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Brain : a Journal of Neurology Sep 2022Variants in RAC3, encoding a small GTPase RAC3 which is critical for the regulation of actin cytoskeleton and intracellular signal transduction, are associated with a...
Variants in RAC3, encoding a small GTPase RAC3 which is critical for the regulation of actin cytoskeleton and intracellular signal transduction, are associated with a rare neurodevelopmental disorder with structural brain anomalies and facial dysmorphism. We investigated a cohort of 10 unrelated participants presenting with global psychomotor delay, hypotonia, behavioural disturbances, stereotyped movements, dysmorphic features, seizures and musculoskeletal abnormalities. MRI of brain revealed a complex pattern of variable brain malformations, including callosal abnormalities, white matter thinning, grey matter heterotopia, polymicrogyria/dysgyria, brainstem anomalies and cerebellar dysplasia. These patients harboured eight distinct de novo RAC3 variants, including six novel variants (NM_005052.3): c.34G > C p.G12R, c.179G > A p.G60D, c.186_188delGGA p.E62del, c.187G > A p.D63N, c.191A > G p.Y64C and c.348G > C p.K116N. We then examined the pathophysiological significance of these novel and previously reported pathogenic variants p.P29L, p.P34R, p.A59G, p.Q61L and p.E62K. In vitro analyses revealed that all tested RAC3 variants were biochemically and biologically active to variable extent, and exhibited a spectrum of different affinities to downstream effectors including p21-activated kinase 1. We then focused on the four variants p.Q61L, p.E62del, p.D63N and p.Y64C in the Switch II region, which is essential for the biochemical activity of small GTPases and also a variation hot spot common to other Rho family genes, RAC1 and CDC42. Acute expression of the four variants in embryonic mouse brain using in utero electroporation caused defects in cortical neuron morphology and migration ending up with cluster formation during corticogenesis. Notably, defective migration by p.E62del, p.D63N and p.Y64C were rescued by a dominant negative version of p21-activated kinase 1. Our results indicate that RAC3 variants result in morphological and functional defects in cortical neurons during brain development through variant-specific mechanisms, eventually leading to heterogeneous neurodevelopmental phenotypes.
Topics: Animals; Humans; Mice; Neurodevelopmental Disorders; Neurons; Phenotype; p21-Activated Kinases; rac GTP-Binding Proteins
PubMed: 35851598
DOI: 10.1093/brain/awac106 -
The Pan African Medical Journal 2022Septo optic dysplasia plus is a rare disease seen in children. Its diagnosis is radiological, based on brain magnetic resonance imaging (MRI). We report the case of a...
Septo optic dysplasia plus is a rare disease seen in children. Its diagnosis is radiological, based on brain magnetic resonance imaging (MRI). We report the case of a child aged 2 years and 4 months, with no particular pathological history; who consulted for psychomotor retardation, strabismus and low vision behavior. An endocrine biological assessment exploring the hypothalomo-pituitary function was carried out, revealing no abnormality. The diagnosis of septo-optic dysplasia plus was retained on the brain MRI data, in front of the agenesis of the septum pellucidum and of the splenium of the corpus callosum, the hypoplasia of the optic pathways and of the pituitary stalk as well as in front of the agenesis of the posterior pituitary. It was associated with a closed schizencephaly. Septo-optic dysplasia is a rare congenital malformation. Our objective is to recall its semiology in imaging and to underline the importance of MRI to establish the diagnosis. Septo-optic dysplasia is a rare clinical entity typically involving midline brain abnormalities, optic nerve hypoplasia, and pituitary insufficiency. The association with cortical malformations such as schizencephaly and polymicrogyria denotes the term septo-optic dysplasia plus. Advances in imaging currently allow early diagnosis, which is essential for adequate management. Antenatal ultrasound may suspect dysplasia, and brain MRI confirms the diagnosis.
Topics: Child; Female; Humans; Hypopituitarism; Magnetic Resonance Imaging; Pregnancy; Schizencephaly; Septo-Optic Dysplasia; Septum Pellucidum
PubMed: 35812255
DOI: 10.11604/pamj.2022.42.17.33198 -
Epilepsia Open Sep 2022Malformations of the polymicrogyria spectrum can be mimicked in rodents through neonatal transcranial focal cortical freeze lesions. The animals presenting the...
Altered excitatory and inhibitory neocortical circuitry leads to increased convulsive severity after pentylenetetrazol injection in an animal model of schizencephaly, but not of microgyria.
OBJECTIVE
Malformations of the polymicrogyria spectrum can be mimicked in rodents through neonatal transcranial focal cortical freeze lesions. The animals presenting the malformations present both altered synaptic events and epileptiform activity in the vicinity of the microgyrus, but the comprehension of their contribution to increased predisposition or severity of seizures require further studies.
METHODS
In order to investigate these issues, we induced both microgyria and schizencephaly in 57 mice and evaluated: their convulsive susceptibility and severity after pentyleneterazol (PTZ) treatment, the quantification of their symmetric and asymmetric synapses, the morphology of their dendritic arbors, and the content of modulators of synaptogenesis, such as SPARC, gephyrin and GAP-43 within the adjacent visual cortex.
RESULTS
Our results have shown that only schizencephalic animals present increased convulsive severity. Nevertheless, both microgyric and schizencephalic cortices present increased synapse number and dendritic complexity of layer IV and layer V-located neurons. Specifically, the microgyric cortex presented reduced inhibitory synapses, while the schizencephalic cortex presented increased excitatory synapses. This altered synapse number is correlated with decreased content of both the anti-synaptogenic factor SPARC and the inhibitory postsynaptic organizer gephyrin in both malformed groups. Besides, GAP-43 content and dendritic spines number are enhanced exclusively in schizencephalic cortices.
SIGNIFICANCE
In conclusion, our study supports the hypothesis that the sum of synaptic alterations drives to convulsive aggravation in animals with schizencephaly, but not microgyria after PTZ treatment. These findings reveal that different malformations of cortical development should trigger epilepsy via different mechanisms, requiring further studies for development of specific therapeutic interventions.
Topics: Animals; Disease Models, Animal; GAP-43 Protein; Mice; Neocortex; Pentylenetetrazole; Polymicrogyria; Schizencephaly; Seizures
PubMed: 35808864
DOI: 10.1002/epi4.12625 -
Life (Basel, Switzerland) May 2022This paper describes the contemporary state of knowledge regarding processes that regulate normal development of the embryonic-fetal central nervous system (CNS). The... (Review)
Review
This paper describes the contemporary state of knowledge regarding processes that regulate normal development of the embryonic-fetal central nervous system (CNS). The processes are described according to the developmental timetable: dorsal induction, ventral induction, neurogenesis, neuronal migration, post-migration neuronal development, and cortical organization. We review the current literature on CNS malformations associated with these regulating processes. We specifically address neural tube defects, holoprosencephaly, malformations of cortical development (including microcephaly, megalencephaly, lissencephaly, cobblestone malformations, gray matter heterotopia, and polymicrogyria), disorders of the corpus callosum, and posterior fossa malformations. Fetal ventriculomegaly, which frequently accompanies these disorders, is also reviewed. Each malformation is described with reference to the etiology, genetic causes, prenatal sonographic imaging, associated anomalies, differential diagnosis, complimentary diagnostic studies, clinical interventions, neurodevelopmental outcome, and life quality.
PubMed: 35743840
DOI: 10.3390/life12060809 -
Biomedicines Jun 2022Sporadic vascular malformations (VMs) are a large group of disorders of the blood and lymphatic vessels caused by somatic mutations in several genes-mainly regulating...
Sporadic vascular malformations (VMs) are a large group of disorders of the blood and lymphatic vessels caused by somatic mutations in several genes-mainly regulating the RAS/MAPK/ERK and PI3K/AKT/mTOR pathways. We performed a cross-sectional study of 43 patients affected with sporadic VMs, who had received molecular diagnosis by high-depth targeted next-generation sequencing in our center. Clinical and imaging features were correlated with the sequence variants identified in lesional tissues. Six of nine patients with capillary malformation and overgrowth (CMO) carried the recurrent somatic mutation p.Arg183Gln, while two had mutations. Unexpectedly, 8 of 11 cases of diffuse CM with overgrowth (DCMO) carried known mutations, and the remaining 3 had pathogenic variants. Recurrent mutations were identified in the patients with megalencephaly-CM-polymicrogyria (MCAP), CLOVES, and Klippel-Trenaunay syndrome. Interestingly, somatic mutations were associated with hand/foot anomalies not only in MCAP and CLOVES, but also in CMO and DCMO. Two patients with blue rubber bleb nevus syndrome carried double somatic mutations, two of which were previously undescribed. In addition, a novel sporadic case of Parkes Weber syndrome (PWS) due to an mosaic pathogenic variant was described. Finally, a girl with a mild PWS and another diagnosed with CMO carried pathogenic somatic variants, showing the variability of phenotypic features associated with mutations. Overall, our findings expand the clinical and molecular spectrum of sporadic VMs, and show the relevance of genetic testing for accurate diagnosis and emerging targeted therapies.
PubMed: 35740480
DOI: 10.3390/biomedicines10061460 -
Cureus May 2022Megalencephaly-capillary malformation-polymicrogyria syndrome (MCAP) is an uncommon malformation syndrome, characterized by primary megalencephaly, capillary...
Megalencephaly-capillary malformation-polymicrogyria syndrome (MCAP) is an uncommon malformation syndrome, characterized by primary megalencephaly, capillary malformations of the midline face and body, or distal limb anomalies such as syndactyly and polymicrogyria. Herein, we report a young male child, who presented with complaints of increasing head size, delay in speech, and one episode of focal seizure with distinctive morphological and neuroradiological manifestations which led to the diagnosis of MCAP. We have also reviewed recently published literature and the various diagnostic criteria proposed by authors to achieve the early clinical diagnosis of these patients in the outpatient department.
PubMed: 35733479
DOI: 10.7759/cureus.25123 -
The Turkish Journal of Pediatrics 2022This study aimed to evaluate the clinical, electrophysiological, etiological features, and treatment response in children with epileptic encephalopathy with electrical...
BACKGROUND
This study aimed to evaluate the clinical, electrophysiological, etiological features, and treatment response in children with epileptic encephalopathy with electrical status epilepticus during slow sleep (ESES).
METHODS
Clinical data, records of electroencephalograms (EEG), and brain magnetic resonance imaging (MRI) findings of 33 patients with ESES who were treated, and followed up for at least one year were retrospectively analyzed.
RESULTS
Of all patients, 57.6% were male, and 42.4% were female. The mean age was 10.45 ± 2.88 years. At first admission, 90% of patients had seizures, and 10% had only school failure. Twelve patients had childhood focal epileptic syndrome. In etiology, asphyxia (n=6), hydrocephalus (n=2), polymicrogyria (n=1), and mesial temporal sclerosis (n=1) were determined. Neurological examination was abnormal in 27.2%, and brain MRI findings were pathological in 36.3% of the patients. During the ESES phase, the spike-wave index (SWI) on the non-rapid eye movement (NREM) sleep EEG was > 85% in 16 patients and 50-85% in 17 patients. Only one patient received one, and the others had at least two antiseizure medications. Benzodiazepines were found to be the most effective treatment. In the two-year follow-up, 24 patients (72.7%) were seizure-free, and nineteen patients (57.5%) had complete recovery of SWI on their NREM sleep EEG. There was a significant correlation with reduction of the SWI on the EEG and seizure control (p < 0.001). In addition, a significant correlation was found between neurocognitive and behavioral scores scored before and after treatment, seizure control, and EEG recovery.
CONCLUSIONS
ESES is an epileptic encephalopathy that can be treated safely with antiseizure medications. Neurocognitive examinations and follow-up of EEG findings are valuable in terms of the treatment response. Benzodiazepines were found to be very effective in additional treatment.
Topics: Adolescent; Benzodiazepines; Child; Electroencephalography; Epilepsies, Partial; Female; Humans; Male; Retrospective Studies; Seizures; Sleep; Status Epilepticus
PubMed: 35611419
DOI: 10.24953/turkjped.2020.2558 -
ELife May 2022Heterozygous, missense mutations in α- or β-tubulin genes are associated with a wide range of human brain malformations, known as tubulinopathies. We seek to...
Heterozygous, missense mutations in α- or β-tubulin genes are associated with a wide range of human brain malformations, known as tubulinopathies. We seek to understand whether a mutation's impact at the molecular and cellular levels scale with the severity of brain malformation. Here, we focus on two mutations at the valine 409 residue of TUBA1A, V409I, and V409A, identified in patients with pachygyria or lissencephaly, respectively. We find that ectopic expression of -V409I/A mutants disrupt neuronal migration in mice and promote excessive neurite branching and a decrease in the number of neurite retraction events in primary rat neuronal cultures. These neuronal phenotypes are accompanied by increased microtubule acetylation and polymerization rates. To determine the molecular mechanisms, we modeled the V409I/A mutants in budding yeast and found that they promote intrinsically faster microtubule polymerization rates in cells and in reconstitution experiments with purified tubulin. In addition, V409I/A mutants decrease the recruitment of XMAP215/Stu2 to plus ends in budding yeast and ablate tubulin binding to TOG (tumor overexpressed gene) domains. In each assay tested, the -V409I mutant exhibits an intermediate phenotype between wild type and the more severe -V409A, reflecting the severity observed in brain malformations. Together, our data support a model in which the V409I/A mutations disrupt microtubule regulation typically conferred by XMAP215 proteins during neuronal morphogenesis and migration, and this impact on tubulin activity at the molecular level scales with the impact at the cellular and tissue levels.
Topics: Animals; Humans; Lissencephaly; Mice; Microtubule-Associated Proteins; Microtubules; Neurogenesis; Neurons; Rats; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Tubulin
PubMed: 35511030
DOI: 10.7554/eLife.76189 -
Journal of Perinatology : Official... Jul 2022To evaluate the utility of the 1 Tesla (1 T) Embrace (Aspect Imaging) neonatal magnetic resonance imaging (MRI) scanner in a level III NICU.
OBJECTIVE
To evaluate the utility of the 1 Tesla (1 T) Embrace (Aspect Imaging) neonatal magnetic resonance imaging (MRI) scanner in a level III NICU.
STUDY DESIGN
Embrace brain MRI findings for 207 infants were reviewed, including 32 scans directly compared within 5 days with imaging on a 3 T Siemens Trio. Clinical MRI scan abnormalities were also compared to cranial ultrasound findings.
RESULT
Of the 207 Embrace brain MRIs, 146 (70.5%) were obtained for clinical indications and 61 (29.5%) were research cases. Abnormal findings were found in 80 scans, most commonly hemorrhage and white matter injury. Notable findings included a stroke, medullary brainstem tumor, and polymicrogyria. In the 1 T versus 3 T comparison cohort, results were discordant in only one infant with punctate foci of susceptibility noted only on the 3 T scan.
CONCLUSION
The Embrace MRI scans detected clinically relevant brain abnormalities and in a subset were clinically comparable to 3 T scans.
Topics: Brain; Brain Injuries; Echoencephalography; Humans; Infant; Infant, Newborn; Intensive Care Units, Neonatal; Magnetic Resonance Imaging; Neuroimaging
PubMed: 35459908
DOI: 10.1038/s41372-022-01387-5 -
Frontiers in Neuroscience 2022Congenital genetic disorders often present with neurological manifestations such as neurodevelopmental disorders, motor developmental retardation, epilepsy, and... (Review)
Review
Congenital genetic disorders often present with neurological manifestations such as neurodevelopmental disorders, motor developmental retardation, epilepsy, and involuntary movement. Through qualitative morphometric evaluation of neuroimaging studies, remarkable structural abnormalities, such as lissencephaly, polymicrogyria, white matter lesions, and cortical tubers, have been identified in these disorders, while no structural abnormalities were identified in clinical settings in a large population. Recent advances in data analysis programs have led to significant progress in the quantitative analysis of anatomical structural magnetic resonance imaging (MRI) and diffusion-weighted MRI tractography, and these approaches have been used to investigate psychological and congenital genetic disorders. Evaluation of morphometric brain characteristics may contribute to the identification of neuroimaging biomarkers for early diagnosis and response evaluation in patients with congenital genetic diseases. This mini-review focuses on the methodologies and attempts employed to study Rett syndrome using quantitative structural brain MRI analyses, including voxel- and surface-based morphometry and diffusion-weighted MRI tractography. The mini-review aims to deepen our understanding of how neuroimaging studies are used to examine congenital genetic disorders.
PubMed: 35450016
DOI: 10.3389/fnins.2022.835964