A cross-disorder dosage sensitivity map of the human genome.

Rare copy-number variants (rCNVs) include deletions and duplications that occur infrequently in the global human population and can confer substantial risk for disease. In this study, we aimed to quantify the properties of haploinsufficiency (i.e., deletion intolerance) and triplosensitivity (i.e., duplication intolerance) throughout the human genome. We harmonized and meta-analyzed rCNVs from nearly one million individuals to construct a genome-wide catalog of dosage sensitivity across 54 disorders, which defined 163 dosage sensitive segments associated with at least one disorder. These segments were typically gene dense and often harbored dominant dosage sensitive driver genes, which we were able to prioritize using statistical fine-mapping. Finally, we designed an ensemble machine-learning model to predict probabilities of dosage sensitivity (pHaplo & pTriplo) for all autosomal genes, which identified 2,987 haploinsufficient and 1,559 triplosensitive genes, including 648 that were uniquely triplosensitive. This dosage sensitivity resource will provide broad utility for human disease research and clinical genetics.

De novo mutation hotspots in homologous protein domains identify function-altering mutations in neurodevelopmental disorders.

Variant interpretation remains a major challenge in medical genetics. We developed Meta-Domain HotSpot (MDHS) to identify mutational hotspots across homologous protein domains. We applied MDHS to a dataset of 45,221 de novo mutations (DNMs) from 31,058 individuals with neurodevelopmental disorders (NDDs) and identified three significantly enriched missense DNM hotspots in the ion transport protein domain family (PF00520). The 37 unique missense DNMs that drive enrichment affect 25 genes, 19 of which were previously associated with NDDs. 3D protein structure modeling supports the hypothesis of function-altering effects of these mutations. Hotspot genes have a unique expression pattern in tissue, and we used this pattern alongside in silico predictors and population constraint information to identify candidate NDD-associated genes. We also propose a lenient version of our method, which identifies 32 hotspot positions across 16 different protein domains. These positions are enriched for likely pathogenic variation in clinical databases and DNMs in other genetic disorders.

Rare genetic variants in genes and loci linked to dominant monogenic developmental disorders cause milder related phenotypes in the general population.

Many rare monogenic diseases are known to be caused by deleterious variants in thousands of genes, however the same variants can also be found in people without the associated clinical phenotypes. The penetrance of these monogenic variants is generally unknown in the wider population, as they are typically identified in small clinical cohorts of affected individuals and families with highly penetrant variants. Here, we investigated the phenotypic effect of rare, potentially deleterious variants in genes and loci where similar variants are known to cause monogenic developmental disorders (DDs) in a large population cohort. We used UK Biobank to investigate phenotypes associated with rare protein-truncating and missense variants in 599 monoallelic DDG2P genes by using whole-exome-sequencing data from ∼200,000 individuals and rare copy-number variants overlapping known DD loci by using SNP-array data from ∼500,000 individuals. We found that individuals with these likely deleterious variants had a mild DD-related phenotype, including lower fluid intelligence, slower reaction times, lower numeric memory scores, and longer pairs matching times compared to the rest of the UK Biobank cohort. They were also shorter, had a higher BMI, and had significant socioeconomic disadvantages: they were less likely to be employed or be able to work and had a lower income and higher deprivation index. Our findings suggest that many genes routinely tested within pediatric genetics have deleterious variants with intermediate penetrance that may cause lifelong sub-clinical phenotypes in the general adult population.

Piezo2 voltage-block regulates mechanical pain sensitivity.

PIEZO2 is a trimeric mechanically-gated ion channel expressed by most sensory neurones in the dorsal root ganglia. Mechanosensitive PIEZO2 channels are also genetically required for normal touch sensation in both mice and humans. We previously showed that PIEZO2 channels are also strongly modulated by membrane voltage. Specifically, it is only at very positive voltages that all channels are available for opening by mechanical force. Conversely, most PIEZO2 channels are blocked at normal negative resting membrane potentials. The physiological function of this unusual biophysical property of PIEZO2 channels, however, remained unknown. We characterized the biophysical properties of three PIEZO2 ion channel mutations at an evolutionarily conserved Arginine (R2756). Using genome engineering in mice we generated Piezo2R2756H/R2756H and Piezo2R2756K/R2756K knock-in mice to characterize the physiological consequences of altering PIEZO2 voltage sensitivity in vivo. We measured endogenous mechanosensitive currents in sensory neurones isolated from the dorsal root ganglia and characterized mechanoreceptor and nociceptor function using electrophysiology. Mice were also assessed behaviourally and morphologically. Mutations at the conserved Arginine (R2756) dramatically changed the biophysical properties of the channel relieving voltage block and lowering mechanical thresholds for channel activation. Piezo2R2756H/R2756H and Piezo2R2756K/R2756K knock-in mice that were homozygous for gain of function mutations were viable and were tested for sensory changes. Surprisingly, mechanosensitive currents in nociceptors, neurones that detect noxious mechanical stimuli, were substantially sensitized in Piezo2 knock-in mice, but mechanosensitive currents in most mechanoreceptors that underlie touch sensation were only mildly affected by the same mutations. Single-unit electrophysiological recordings from sensory neurones innervating the glabrous skin revealed that rapidly-adapting mechanoreceptors that innervate Meissner's corpuscles exhibited slightly decreased mechanical thresholds in Piezo2 knock-in mice. Consistent with measurements of mechanically activated currents in isolated sensory neurones essentially all cutaneous nociceptors, both fast conducting Aδ-mechanonociceptors and unmyelinated C-fibre nociceptors were substantially more sensitive to mechanical stimuli and indeed acquired receptor properties similar to ultrasensitive touch receptors in Piezo2 knock-in mice. Mechanical stimuli also induced enhanced ongoing activity in cutaneous nociceptors in Piezo2 knock-in mice and hyper-sensitive PIEZO2 channels were sufficient alone to drive ongoing activity, even in isolated nociceptive neurones. Consistently, Piezo2 knock-in mice showed substantial behaviourally hypersensitivity to noxious mechanical stimuli. Our data indicate that ongoing activity and sensitization of nociceptors, phenomena commonly found in human chronic pain syndromes, can be driven by relieving the voltage-block of PIEZO2 ion channels. Indeed, membrane depolarization caused by multiple noxious stimuli may sensitize nociceptors by relieving voltage-block of PIEZO2 channels.

Central role of the habenulo-interpeduncular system in the neurodevelopmental basis of susceptibility and resilience to anxiety in mice.

Having experienced stress during sensitive periods of brain development strongly influences how individuals cope with later stress. Some are prone to develop anxiety or depression, while others appear resilient. The as-yet-unknown mechanisms underlying these differences may lie in how genes and environmental stress interact to shape the circuits that control emotions. Here, we investigated the role of the habenulo-interpeduncular system (HIPS), a critical node in reward circuits, in early stress-induced anxiety in mice. We found that habenular and IPN components characterized by the expression of Otx2 are synaptically connected and particularly sensitive to chronic stress (CS) during the peripubertal period. Stress-induced peripubertal activation of this HIPS subcircuit elicits both HIPS hypersensitivity to later stress and susceptibility to develop anxiety. We also show that HIPS silencing through conditional Otx2 knockout counteracts these effects of stress. Together, these results demonstrate that a genetic factor, Otx2, and stress interact during the peripubertal period to shape the stress sensitivity of the HIPS, which is shown to be a key modulator of susceptibility or resilience to develop anxiety.

Detecting cryptic clinically relevant structural variation in exome-sequencing data increases diagnostic yield for developmental disorders.

Structural variation (SV) describes a broad class of genetic variation greater than 50 bp in size. SVs can cause a wide range of genetic diseases and are prevalent in rare developmental disorders (DDs). Individuals presenting with DDs are often referred for diagnostic testing with chromosomal microarrays (CMAs) to identify large copy-number variants (CNVs) and/or with single-gene, gene-panel, or exome sequencing (ES) to identify single-nucleotide variants, small insertions/deletions, and CNVs. However, individuals with pathogenic SVs undetectable by conventional analysis often remain undiagnosed. Consequently, we have developed the tool InDelible, which interrogates short-read sequencing data for split-read clusters characteristic of SV breakpoints. We applied InDelible to 13,438 probands with severe DDs recruited as part of the Deciphering Developmental Disorders (DDD) study and discovered 63 rare, damaging variants in genes previously associated with DDs missed by standard SNV, indel, or CNV discovery approaches. Clinical review of these 63 variants determined that about half (30/63) were plausibly pathogenic. InDelible was particularly effective at ascertaining variants between 21 and 500 bp in size and increased the total number of potentially pathogenic variants identified by DDD in this size range by 42.9%. Of particular interest were seven confirmed de novo variants in MECP2, which represent 35.0% of all de novo protein-truncating variants in MECP2 among DDD study participants. InDelible provides a framework for the discovery of pathogenic SVs that are most likely missed by standard analytical workflows and has the potential to improve the diagnostic yield of ES across a broad range of genetic diseases.

Non-coding region variants upstream of MEF2C cause severe developmental disorder through three distinct loss-of-function mechanisms.

Clinical genetic testing of protein-coding regions identifies a likely causative variant in only around half of developmental disorder (DD) cases. The contribution of regulatory variation in non-coding regions to rare disease, including DD, remains very poorly understood. We screened 9,858 probands from the Deciphering Developmental Disorders (DDD) study for de novo mutations in the 5' untranslated regions (5' UTRs) of genes within which variants have previously been shown to cause DD through a dominant haploinsufficient mechanism. We identified four single-nucleotide variants and two copy-number variants upstream of MEF2C in a total of ten individual probands. We developed multiple bespoke and orthogonal experimental approaches to demonstrate that these variants cause DD through three distinct loss-of-function mechanisms, disrupting transcription, translation, and/or protein function. These non-coding region variants represent 23% of likely diagnoses identified in MEF2C in the DDD cohort, but these would all be missed in standard clinical genetics approaches. Nonetheless, these variants are readily detectable in exome sequence data, with 30.7% of 5' UTR bases across all genes well covered in the DDD dataset. Our analyses show that non-coding variants upstream of genes within which coding variants are known to cause DD are an important cause of severe disease and demonstrate that analyzing 5' UTRs can increase diagnostic yield. We also show how non-coding variants can help inform both the disease-causing mechanism underlying protein-coding variants and dosage tolerance of the gene.

Combined HRAS and NRAS ablation induces a RASopathy phenotype in mice.

BACKGROUND: HRASKO/NRASKO double knockout mice exhibit exceedingly high rates of perinatal lethality due to respiratory failure caused by a significant lung maturation delay. The few animals that reach adulthood have a normal lifespan, but present areas of atelectasis mixed with patches of emphysema and normal tissue in the lung. METHODS: Eight double knockout and eight control mice were analyzed using micro-X-ray computerized tomography and a Small Animal Physiological Monitoring system. Tissues and samples from these mice were analyzed using standard histological and Molecular Biology methods and the significance of the results analyzed using a Student´s T-test. RESULTS: The very few double knockout mice surviving up to adulthood display clear craniofacial abnormalities reminiscent of those seen in RASopathy mouse models, as well as thrombocytopenia, bleeding anomalies, and reduced platelet activation induced by thrombin. These surviving mice also present heart and spleen hyperplasia, and elevated numbers of myeloid-derived suppressor cells in the spleen. Mechanistically, we observed that these phenotypic alterations are accompanied by increased KRAS-GTP levels in heart, platelets and primary mouse embryonic fibroblasts from these animals. CONCLUSIONS: Our data uncovers a new, previously unidentified mechanism capable of triggering a RASopathy phenotype in mice as a result of the combined removal of HRAS and NRAS.

Molecular Function and Contribution of TBX4 in Development and Disease.

Over the past decade, recognition of the profound impact of the TBX4 (T-box 4) gene, which encodes a member of the evolutionarily conserved family of T-box-containing transcription factors, on respiratory diseases has emerged. The developmental importance of TBX4 is emphasized by the association of TBX4 variants with congenital disorders involving respiratory and skeletal structures; however, the exact role of TBX4 in human development remains incompletely understood. Here, we discuss the developmental, tissue-specific, and pathological TBX4 functions identified through human and animal studies and review the published TBX4 variants resulting in variable disease phenotypes. We also outline future research directions to fill the gaps in our understanding of TBX4 function and of how TBX4 disruption affects development.

Association of preterm birth and birth size status with neurodevelopmental and psychiatric disorders in spontaneous births.

Preterm birth (PTB) or small birth size are risk factors for certain neurodevelopmental disorders. The magnitude of these associations in spontaneous births, and of associations for combined PTB and birth size status on neurodevelopmental and psychiatric disorders is unexplored. We investigated whether PTB and small/large for gestational age (SGA/LGA), separately or combined, in spontaneous births, are associated with a wide spectrum of neurodevelopmental and psychiatric disorders. In this population-based registry cohort study, all singleton spontaneous births in Finland from 1996 to 2014 were followed until 2018 (n = 819 764). We show that PTB across gestational ages, and SGA, were associated with higher risks for anxiety disorders, intellectual disabilities, specific developmental disorders (SDD), autism spectrum disorders (ASD), attention-deficit/hyperactivity disorders (ADHD) and other emotional and behavioural disorders (F98). Most of these associations were not attributed to familial factors. Larger effect sizes were observed with lower gestational ages. Extremely PTB was associated at highest risks with intellectual disabilities (HR, 10.70 [95%CI, 8.69-13.17]) and SDD (HR, 8.91 [95%CI, 8.18-9.71]). Moreover, very preterm birth combined with SGA was associated with a higher risk for SDD (HR, 7.55 [95%CI, 6.61-8.62]) than that of very preterm or SGA birth alone. Conversely, LGA birth lowered the risk for SDD and other emotional and behavioural disorders among individuals born very preterm. In conclusion, PTB along with SGA is associated with higher risks for SDD than one exposure alone, whereas LGA lowers the risks for SDD and other emotional and behavioural disorders in individuals born spontaneously.

Three types of university students with subthreshold depression characterized by distinctive cognitive behavioral skills.

Subthreshold depression impairs young people's quality of life and places them at greater risk of developing major depression. Cognitive behavioral therapy (CBT) is an evidence-based approach for addressing such depressive states. This study identified subtypes of university students with subthreshold depression and revealed discrete profiles of five CBT skills: self-monitoring, cognitive restructuring, behavioral activation, assertive communication, and problem solving. Using data from the Healthy Campus Trial (registration number: UMINCTR-000031307), a hierarchical clustering analysis categorized 1,080 students into three clusters: Reflective Low-skilled, Non-reflective High-skilled, and Non-reflective Low-skilled students. Non-reflective Low-skilled students were significantly more depressed than other students (p < .001). The severity of depression seemed to be related to the combination of self-monitoring skills and other CBT skills. Considering the high prevalence of poor self-monitoring skills in persons with autism, the most severe depression was observed in the significant association between Non-reflective Low-skilled students and autistic traits (p = .008). These findings suggest that subthreshold depression can be categorized into three subtypes based on CBT skill profiles. The assessment of autistic traits is also suggested when we provide CBT interventions for Non-reflective Low-skilled students.

Barriers and facilitators to achieving employment in mainstream settings in adults with autism spectrum disorder without intellectual developmental disorders: A scoping review.

Autistic people without Intellectual Developmental Disorders (IDD) have a significantly lower employment rate compared to the general population even though employment favors social integration and quality of life. AIMS: To examine the barriers and facilitators to employability in mainstream settings for autistic adults without intellectual disability. METHODS: Following the scoping review guidelines, we searched the Cochrane, PubMed and PsycINFO databases for references published between 01/01/2000 to 01/08/2023. RESULTS: A review of the 44 identified articles suggests the existence of multiple individual and environmental factors influencing job access and retention. CONCLUSIONS: This is the first review to assess the facilitators and barriers to employment support for autistic people without intellectual disability. The results underline the need for studying strategies to promote access to employment and job retention for autistic people. Future research should explore the mediating and moderating factors leading to the improvement of employability of autistic people WIDD.

Forensic interviews conducted with autistic adults in Japan: a review of the literature and directions for future research.

The interviewing of victims, witnesses and suspects is important in helping resolve criminal investigations. In Japan, developments have recently occurred in the training of the police and their public prosecutors in these key tasks. Whilst literature exists on autism in Japan, studies examining police/public prosecutor interviews with autistic adults conducted in that country (and indeed, any other) remain scant. As elsewhere in the world, identification of those who manifest characteristics prevalent on the autism spectrum disorder (ASD) scale, has been found to be problematical to criminal justice professionals. To help address this deficit in understanding, we provide an overview of the literature concerning contemporary understanding of the challenges facing autistic adults as they attempt to reveal their verbal accounts, as well as suggested techniques when interviewing adults on the ASD scale during criminal investigations, offering lessons learned from research conducted around the world that provide potentially promising solutions for Japan.

Genomically Aided Diagnosis of Severe Developmental Disorders.

Our ability to make accurate and specific genetic diagnoses in individuals with severe developmental disorders has been transformed by data derived from genomic sequencing technologies. These data reveal both the patterns and rates of different mutational mechanisms and identify regions of the human genome with fewer mutations than would be expected. In outbred populations, the most common identifiable cause of severe developmental disorders is de novo mutation affecting the coding region in one of approximately 500 different genes, almost universally showing constraint. Simply combining the location of a de novo genomic event with its predicted consequence on the gene product gives significant diagnostic power. Our knowledge of the diversity of phenotypic consequences associated with comparable diagnostic genotypes at each locus is improving. Computationally useful phenotype data will improve diagnostic interpretation of ultrarare genetic variants and, in the long run, indicate which specific embryonic processes have been perturbed.

Hi-C Identifies Complex Genomic Rearrangements and TAD-Shuffling in Developmental Diseases.

Genome-wide analysis methods, such as array comparative genomic hybridization (CGH) and whole-genome sequencing (WGS), have greatly advanced the identification of structural variants (SVs) in the human genome. However, even with standard high-throughput sequencing techniques, complex rearrangements with multiple breakpoints are often difficult to resolve, and predicting their effects on gene expression and phenotype remains a challenge. Here, we address these problems by using high-throughput chromosome conformation capture (Hi-C) generated from cultured cells of nine individuals with developmental disorders (DDs). Three individuals had previously been identified as harboring duplications at the SOX9 locus and six had been identified with translocations. Hi-C resolved the positions of the duplications and was instructive in interpreting their distinct pathogenic effects, including the formation of new topologically associating domains (neo-TADs). Hi-C was very sensitive in detecting translocations, and it revealed previously unrecognized complex rearrangements at the breakpoints. In several cases, we observed the formation of fused-TADs promoting ectopic enhancer-promoter interactions that were likely to be involved in the disease pathology. In summary, we show that Hi-C is a sensible method for the detection of complex SVs in a clinical setting. The results help interpret the possible pathogenic effects of the SVs in individuals with DDs.

The impact of phosphorylated PTEN at threonine 366 on cortical connectivity and behaviour.

The lipid phosphatase PTEN (phosphatase and tensin homologue on chromosome 10) is a key tumour suppressor gene and an important regulator of neuronal signalling. PTEN mutations have been identified in patients with autism spectrum disorders, characterized by macrocephaly, impaired social interactions and communication, repetitive behaviour, intellectual disability, and epilepsy. PTEN enzymatic activity is regulated by a cluster of phosphorylation sites at the C-terminus of the protein. Here, we focused on the role of PTEN T366 phosphorylation and generated a knock-in mouse line in which Pten T366 was substituted with alanine (PtenT366A/T366A). We identify that phosphorylation of PTEN at T366 controls neuron size and connectivity of brain circuits involved in sensory processing. We show in behavioural tests that PtenT366/T366A mice exhibit cognitive deficits and selective sensory impairments, with significant differences in male individuals. We identify restricted cellular overgrowth of cortical neurons in PtenT366A/T366A brains, linked to increases in both dendritic arborization and soma size. In a combinatorial approach of anterograde and retrograde monosynaptic tracing using rabies virus, we characterize differences in connectivity to the primary somatosensory cortex of PtenT366A/T366A brains, with imbalances in long-range cortico-cortical input to neurons. We conclude that phosphorylation of PTEN at T366 controls neuron size and connectivity of brain circuits involved in sensory processing and propose that PTEN T366 signalling may account for a subset of autism-related functions of PTEN.

Association of physical activity with psychological distress and happiness in mothers of children with autism spectrum disorders during the COVID-19 pandemic.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic may have severely impacted the psychological status of mothers of children with autism spectrum disorder (ASD). Although a previous study reported that physical activity (PA) moderated psychological distress in parents of children with ASD during the COVID-19 pandemic, the effect of PA on the happiness levels of such parents during the pandemic remains unclear. This study investigated the associations among PA, psychological distress, and happiness in mothers of children with ASD during the COVID-19 pandemic. METHODS: This cross-sectional study was designed to evaluate mothers of children with disabilities. Questionnaires were collected from mothers living in Yamaguchi and Okayama Prefectures, Japan, between February and December 2022. During this period, three large waves of the COVID-19 pandemic occurred in Japan. Of the 601 respondents, 334 mothers had children with ASD and offered valid data. PA was assessed using the short form of the International Physical Activity Questionnaire. Psychological distress and happiness were assessed using the six-item Kessler Psychological Distress Scale (K6) and the Subjective Happiness Scale (SHS). RESULTS: The mothers had markedly higher K6 scores (6.49) and more than half of them had moderate-to-severe psychological distress, whereas the SHS scores (4.46) were similar to that of the general Japanese population. In a multivariable-adjusted model based on the analysis of covariance, the K6 score was not associated with any PA items. In contrast, SHS scores were positively associated with moderate-intensity PA (MPA) and total moderate- to vigorous-intensity PA (MVPA), independent of K6. In the post-hoc test, mothers who did some (4.52) or enough (≥ 150 min/week) MPA (4.56) had a higher SHS score than those who did not (4.09). Similarly, mothers who engaged in sufficient (≥ 600 MET-min/week) total MVPA had higher SHS scores (4.57) than those who did not engage in MVPA (4.12). CONCLUSIONS: The mothers of children with ASD during the COVID-19 pandemic had markedly higher psychological distress, though none of the PA items were associated with stress levels. However, PA was positively associated with happiness in mothers of children with ASD independent of their stress levels.

Invisible scars: exploring the impact of childhood left-behind experience on children's emotional development and well-being.

Childhood trauma experience and mental health issues can significantly impact children's emotional development and overall well-being. It is crucial to recognize and address the invisible scars left by childhood left-behind experience. By acknowledging the impact of childhood left-behind experience and providing appropriate support and interventions, we can help these children to heal, thrive and develop into emotionally resilient individuals.

Tocolytic treatment and maternal characteristics, obstetric outcomes, and offspring childhood outcomes among births at and after 37 weeks of gestation: the Japan environment and children's study.

PURPOSE: To evaluate differences in maternal characteristics and obstetric and offspring childhood outcomes between births at and after 37 weeks of gestation (referred to as term and post-term births) according to the use of tocolytic treatment. METHODS: Data for 63,409 women with singleton births at and after 37 weeks of gestation were analyzed using data from the Japan Environment and Children's Study (JECS). We compared maternal characteristics, obstetric outcomes, and offspring childhood outcomes between term and post-term births exposed and not exposed to tocolytic treatment. Additionally, multivariable logistic regression models were used to calculate adjusted odds ratios for offspring childhood outcomes with significant between-group differences in the univariable analysis, with term and post-term births without tocolytic agents as the reference group. RESULTS: We observed differences in maternal characteristics and obstetric outcomes between term and post-term births exposed and not exposed to tocolytic treatment. The incidence of offspring childhood developmental disorders showed no significant between-group differences. However, participants exposed to tocolytic agents had higher incidence of offspring childhood allergic disorders. The adjusted odds ratio for any of the offspring childhood allergic disorders in term and post-term births with tocolytic agents was 1.08 (95% confidence interval, 1.03-1.13). CONCLUSION: This study found no significant difference in the incidence of offspring developmental disorders between term and post-term births exposed and not exposed to tocolytic treatment. However, tocolytic treatment was associated with differences in maternal characteristics and obstetric outcomes, along with a marginal increase in the incidence of childhood allergic disorders in offspring.

The Central Noradrenergic System in Neurodevelopmental Disorders: Merging Experimental and Clinical Evidence.

The aim of this article is to highlight the potential role of the locus-coeruleus-noradrenergic (LC-NA) system in neurodevelopmental disorders (NdDs). The LC is the main brain noradrenergic nucleus, key in the regulation of arousal, attention, and stress response, and its early maturation and sensitivity to perinatal damage make it an interesting target for translational research. Clinical data shows the involvement of the LC-NA system in several NdDs, suggesting a pathogenetic role in the development of such disorders. In this context, a new neuroimaging tool, LC Magnetic Resonance Imaging (MRI), has been developed to visualize the LC in vivo and assess its integrity, which could be a valuable tool for exploring morphological alterations in NdD in vivo in humans. New animal models may be used to test the contribution of the LC-NA system to the pathogenic pathways of NdD and to evaluate the efficacy of NA-targeting drugs. In this narrative review, we provide an overview of how the LC-NA system may represent a common pathophysiological and pathogenic mechanism in NdD and a reliable target for symptomatic and disease-modifying drugs. Further research is needed to fully understand the interplay between the LC-NA system and NdD.