo-electron microscopy and functional studies to reveal at near-atomic resolution how the first calponin homology domain (CH1) and residues immediately N-terminal to it engage actin. We further show that reorientation of CH2 relative to CH1 is required to avoid clashes with actin and to expose F-actin-binding residues on CH1. Our data explain localization of disease-associated loss-of-function mutations to FLNaCH1 and gain-of-function mutations to the regulatory FLNaCH2. Sequence conservation argues that this provides a general model for ABD-F-actin binding.

Periventricular nodular heterotopia in 22q11.2 deletion and frontal lobe migration

Objective

We aimed to delineate the distribution of periventricular nodular heterotopia (PNH) in patients with 22q11.2 microdeletion syndrome (22q11.2DS) and place this in the context of other genetic forms of PNH.

Methods

We retrospectively analyzed brain imaging and postmortem data available for adult patients with 22q11.2DS. We included only those with good quality MRI data (n = 29) in addition to two patients with PNH identified through postmortem studies. We also reviewed the pattern of PNH in all genetic conditions reported with this phenotype.

Results

Of the total seven patients (M = 4, F = 3; age: 19–61 years) identified to have PNH, six had a history of seizures, six had schizophrenia, six had variable levels of intellectual disability, and two had obsessive compulsive disorder. In all seven patients, the nodules were located over the dorsal pole of the frontal horn of the lateral ventricles. The nodules were small, noncontiguous, and ranged in number from 1 to 10 per individual. Our review identified 37 genetic conditions associated with PNH. With the cases reported here, 22q11.2DS becomes the fifth most commonly reported genetic condition, and the third most common copy number variation, associated with PNH.

Interpretation

The neuropsychiatric manifestations in our patients with PNH support other data indicating abnormal neurodevelopment as part of the pathogenesis of 22q11.2DS.The location and cellular characteristics of PNH in 22q11.2DS overlaps with a group of migrating postnatal interneurons termed Arc cells, although more research is needed to confirm that PNH in 22q11.2DS represents Arc cells arrested in their migratory pathway.

Rainer W. Guillery and the genetic analysis of brain development

Ray Guillery had broad research interests that spanned cellular neuroanatomy, but was perhaps best known for his investigation of the connectivity and function of the thalamus, especially the visual pathways. His work on the genetics of abnormal vision in albino mammals served as an early paradigm for genetic approaches for studying brain connectivity of complex species in general, and remains of major relevance today. This work, especially on the Siamese cat, illustrates the complex relationship between genotype and physiology of cerebral cortical circuits, and anticipated many of the issues underlying the imperfect relationship between genes, circuits, and behavior in mammalian species including human. This review also briefly summarizes studies from our own lab inspired by Ray Guillery's legacy that continues to explore the relationship between genes, structure, and behavior in human cerebral cortex.

FLNA mutations in surviving males presenting with connective tissue findings: two new case reports and review of the literature

Background

Mutations in the X-linked gene filamin A (FLNA), encoding the actin-binding protein FLNA, cause a wide spectrum of connective tissue, skeletal, cardiovascular and/or gastrointestinal manifestations. Males are typically more severely affected than females with common pre- or perinatal death.

Case presentation

We provide a genotype- and phenotype-oriented literature overview of FLNA hemizygous mutations and report on two live-born male FLNA mutation carriers. Firstly, we identified a de novo, missense mutation (c.238C > G, p.(Leu80Val)) in a five-year old Indian boy who presented with periventricular nodular heterotopia, increased skin laxity, joint hypermobility, mitral valve prolapse with regurgitation and marked facial features (e.g. a flat face, orbital fullness, upslanting palpebral fissures and low-set ears). Secondly, we identified two cis-located FLNA mutations (c.7921C > G, p.(Pro2641Ala); c.7923delC, p.(Tyr2642Thrfs*63)) in a Bosnian patient with Ehlers-Danlos syndrome-like features such as skin translucency and joint hypermobility. This patient also presented with brain anomalies, pectus excavatum, mitral valve prolapse, pulmonary hypertension and dilatation of the pulmonary arteries. He died from heart failure in his second year of life.

Conclusions

These two new cases expand the list of live-born FLNA mutation-positive males with connective tissue disease from eight to ten, contributing to a better knowledge of the genetic and phenotypic spectrum of FLNA-related disease.

Electronic supplementary material

The online version of this article (10.1186/s12881-018-0655-0) contains supplementary material, which is available to authorized users.

In-frame Variants in FLNA Proximal Rod 1 Domain Associate With a Predominant Cardiac Valvular Phenotype

INTRODUCTION AND OBJECTIVES

X-linked cardiac valvular dysplasia is a rare form of male-specific congenital heart defect mainly characterized by myxomatous degeneration of the atrioventricular valves with variable hemodynamic consequences. It is caused by genetic defects in FLNA-encoded filamin A, a widely expressed actin-binding protein that regulates cytoskeleton organization. Filamin A loss of function has also been associated with often concurring neurologic and connective tissue manifestations, with mutations in the first half of the Rod 1 domain apparently expressing the full cardiac phenotype. We contribute to previous genotype-phenotype correlations with a multidisciplinary approach in a newly-described family.

METHODS

Cardiologic, dysmorphologic, and genetic evaluation of available members were complemented with transcriptional and X-chromosome inactivation studies.

RESULTS

A novel FLNA mutation c.1066-3C>G cosegregated with a male-expressed, apparently isolated, cardiac phenotype with no skewed X-inactivation pattern in female carriers. This variant was shown to result in an in-frame deletion of 8 amino acid residues near the N-terminal region of the protein.

CONCLUSIONS

A nonimprinted, partial loss of function of filamin A proximal Rod 1 domain seems to be the pathogenetic mechanism of cardiac valvular dysplasia, with some cases occasionally expressing associated extracardiac manifestations.

Differential regulation of two FLNA transcripts explains some of the phenotypic heterogeneity in the loss-of-function filaminopathies

Loss-of-function mutations in the X-linked gene FLNA can lead to abnormal neuronal migration, vascular and cardiac defects, and congenital intestinal pseudo-obstruction (CIPO), the latter characterized by anomalous intestinal smooth muscle layering. Survival in male hemizygotes for such mutations is dependent on retention of residual FLNA function but it is unclear why a subgroup of males with mutations in the 5' end of the gene can present with CIPO alone. Here, we demonstrate evidence for the presence of two FLNA isoforms differing by 28 residues at the N-terminus initiated at ATG⁺¹ and ATG⁺⁸² . A male with CIPO (c.18_19del) exclusively expressed FLNA ATG⁺⁸² , implicating the longer protein isoform (ATG⁺¹ ) in smooth muscle development. In contrast, mutations leading to reduction of both isoforms are associated with compound phenotypes affecting the brain, heart, and intestine. RNA-seq data revealed three distinct transcription start sites, two of which produce a protein isoform utilizing ATG⁺¹ while the third utilizes ATG⁺⁸² . Transcripts sponsoring translational initiation at ATG⁺¹ predominate in intestinal smooth muscle, and are more abundant compared with the level measured in fibroblasts. Together these observations describe a new mechanism of tissue-specific regulation of FLNA that could reflect the differing mechanical requirements of these cell types during development.

Integrity of the corpus callosum in patients with periventricular nodular heterotopia related epilepsy by FLNA mutation

Objective

To investigate the quantitative diffusion properties of the corpus callosum (CC) in a large group of patients with periventricular nodular heterotopia (PNH) related epilepsy and to further investigate the effect of Filamin A (FLNA) mutation on these properties.

Methods

Patients with PNH (n = 34), subdivided into FLNA-mutated (n = 11) and FLNA-nonmutated patients (n = 23) and healthy controls (n = 34), underwent 3.0 T structural MRI and diffusion imaging scan (64 direction). Fractional anisotropy (FA) and mean diffusivity (MD) were measured in the three major subdivisions of the CC (genu, body and splenium). Correlations between DTI metric changes and clinical parameters were also evaluated. Furthermore, the effect of FLNA mutation on structural integrity of the corpus callosum was examined.

Results

Patients with PNH and epilepsy had significant reductions in FA for the genu and splenium of the CC, accompanied by increases in MD for the splenium, as compared to healthy controls. There were no correlations between clinical parameters of epilepsy and MD. The FA value in the splenium negatively correlated with epilepsy duration. Interestingly, FLNA-mutated patients showed significantly decreased FA for all three major subdivisions of the CC, and increased MD for the genu and splenium, as compared to HCs and FLNA-nonmutated patients.

Conclusions

These findings support the conclusion that patients with epilepsy secondary to PNH present widespread microstructural changes found in the corpus callosum that extend beyond the macroscopic MRI-visible lesions. This study also indicates that FLNA may affect white matter integrity in this disorder.

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PNH patients presented diffusion abnormality in splenium segment of the CC.

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Only the FA value for the splenium negatively correlated with epilepsy duration.

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In PNH, DTI changes of CC differentiate FLNA-mutated from nonmutated subjects.

Lung Transplantation for FLNA-Associated Progressive Lung Disease

OBJECTIVE

To describe a series of patients with pathogenic variants in FLNA and progressive lung disease necessitating lung transplantation.

STUDY DESIGN

We conducted a retrospective chart review of 6 female infants with heterozygous presumed loss-of-function pathogenic variants in FLNA whose initial presentation was early and progressive respiratory failure.

RESULTS

Each patient received lung transplantation at an average age of 11 months (range, 5-15 months). All patients had pulmonary arterial hypertension and chronic respiratory failure requiring tracheostomy and escalating levels of ventilator support before transplantation. All 6 patients survived initial lung transplantation; however, 1 patient died after a subsequent heart-lung transplant. The remaining 5 patients are living unrestricted lives on chronic immunosuppression at most recent follow-up (range, 19 months to 11.3 years post-transplantation). However, in all patients, severe ascending aortic dilation has been observed with aortic regurgitation.

CONCLUSIONS

Respiratory failure secondary to progressive obstructive lung disease during infancy may be the presenting phenotype of FLNA-associated periventricular nodular heterotopia. We describe a cohort of patients with progressive respiratory failure related to a pathogenic variant in FLNA and present lung transplantation as a viable therapeutic option for this group of patients.

IRaPPA: information retrieval based integration of biophysical models for protein assembly selection

MOTIVATION

In order to function, proteins frequently bind to one another and form 3D assemblies. Knowledge of the atomic details of these structures helps our understanding of how proteins work together, how mutations can lead to disease, and facilitates the designing of drugs which prevent or mimic the interaction.

RESULTS

Atomic modeling of protein-protein interactions requires the selection of near-native structures from a set of docked poses based on their calculable properties. By considering this as an information retrieval problem, we have adapted methods developed for Internet search ranking and electoral voting into IRaPPA, a pipeline integrating biophysical properties. The approach enhances the identification of near-native structures when applied to four docking methods, resulting in a near-native appearing in the top 10 solutions for up to 50% of complexes benchmarked, and up to 70% in the top 100.

AVAILABILITY AND IMPLEMENTATION

IRaPPA has been implemented in the SwarmDock server ( http://bmm.crick.ac.uk/∼SwarmDock/ ), pyDock server ( http://life.bsc.es/pid/pydockrescoring/ ) and ZDOCK server ( http://zdock.umassmed.edu/ ), with code available on request.

CONTACT

moal@ebi.ac.uk.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Divergence and inheritance of neocortical heterotopia in inbred and genetically-engineered mice

Cortical function emerges from the intrinsic properties of neocortical neurons and their synaptic connections within and across lamina. Neurodevelopmental disorders affecting migration and lamination of the neocortex result in cognitive delay/disability and epilepsy. Molecular layer heterotopia (MLH), a dysplasia characterized by over-migration of neurons into layer I, are associated with cognitive deficits and neuronal hyperexcitability in humans and mice. The breadth of different inbred mouse strains that exhibit MLH and inheritance patterns of heterotopia remain unknown. A neuroanatomical survey of numerous different inbred mouse strains, 2 first filial generation (F1) hybrids, and one consomic strain (C57BL/6J-Chr 1^A/J/NaJ) revealed MLH only in C57BL/6 mice and the consomic strain. Heterotopia were observed in numerous genetically-engineered mouse lines on a congenic C57BL/6 background. These data indicate that heterotopia formation is a weakly penetrant trait requiring homozygosity of one or more C57BL/6 alleles outside of chromosome 1. These data are relevant toward understanding neocortical development and disorders affecting neocortical lamination.

Role of a heterotrimeric G-protein, Gi2, in the corticogenesis: possible involvement in periventricular nodular heterotopia and intellectual disability

We analyzed the role of a heterotrimeric G-protein, Gi2, in the development of the cerebral cortex. Acute knockdown of the α-subunit (Gαi2) with in utero electroporation caused delayed radial migration of excitatory neurons during corticogenesis, perhaps because of impaired morphology. The migration phenotype was rescued by an RNAi-resistant version of Gαi2. On the other hand, silencing of Gαi2 did not affect axon elongation, dendritic arbor formation or neurogenesis at ventricular zone in vivo. When behavior analyses were conducted with acute Gαi2-knockdown mice, they showed defects in social interaction, novelty recognition and active avoidance learning as well as increased anxiety. Subsequently, using whole-exome sequencing analysis, we identified a de novo heterozygous missense mutation (c.680C>T; p.Ala227Val) in the GNAI2 gene encoding Gαi2 in an individual with periventricular nodular heterotopia and intellectual disability. Collectively, the phenotypes in the knockdown experiments suggest a role of Gαi2 in the brain development, and impairment of its function might cause defects in neuronal functions which lead to neurodevelopmental disorders.

Refilins are short-lived Actin-bundling proteins that regulate lamellipodium protrusion dynamics

Refilins (RefilinA and RefilinB) are members of a novel family of Filamin binding proteins that function as molecular switches to conformationally alter the Actin filament network into bundles. We show here that Refilins are extremely labile proteins. An N-terminal PEST/DSG(X)_2-4S motif mediates ubiquitin-independent rapid degradation. A second degradation signal is localized within the C-terminus. Only RefilinB is protected from rapid degradation by an auto-inhibitory domain that masks the PEST/DSG(X)_2-4S motif. Dual regulation of RefilinA and RefilinB stability was confirmed in rat brain NG2 precursor cells (polydendrocyte). Using loss- and gain-of-function approaches we show that in these cells, and in U373MG cells, Refilins contribute to the dynamics of lamellipodium protrusion by catalysing Actin bundle formation within the lamella Actin network. These studies extend the Actin bundling function of the Refilin-Filamin complex to dynamic regulation of cell membrane remodelling.

Summary: The newly identified Refilin protein family are unique short-lived proteins that complex with Filamin to regulate plasma membrane dynamics though the promotion of Actin filament bundling.

Ehlers-Danlos syndrome with lethal cardiac valvular dystrophy in males carrying a novel splice mutation in FLNA

Filamin A is an X-linked, ubiquitous actin-binding protein whose mutations are associated to multiple disorders with limited genotype-phenotype correlations. While gain-of-function mutations cause various bone dysplasias, loss-of-function variants are the most common cause of periventricular nodular heterotopias with variable soft connective tissue involvement, as well as X-linked cardiac valvular dystrophy (XCVD). The term "Ehlers-Danlos syndrome (EDS) with periventricular heterotopias" has been used in females with neurological, cardiovascular, integument and joint manifestations, but this nosology is still a matter of debate. We report the clinical and molecular update of an Italian family with an X-linked recessive soft connective tissue disorder and which was described, in 1975, as the first example of EDS type V of the Berlin nosology. The cutaneous phenotype of the index patient was close to classical EDS and all males died for a lethal cardiac valvular dystrophy. Whole exome sequencing identified the novel c.1829-1G>C splice variation in FLNA in two affected cousins. The nucleotide change was predicted to abolish the canonical splice acceptor site of exon 13 and to activate a cryptic acceptor site 15 bp downstream, leading to in frame deletion of five amino acid residues (p.Phe611_Gly615del). The predicted in frame deletion clusters with all the mutations previously identified in XCVD and falls within the N-terminus rod 1 domain of filamin A. Our findings expand the male-specific phenotype of FLNA mutations that now includes classical-like EDS with lethal cardiac valvular dystrophy, and offer further insights for the genotype-phenotype correlations within this spectrum. © 2016 Wiley Periodicals, Inc.

Upregulation of neurovascular communication through filamin abrogation promotes ectopic periventricular neurogenesis

Neuronal fate-restricted intermediate progenitors (IPs) are derived from the multipotent radial glia (RGs) and serve as the direct precursors for cerebral cortical neurons, but factors that control their neurogenic plasticity remain elusive. Here we report that IPs’ neuron production is enhanced by abrogating filamin function, leading to the generation of periventricular neurons independent of normal neocortical neurogenesis and neuronal migration. Loss of Flna in neural progenitor cells (NPCs) led RGs to undergo changes resembling epithelial-mesenchymal transition (EMT) along with exuberant angiogenesis that together changed the microenvironment and increased neurogenesis of IPs. We show that by collaborating with β-arrestin, Flna maintains the homeostatic signaling between the vasculature and NPCs, and loss of this function results in escalated Vegfa and Igf2 signaling, which exacerbates both EMT and angiogenesis to further potentiate IPs’ neurogenesis. These results suggest that the neurogenic potential of IPs may be boosted in vivo by manipulating Flna-mediated neurovascular communication.

DOI:http://dx.doi.org/10.7554/eLife.17823.001

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.