Findings provide strong genetic and functional evidence for a disease-causing role of NEK1 kinase disruption in NEK1-ALS and provide immediate diagnostic and therapeutic implications, particularly for the functional interpretation of missense variants of uncertain significance and the development of targeted treatment strategies.
Abstract
Heterozygous truncating loss-of-function (LoF) variants in NEK1 are a known cause of amyotrophic lateral sclerosis (ALS). NEK1 encodes the pleiotropic serine/threonine kinase NIMA-related kinase 1, and prior in vitro studies have implicated kinase dysfunction as the principal pathogenic mechanism underlying NEK1-associated ALS. However, bona fide pathogenic missense variants causally linked to ALS have not previously been reported, leaving this hypothesis unconfirmed. Here, we identify a rare NEK1 missense variant, p.N598S, that co-segregates with disease in a familial ALS pedigree and is enriched in European ALS cohorts. This variant exhibits normal protein expression levels, indicating a functional rather than quantitative defect. Using isogenic human motor neurons, we directly compared the effects of p.N598S with those of the ALS-associated truncating variant p.R812* to delineate disease mechanisms. The p.N598S variant induced pathological phenotypes consistent with NEK1 haploinsufficiency, including increased susceptibility to DNA damage, increased apoptosis, ciliary dysmorphia, and nucleocytoplasmic translocation of TDP-43. Importantly, p.N598S impaired NEK1 kinase activity, and pharmacological inhibition of NEK1 recapitulated the cellular phenotypes observed in both p.N598S- and p.R812*-mutant motor neurons. Collectively, these findings provide strong genetic and functional evidence for a disease-causing role of NEK1 kinase disruption in NEK1-ALS. Our findings provide immediate diagnostic and therapeutic implications, particularly for the functional interpretation of missense variants of uncertain significance and the development of targeted treatment strategies.
Pathogenic variants in leucine-rich repeat kinase 2 (LRRK2) 1 are among the most frequent monogenic causes of Parkinson's disease (PD) and act through a gain-of-function mechanism of increased kinase activity. LRRK2-targeted therapies are in clinical development, but interpretation of the rapidly expanding catalogue of rare LRRK2 variants remains a barrier to translation. Here, we present functionally annotated data on more than 350 LRRK2 variants using a standardized cellular assay with Rab10 phosphorylation as a readout of kinase activity and integrated these data with curated genetic and clinical annotations from the Movement Disorders Society Genetic Mutation Database (MDSGene). Variants differed in activation magnitude, ranging from modest increases (e.g., p.G2019S) to strongly activating substitutions such as p.Y1699C or p.L1795F. Activating variants occurred across the full length of LRRK2, although the largest effects clustered within the ROC-COR regulatory hub, where structural analysis identified subdomains forming an allosteric scaffold controlling kinase output. All known/established pathogenic variants showed increased activity, whereas benign and likely benign variants remained within the wild-type range. Functional effect sizes correlated with pathway activation in patient-derived immune cells, altogether providing a framework for ACMG-based variant interpretation in which kinase activation can support PS3 functional evidence for reclassification of variants.
Anthea Cheung, Neringa Pratuseviciute, Kirsten Black et al.· medRxiv· 0 citations
Using patient-derived iPSCs and multi-omics profiling, it is demonstrated that early-truncating variants cause loss-of-function via nonsense-mediated decay (NMD), while late-truncating variants that escape NMD cause gain-of-function effects.
A. Nava, Y. Pérez-Rodríguez, T. Hsieh et al.· medRxiv· 0 citations
SLC25A4, solute carrier family 25 member 4, gene is a member of the mitochondrial carrier subfamily within the solute carrier protein family. Pathogenic variants in SLC25A4 are associated with a spectrum of mitochondrial disorders that exhibit variable inheritance patterns and clinical manifestations. Specifically, dominantly inherited variants are typically associated with progressive external ophthalmoplegia with mitochondrial DNA deletions, recessively inherited variants are linked to myopathy and cardiomyopathy, and de novo variants can result in early-onset fatal disease presentations. In this study, we aimed to identify and characterize the disease-causing mutation(s) in a nine-year-old female patient from a consanguineous Saudi family. The patient was asymptomatic until the age of 3 years, when she presented with cardiomyopathy and myopathy. Comprehensive genetic analysis inclusive of whole exome sequencing and segregation analysis using Sanger sequencing identified an SLC25A4 variant (NM_001151.4: exon 2: c.112-1G>C) as the most likely cause of the disease. To assess transcript-level effects, we performed RT-PCR on RNA extracted from the patient’s cultured lymphoblast cell lines (LCLs) and fibroblast cell lines (FCLs). RT-PCR analysis demonstrated that the variant causes aberrant splicing, resulting in a 6 bp in-frame deletion (p.Gln37_Val38del) in the ANT1 protein. Quantitative RT-PCR demonstrated reduced SLC25A4 transcript levels in both FCLs and LCLs. Quantitative PCR analysis of mitochondrial DNA demonstrated a trend toward increased mtDNA copy number in patient-derived FCLs compared with controls, suggesting a possible compensatory response to mitochondrial dysfunction. Furthermore, Seahorse assays revealed marked reductions in both oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) in patient-derived FCLs compared with controls. These findings expand the molecular and functional spectrum of SLC25A4-associated disease and may inform clinical practice, including genetic interventions such as preimplantation genetic diagnosis, premarital genetic screening, targeted genetic counseling, and cascade testing of at-risk family members.
Mazhor Aldosary, Hanan Alqudairy, Nourah Alshalan et al.· International Journal of Mol...· 0 citations
Idiopathic achalasia is a rare esophageal motility disorder characterized by the selective degeneration of inhibitory myenteric neurons. Its genetic basis remains poorly defined. We investigated whether rare coding variants may contribute to disease susceptibility. Exome sequencing was performed in 31 individuals with idiopathic achalasia and seven unaffected relatives. Candidate variants were prioritized using phenotype-driven filtering and assessed through in silico and structural analysis of publicly available gene expression and single-cell transcriptomic datasets. No pathogenic or likely pathogenic variants were identified in achalasia-associated genes. A gene-agnostic analysis identified two rare heterozygous missense variants in unrelated patients: AFG3L2 c.2105G>A (p.Arg702Gln) and POLG c.1760C>T (p.Pro587Leu). Both genes encode mitochondrial proteins involved in neuronal homeostasis. The variants affected conserved residues, mapped to functionally relevant protein regions, and were predicted by multiple computational approaches to affect protein stability and function. Both genes were highly expressed in esophageal tissue, with AFG3L2 showing enrichment in enteric neuronal populations. These exploratory findings support a potential link between mitochondrial dysfunction, enteric neurodegeneration, and idiopathic achalasia. Rare mitochondrial-related variants may contribute to disease susceptibility in selected individuals by increasing vulnerability of inhibitory enteric neurons, although functional validation and larger studies are required. Accordingly, our findings should be considered hypothesis-generating rather than evidence of causality.
A. Latiano, F. Tavano, L. Micale et al.· International Journal of Mol...· 0 citations
This study may expand the mutation and phenotypic spectrum of SETD1A-related disorders, establishing the relationship between SETD1A variants and isolated early-onset epilepsy without accompanying severe neurodevelopmental deficits, and highlighting the value of genetic testing in infants with unexplained epilepsy.
Rina Su, Lei Zhu, Lin Jiang et al.· Frontiers in Neuroscience· 0 citations