The ADAT2/ADAT3 (ADAT) complex catalyses the adenosine to inosine modification at the wobble position of eukaryotic tRNAs. Mutations in ADAT3, the catalytically inactive subunit of the ADAT2/ADAT3 complex, have been identified in patients presenting with severe neurodevelopmental disorders. Yet, the physiological function of the ADAT2/ADAT3 complex during brain development remains totally unknown.Here, we investigated the role of the ADAT2/ADAT3 complex in cortical development. First, we report 21 neurodevelopmental disorders patients carrying biallelic variants in ADAT3. Second, we used structural, biochemical and enzymatic assays to deeply characterize the impact of those variants on the ADAT2/ADAT3 structure, biochemical properties, enzymatic activity, and tRNAs editing and abundance. Finally, in vivo complementation assays were performed to correlate functional deficits with neuronal migration defects in the developing mouse cortex.Our results showed that maintaining a proper level of ADAT2/ADAT3 catalytic activity is essential for radial migration of projection neurons in the developing mouse cortex. We demonstrated that the identified ADAT3 variants significantly impaired the abundance and, for some, the activity of the complex, leading to a substantial decrease in inosine 34 levels with direct consequence on tRNAs steady state. We correlated the severity of the migration phenotype with the degree of loss of function caused by the variants.Altogether, our results highlight the critical role of ADAT2/ADAT3 during cortical development and provide cellular and molecular insights into the pathogenic mechanisms underlying ADAT3-related neurodevelopmental disorders.

Children who have experienced moderate perinatal hypoxia are at risk of developing long-lasting subtle cognitive and behavioural deficits, including learning disabilities and emotional problems. Understanding the underlying mechanisms is an essential step for designing targeted therapy. Fast-spiking, parvalbumin (PV)-positive GABAergic interneurons modulate the generation of gamma oscillations, which, in turn, regulate many cognitive functions, including goal-directed attentional processing and cognitive flexibility. Owing to their fast firing rate, PV cell function requires high levels of energy, which might render them highly vulnerable to conditions of metabolic and oxidative stress caused by perinatal hypoxia.Here, we show that adult mice that experienced moderate perinatal hypoxia have decreased cortical PV expression levels in addition to specific impairments in recognition memory and cognitive flexibility. We also found that the expression level of the neurotrophin receptor p75NTR, which limits PV cell maturation during the first postnatal weeks, is increased in mice that experienced moderate perinatal hypoxia. Genetic deletion of p75NTR in GABAergic neurons expressing the transcription factor Nkx2.1, which include PV cells, protects mice from PV expression loss and the long-term cognitive effects of moderate perinatal hypoxia. Finally, treatment with a p75NTR inhibitor starting after moderate perinatal hypoxia and lasting for 1 week prevented PV expression loss and the occurrence of cognitive and cortical activity deficits in adult mice.Altogether, our data reveal p75NTR-mediated signalling as a potential molecular target for treatment of the cognitive alterations caused by moderate perinatal hypoxia.

Proteins are involved in multiple biological functions. High-throughput technologies have allowed the measurement of thousands of proteins in population biobanks. In this study, we aimed to identify proteins related to Alzheimer’s disease, Parkinson’s disease, multiple sclerosis and amyotrophic lateral sclerosis by leveraging large-scale genetic and proteomic data.We performed a two-sample cis Mendelian randomization study by selecting instrumental variables for the abundance of >2700 proteins measured by either Olink or SomaScan platforms in plasma from the UK Biobank and the deCODE Health Study. We also used the latest publicly available genome-wide association studies for the neurodegenerative diseases of interest. The potentially causal effect of proteins on neurodegenerative diseases was estimated based on the Wald ratio.We tested 13 377 protein–disease associations, identifying 169 associations that were statistically significant (5% false discovery rate). Evidence of co-localization between plasma protein abundance and disease risk (posterior probability > 0.80) was identified for 61 protein–disease pairs, leading to 50 unique protein–disease associations. Notably, 23 of 50 protein–disease associations corresponded to genetic loci not previously reported by genome-wide association studies. The two-sample Mendelian randomization and co-localization analysis also showed that APOE abundance in plasma was associated with three subcortical volumes (hippocampus, amygdala and nucleus accumbens) and white matter hyper-intensities, whereas PILRA and PILRB abundance in plasma was associated with caudate nucleus volume.Our study provided a comprehensive assessment of the effect of the human proteome that is currently measurable through two different platforms on neurodegenerative diseases. The newly associated proteins indicated the involvement of complement (C1S and C1R), microglia (SIRPA, SIGLEC9 and PRSS8) and lysosomes (CLN5) in Alzheimer’s disease; the interleukin-6 pathway (CTF1) in Parkinson’s disease; lysosomes (TPP1), blood–brain barrier integrity (MFAP2) and astrocytes (TNFSF13) in amyotrophic lateral sclerosis; and blood–brain barrier integrity (VEGFB), oligodendrocytes (PARP1), node of Ranvier and dorsal root ganglion (NCS1, FLRT3 and CDH15) and the innate immune system (CR1, AHSG and WARS) in multiple sclerosis. Our study demonstrates how harnessing large-scale genomic and proteomic data can yield new insights into the role of the plasma proteome in the pathogenesis of neurodegenerative diseases.

We present a comprehensive global analysis of genetic variants associated with autosomal-dominant Alzheimer’s disease (ADAD). A total of 550 variants in the APP, PSEN1 and PSEN2 genes were identified, of which 279 were classified as pathogenic or likely pathogenic based on American College of Medical Genetics and Genomics and the Association for Molecular Pathology criteria, utilizing data from the Dominantly Inherited Alzheimer Network (DIAN), literature and public databases. Symptomatic age at onset (AAO) data were estimated for 227 of these variants, allowing detailed characterization of their frequency, pathogenicity and AAO.Importantly, 226 variants met eligibility criteria for inclusion in disease-modifying clinical trials. Furthermore, we demonstrated the predictive value of mean variant AAO and parental AAO in predicting symptomatic AAO, validated against converters who became symptomatic during follow-up in the DIAN Observational Study. This dataset provides critical insights into the global landscape of ADAD and reveals the genetic and AAO heterogeneity of ADAD variants while refining variant trial eligibility criteria.

Multiple sclerosis (MS) is a highly heterogeneous disease, with varying remyelination potential across individuals and between lesions. However, the molecular mechanisms underlying the potential to remyelinate remain poorly understood. In this study, we aimed to take advantage of the intrinsic heterogeneity in remyelinating capacity between MS donors and lesions to uncover known and novel pro-remyelinating molecules for MS therapies.To elucidate distinct molecular signatures underlying the potential to remyelinate, we stratified MS donors from the Netherlands Brain Bank cohort (n = 239), based on proportions of remyelinated lesions (RLs), into efficiently remyelinating donors (ERDs; n = 21) and poorly remyelinating donors (PRDs; n = 19). We performed bulk RNA sequencing of RLs, active lesions with ramified and amoeboid microglia/macrophage morphology (ALs non-foamy), active lesions with foamy microglia/macrophage morphology (ALs foamy) and normal-appearing white matter (NAWM) from ERDs and PRDs.We found that ALs non-foamy were positively correlated with remyelination, whereas ALs foamy were not, indicating a role for microglia/macrophage state in influencing remyelination potential. Bioinformatics analyses were performed to identify key pathways and molecules implicated in the remyelination process. We found distinct differences between the donors with differing remyelination potential in comparable MS lesion types. The RLs and ALs non-foamy of ERDs versus PRDs showed upregulation of the epithelial–mesenchymal transition pathway, whereas in ALs foamy of PRDs, inflammation and damage-associated pathways (i.e. MTORC1 signalling, TNF signalling and oxidative phosphorylation) were upregulated in comparison to ALs foamy of ERDs, suggesting that these latter pathways might counteract remyelination. We found genes significantly upregulated in RLs and/or ALs non-foamy of ERDs that have previously been associated with remyelination, including CXCL12, EGF, HGF, IGF2, IL10, PDGFB, PPARG and TREM2, illustrating the strength of our donor and lesion stratification. TGFB1, TGFB2, EGF and IGF1 were determined to be key upstream regulators of genes upregulated in RLs and ALs non-foamy of ERDs. We also identified potential novel pro-remyelinating molecules, such as BTC, GDF10, GDF15, CCN1, CCN4, FGF5, FGF10 and INHBB.Our study identified both known and novel genes associated with efficient remyelination that might facilitate the development of therapeutic strategies to promote tissue repair and clinical recovery in MS.

Evidence from neuropathological cohorts indicates that a CSF α-synuclein (α-syn) seed amplification assay (SAA) might provide quantitative kinetic parameters correlating with α-syn pathology burden in patients with Lewy body disease (LBD). Studies are needed to assess their longitudinal trend during the presymptomatic and clinical disease phases and their correlation with measures of disease progression.We aimed to assess the baseline α-syn CSF SAA kinetic parameters, their longitudinal variations and associations with clinical outcomes in a longitudinal cohort of repeatedly sampled LBD patients, including clinically unimpaired (asymptomatic LBD) and neurologically impaired individuals. Participants from the prospective BioFINDER-1 study with longitudinal CSF collections (n = 718) were screened by α-syn SAA. CSF samples were tested in four replicates blinded to clinical diagnoses. The number of positive replicates (Nrep), the time needed by the fluorescence signal to reach the threshold (Lag) and the highest intensity of the fluorescent signal were analysed at baseline (time of first positive SAA) in all participants and longitudinally in those with at least two α-syn-positive CSF samples available.One hundred and ninety-six individuals (whole cohort) showing α-syn seeding activity were included. Of those, 170 participants tested positive by SAA in all available samples, while 26 converted from a negative to a positive test result during follow-up (LBD-converters), suggesting an early LBD stage. At baseline, LBD-converters showed lower Nrep (P = 0.001) and a longer Lag (P = 0.001) than subjects displaying α-syn seeding activity from the first available sample. The Nrep increased longitudinally in the whole cohort [β = 0.09, 95% confidence interval (95% CI) 0.06–0.12, P < 0.001], in asymptomatic LBD (β = 0.15, 95% CI 0.09–0.21, P < 0.001) and in Parkinson’s disease individuals without dementia (β = 0.07, 95% CI 0.02–0.12, P = 0.01). The Lag decreased longitudinally in asymptomatic LBD (β = −0.24, 95% CI −0.42 to −0.06, P = 0.008). Baseline Nrep predicted the subsequent appearance of dementia in the whole cohort [hazard ratio (HR) 1.57, 95% CI 1.19–2.07, P = 0.001] and the Parkinson’s disease subgroup (HR 1.83, 95% CI 1.17–2.85, P = 0.008). The difference between the Lag at each sampling and that at baseline was negatively associated with the appearance of dementia in the whole cohort (HR 0.76, 95% CI 0.59–0.99, P = 0.04) and in the Parkinson’s disease subgroup (HR 0.69, 95% CI 0.50–0.95, P = 0.02).The α-syn SAA parameters Nrep and Lag showed associations with the LBD stage and the development of dementia. Furthermore, their longitudinal variation is coherent with progression of pathology over time. These data support the use of SAA kinetic parameters to monitor disease progression and therapeutic response.

Mutations in the gene encoding the alpha3 Na+/K+-ATPase isoform (ATP1A3) lead to movement disorders that manifest with dystonia, a common neurological symptom with many different origins, but for which the underlying molecular mechanisms remain poorly understood.We have generated an ATP1A3 mutant mouse that displays motor impairments and a hyperexcitable motor phenotype compatible with dystonia. We show that neurons harbouring this mutation are compromised in their ability to extrude raised levels of intracellular sodium, highlighting a profound deficit in neuronal sodium homeostasis. We show that the spinal motor network in ATP1A3 mutant mice has a reduced responsiveness to activity-dependent rises in intracellular sodium and that this is accompanied by loss of the Na+/K+-ATPase-mediated afterhyperpolarization in motor neurons.Taken together, our data support that the alpha3 Na+/K+-ATPase is important for cellular and spinal motor network homeostasis. These insights suggest that it may be useful to consider ways to compensate for this loss of a critical afterhyperpolarization-dependent control of neuronal excitability when developing future therapies for dystonia.

In drug-resistant focal epilepsy, planning surgical resection can involve presurgical intracranial EEG (iEEG) recordings to detect seizures and other iEEG patterns to improve postsurgical seizure outcome. We hypothesized that resection of tissue generating interictal high-frequency oscillations (HFOs, 80–500 Hz) in the iEEG predicts surgical outcome.In eight international epilepsy centres, iEEG was recorded during the presurgical evaluation of patients. The patients were of all ages, had epilepsy of all types, and underwent surgical resection of a single focus aiming at seizure freedom. In a prospective analysis, we applied a fully automated definition of HFO that was independent of the dataset. Using an observational cohort design that was blinded to postsurgical seizure outcome, we analysed HFO rates during non-rapid-eye-movement sleep. If channels had consistently high rates over multiple epochs, they were labelled the ‘HFO area’. After HFO analysis, centres provided the electrode contacts located in the resected volume and the seizure outcome at follow-up ≥24 months after surgery. The study was registered at www.clinicaltrials.gov (NCT05332990).We received 160 iEEG datasets. In 146 datasets (91%), the HFO area could be defined. The patients with a completely resected HFO area were more likely to achieve seizure freedom in comparison to those without [odds ratio 2.61, 95% confidence interval (CI) 1.15–5.91, P = 0.02]. Among seizure-free patients, the HFO area was completely resected in 31 and not completely resected in 43. Among patients with recurrent seizures, the HFO area was completely resected in 14 and not completely resected in 58. When predicting seizure freedom, the negative predictive value of the HFO area (68%, CI 52–81) was higher than that for the resected volume as a predictor by itself (51%, CI 42–59, P = 4 × 10−5). The sensitivity and specificity for complete HFO area resection were 0.88 (CI 0.72–0.98) and 0.39 (CI 0.25–0.54), respectively, and the area under the curve was 0.83 (CI 0.58–0.97), indicating good predictive performance.In a blinded cohort study from independent epilepsy centres, applying a previously validated algorithm for HFO marking without the need for adjusting to new datasets allowed us to validate the clinical relevance of HFOs to plan the surgical resection.

Advanced pathological and genetic approaches have revealed that mutations in fused in sarcoma/translated in liposarcoma (FUS/TLS), which is pivotal for DNA repair, alternative splicing, translation and RNA transport, cause familial amyotrophic lateral sclerosis (ALS). The generation of suitable animal models for ALS is essential for understanding its pathogenesis and developing therapies. Therefore, we used CRISPR-Cas9 to generate FUS-ALS mutation in the non-classical nuclear localization signal (NLS), H517D (mouse position: H509D) and genome-edited mice.FusWT/H509D mice showed progressive motor impairment (accelerating rotarod and DigiGait system) with age, which was associated with the loss of motor neurons and disruption of the nuclear lamina and nucleoporins and DNA damage in spinal cord motor neurons. We confirmed the validity of our model by showing that nuclear lamina and nucleoporin disruption were observed in lower motor neurons differentiated from patient-derived human induced pluripotent stem cells (hiPSC-LMNs) with FUS-H517D and in the post-mortem spinal cord of patients with ALS. RNA sequence analysis revealed that most nuclear lamina and nucleoporin-linking genes were significantly decreased in FUS-H517D hiPSC-LMNs.This evidence suggests that disruption of the nuclear lamina and nucleoporins is crucial for ALS pathomechanisms. Combined with patient-derived hiPSC-LMNs and autopsy samples, this mouse model might provide a more reliable understanding of ALS pathogenesis and might aid in the development of therapeutic strategies.