Loss of Function of RIMS2 Causes a Syndromic Congenital Cone-Rod Synaptic Disease with Neurodevelopmental and Pancreatic Involvement.

Congenital cone-rod synaptic disorder (CRSD), also known as incomplete congenital stationary night blindness (iCSNB), is a non-progressive inherited retinal disease (IRD) characterized by night blindness, photophobia, and nystagmus, and distinctive electroretinographic features. Here, we report bi-allelic RIMS2 variants in seven CRSD-affected individuals from four unrelated families. Apart from CRSD, neurodevelopmental disease was observed in all affected individuals, and abnormal glucose homeostasis was observed in the eldest affected individual. RIMS2 regulates synaptic membrane exocytosis. Data mining of human adult bulk and single-cell retinal transcriptional datasets revealed predominant expression in rod photoreceptors, and immunostaining demonstrated RIMS2 localization in the human retinal outer plexiform layer, Purkinje cells, and pancreatic islets. Additionally, nonsense variants were shown to result in truncated RIMS2 and decreased insulin secretion in mammalian cells. The identification of a syndromic stationary congenital IRD has a major impact on the differential diagnosis of syndromic congenital IRD, which has previously been exclusively linked with degenerative IRD.

Hypersensitivity to Rituximab in Children.

Biological agents have had an increased usage during the past years, also in pediatric population. Monoclonal antibodies can cause adverse drug reactions with different pathomechanisms, including type I IgE-mediated hypersensitivity reactions (HR). In this report, we describe 2 children who had a diagnosis of anaphylaxis to rituximab (RTX), confirmed by positive in vivo tests in both cases and elevated tryptase value in one case. We also made a review of the few cases of HR to RTX in pediatric population reported in literature and discuss differential diagnosis and utility of allergy investigations.

WDR81 mutations cause extreme microcephaly and impair mitotic progression in human fibroblasts and Drosophila neural stem cells.

Microlissencephaly is a rare brain malformation characterized by congenital microcephaly and lissencephaly. Microlissencephaly is suspected to result from abnormalities in the proliferation or survival of neural progenitors. Despite the recent identification of six genes involved in microlissencephaly, the pathophysiological basis of this condition remains poorly understood. We performed trio-based whole exome sequencing in seven subjects from five non-consanguineous families who presented with either microcephaly or microlissencephaly. This led to the identification of compound heterozygous mutations in WDR81, a gene previously associated with cerebellar ataxia, intellectual disability and quadrupedal locomotion. Patient phenotypes ranged from severe microcephaly with extremely reduced gyration with pontocerebellar hypoplasia to moderate microcephaly with cerebellar atrophy. In patient fibroblast cells, WDR81 mutations were associated with increased mitotic index and delayed prometaphase/metaphase transition. Similarly, in vivo, we showed that knockdown of the WDR81 orthologue in Drosophila led to increased mitotic index of neural stem cells with delayed mitotic progression. In summary, we highlight the broad phenotypic spectrum of WDR81-related brain malformations, which include microcephaly with moderate to extremely reduced gyration and cerebellar anomalies. Our results suggest that WDR81 might have a role in mitosis that is conserved between Drosophila and humans.

Recurrent KIF2A mutations are responsible for classic lissencephaly.

Kinesins play a critical role in the organization and dynamics of the microtubule cytoskeleton, making them central players in neuronal proliferation, neuronal migration, and postmigrational development. Recently, KIF2A mutations were identified in cortical malformation syndromes associated with microcephaly. Here, we detected two de novo p.Ser317Asn and p.His321Pro mutations in KIF2A in two patients with lissencephaly and microcephaly. In parallel, we re-evaluated the two previously reported cases showing de novo mutations of the same residues. The identification of mutations only in the residues Ser317 and His321 suggests these are hotspots for de novo mutations. Both mutations lead to a classic form of lissencephaly, with a posterior to anterior gradient, almost indistinguishable from LIS1-related lissencephaly. However, three fourths of patients also showed variable congenital and postnatal microcephaly, up to -5 SD. Located in the motor domain of the KIF2A protein, the Ser317 and His321 alterations are expected to disrupt binding or hydrolysis of ATP and consequently the MT depolymerizing activity. This report also establishes that KIF2A mutations represent significant causes of classic lissencephaly with microcephaly.

Prenatal and postnatal presentations of corpus callosum agenesis with polymicrogyria caused by EGP5 mutation.

EPG5-related Vici syndrome is a rare multisystem autosomal recessive disorder characterized by corpus callosum agenesis (ACC), hypopigmentation, cataracts, acquired microcephaly, failure to thrive, cardiomyopathy and profound developmental delay, and immunodeficiency. We report here the first case of prenatally diagnosed Vici syndrome with delayed gyration associated with ACC. Trio based exome sequencing allowed the identification of a compound heterozygous mutation in the EPG5 gene. Our patient subsequently demonstrated severe developmental delay, hypopigmentation, progressive microcephaly, and failure to thrive which led to suspicion of the diagnosis. Her MRI demonstrated ACC with frontoparietal polymicrogyria, severe hypomyelination, and pontocerebellar atrophy. This prenatal presentation of malformations of cortical development in combination with ACC expands the EPG5-related phenotypic spectrum. Our report supports the idea that EPG5-related Vici syndrome is both a neurodevelopmental and neurodegenerative disorder. © 2017 Wiley Periodicals, Inc.

GLUT1-DS Italian registry: past, present, and future: a useful tool for rare disorders.

BACKGROUND: GLUT1 deficiency syndrome is a rare, genetically determined neurological disorder for which Ketogenic Dietary Treatment represents the gold standard and lifelong treatment. Patient registries are powerful tools providing insights and real-world data on rare diseases. OBJECTIVE: To describe the implementation of a national web-based registry for GLUT1-DS. METHODS: This is a retrospective and prospective, multicenter, observational registry developed in collaboration with the Italian GLUT1-DS association and based on an innovative, flexible and configurable cloud computing technology platform, structured according to the most rigorous requirements for the management of patient's sensitive data. The Glut1 Registry collects baseline and follow-up data on the patient's demographics, history, symptoms, genotype, clinical, and instrumental evaluations and therapies. RESULTS: Five Centers in Italy joined the registry, and two more Centers are currently joining. In the first two years of running, data from 67 patients (40 females and 27 males) have been collected. Age at symptom onset was within the first year of life in most (40, 60%) patients. The diagnosis was formulated in infancy in almost half of the cases (34, 51%). Symptoms at onset were mainly paroxysmal (mostly epileptic seizure and paroxysmal ocular movement disorder) or mixed paroxysmal and fixed symptoms (mostly psychomotor delay). Most patients (53, 79%) are currently under Ketogenic dietary treatments. CONCLUSIONS: We describe the principles behind the design, development, and deployment of the web-based nationwide GLUT1-DS registry. It represents a stepping stone towards a more comprehensive understanding of the disease from onset to adulthood. It also represents a virtuous model from a technical, legal, and organizational point of view, thus representing a possible paradigmatic example for other rare disease registry implementation.

Is Focal Cortical Dysplasia/Epilepsy Caused by Somatic MTOR Mutations Always a Unilateral Disorder?

OBJECTIVE: To alert about the wide margin of unpredictability that distribution of somatic MTOR mosaicism may have in the brain and the risk for independent epileptogenesis arising from the seemingly healthy contralateral hemisphere after complete removal of epileptogenic focal cortical dysplasia (FCD). METHODS: Clinical, EEG, MRI, histopathology, and molecular genetics in 2 patients (1 and 2) treated with focal resections and subsequent complete hemispherectomy for epileptogenic FCD due to somatic MTOR mutations. Autoptic brain study of bilateral asymmetric hemispheric dysplasia and identification of alternative allele fraction (AAF) rates for AKT1 (patient 3). RESULTS: The strongly hyperactivating p.Ser2215Phe (patient 1) and p.Leu1460Pro (patient 2) MTOR mutations were at low-level AAF in the dysplastic tissue. After repeated resections and eventual complete hemispherectomy, both patients manifested intractable seizures arising from the contralateral, seemingly healthy hemisphere. In patient 3, the p.Glu17Lys AKT1 mutation exhibited random distribution and AAF rates in different tissues with double levels in the more severely dysplastic cerebral hemisphere. CONCLUSIONS: Our understanding of the distribution of somatic mutations in the brain in relation to the type of malformation and its hypothesized time of origin may be faulty. Large studies may reveal that the risk of a first surgery being disappointing might be related more to the specific somatic mammalian target of rapamycin mutation identified than to completeness of resection and that the advantages of repeated resections after a first unsuccessful operation should be weighed against the risk of the contralateral hemisphere becoming in turn epileptogenic.

Basal Ganglia Dysmorphism in Patients With Aicardi Syndrome.

OBJECTIVE: Aiming to detect associations between neuroradiologic and EEG evaluations and long-term clinical outcome in order to detect possible prognostic factors, a detailed clinical and neuroimaging characterization of 67 cases of Aicardi syndrome (AIC), collected through a multicenter collaboration, was performed. METHODS: Only patients who satisfied Sutton diagnostic criteria were included. Clinical outcome was assessed using gross motor function, manual ability, and eating and drinking ability classification systems. Brain imaging studies and statistical analysis were reviewed. RESULTS: Patients presented early-onset epilepsy, which evolved into drug-resistant seizures. AIC has a variable clinical course, leading to permanent disability in most cases; nevertheless, some cases presented residual motor abilities. Chorioretinal lacunae were present in 86.56% of our patients. Statistical analysis revealed correlations between MRI, EEG at onset, and clinical outcome. On brain imaging, 100% of the patients displayed corpus callosum malformations, 98% cortical dysplasia and nodular heterotopias, and 96.36% intracranial cysts (with similar rates of 2b and 2d). As well as demonstrating that posterior fossa abnormalities (found in 63.63% of cases) should also be considered a common feature in AIC, our study highlighted the presence (in 76.36%) of basal ganglia dysmorphisms (never previously reported). CONCLUSION: The AIC neuroradiologic phenotype consists of a complex brain malformation whose presence should be considered central to the diagnosis. Basal ganglia dysmorphisms are frequently associated. Our work underlines the importance of MRI and EEG, both for correct diagnosis and as a factor for predicting long-term outcome. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that for patients with AIC, specific MRI abnormalities and EEG at onset are associated with clinical outcomes.

Mutations in TBR1 gene leads to cortical malformations and intellectual disability.

The advent of next generation sequencing has improved gene discovery in neurodevelopmental disorders. A greater understanding of the genetic basis of these disorders has expanded the spectrum of pathogenic genes, thus enhancing diagnosis and therapeutic management. Genetic overlap between distinct neurodevelopmental disorders has also been revealed, which can make determining a strict genotype-phenotype correlation more difficult. Intellectual disability and cortical malformations are two neurodevelopmental disorders particularly confronted by this difficulty. Indeed, for a given pathogenic gene, intellectual disability can be associated, or not, with cortical malformations. Here, we report for the first time, two individuals with the same de novo mutation in TBR1, leading to a frameshift starting at codon Thr532, and resulting in a premature stop codon 143 amino acids downstream (c.1588_1594dup, p.(Thr532Argfs*144)). These individuals presented with a developmental encephalopathy characterized by frontal pachygyria and severe intellectual disability. Remarkably, 11 TBR1 gene mutations were previously reported in intellectual disability and autism spectrum disorders. Our study supports the observation that TBR1-related disorders range from intellectual disability to frontal pachygyria. We also highlight the need for first-line, good quality neuroimaging for patients with intellectual disability.

Recurrent RTTN mutation leading to severe microcephaly, polymicrogyria and growth restriction.

Autosomal recessive missense Rotatin (RTTN) mutations are responsible for syndromic forms of malformation of cortical development, ranging from isolated polymicrogyria to microcephaly associated with primordial dwarfism and other major malformations. We identified, by trio based whole exome sequencing, a homozygous missense mutation in the RTTN gene (c.2953A > G; p.(Arg985Gly)) in one Moroccan patient from a consanguineous family. The patient showed early onset primary microcephaly, detected in the fetal period, postnatal growth restriction, encephalopathy with hyperkinetic movement disorders and self-injurious behavior with sleep disturbance. Brain MRI showed an extensive dysgyria associated with nodular heterotopia, large interhemispheric arachnoid cyst and corpus callosum hypoplasia.

TLE1, a key player in neurogenesis, a new candidate gene for autosomal recessive postnatal microcephaly.

Postnatal microcephaly comprises a heterogeneous group of neurodevelopmental disorders of varying severity, characterized by normal head size at birth, followed by a postnatal deceleration in head circumference of greater than 3 standard deviations (SD) below the mean. Many postnatal microcephaly syndromes are caused by mutations in genes known to be important for the regulation of gene expression in the developing forebrain. We studied a consanguineous Pakistani family with postnatal microcephaly, orofacial dyskinesia, spastic quadriplegia and, on MRI, cortical atrophy with myelination delay, suggestive of a FOXG1-like presentation. Using trio-based exome sequencing, we identified a homozygous missense mutation in the Transducin-like enhancer of split-1 (TLE1) gene, encoding for a non DNA-binding transcriptional corepressor, highly expressed in the postnatal brain. The regulation of the post-mitotic neural survival activity of TLE1 depends critically on an interaction with FOXG1, a gene shown to be involved in a postnatal microcephaly syndrome. Functional analysis on affected dermal fibroblasts showed a significant decrease in mitotic and proliferative index, indicating a lengthening of the cell cycle and a delay in mitosis, supporting that this gene could be a new candidate for postnatal microcephaly.

Further refinement of COL4A1 and COL4A2 related cortical malformations.

Mutations in COL4A1 have been reported in schizencephaly and porencephaly combined with microbleeds or calcifications, often associated with ocular and renal abnormalities, myopathy, elevated creatine kinase levels and haemolytic anaemia. In this study, we aimed to clarify the phenotypic spectrum of COL4A1/A2 mutations in the context of cortical malformations that include schizencephaly, polymicrogyria and/or heterotopia. METHODS: We screened for COL4A1/A2 mutations in 9 patients with schizencephaly and/or polymicrogyria suspected to be caused by vascular disruption and leading to a cerebral haemorrhagic ischaemic event. These included 6 cases with asymmetrical or unilateral schizencephaly and/or polymicrogyria and 3 cases with bilateral schizencephaly. RESULTS: One de novo missense COL4A1 mutation (c.3715 G > A, p.(Gly1239Arg)) and two COL4A2 mutations were found, respectively in one familial case (c.4129G > A, p.(Gly1377Arg)) and one sporadic patient (c.1776+1G > A). In three other cases, COL4A1 variants of unknown significance were identified. None of our patients demonstrated neuromuscular or hematological anomalies. Brain malformations included a combination of schizencephaly, mainly asymmetrical, with porencephaly or ventriculomegaly (3/3 mutated patients). We did not observe microbleeds or microcalcifications in any of our cases, hence we do not believe that they represent a distinctive feature of COL4A1/A2 mutations. CONCLUSIONS: Our study further emphasizes the need to search for both COL4A1 and COL4A2 mutations in children presenting with uni- or bilateral polymicrogyria with schizencephaly, even in the absence of intracranial microbleeds, calcification or associated systemic features.

Delineating FOXG1 syndrome: From congenital microcephaly to hyperkinetic encephalopathy.

OBJECTIVE: To provide new insights into the FOXG1-related clinical and imaging phenotypes and refine the phenotype-genotype correlation in FOXG1 syndrome. METHODS: We analyzed the clinical and imaging phenotypes of a cohort of 45 patients with a pathogenic or likely pathogenic FOXG1 variant and performed phenotype-genotype correlations. RESULTS: A total of 37 FOXG1 different heterozygous mutations were identified, of which 18 are novel. We described a broad spectrum of neurodevelopmental phenotypes, characterized by severe postnatal microcephaly and developmental delay accompanied by a hyperkinetic movement disorder, stereotypes and sleep disorders, and epileptic seizures. Our data highlighted 3 patterns of gyration, including frontal pachygyria in younger patients (26.7%), moderate simplified gyration (24.4%) and mildly simplified or normal gyration (48.9%), corpus callosum hypogenesis mostly in its frontal part, combined with moderate-to-severe myelination delay that improved and normalized with age. Frameshift and nonsense mutations in the N-terminus of FOXG1, which are the most common mutation types, show the most severe clinical features and MRI anomalies. However, patients with recurrent frameshift mutations c.460dupG and c.256dupC had variable clinical and imaging presentations. CONCLUSIONS: These findings have implications for genetic counseling, providing evidence that N-terminal mutations and large deletions lead to more severe FOXG1 syndrome, although genotype-phenotype correlations are not necessarily straightforward in recurrent mutations. Together, these analyses support the view that FOXG1 syndrome is a specific disorder characterized by frontal pachygyria and delayed myelination in its most severe form and hypogenetic corpus callosum in its milder form.

Neuropathological Hallmarks of Brain Malformations in Extreme Phenotypes Related to DYNC1H1 Mutations.

Dyneins play a critical role in a wide variety of cellular functions such as the movement of organelles and numerous aspects of mitosis, making it central player in neocortical neurogenesis and migration. Recently, cytoplasmic dynein-1, heavy chain-1 (DYNC1H1) mutations have been found to cause a wide spectrum of brain cortical malformations. We report on the detailed neuropathological features of brain lesions from 2 fetuses aged 36 and 22 weeks of gestation (WG), respectively, carrying de novo DYNC1H1 mutations, p.Arg2720Lys and p.Val3951Ala and presenting the most severe phenotype reported to date. Analysis using the Dictyostelium discoideum dynein motor crystal structure showed that the mutations are both predicted to have deleterious consequences on the function of the motor domain. Both fetuses showed a similar macroscopic and histological brain malformative complex associating bilateral fronto-parietal polymicrogyria (PMG), dysgenesis of the corpus callosum and of the cortico-spinal tracts, along with brainstem and cerebellar abnormalities. Both exhibited extremely severe disrupted cortical lamination. Immunohistochemical studies provided the evidence for defects in cell proliferation and postmitotic neuroblast ability to exit from the subventricular zone resulting in a failure of radial migration toward the cortical plate, thus providing new insights for the understanding of the pathophysiology in these cortical malformations.

De novo TUBB2B mutation causes fetal akinesia deformation sequence with microlissencephaly: An unusual presentation of tubulinopathy.

Tubulinopathies are increasingly emerging major causes underlying complex cerebral malformations, particularly in case of microlissencephaly often associated with hypoplastic or absent corticospinal tracts. Fetal akinesia deformation sequence (FADS) refers to a clinically and genetically heterogeneous group of disorders with congenital malformations related to impaired fetal movement. We report on an early foetal case with FADS and microlissencephaly due to TUBB2B mutation. Neuropathological examination disclosed virtually absent cortical lamination, foci of neuronal overmigration into the leptomeningeal spaces, corpus callosum agenesis, cerebellar and brainstem hypoplasia and extremely severe hypoplasia of the spinal cord with no anterior and posterior horns and almost no motoneurons. At the cellular level, the p.Cys239Phe TUBB2B mutant leads to tubulin heterodimerization impairment, decreased ability to incorporate into the cytoskeleton, microtubule dynamics alteration, with an accelerated rate of depolymerization. To our knowledge, this is the first case of microlissencephaly to be reported presenting with a so severe and early form of FADS, highlighting the importance of tubulin mutation screening in the context of FADS with microlissencephaly.

Rare ACTG1 variants in fetal microlissencephaly.

Heterozygous ACTG1 mutations are responsible for Baraitser-Winter cerebrofrontofacial syndrome which cortical malformation is characterized by pachygyria with frontal to occipital gradient of severity. We identified by whole exome sequencing in a cohort of 12 patients with prenatally diagnosed microlissencephaly, 2 foetal cases with missense mutations in the ACTG1 gene and in one case of living patient with typical Baraitser-Winter syndrome. Both foetuses and child exhibited microcephaly and facial dysmorphism consisting of microretrognatism, hypertelorism and low-set ears. Brain malformations included lissencephaly with an immature cortical plate, dysmorphic (2/3) or absent corpus callosum and vermian hypoplasia (2/3). Our results highlight the powerful diagnostic value of exome sequencing for patients with microlissencephaly, that may expand the malformation spectrum of ACTG1-related Baraitser-Winter cerebrofrontofacial syndrome and may suggest that ACTG1 could be added to the list of genes for assessing microlissencephaly.

Mutations in B9D1 and MKS1 cause mild Joubert syndrome: expanding the genetic overlap with the lethal ciliopathy Meckel syndrome.

Joubert syndrome is a clinically and genetically heterogeneous ciliopathy characterized by a typical cerebellar and brainstem malformation (the "molar tooth sign"), and variable multiorgan involvement. To date, 24 genes have been found mutated in Joubert syndrome, of which 13 also cause Meckel syndrome, a lethal ciliopathy with kidney, liver and skeletal involvement. Here we describe four patients with mild Joubert phenotypes who carry pathogenic mutations in either MKS1 or B9D1, two genes previously implicated only in Meckel syndrome.