Developmental Consequences of Defective ATG7-Mediated Autophagy in Humans.

BACKGROUND: Autophagy is the major intracellular degradation route in mammalian cells. Systemic ablation of core autophagy-related (ATG) genes in mice leads to embryonic or perinatal lethality, and conditional models show neurodegeneration. Impaired autophagy has been associated with a range of complex human diseases, yet congenital autophagy disorders are rare. METHODS: We performed a genetic, clinical, and neuroimaging analysis involving five families. Mechanistic investigations were conducted with the use of patient-derived fibroblasts, skeletal muscle-biopsy specimens, mouse embryonic fibroblasts, and yeast. RESULTS: We found deleterious, recessive variants in human ATG7, a core autophagy-related gene encoding a protein that is indispensable to classical degradative autophagy. Twelve patients from five families with distinct ATG7 variants had complex neurodevelopmental disorders with brain, muscle, and endocrine involvement. Patients had abnormalities of the cerebellum and corpus callosum and various degrees of facial dysmorphism. These patients have survived with impaired autophagic flux arising from a diminishment or absence of ATG7 protein. Although autophagic sequestration was markedly reduced, evidence of basal autophagy was readily identified in fibroblasts and skeletal muscle with loss of ATG7. Complementation of different model systems by deleterious ATG7 variants resulted in poor or absent autophagic function as compared with the reintroduction of wild-type ATG7. CONCLUSIONS: We identified several patients with a neurodevelopmental disorder who have survived with a severe loss or complete absence of ATG7, an essential effector enzyme for autophagy without a known functional paralogue. (Funded by the Wellcome Centre for Mitochondrial Research and others.).

Autoimmune Cerebellar Ataxia Associated with Anti-Glutamate Receptor δ2 Antibodies: a Rare but Treatable Entity.

We report two novel cases of autoimmune cerebellar ataxia (ACA) associated with anti-glutamate receptor δ2 antibodies (Gluδ2-Abs). The first case was confirmed by indirect immunofluorescence and cell-based assays: a 29-year-old woman presented after 5 days of headache and vomiting, a pancerebellar syndrome, downbeat nystagmus, decreased visual acuity linked to bilateral retrobulbar optic neuritis (RON), and lymphocytic pleocytosis in the cerebrospinal fluid (CSF) without any abnormality detected using cerebral magnetic resonance imaging (MRI). Second-line immunotherapy allowed progressive clinical improvement, with full recovery achieved after a 4-year follow-up. Thereafter, we retrospectively tested Gluδ2-Abs in 350 patients with a suspicion of autoimmune encephalitis without characterized autoantibody. We identified a second case, a 12-year-old boy who developed 10 days after a respiratory infection, a static cerebellar syndrome with lymphocytosis in the CSF, and right cerebellum hyperintensity in MRI. Five days of corticosteroid treatment allowed a quick clinical improvement. No tumor was identified in both cases, whereas laboratory analyses revealed autoimmune stigma. The present cases suggested that ACA associated with Gluδ2-Abs is an extremely rare but treatable disease. Therefore, testing for Gluδ2-Abs might be considered in the setting of suspected ACA and no initial antibody identification. The visual deficits and ocular motility abnormalities observed in the first reported case might be part of the clinical spectrum of Gluδ2-Abs ACA. Young age, infectious prodromes, lymphocytic pleocytosis, and autoimmune background usually appear together with this syndrome and should lead to discuss the initiation of immunotherapy (after ruling out differential diagnosis, especially infectious causes).

Long-term outcomes of paediatric Guillain-Barré syndrome.

AIM: To study long-term sequelae in children with Guillain-Barré syndrome (GBS). METHOD: This was a prospective observational study with children from two French tertiary centres. Data were from clinical and several standardized scales or questionnaires. RESULTS: Fifty-one patients were included with a median follow-up of 6 years 4 months (range 3-20 years) after the acute phase. The sequelae rate was 67% (95% confidence interval [CI] 53-78) and did not vary with time. Most children had minor sequelae (Guillain-Barré Syndrome Disability Score [GBSDS] = 1); only one was unable to run (GBSDS = 2). The most frequent complaints were paraesthesia (43%), pain (35%), and fatigue (31%). The neurological examination was abnormal in 18% of children, autonomy was compromised in 14%, and symptoms of depression occurred in 34%. The factors associated with late-onset sequelae were correlated with severity during the initial phase (i.e. initial GBSDS >4, odds ratio 6.6, 95% CI 1.8-33; p = 0.009). The predictive factors of more severe late-onset conditions were initial severity (p = 0.002) and sex (female patients; p = 0.01). INTERPRETATION: Two-thirds of children with GBS had late-onset sequelae following an episode, often minor, but sometimes with continuing effects on their everyday lives. Particularly affected were those who had severe GBS during the acute phase and who lost the ability to walk. WHAT THIS PAPER ADDS: Two-thirds of children with Guillain-Barré syndrome (GBS) had persistent sequelae. Sequelae were often minor, but daily repercussions of them were sometimes serious. Sequelae were significantly associated with severe GBS during the acute phase.

Efficacy of intravenous clonazepam for paediatric convulsive status epilepticus.

AIM: To compare the efficacy of intravenous clonazepam (CLZ) for the initial management of convulsive status epilepticus (CSE) in children as a function of the first-line in-hospital dose used. METHOD: This monocentric retrospective study included children who received a first dose of CLZ for CSE at Montpellier University Hospital, France, between January 2016 and June 2019. Data from medical records (clinical, treatment, course) were collected and compared as a function of the first CLZ dose used. RESULTS: Among the 310 children treated for CSE, 105 received at least one CLZ dose (median age 3 years; quartile 1-quartile 3 [Q1-Q3] = 1 years 2 months-6 years 6 months). Among these 105 patients, 24 (22%) received a dose less than 0.03 mg/kg (low dose) and 69 (65%) received a dose of at least 0.03 mg/kg (high dose). Seizure cessation rate was not different between the low- and high-dose groups (62.5% vs 76%; odds ratio 0.53, 95% confidence interval [CI] 0.19-1.44, p = 0.29). The administration of a second dose of CLZ was more frequent in the low- than the high-dose group (37.5% vs 16%; odds ratio 3.2, 95% CI 1.1-9.1, p = 0.04). INTERPRETATION: Our study did not find any difference in seizure termination rate as a function of CLZ dose in children with CSE. However, a second CLZ dose was more frequently needed in the group receiving low (less than 0.03 mg/kg) CLZ.

Plasma p-tau231, p-tau181, PET Biomarkers, and Cognitive Change in Older Adults.

OBJECTIVE: The objective of this study was to evaluate novel plasma p-tau231 and p-tau181, as well as Aß40 and Aß42 assays as indicators of tau and Aß pathologies measured with positron emission tomography (PET), and their association with cognitive change, in cognitively unimpaired older adults. METHODS: In a cohort of 244 older adults at risk of Alzheimer's disease (AD) owing to a family history of AD dementia, we measured single molecule array (Simoa)-based plasma tau biomarkers (p-tau231 and p-tau181), Aß40 and Aß42 with immunoprecipitation mass spectrometry, and Simoa neurofilament light (NfL). A subset of 129 participants underwent amyloid-ß (18 F-NAV4694) and tau (18 F-flortaucipir) PET assessments. We investigated plasma biomarker associations with Aß and tau PET at the global and voxel level and tested plasma biomarker combinations for improved detection of Aß-PET positivity. We also investigated associations with 8-year cognitive change. RESULTS: Plasma p-tau biomarkers correlated with flortaucipir binding in medial temporal, parietal, and inferior temporal regions. P-tau231 showed further associations in lateral parietal and occipital cortices. Plasma Aß42/40 explained more variance in global Aß-PET binding than Aß42 alone. P-tau231 also showed strong and widespread associations with cortical Aß-PET binding. Combining Aß42/40 with p-tau231 or p-tau181 allowed for good distinction between Aß-negative and -positive participants (area under the receiver operating characteristic curve [AUC] range = 0.81-0.86). Individuals with low plasma Aß42/40 and high p-tau experienced faster cognitive decline. INTERPRETATION: Plasma p-tau231 showed more robust associations with PET biomarkers than p-tau181 in presymptomatic individuals. The combination of p-tau and Aß42/40 biomarkers detected early AD pathology and cognitive decline. Such markers could be used as prescreening tools to reduce the cost of prevention trials. ANN NEUROL 2022;91:548-560.

Cerebral sinovenous thrombosis associated with head/neck infection in children: Clues for improved management.

AIM: To compare paediatric patients with cerebral sinovenous thrombosis (CSVT) with and without head/neck infection to improve management of the condition. METHOD: We conducted a bicentric retrospective study of consecutive children (neonates excluded) with radiologically confirmed CSVT, comparing children with a concurrent head/neck infection and children with other causes. RESULTS: A total of 84 consecutive patients (46 males and 38 females) with a median age of 4 years 6 months (range 3 months-17 years 5 months) were included. Associated head/neck infection was identified in 65.4% of cases and represented the main identified CSVT aetiology. Children in the head/neck infection group displayed a milder clinical presentation and less extensive CSVT. Median time to complete recanalization was significantly shorter in this group (89 days [interquartile range 35-101] vs 112.5 days [interquartile range 83-177], p = 0.005). These findings were even more pronounced in the subgroup of patients with otogenic infection and no neurological sign. INTERPRETATION: As CSVT in the setting of an otogenic infection and no neurological sign seems to represent a milder condition with a shorter course, these results suggest adapting current recommendations: consider earlier control imaging in paediatric otogenic CSVT, and shorter anticoagulant treatment if recanalization is obtained. WHAT THIS PAPER ADDS: Children with cerebral sinovenous thrombosis related to head/neck infections have a milder clinical presentation. They also have a shorter recanalization time, especially if there is otogenic infection without neurological symptoms.

Longitudinal blood biomarker trajectories in preclinical Alzheimer's disease.

INTRODUCTION: Plasma biomarkers are altered years prior to Alzheimer's disease (AD) clinical onset. METHODS: We measured longitudinal changes in plasma amyloid-beta (Aß)42/40 ratio, pTau181, pTau231, neurofilament light chain (NfL), and glial fibrillary acidic protein (GFAP) in a cohort of older adults at risk of AD (n = 373 total, n = 229 with Aß and tau positron emission tomography [PET] scans) considering genetic and demographic factors as possible modifiers of these markers' progression. RESULTS: Aß42/40 ratio concentrations decreased, while NfL and GFAP values increased over the 4-year follow-up. Apolipoprotein E (APOE) ε4 carriers showed faster increase in plasma pTau181 than non-carriers. Older individuals showed a faster increase in plasma NfL, and females showed a faster increase in plasma GFAP values. In the PET subsample, individuals both Aß-PET and tau-PET positive showed faster plasma pTau181 and GFAP increase compared to PET-negative individuals. DISCUSSION: Plasma markers can track biological change over time, with plasma pTau181 and GFAP markers showing longitudinal change in individuals with preclinical AD. HIGHLIGHTS: Longitudinal increase of plasma pTau181 and glial fibrillary acidic protein (GFAP) can be measured in the preclinical phase of AD. Apolipoprotein E Îµ4 carriers experience faster increase in plasma pTau181 over time than non-carriers. Female sex showed accelerated increase in plasma GFAP over time compared to males. Aß42/40 and pTau231 values are already abnormal at baseline in individuals with both amyloid and tau PET burden.

Clinical Features and Risk of Relapse in Children and Adults with Myelin Oligodendrocyte Glycoprotein Antibody-Associated Disease.

OBJECTIVE: The main objective was to compare clinical features, disease course, and myelin oligodendrocyte glycoprotein (MOG) antibody (Ab) dynamics between children and adults with MOG-Ab-associated disease (MOGAD). METHODS: This retrospective multicentric, national study included 98 children and 268 adults with MOGAD between January 2014 and September 2019. Cox regression model for recurrent time-to-event data and Kaplan-Meier curves for time to antibody negativity were performed for the objectives. RESULTS: Isolated optic neuritis was the most frequent clinical presentation in both children (40.8%) and adults (55.9%, p = 0.013), and acute disseminated encephalomyelitis syndrome was more frequent in children (36.7% vs 5.6%, p < 0.001). Compared to adults, children displayed better recovery (Expanded Disability Status Scale ≥ 3.0 at last follow-up reached only by 10 of 97 [10.3%] vs 66/247 [26.7%], p < 0.001). In the multivariate analysis, adults were at higher risk of relapse than children (hazard ratio = 1.41, 95% confidence interval [CI] = 1.12-1.78, p = 0.003). At 2 years, 64.2% (95% CI = 40.9-86.5) of nonrelapsing children became MOG-Ab negative compared to 14.1% (95% CI = 4.7-38.3) of relapsing children (log-rank p < 0.001), with no differences observed in adults (log-rank p = 0.280). INTERPRETATION: MOGAD patients differ in the clinical presentation at onset, showing an age-related shift in the clinical features across age groups. Compared to children, adults have a higher risk of relapse and worse functional recovery. Finally, children with monophasic disease become MOG-Ab negative earlier than relapsing children, but this is not true in adults. Considering these differences, management and treatment guidelines should be considered independently in children and adults. ANN NEUROL 2021;89:30-41.

Molecular and clinical descriptions of patients with GABAA receptor gene variants (GABRA1, GABRB2, GABRB3, GABRG2): A cohort study, review of literature, and genotype-phenotype correlation.

OBJECTIVE: γ-Aminobutyric acid (GABA)A -receptor subunit variants have recently been associated with neurodevelopmental disorders and/or epilepsy. The phenotype linked with each gene is becoming better known. Because of the common molecular structure and physiological role of these phenotypes, it seemed interesting to describe a putative phenotype associated with GABAA -receptor-related disorders as a whole and seek possible genotype-phenotype correlations. METHODS: We collected clinical, electrophysiological, therapeutic, and molecular data from patients with GABAA -receptor subunit variants (GABRA1, GABRB2, GABRB3, and GABRG2) through a national French collaboration using the EPIGENE network and compared these data to the one already described in the literature. RESULTS: We gathered the reported patients in three epileptic phenotypes: 15 patients with fever-related epilepsy (40%), 11 with early developmental epileptic encephalopathy (30%), 10 with generalized epilepsy spectrum (27%), and 1 patient without seizures (3%). We did not find a specific phenotype for any gene, but we showed that the location of variants on the transmembrane (TM) segment was associated with a more severe phenotype, irrespective of the GABAA -receptor subunit gene, whereas N-terminal variants seemed to be related to milder phenotypes. SIGNIFICANCE: GABAA -receptor subunit variants are associated with highly variable phenotypes despite their molecular and physiological proximity. None of the genes described here was associated with a specific phenotype. On the other hand, it appears that the location of the variant on the protein may be a marker of severity. Variant location may have important weight in the development of targeted therapeutics.

Head to head comparison of quantitative flow ratio using 4-French and 6-French catheters versus fractional flow reserve.

OBJECTIVES: To validate QFR using 4-F diagnostic catheters compared to using 6-F guiding catheters, with conventional guidewire-based FFR as the reference standard, using independent core laboratory analysis. BACKGROUND: Quantitative Flow Ratio (QFR) allows Fractional Flow Reserve (FFR) calculation based on the coronary angiogram, using 5- or 6-French (F) catheters. However, the use of 4-F diagnostic catheters to perform coronary angiography is currently routine in some centers. METHODS: We included all consecutive patients with stable coronary artery disease and indicated for physiological assessment. QFR was performed using a 4-F diagnostic catheter, then QFR was performed using a 6-F guiding catheter while conventional FFR was measured using a pressure guidewire. Angiograms were sent to two separate core laboratories. RESULTS: One hundred lesions in 67 consecutive patients with QFR performed using 4-F and 6-F catheters, and with conventional FFR, were included. Pearson's correlation coefficient was for QFR 4-F vs. FFR 0.91 [0.87-0.94], for QFR 6-F vs. FFR 0.90 [0.86-0.94], and for QFR 4-F vs. QFR 6-F 0.93 [0.90-0.95]. Receiver-operator characteristic curves (ROC) comparing the ability to predict an FFR value above or below 0.80 with QFR 4-F and 6-F were generated. The area under the ROC curve (AUC) vs. FFR was 0.972 [0.95-0.99] for QFR 4-F and 0.970 [0.94-0.99] for QFR 6-F. CONCLUSIONS: Our study demonstrated the feasibility of performing QFR analysis from angiograms obtained by 4-F catheters, and showed a good correlation with QFR performed using 6-F catheters as well as with conventional FFR performed using a pressure guidewire.

Movement disorders in valine métabolism diseases caused by HIBCH and ECHS1 deficiencies.

BACKGROUND AND PURPOSE: HIBCH and ECHS1 genes encode two enzymes implicated in the critical steps of valine catabolism, 3-hydroxyisobutyryl-coenzyme A (CoA) hydrolase (HIBCH) and short-chainenoyl-CoA hydratase (ECHS1), respectively. HIBCH deficiency (HIBCHD) and ECHS1 deficiency (ECHS1D) generate rare metabolic dysfunctions, often revealed by neurological symptoms. The aim of this study was to describe movement disorders spectrum in patients with pathogenic variants in ECHS1 and HIBC. METHODS: We reviewed a series of 18 patients (HIBCHD: 5; ECHS1D: 13) as well as 105 patients from the literature. We analysed the detailed phenotype of HIBCHD (38 patients) and ECHS1D (85 patients), focusing on MDs. RESULTS: The two diseases have a very similar neurological phenotype, with an early onset before 10 years of age for three clinical presentations: neonatal onset, Leigh-like syndrome (progressive onset or acute neurological decompensation), and isolated paroxysmal dyskinesia. Permanent or paroxysmal MDs were recorded in 61% of HIBCHD patients and 72% of ECHS1D patients. Patients had a variable combination of either isolated or combined MD, and dystonia was the main MD. These continuous MDs included dystonia, chorea, parkinsonism, athetosis, myoclonus, tremors, and abnormal eye movements. Patients with paroxysmal dyskinesia (HIBCHD: 4; ECHS1D: 9) usually had pure paroxysmal dystonia with normal clinical examination and no major impairment in psychomotor development. No correlation could be identified between clinical pattern (especially MD) and genetic pathogenic variants. CONCLUSIONS: Movement disorders, including abnormal ocular movements, are a hallmark of HIBCHD and ECHS1D. MDs are not uniform; dystonia is the most frequent, and various types of MD are combined in single patient.

Adaptive behavior and psychiatric comorbidities in KCNB1 encephalopathy.

AIM: KCNB1 encephalopathy encompasses a broad phenotypic spectrum associating intellectual disability, behavioral disturbances, and epilepsies of various severity. Using standardized parental questionnaires, we aimed to capture the heterogeneity of the adaptive and behavioral features in a series of patients with KCNB1 pathogenic variants. METHODS: We included 25 patients with a KCNB1 encephalopathy, aged from 3.2 to 34.1 years (median = 10 years). Adaptive functioning was assessed in all patients using the French version of the Vineland Adaptive Behavior Scales, Second Edition (VABS-II) questionnaire. We screened global behavior with the Childhood Behavioral Check-List (CBCL, Achenbach) and autism spectrum disorder (ASD) with the Social Communication Questionnaire (SCQ). We used a cluster analysis to identify subgroups of adaptive profiles. RESULTS: VABS-II questionnaire showed pathological adaptive behavior in all participants with a severity of adaptive deficiency ranging from mild in 8/20 to severe in 7/20. Eight out of 16 were at risk of Attention Problems at the CBCL and 13/18 were at risk of autism spectrum disorder (ASD). The adaptive behavior composite score significantly decreased with age (Spearman's Rho=-0.72, p<0.001) but not the equivalent ages, suggesting stagnation and slowing but no regression over time. The clustering analysis identified two subgroups of patients, one showing more severe adaptive behavior. The severity of the epilepsy phenotype predicted the severity of the behavioral profile with a sensitivity of 70% and a specificity of 90.9%. CONCLUSION: This study confirms the deleterious consequences of early-onset epilepsy in addition to the impact of the gene dysfunction in patients with KCNB1 encephalopathy. ASD and attention disorders are frequent. Parental questionnaires should be considered as useful tools for early screening and care adaptation.

Dual function of Langerhans cells in skin TSLP-promoted TFH differentiation in mouse atopic dermatitis.

BACKGROUND: Atopic dermatitis (AD) is among the most common chronic inflammatory skin diseases, usually occurring early in life, and often preceding other atopic diseases such as asthma. TH2 has been believed to play a crucial role in cellular and humoral response in AD, but accumulating evidence has shown that follicular helper T cell (TFH), a critical player in humoral immunity, is associated with disease severity and plays an important role in AD pathogenesis. OBJECTIVES: This study aimed at investigating how TFHs are generated during the pathogenesis of AD, particularly what is the role of keratinocyte-derived cytokine TSLP and Langerhans cells (LCs). METHODS: Two experimental AD mouse models were employed: (1) triggered by the overproduction of TSLP through topical application of MC903, and (2) induced by epicutaneous allergen ovalbumin (OVA) sensitization. RESULTS: This study demonstrated that the development of TFHs and germinal center (GC) response were crucially dependent on TSLP in both the MC903 model and the OVA sensitization model. Moreover, we found that LCs promoted TFH differentiation and GC response in the MC903 model, and the depletion of Langerin+ dendritic cells (DCs) or selective depletion of LCs diminished the TFH/GC response. By contrast, in the model with OVA sensitization, LCs inhibited TFH/GC response and suppressed TH2 skin inflammation and the subsequent asthma. Transcriptomic analysis of Langerin+ and Langerin- migratory DCs revealed that Langerin+ DCs became activated in the MC903 model, whereas these cells remained inactivated in OVA sensitization model. CONCLUSIONS: Together, these studies revealed a dual functionality of LCs in TSLP-promoted TFH and TH2 differentiation in AD pathogenesis.

The epidemiology is promising, but the trial evidence is weak. Why pharmacological dementia risk reduction trials haven't lived up to expectations, and where do we go from here?

There is an urgent need for interventions that can prevent or delay cognitive decline and dementia. Decades of epidemiological research have identified potential pharmacological strategies for risk factor modification to prevent these serious conditions, but clinical trials have failed to confirm the potential efficacy for such interventions. Our multidisciplinary international group reviewed seven high-potential intervention strategies in an attempt to identify potential reasons for the mismatch between the observational and trial results. In considering our findings, we offer constructive recommendations for the next steps. Overall, we observed some differences in the observational evidence base for the seven strategies, but several common methodological themes that emerged. These themes included the appropriateness of trial populations and intervention strategies, including the timing of interventions and other aspects of trials methodology. To inform the design of future clinical trials, we provide recommendations for the next steps in finding strategies for effective dementia risk reduction.

Vascular risk factors are associated with a decline in resting-state functional connectivity in cognitively unimpaired individuals at risk for Alzheimer's disease: Vascular risk factors and functional connectivity changes.

Resting-state functional connectivity is suggested to be cross-sectionally associated with both vascular burden and Alzheimer's disease (AD) pathology. However, evidence is lacking regarding longitudinal changes in functional connectivity. This study includes 247 cognitively unimpaired individuals with a family history of sporadic AD (185 women/ 62 men; mean [SD] age of 63 [5.3] years). Plasma total-, HDL-, and LDL-cholesterol and systolic and diastolic blood pressure were measured at baseline. Global (whole-brain) brain functional connectivity and connectivity from canonical functional networks were computed from resting-state functional MRI obtained at baseline and ~3.5 years of annual follow-ups, using a predefined functional parcellation. A subsample underwent Aß- and tau-PET (n=91). Linear mixed-effects models demonstrated that global functional connectivity increased over time across the entire sample. In contrast, higher total-cholesterol and LDL-cholesterol levels were associated with greater reduction of functional connectivity in the default-mode network over time. In addition, higher diastolic blood pressure was associated with global functional connectivity reduction. The associations were similar when the analyses were repeated using two other functional brain parcellations. Aß and tau deposition in the brain were not associated with changes in functional connectivity over time in the subsample. These findings provide evidence that vascular burden is associated with a decrease in functional connectivity over time in older adults with elevated risk for AD. Future studies are needed to determine if the impact of vascular risk factors on functional brain changes precede the impact of AD pathology on functional brain changes.

High rate of hypomorphic variants as the cause of inherited ataxia and related diseases: study of a cohort of 366 families.

PURPOSE: Diagnosis of inherited ataxia and related diseases represents a real challenge given the tremendous heterogeneity and clinical overlap of the various causes. We evaluated the efficacy of molecular diagnosis of these diseases by sequencing a large cohort of undiagnosed families. METHODS: We analyzed 366 unrelated consecutive patients with undiagnosed ataxia or related disorders by clinical exome-capture sequencing. In silico analysis was performed with an in-house pipeline that combines variant ranking and copy-number variant (CNV) searches. Variants were interpreted according to American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) guidelines. RESULTS: We established the molecular diagnosis in 46% of the cases. We identified 35 mildly affected patients with causative variants in genes that are classically associated with severe presentations. These cases were explained by the occurrence of hypomorphic variants, but also rarely suspected mechanisms such as C-terminal truncations and translation reinitiation. CONCLUSION: A significant fraction of the clinical heterogeneity and phenotypic overlap is explained by hypomorphic variants that are difficult to identify and not readily predicted. The hypomorphic C-terminal truncation and translation reinitiation mechanisms that we identified may only apply to few genes, as it relies on specific domain organization and alterations. We identified PEX10 and FASTKD2 as candidates for translation reinitiation accounting for mild disease presentation.

New insights into the clinical and molecular spectrum of the novel CYFIP2-related neurodevelopmental disorder and impairment of the WRC-mediated actin dynamics.

PURPOSE: A few de novo missense variants in the cytoplasmic FMRP-interacting protein 2 (CYFIP2) gene have recently been described as a novel cause of severe intellectual disability, seizures, and hypotonia in 18 individuals, with p.Arg87 substitutions in the majority. METHODS: We assembled data from 19 newly identified and all 18 previously published individuals with CYFIP2 variants. By structural modeling and investigation of WAVE-regulatory complex (WRC)-mediated actin polymerization in six patient fibroblast lines we assessed the impact of CYFIP2 variants on the WRC. RESULTS: Sixteen of 19 individuals harbor two previously described and 11 novel (likely) disease-associated missense variants. We report p.Asp724 as second mutational hotspot (4/19 cases). Genotype-phenotype correlation confirms a consistently severe phenotype in p.Arg87 patients but a more variable phenotype in p.Asp724 and other substitutions. Three individuals with milder phenotypes carry putative loss-of-function variants, which remain of unclear pathogenicity. Structural modeling predicted missense variants to disturb interactions within the WRC or impair CYFIP2 stability. Consistent with its role in WRC-mediated actin polymerization we substantiate aberrant regulation of the actin cytoskeleton in patient fibroblasts. CONCLUSION: Our study expands the clinical and molecular spectrum of CYFIP2-related neurodevelopmental disorder and provides evidence for aberrant WRC-mediated actin dynamics as contributing cellular pathomechanism.

Paroxysmal Dyskinesias Revealing 3-Hydroxy-Isobutyryl-CoA Hydrolase (HIBCH) Deficiency.

Paroxysmal dyskinesias (PD) are rare movement disorders characterized by recurrent attacks of dystonia, chorea, athetosis, or their combination, with large phenotypic and genetic heterogeneity. 3-Hydroxy-isobutyryl-CoA hydrolase (HIBCH) deficiency is a neurodegenerative disease characterized in most patients by a continuous decline in psychomotor abilities or a secondary regression triggered by febrile infections and metabolic crises.We describe two PD patients from two pedigrees, both carrying a homozygous c.913A > G, p.Thr305Ala mutation in the HIBCH gene, associated with an unusual clinical presentation. The first patient presented in the second year of life with right paroxysmal hemidystonia lasting for 30 minutes, without any loss of consciousness and without any triggering factor. The second patient has presented since the age of 3 recurrent exercise-induced PD episodes which have been described as abnormal equinovarus, contractures of the lower limbs, lasting for 1 to 4 hours, associated with choreic movements of the hands. Their neurological examination and metabolic screening were normal, while brain magnetic resonance imaging showed abnormal signal of the pallidi.We suggest that HIBCH deficiency, through the accumulation of metabolic intermediates of the valine catabolic pathway, leads to a secondary defect in respiratory chain activity and pyruvate dehydrogenase (PDH) activity and to a broad phenotypic spectrum ranging from Leigh syndrome to milder phenotypes. The two patients presented herein expand the spectrum of the disease to include unusual paroxysmal phenotypes and HIBCH deficiency should be considered in the diagnostic strategy of PD to enable adequate preventive treatment.

Skeletal Ryanodine Receptors Are Involved in Impaired Myogenic Differentiation in Duchenne Muscular Dystrophy Patients.

Duchenne muscular dystrophy (DMD) is characterized by progressive muscle wasting following repeated muscle damage and inadequate regeneration. Impaired myogenesis and differentiation play a major role in DMD as well as intracellular calcium (Ca2+) mishandling. Ca2+ release from the sarcoplasmic reticulum is mostly mediated by the type 1 ryanodine receptor (RYR1) that is required for skeletal muscle differentiation in animals. The study objective was to determine whether altered RYR1-mediated Ca2+ release contributes to myogenic differentiation impairment in DMD patients. The comparison of primary cultured myoblasts from six boys with DMD and five healthy controls highlighted delayed myoblast differentiation in DMD. Silencing RYR1 expression using specific si-RNA in a healthy control induced a similar delayed differentiation. In DMD myotubes, resting intracellular Ca2+ concentration was increased, but RYR1-mediated Ca2+ release was not changed compared with control myotubes. Incubation with the RYR-calstabin interaction stabilizer S107 decreased resting Ca2+ concentration in DMD myotubes to control values and improved calstabin1 binding to the RYR1 complex. S107 also improved myogenic differentiation in DMD. Furthermore, intracellular Ca2+ concentration was correlated with endomysial fibrosis, which is the only myopathologic parameter associated with poor motor outcome in patients with DMD. This suggested a potential relationship between RYR1 dysfunction and motor impairment. Our study highlights RYR1-mediated Ca2+ leakage in human DMD myotubes and its key role in myogenic differentiation impairment. RYR1 stabilization may be an interesting adjunctive therapeutic strategy in DMD.

Expanding the genetic and phenotypic relevance of KCNB1 variants in developmental and epileptic encephalopathies: 27 new patients and overview of the literature.

Developmental and epileptic encephalopathies (DEE) refer to a heterogeneous group of devastating neurodevelopmental disorders. Variants in KCNB1 have been recently reported in patients with early-onset DEE. KCNB1 encodes the α subunit of the delayed rectifier voltage-dependent potassium channel Kv 2.1. We review the 37 previously reported patients carrying 29 distinct KCNB1 variants and significantly expand the mutational spectrum describing 18 novel variants from 27 unreported patients. Most variants occur de novo and mainly consist of missense variants located on the voltage sensor and the pore domain of Kv 2.1. We also report the first inherited variant (p.Arg583*). KCNB1-related encephalopathies encompass a wide spectrum of neurodevelopmental disorders with predominant language difficulties and behavioral impairment. Eighty-five percent of patients developed epilepsies with variable syndromes and prognosis. Truncating variants in the C-terminal domain are associated with a less-severe epileptic phenotype. Overall, this report provides an up-to-date review of the mutational and clinical spectrum of KCNB1, strengthening its place as a causal gene in DEEs and emphasizing the need for further functional studies to unravel the underlying mechanisms.