Comprehensive analysis of GABAA-A1R developmental alterations in Rett Syndrome: setting the focus for therapeutic targets in the time frame of the disease

Rett syndrome, a serious neurodevelopmental disorder, has been associated with an altered expression of different synaptic-related proteins and aberrant glutamatergic and γ-aminobutyric acid (GABA)ergic neurotransmission. Despite its severity, it lacks a therapeutic option. Through this work we aimed to define the relationship between MeCP2 and GABAA.-A1 receptor expression, emphasizing the time dependence of such relationship. For this, we analyzed the expression of the ionotropic receptor subunit in different MeCP2 gene-dosage and developmental conditions, in cells lines, and in primary cultured neurons, as well as in different developmental stages of a Rett mouse model. Further, RNAseq and systems biology analysis was performed from post-mortem brain biopsies of Rett patients. We observed that the modulation of the MeCP2 expression in cellular models (both Neuro2a (N2A) cells and primary neuronal cultures) revealed a MeCP2 positive effect on the GABAA.-A1 receptor subunit expression, which did not occur in other proteins such as KCC2 (Potassium-chloride channel, member 5). In the Mecp2+/- mouse brain, both the KCC2 and GABA subunits expression were developmentally regulated, with a decreased expression during the pre-symptomatic stage, while the expression was variable in the adult symptomatic mice. Finally, the expression of the gamma-aminobutyric acid (GABA) receptor-related synaptic proteins from the postmortem brain biopsies of two Rett patients was evaluated, specifically revealing the GABA A1R subunit overexpression. The identification of the molecular changes along with the Rett syndrome prodromic stages strongly endorses the importance of time frame when addressing this disease, supporting the need for a neurotransmission-targeted early therapeutic intervention

Whole exome sequencing of Rett syndrome-like patients reveals the mutational diversity of the clinical phenotype

Classical Rett syndrome (RTT) is a neurodevelopmental disorder where most of cases carry MECP2 mutations. Atypical RTT variants involve mutations in CDKL5 and FOXG1. However, a subset of RTT patients remains that do not carry any mutation in the described genes. Whole exome sequencing was carried out in a cohort of 21 female probands with clinical features overlapping with those of RTT, but without mutations in the customarily studied genes. Candidates were functionally validated by assessing the appearance of a neurological phenotype in Caenorhabditis elegans upon disruption of the corresponding ortholog gene. We detected pathogenic variants that accounted for the RTT-like phenotype in 14 (66.6 %) patients. Five patients were carriers of mutations in genes already known to be associated with other syndromic neurodevelopmental disorders. We determined that the other patients harbored mutations in genes that have not previously been linked to RTT or other neurodevelopmental syndromes, such as the ankyrin repeat containing protein ANKRD31 or the neuronal acetylcholine receptor subunit alpha-5 (CHRNA5). Furthermore, worm assays demonstrated that mutations in the studied candidate genes caused locomotion defects. Our findings indicate that mutations in a variety of genes contribute to the development of RTT-like phenotypes

Cognitive stimulation has potential for brain activation in individuals with Rett syndrome

Background: Knowledge regarding neuropsychological training in Rett syndrome (RS) is scarce. The aim of this study was to assess the outcome and the duration of the effect of cognitive stimulation on topographic EEG data in RS. Method: Twenty female children diagnosed with RS were included in the analysis. Girls with RS conducted a cognitive task using an eye-tracker designed to evaluate access and choice skills. EEG data was acquired during the experimental procedure including two 10-minutes baseline stages before and after the task. Topographical changes of several EEG spectral markers including absolute and relative powers, brain symmetry index and entropy were assessed. Results: Topographic significance probability maps suggested statistical decreases on delta activity and increases on beta rhythm associated with the cognitive task. Entropy increased during and after the task, likely related to more complex brain activity. A significant positive interaction was obtained between brain symmetry index (BSI) and age showing that the improvement of interhemispheric symmetry was higher in younger girls (5-10 years). Conclusions: According to our findings, significant alterations of brain rhythms were observed during and after cognitive stimulation, suggesting that cognitive stimulation may have effects on brain activity beyond the stimulation period. Finally, our promising results also showed an increased brain symmetry that was especially relevant for the younger group. This could suggest an interaction of the eye-tracking cognitive task, however, further studies in this field are needed to assess the relation between brain asymmetries and age.We would like to acknowledge specific funding support from the Spanish Patient Associations Mi Princesa Rett and Rettando al Síndrome de Rett. This project has also received funding from Torrons Vicens and the Ministry of Science and Innovation (MICINN), Spain, under contract PID2020-117751RB-I00. CIBER-BBN is an initiative of the Instituto de Salud Carlos III, Spain. A. Bachiller is a Serra Húnter Fellow. A.García-Cazorla is supported by FIS P118/00111 “Instituto de Salud Carlos III (ISCIII)” and “Fondo Europeo de desarrollo regional (FEDER)”. A. Tost has received the predoctoral scholarship FI-AGAUR from the Generalitat de Catalunya.Peer ReviewedPostprint (author's final draft

Mutational spectrum by phenotype: panel-based NGS testing of patients with clinical suspition of RASopathy and children with multiple café-au-lait macules

Children with neurofibromatosis type 1 (NF1) may exhibit an incomplete clinical presentation, making difficult to reach a clinical diagnosis. A phenotypic overlap may exist in children with other RASopathies or with other genetic conditions if only multiple café‐au‐lait macules (CALMs) are present. The syndromes that can converge in these inconclusive phenotypes have different clinical courses. In this context, an early genetic testing has been proposed to be clinically useful to manage these patients. We present the validation and implementation into diagnostics of a custom NGS panel (I2HCP, ICO‐IMPPC Hereditary Cancer Panel) for testing patients with a clinical suspicion of a RASopathy (n = 48) and children presenting multiple CALMs (n = 102). We describe the mutational spectrum and the detection rates identified in these two groups of individuals. We identified pathogenic variants in 21 out of 48 patients with clinical suspicion of RASopathy, with mutations in NF1 accounting for 10% of cases. Furthermore, we identified pathogenic mutations mainly in the NF1 gene, but also in SPRED1, in more than 50% of children with multiple CALMs, exhibiting an NF1 mutational spectrum different from a group of clinically diagnosed NF1 patients (n = 80). An NGS panel strategy for the genetic testing of these two phenotype‐defined groups outperforms previous strategie

GDF-15 is elevated in children with mitochondrial diseases and is induced by mitochondrial dysfunction

Background We previously described increased levels of growth and differentiation factor 15 (GDF-15) in skeletal muscle and serum of patients with mitochondrial diseases. Here we evaluated GDF-15 as a biomarker for mitochondrial diseases affecting children and compared it to fibroblast-growth factor 21 (FGF-21). To investigate the mechanism of GDF-15 induction in these pathologies we measured its expression and secretion in response to mitochondrial dysfunction. Methods We analysed 59 serum samples from 48 children with mitochondrial disease, 19 samples from children with other neuromuscular diseases and 33 samples from aged-matched healthy children. GDF-15 and FGF-21 circulating levels were determined by ELISA. Results Our results showed that in children with mitochondrial diseases GDF-15 levels were on average increased by 11-fold (mean 4046pg/ml, 1492 SEM) relative to healthy (350, 21) and myopathic (350, 32) controls. The area under the curve for the receiver-operating-characteristic curve for GDF-15 was 0.82 indicating that it has a good discriminatory power. The overall sensitivity and specificity of GDF-15 for a cut-off value of 550pg/mL was 67.8% (54.4%-79.4%) and 92.3% (81.5%-97.9%), respectively. We found that elevated levels of GDF-15 and or FGF-21 correctly identified a larger proportion of patients than elevated lev- els of GDF-15 or FGF-21 alone. GDF-15, as well as FGF-21, mRNA expression and protein secretion, were significantly induced after treatment of myotubes with oligomycin and that levels of expression of both factors significantly correlated. Conclusions Our data indicate that GDF-15 is a valuable serum quantitative biomarker for the diagnosis of mitochondrial diseases in children and that measurement of both GDF-15 and FGF-21 improves the disease detection ability of either factor separately. Finally, we demonstrate for the first time that GDF-15 is produced by skeletal muscle cells in response to mitochon- drial dysfunction and that its levels correlate in vitro with FGF-21 level

La amnesia global transitoria: entidad infrecuente en la infancia

Introducción: la amnesia global transitoria (AGT) es un cuadro de presentación súbita caracterizado por una intensa amnesia anterógrada y una amnesia retrógada variable. La memoria inmediata está conservada y el resto de la exploración neurológica es normal. La recuperación es progresiva en pocas horas. Suele presentarse en pacientes adultos de mediana edad y en ancianos. Caso clínico: niña de 9 años de edad que presenta una amnesia anterógrada de inicio brusco, con memoria inmediata conservada y algún trastorno de la memoria retrógada, asociados a cefalea de intensidad leve. La exploración neurológica es normal. El episodio cede de forma espontánea en unas 4 horas. Posteriormente, la paciente presenta una cefalea leve y una amnesia del episodio. Se realiza una tomografía computarizada craneal, que es normal, por lo que el cuadro se orienta como AGT. Discusión: la clínica descrita es característica de la AGT. La aparición de este cuadro suele ser espontánea, aunque puede existir un factor desencadenante. Se ha postulado que podría deberse a un fenómeno vascular amplio con isquemia transitoria del territorio de la vertebrobasilar, o a un fenómeno epiléptico o migrañoso. La migraña confusional aguda, típica de la infancia, tiene manifestaciones clínicas similares a las de la AGT. El diagnóstico de este proceso es clínico. Tiene un excelente pronóstico, con poca tendencia a la recidiva. Dada la presentación poco habitual en la edad pediátrica, en nuestro caso se realizó una prueba de imagen para descartar un accidente cerebrovascular. La clínica típica y la normalidad de las pruebas de imagen deben hacernos considerar este diagnóstico también en la edad pediátrica

GDF-15 is elevated in children with mitochondrial diseases and is induced by mitochondrial dysfunction

Background We previously described increased levels of growth and differentiation factor 15 (GDF-15) in skeletal muscle and serum of patients with mitochondrial diseases. Here we evaluated GDF-15 as a biomarker for mitochondrial diseases affecting children and compared it to fibroblast-growth factor 21 (FGF-21). To investigate the mechanism of GDF-15 induction in these pathologies we measured its expression and secretion in response to mitochondrial dysfunction. Methods We analysed 59 serum samples from 48 children with mitochondrial disease, 19 samples from children with other neuromuscular diseases and 33 samples from aged-matched healthy children. GDF-15 and FGF-21 circulating levels were determined by ELISA. Results Our results showed that in children with mitochondrial diseases GDF-15 levels were on average increased by 11-fold (mean 4046pg/ml, 1492 SEM) relative to healthy (350, 21) and myopathic (350, 32) controls. The area under the curve for the receiver-operating-characteristic curve for GDF-15 was 0.82 indicating that it has a good discriminatory power. The overall sensitivity and specificity of GDF-15 for a cut-off value of 550pg/mL was 67.8% (54.4%-79.4%) and 92.3% (81.5%-97.9%), respectively. We found that elevated levels of GDF-15 and or FGF-21 correctly identified a larger proportion of patients than elevated lev- els of GDF-15 or FGF-21 alone. GDF-15, as well as FGF-21, mRNA expression and protein secretion, were significantly induced after treatment of myotubes with oligomycin and that levels of expression of both factors significantly correlated. Conclusions Our data indicate that GDF-15 is a valuable serum quantitative biomarker for the diagnosis of mitochondrial diseases in children and that measurement of both GDF-15 and FGF-21 improves the disease detection ability of either factor separately. Finally, we demonstrate for the first time that GDF-15 is produced by skeletal muscle cells in response to mitochon- drial dysfunction and that its levels correlate in vitro with FGF-21 level