Mutations in ARFGEF2 implicate vesicle trafficking in neural progenitor proliferation and migration in the human cerebral cortex

Disruption of human neural precursor proliferation can give rise to a small brain (microcephaly), and failure of neurons to migrate properly can lead to an abnormal arrest of cerebral cortical neurons in proliferative zones near the lateral ventricles (periventricular heterotopia). Here we show that an autosomal recessive condition characterized by microcephaly and periventricular heterotopia maps to chromosome 20 and is caused by mutations in the gene ADP-ribosylation factor guanine nucleotide-exchange factor-2 (ARFGEF2). By northern-blot analysis, we found that mouse Arfgef2 mRNA levels are highest during embryonic periods of ongoing neuronal proliferation and migration, and by in situ hybridization, we found that the mRNA is widely distributed throughout the embryonic central nervous system (CNS). ARFGEF2 encodes the large (>200 kDa) brefeldin A (BFA)-inhibited GEF2 protein (BIG2), which is required for vesicle and membrane trafficking from the trans-Golgi network (TGN). Inhibition of BIG2 by BFA, or by a dominant negative ARFGEF2 cDNA, decreases cell proliferation in vitro, suggesting a cell-autonomous regulation of neural expansion. Inhibition of BIG2 also disturbed the intracellular localization of such molecules as E-cadherin and beta-catenin by preventing their transport from the Golgi apparatus to the cell surface. Our findings show that vesicle trafficking is an important regulator of proliferation and migration during human cerebral cortical development.

Clinical, environmental, and genetic determinants of multiple sclerosis in children with acute demyelination: a prospective national cohort study

BACKGROUND

HLA-DRB1*15 genotype, previous infection with Epstein-Barr virus, and vitamin D insufficiency are susceptibility factors for multiple sclerosis, but whether they act synergistically to increase risk is unknown. We aimed to assess the contributions of these risk factors and the effect of established precursors of multiple sclerosis, such as brain lesions on MRI and oligoclonal bands in CSF at the time of incident demyelination, on development of multiple sclerosis in children.

METHODS

In our prospective national cohort study, we assessed children who presented with incident CNS demyelination to any of the 16 paediatric health-care facilities or seven regional health-care facilities in Canada. We did univariate and multivariable analyses to assess contributions of HLA-DRB1*15, Epstein-Barr virus, vitamin D status, MRI evidence of brain lesions, and CSF oligoclonal bands as determinants of multiple sclerosis. We used classification and regression tree analyses to generate a risk stratification algorithm for clinical use.

FINDINGS

Between Sept 1, 2004, and June 30, 2010, we screened 332 children of whom 302 (91%) were eligible and followed-up for a median of 3·14 years (IQR 1·61-4·51). 63 (21%) children were diagnosed with multiple sclerosis after a median of 127 days (99-222). Although the risk of multiple sclerosis was increased with presence of one or more HLA-DRB1*15 alleles (hazard ratio [HR] 2·32, 95% CI 1·25-4·30), reduced serum 25-hydroxyvitamin D concentration (HR per 10 nmol/L decrease 1·11, 1·00-1·25), and previous Epstein-Barr-virus infection (HR 2·04, 0·99-4·20), no interactions between these variables were detected on multivariate analysis. Multiple sclerosis was strongly associated with baseline MRI evidence of one or more brain lesion (HR 37·9, 5·26-273·85) or CSF oligoclonal bands (6·33, 3·35-11·96), suggesting established disease. One patient diagnosed with multiple sclerosis had a normal MRI scan, and therefore sensitivity of an abnormal MRI scan for multiple sclerosis diagnosis was 98·4%.

INTERPRETATION

Risk of multiple sclerosis in children can be stratified by presence of HLA-DRB1*15 alleles, remote Epstein-Barr virus infection, and low serum 25-hydroxyvitamin D concentrations. Similar to previous studies in adults, brain lesions detected on MRI and CSF oligoclonal bands in children are probable precursors to the clinical onset of multiple sclerosis. Children with a normal MRI are very likely to have a monophasic illness.

FUNDING

Canadian Multiple Sclerosis Scientific Research Foundation.

Blue native polyacrylamide gel electrophoresis: a powerful tool in diagnosis of oxidative phosphorylation defects

Catalytic activity of oxidative phosphorylation complexes is maintained following separation by Blue Native polyacrylamide gel electrophoresis (BN-PAGE). In BN-PAGE gels, using histochemical staining methods, we have demonstrated enzymatic activity of the complexes I, II, IV, and V in heart and skeletal muscle, liver, and cultured skin fibroblasts. The combination of BN-PAGE and catalytic staining can be successfully applied for detection of complex deficiencies. Tissues from 18 patients with deficiency in the oxidative phosphorylation as detected by spectrophotometric assay were used (10 patients complex IV, three patients complex I, one patient complex II, one patient complex I+III, three patients complex I+IV). The gene defect was located in nuclear DNA in five patients and mitochondrial DNA in one patient. In samples from patients with a severe deficiency, almost complete absence of the corresponding enzyme band is observed after catalytic staining in the gel. In patients with known partial deficiency, a milder decrease of the corresponding enzyme band is demonstrated. The amount of protein in complexes I, V, and III can easily be evaluated in samples from heart and skeletal muscle after separation by BN-PAGE using silver or Coomassie staining. The protein amount in complex IV is difficult to visualize by silver staining but easier by the Coomassie technique. In samples from liver and cultured skin fibroblasts, evaluation of protein amount is more difficult due to high background staining. In these tissues, immunoblotting can be done after BN-PAGE and subsequent transfer to a nitrocellulose membrane.

Perinatal exposure to low-dose BDE-47, an emergent environmental contaminant, causes hyperactivity in rat offspring

BACKGROUND

Polybrominated diphenyl ethers (PBDE) are a group of environmental contaminants increasing in North America. Few data are available on neurobehavioral effects at low-dose exposure.

OBJECTIVES

Our goal in the present study was to evaluate whether low-dose BDE-47, which is the most abundant PBDE in human samples, affects the neurobehavioral development of rats.

METHODS

Dams were exposed to vehicle or low-dose BDE-47 (0.002, 0.02 and 0.2 mg/kg body weight) each 5 days from gestational day 15 to postnatal day (PND) 20 by intravenous injections. Spontaneous locomotor activity of pups was assessed using the open field test on PND 15, 20 and 25. Sensorimotor coordination was assessed using a RotaRod on PND 30.

RESULTS

Exposure to BDE-47 increased locomotor activity of pups. Developmental landmarks and sensorimotor coordination were not influenced by exposure to BDE-47. BDE-47 content in adipose tissue of exposed rats was similar to that known for human populations.

CONCLUSION

These results indicate neurodevelopmental disruption induced in rats by BDE-47 at levels found in the human population.

Acute inflammatory demyelinating polyradiculopathy in children: clinical and electrodiagnostic studies

Clinical and electrophysiological features in 43 children with acute inflammatory demyelinating polyradiculoneuropathy (AIDP) were retrospectively studied. More than one-third of these children were less than 3 years old. Some distinctive clinical features specific to adults or to children were identified. Initial symptoms such as ataxia and severe limb or back pain were more frequent in children. By using the criteria suggested here, according to our neurophysiological findings, the diagnosis of AIDP could be proposed as early of the first days of illness in 90% of the children and is confirmed during the second week. The neurophysiological evolution was very similar in children and adults except that recovery occurred sooner in children. Prognosis was better in childhood (complete recovery in all but 2 patients with minor disabilities).

Spinal Cord Arteriovenous Malformations in a Pediatric Population Children below 15 Years of Age the Place of Endovascular Management

Among a global group of 164 spinal arteriovenous shunts, a series of 16 spinal cord arteriovenous malformations (SCAVMs) were diagnosed in a pediatric population below 15 years of age.

The majority of the lesions affected the male population; 6 were located in the cervical spine and 10 at the thoracolumbar level. Hemorrhage was the most frequent symptom encountered (63%). Half of the bleeds occurred only in the subarachnoid spaces. Neurological deficits (acute or progressive) revealed the SCAVM in 31% of patients.

The lesion was an incidental finding in one patient (6%). All the diagnoses (except one) were made by MRI. Selective angiography confirmed the diagnosis and identified the type of the lesion (nidus or fistula) and its angioarchitecture, stressing that the veins and their related features are the key point in the clinical eloquence of SCAVMs.

All the treatments performed were endovascular; no patient was deemed a surgical candidate. Therapeutic abstention was decided in 37% of cases, mainly for anatomical reasons. All the patients in this group improved (50% being normal and 50% presenting slight non-handicapping deficits due to the initial accidents). Embolisation was indicated in 10 patients (63%) and was performed with fluid agents (histoacryl*) except in the first patient who had been treated with particles.

Twelve percent of patients were cured (fistula), the remaining 88% having their lesion controlled to more than 50%. This partial treatment was always targetted towards the angioarchitectural weak points of the lesion.

All patients improved after embolisation, 45% of them being neurologically normal. Follow-up in this group ranges from 1.5 to 13 Years. No complications occurred after embolisation. No bleed, rebleed or clinical worsening has occurred after endovascular treatment.

The results in this series suggest that endovascular treatment (even partial but targetted) represents a safe and stable therapeutic alternative in the management of SCAVMs in this population.

Involvement of neuronal IL-1β in acquired brain lesions in a rat model of neonatal encephalopathy

Background

Infection-inflammation combined with hypoxia-ischemia (HI) is the most prevalent pathological scenario involved in perinatal brain damage leading to life-long neurological disabilities. Following lipopolysaccharide (LPS) and/or HI aggression, different patterns of inflammatory responses have been uncovered according to the brain differentiation stage. In fact, LPS pre-exposure has been reported to aggravate HI brain lesions in post-natal day 1 (P1) and P7 rat models that are respectively equivalent - in terms of brain development - to early and late human preterm newborns. However, little is known about the innate immune response in LPS plus HI-induced lesions of the full-term newborn forebrain and the associated neuropathological and neurobehavioral outcomes.

Methods

An original preclinical rat model has been previously documented for the innate neuroimmune response at different post-natal ages. It was used in the present study to investigate the neuroinflammatory mechanisms that underline neurological impairments after pathogen-induced inflammation and HI in term newborns.

Results

LPS and HI exerted a synergistic detrimental effect on rat brain. Their effect led to a peculiar pattern of parasagittal cortical-subcortical infarcts mimicking those in the human full-term newborn with subsequent severe neurodevelopmental impairments. An increased IL-1β response in neocortical and basal gray neurons was demonstrated at 4 h after LPS + HI-exposure and preceded other neuroinflammatory responses such as microglial and astroglial cell activation. Neurological deficits were observed during the acute phase of injury followed by a recovery, then by a delayed onset of profound motor behavior impairment, reminiscent of the delayed clinical onset of motor system impairments observed in humans. Interleukin-1 receptor antagonist (IL-1ra) reduced the extent of brain lesions confirming the involvement of IL-1β response in their pathophysiology.

Conclusion

In rat pups at a neurodevelopmental age corresponding to full-term human newborns, a systemic pre-exposure to a pathogen component amplified HI-induced mortality and morbidities that are relevant to human pathology. Neuronal cells were the first cells to produce IL-1β in LPS + HI-exposed full-term brains. Such IL-1β production might be responsible for neuronal self-injuries via well-described neurotoxic mechanisms such as IL-1β-induced nitric oxide production, or IL-1β-dependent exacerbation of excitotoxic damage.

Transplacental Transfer of Interleukin-1 Receptor Agonist and Antagonist Following Maternal Immune Activation

PROBLEM

Prenatal exposure to inflammation increases the incidence of neonatal brain injury. This raise the question whether maternally produced cytokines, especially interleukin (IL)-1 elevated in pathological pregnancies and known to alter fetal development, can cross the placental barrier and affect the fetus directly.

METHOD OF STUDY

We addressed if IL-1 agonist/antagonist could cross the placenta.

RESULTS

Radiolabelled-IL-1 injected maternally reached the fetus in minimal amount. 3% of the amount detected within the placenta was transferred into the fetal liver and less than 1% recovered in the fetal brain 30 min after the injection Importantly, transfer of IL-1 was not affected by maternal exposure to LPS. Maternal administration of IL-1 receptor antagonist also reached the fetus in low concentration.

CONCLUSIONS

This suggests that minimal amount of maternally produced IL-1 family members cross the placental barrier. Their negative effects are likely indirect, through their deleterious placental actions.

Pathogenic Variants in CEP85L Cause Sporadic and Familial Posterior Predominant Lissencephaly

Lissencephaly (LIS), denoting a "smooth brain," is characterized by the absence of normal cerebral convolutions with abnormalities of cortical thickness. Pathogenic variants in over 20 genes are associated with LIS. The majority of posterior predominant LIS is caused by pathogenic variants in LIS1 (also known as PAFAH1B1), although a significant fraction remains without a known genetic etiology. We now implicate CEP85L as an important cause of posterior predominant LIS, identifying 13 individuals with rare, heterozygous CEP85L variants, including 2 families with autosomal dominant inheritance. We show that CEP85L is a centrosome protein localizing to the pericentriolar material, and knockdown of Cep85l causes a neuronal migration defect in mice. LIS1 also localizes to the centrosome, suggesting that this organelle is key to the mechanism of posterior predominant LIS.

Haemorrhagic shock and encephalopathy syndrome: neurological course and predictors of outcome

The haemorrhagic shock and encephalopathy syndrome (HSES) is a devastating disease. The aetiology of this syndrome is unknown, and, despite intensive treatment, the outcome is often fatal or associated with severe neurological sequelae.

OBJECTIVE

To assess the neurological features and potential prognostic markers of the disease.

DESIGN

Retrospective study.

SETTING

Division of Neuropaediatrics in a children's university hospital.

PATIENTS AND METHODS

Fourteen patients fulfilling the HSES criteria out of 42 children admitted with fever and shock to the Paediatric Intensive Care Unit between 1986 and 1994, were analysed for clinical, biological, neuroradiological, EEG and neuropathological findings.

RESULTS

The patients (age range from 2 to 33 months) were found at night or in the morning either comatous (n = 3) or convulsing (n = 11). All but one were healthy before admission, although eight had had a brief prodromal infectious disease. All were febrile (mean body temperature 39.9 degrees C +/-0.9 degrees). Seasonal clustering during the winter months was observed. Coma and seizures with frequent status epilepticus were the main neurological manifestations. All children recovered from their multiple organ failure within a few days. Seven died (50%); four survivors had neurological sequelae (29%) with a developmental quotient (DQ) of 50% or less in three and a DQ of 75% in one and three infants (21%) had normal outcomes. Computed tomography (CT) displayed a diffuse area of low density mainly in the cerebral cortex and intraventricular and parenchymal haemorrhages. Magnetic resonance imaging (MRI) showed haemorrhagic cortical lesions. Postmortem examination of the brain conducted in three patients showed necrotic and haemorrhagic lesions, mainly in cortical areas. Comparison of the children with adverse outcome (death or neurological sequelae) with those with normal outcome revealed that predictors of poor outcome were status epilepticus (p = 0.003) and coma for more than 24 h (p = 0.01). Infants without disseminated intravascular coagulation, without a biphasic course and without brain hypodensities or haemorrhages on CT scans performed at least 4 days after onset had a normal neurodevelopmental outcome.

CONCLUSION

The central nervous system appeared to be the main target of the HSES lesions. The most common outcome was brain death or severe brain damage. Further studies with a larger sample are necessary to determine whether the prognostic indicators we identified are reliable.

Plasma exchange in Rasmussen's encephalitis

The authors observed a 4-year-old girl who has Rasmussen's encephalitis. She started with frequent localized and generalized seizures. Standard antiepileptic treatment was almost ineffective. The frequency of the generalized seizures decreased, but the myoclonic jerks of the left part of the body persisted. An EEG showed partial status epilepticus. The results of the CT scan were normal. Antibodies to viruses were absent from the blood and cerebrospinal fluid. An MR scan showed a T2-weighted hypersignal zone in the right frontal region. Intravenous bolus injections of corticosteroids and drips of immunoglobulins were inefficient, and we started plasma exchanges which have continued for 9 months. The clinical state stabilized, and the images on the MR scan improved, but the results of the EEG did not improve. The authors discuss the effect of the plasma exchange, the use of which is questionable in this disease.

De novo heterozygous missense and loss-of-function variants in CDC42BPB are associated with a neurodevelopmental phenotype

CDC42BPB encodes MRCKβ (myotonic dystrophy-related Cdc42-binding kinase beta), a serine/threonine protein kinase, and a downstream effector of CDC42, which has recently been associated with Takenouchi-Kosaki syndrome, an autosomal dominant neurodevelopmental disorder. We identified 12 heterozygous predicted deleterious variants in CDC42BPB (9 missense, 2 frameshift, and 1 nonsense) in 14 unrelated individuals (confirmed de novo in 11/14) with neurodevelopmental disorders including developmental delay/intellectual disability, autism, hypotonia, and structural brain abnormalities including cerebellar vermis hypoplasia and agenesis/hypoplasia of the corpus callosum. The frameshift and nonsense variants in CDC42BPB are expected to be gene-disrupting and lead to haploinsufficiency via nonsense-mediated decay. All missense variants are located in highly conserved and functionally important protein domains/regions: 3 are found in the protein kinase domain, 2 are in the citron homology domain, and 4 in a 20-amino acid sequence between 2 coiled-coil regions, 2 of which are recurrent. Future studies will help to delineate the natural history and to elucidate the underlying biological mechanisms of the missense variants leading to the neurodevelopmental and behavioral phenotypes.

Enhanced tumor necrosis factor alpha in coronavirus but not in paracetamol-induced acute hepatic necrosis in mice

Previous reports have demonstrated that tumor necrosis factor alpha (TNF-alpha) plays an important role in the pathogenesis of fulminant hepatic necrosis. The purpose of this experimental study was to measure TNF-alpha blood activity in paracetamol-induced liver necrosis and in coronavirus (MHV3)-induced fulminant hepatitis in mice. No elevation of TNF-alpha activity was found in hepatic failure complicating paracetamol poisoning. In contrast, TNF-alpha activity significantly increased in response to MHV3, reaching 16.3 +/- 5.5 U/ml from 24 h post infection (P less than 0.01). This augmentation was observed even though the virus was not detectable in the liver. Serum alanine aminotransferase levels were low and no histological lesion was observed. In conclusion, our study further supports the implication of TNF-alpha in virus-induced hepatitis failure and confirms that paracetamol poisoning does not cause increased TNF-alpha activity in the circulation.

Protective Effects of Interleukin-1 Blockade on Group B Streptococcus-Induced Chorioamnionitis and Subsequent Neurobehavioral Impairments of the Offspring

Group B Streptococcus (GBS) is one of the most common bacteria isolated in human chorioamnionitis. Placental infection due to GBS is a major risk factor for fetal organ injuries, preterm birth, perinatal morbidity and mortality, and life-long multiorgan morbidities. Preclinical and clinical studies have shown that GBS-induced infection drives polymorphonuclear (PMN) cell infiltration within the placenta, the hallmark of human chorioamnionitis. In preclinical and clinical studies, the upregulation of interleukin(IL)-1β in the placenta and maternal/fetal blood was associated with a high risk of neurodevelopmental impairments in the progeny. We hypothesized that targeted IL-1 blockade administered to the dam alleviates GBS-induced chorioamnionitis and the downstream fetal inflammatory response syndrome (FIRS). IL-1 receptor antagonist (IL-1Ra) improved the gestational weight gain of GBS-infected dams and did not worsen the infectious manifestations. IL-1Ra reduced the IL-1β titer in the maternal sera of GBS-infected dams. IL-1Ra decreased the levels of IL-1β, IL-6, chemokine (C-X-C motif) ligand 1 (CXCL1), and polymorphonuclear (PMN) infiltration in GBS-infected placenta. IL-1Ra treatment reduced the IL-1β titer in the fetal sera of GBS-exposed fetuses. IL-1 blockade also alleviated GBS-induced FIRS and subsequent neurobehavioral impairments of the offspring without worsening the outcome of GBS infection. Altogether, these results showed that IL-1 plays a key role in the physiopathology of live GBS-induced chorioamnionitis and consequent neurobehavioral impairments.

Lateral Medullary Syndrome Due to Left Vertebral Artery Occlusion in a Boy Postflexion Neck Injury

Lateral medullary syndrome is rare in pediatrics. It is characterized by neurological deficits due to an ischemic lesion in the lateral medulla. The authors describe a 17-year-old boy who developed lateral medullary syndrome in the context of a hyperflexion neck injury while diving in shallow water with traumatic vascular injury. He had “crossed” neurological deficits above and below the neck. His magnetic resonance angiography showed intra- and extracranial left vertebral artery occlusion and his magnetic resonance imaging showed signal abnormality involving the left lateral medulla and inferomedial cerebellum in keeping with an infarct secondary to left vertebral artery and left posterior inferior cerebellar artery occlusion. Good neurological recovery was observed on heparin therapy started after surgical treatment of traumatic injury. To our knowledge, this is the first reported case of lateral medullary syndrome in a pediatric population related to a flexion neck injury. The authors emphasize the importance of a high level of suspicion for accurate diagnosis.

Abstract 389: Gestational Inflammation and Perinatal Arterial Ischemic Stroke: A Causal Connection?

Introduction: Perinatal arterial ischemic strokes affect about 1/3,000 newborn and are the main cause of hemiplegic cerebral palsy. The large cerebral arteries from the anterior system, namely the intra-cranial carotid bifurcation, are the most affected, ischemic stroke being located in its territory in 85% of cases. The classic, but unproven, pathophysiological hypothesis postulated that arterial occlusion was caused by emboli from placental origin. This remains controversial due to the major unbalance of brain infarcts between anterior and posterior distribution, and to the absence of associated extra-cerebral infarcts. A new pathophysiological perspective emerged from the epidemiological association between gestational inflammation and perinatal stroke. Our hypothesis is that materno-foetal inflammation, induced by gestational exposure to pathogens, leads to a site-specific vasculitis affecting the carotid bifurcation and then triggering a focal thrombosis.

Material and methods: Dams were injected with saline or lipopolysaccharide (LPS) from Escherichia coli (200 μg/kg/12h) between gestational day (G) 21 and 22. Brains were harvested at G21, G22 and postnatal day 1 (P1). At P1, a prothrombotic stress (transcutaneous photothrombosis) was applied on middle cerebral arteries to compare its susceptibility to thrombosis between LPS-exposed or unexposed pups. Immunohistochemistry and ELISA detected maternal, placental and fetal/neonatal inflammatory markers.

Results: Our results showed a maternal, placental and fetal inflammation mediated by IL-1β, TNF-α and MCP-1 as well as an arterial inflammation in relation with the clinical pattern of perinatal arterial ischemic strokes. LPS+photothrombosis pups presented ischemic strokes and motor impairments, which were not detected when photothrombosis was applied without prior treatment with LPS.

Conclusion: Preliminary results from our new pre-clinical model support our hypothesis of increased susceptibility of anterior cerebral arteries to gestational inflammation, and open a new vasculitic pathophysiological avenue to understand perinatal stroke.