Nat Commun. 2026 May 30. doi: 10.1038/s41467-026-73455-9. Online ahead of print. ABSTRACT Primary mitochondrial diseases (PMDs) affect approximately 1 in 4300 individuals and cause early-onset neuromuscular and multisystem dysfunction with reduced lifespan. They result from pathogenic variants in mitochondrial or nuclear DNA that impair oxidative phosphorylation. Cytochrome c oxidase (COX; complex IV) deficiency is a well-established cause of PMD, leading to a broad spectrum of phenotypes. COXFA4 (cytochrome c oxidase subunit FA4), formerly NDUFA4, is a nuclear-encoded COX subunit, but its role in disease remains poorly defined. We report the largest genetically confirmed cohort of COXFA4-related PMD to date, comprising 13 individuals from 12 families with biallelic pathogenic COXFA4 variants. All present with Leigh-like encephalopathy and complete loss of COXFA4 protein; however, patient-derived fibroblasts retain residual COX activity, with upregulation of COXFA4L2 (cytochrome c oxidase subunit FA4-like 2), a poorly characterised paralog. Here, we show that COXFA4 is a late-stage COX assembly subunit and identify a paralog-mediated compensatory mechanism with translational potential. PMID:42218136 | DOI:10.1038/s41467-026-73455-9

Genome Med. 2026 May 28. doi: 10.1186/s13073-026-01676-0. Online ahead of print. ABSTRACT BACKGROUND: Extrachromosomal DNA (ecDNA) is a structural variant linked to poor prognosis in pediatric cancers. Patient-derived xenograft (PDX) models are crucial tools for cancer research, as they are believed to recapitulate the molecular features and intratumoral heterogeneity in patient tumors. However, ecDNA demonstrates unique evolutionary dynamics under selective pressure, and its behavior during PDX development remains largely uncharacterized. This study investigates the fidelity of PDX models in representing ecDNA from primary tumors. By analyzing ecDNA sequence composition and copy number conservation across pediatric solid cancers, we assess how well PDX models recapitulate the ecDNA landscape observed in human tumors. METHODS: AmpliconArchitect was used to analyze whole-genome sequencing (WGS) of 338 PDX models and 127 corresponding primary tumors. ecDNA status, sequence, copy number, and associated genes were compared between PDX models and their matched human tumors. Additionally, multiome RNA and ATAC single-cell sequencing of a PDX tumor enabled comparison of ecDNA intratumoral heterogeneity relative to similar data from the primary tumor. RESULTS: ecDNA in PDX models largely recapitulated oncogene amplifications observed in human tumors, with MYCN being the most frequently amplified. ecDNA status remained unchanged for a majority of the PDX models (105/127, 83%) compared to primary tumors, with 20% of previously ecDNA-negative cases acquiring ecDNA during PDX development. Consequently, ecDNA was more prevalent in the PDX models than in their corresponding human tumors (McNemar’s test, p = 0.00086). Detailed examination of ecDNA sequences in tumor-PDX pairs showed substantial conservation (67% with > 90% sequence overlap) but variable breakpoint concordance. Single-cell analysis demonstrated that rare ecDNA-positive cells from the primary tumor preferentially drive PDX tumor development. CONCLUSION: This study highlights the prevalence, oncogenic content, and conservation of ecDNA in PDX models relative to pediatric patient tumors. We observed that ecDNA frequently recapitulates oncogene amplifications found in human cancers, is generally preserved during PDX establishment, and reflects subtype-specific patterns across tumor types. These findings support the utility of PDX models in studying ecDNA biology in pediatric cancer progression and therapy. Longitudinal sampling during PDX tumor growth and under therapeutic pressure could provide insights into molecular evolution, clonal selection, and ecDNA-driven therapy resistance. PMID:42210429 | DOI:10.1186/s13073-026-01676-0

Clin Ther. 2026 May 28:S0149-2918(26)00184-0. doi: 10.1016/j.clinthera.2026.05.020. Online ahead of print. ABSTRACT Genomic sequencing (GS) in the neonatal period has advanced over the past several years. Results are available within days in many centers and cost-effectiveness and utility data continue to accumulate. Though less prevalent in clinical practice, prenatal GS is also demonstrating increasing evidence of efficacy. Clearly, information on a genetic disorder’s presence or absence is very useful for families and providers, both during pregnancy and postnatally in the intensive care units. Precision therapies for genetic disorders continue to advance in the pediatric space and, in some instances, are being considered for prenatal therapy. Despite caring for the same families along a continuum of care, prenatal and neonatal discussions about genomic sequencing are often siloed. We urge providers in the prenatal and neonatal spaces to align genomic medicine service delivery and consider offering GS prenatally or, at least, prenatally coordinating postnatal rapid GS in the third trimester to facilitate rapid diagnosis and patient-centered care. PMID:42209309 | DOI:10.1016/j.clinthera.2026.05.020

Parkinsonism Relat Disord. 2026 May 22;148:108367. doi: 10.1016/j.parkreldis.2026.108367. Online ahead of print. ABSTRACT BACKGROUND: While genetic testing in Movement Disorders (MD) has expanded enormously, access to genetic testing and genetic counseling remains asymmetric at the global scale. Guidance on efficient testing strategies for clinicians, governments and stakeholders is crucial. OBJECTIVES: Establish a list of genetic movement disorders considered essential as determined by a group of MD experts. METHODS: All genes associated with MD were searched using the OMIM and MDS Gene database. We collected all additional tests available at 4 different laboratories from the EuroGentest database. The results were compiled in 6 questionnaires. A genetic test was considered essential if molecular testing had a direct impact in the management of the patient, including treatment of the disease or its comorbidities, or genetic counseling of the patient and family members. Two Delphi rounds were conducted asking MD experts which specific tests they considered essential in an adult MD clinic. RESULTS: Fifty-nine disorders were considered essential to genetically identify by the MD experts. This included 25 genes associated with ataxia, 15 with parkinsonism, 14 with dystonia, eight with chorea, five with paroxysmal disorders, four with myoclonus, four with hereditary spastic paraparesis, and one with tremor. Sixteen disorders reached 100% consensus among experts: Huntington’s disease, PxMD-PPRT2, Wilson’s disease, DYT-SGCE, DYT-THAP1, DYT-TOR1A, DYT/PARK-GCH1, Fragile-X Tremor-ataxia syndrome, PARK-GBA, PARK-LRRK2, PARK-PINK1, PARK-PRKN, PARK-SNCA, Cerebrotendinous Xanthomatosis, Ataxia-Telangiectasia, and Niemann-Pick disease type C. CONCLUSION: This study provides a list of genetic MD that should be molecularly tested in adult centers with a compatible phenotype according to a group of MD experts. PMID:42202611 | DOI:10.1016/j.parkreldis.2026.108367

Orphanet J Rare Dis. 2026 May 21. doi: 10.1186/s13023-026-04388-1. Online ahead of print. ABSTRACT Individualized medicine has the potential to be a transformative approach to healthcare that tailors medical treatments to the unique makeup of each patient. This report explores the potential of individualized genetic medicines to meet the pressing need for effective treatments for individuals with rare genetic diseases, and funding models to support these treatments. Although recent successes have been achieved, significant administrative and financial challenges remain in implementing individualized treatment trials. This report investigates funding associated with such therapeutics. Funding challenges, key strategic operational factors, potential payor support, historic funding models, and ethical elements ultimately leading to financial support of patient treatment are considered. By addressing these questions, this report aims to provide an overview of the complex issues surrounding individualized medicine, offering insights into balancing its promises with practical and ethical considerations as the field and associated funding models continue to evolve. PMID:42169148 | DOI:10.1186/s13023-026-04388-1

Cell Genom. 2026 Mar 9:101186. doi: 10.1016/j.xgen.2026.101186. Online ahead of print. ABSTRACT Long-read whole-genome sequencing (LR-WGS) technologies enhance the discovery of structural variants (SVs) and tandem repeats (TRs). We performed LR-WGS on 267 individuals from 63 autism spectrum disorder (ASD) families and generated an integrated call set combining long- and short-read data. LR-WGS increased detection of gene-disrupting SVs and TRs by 33% and 38%, respectively, and enabled identification of novel exonic de novo germline and somatic SVs. We observed complex SV patterns, including a class of nested duplication-deletion events. By joint analysis of phased genetic variation and DNA methylation, we identified deletions of imprinted genes and demonstrated the effect of intermediate TR expansions (35-54 CGG) on the methylation of FMR1 promoter. Rare SVs, TRs, and damaging SNVs together accounted for 7.4% (95% confidence interval [CI], 2.7%-17%) of the heritability of ASD. These findings demonstrate how LR-WGS can resolve complex genetic variation and its functional consequences and regulatory effects in a single assay. PMID:41806827 | DOI:10.1016/j.xgen.2026.101186

Nature. 2026 Apr 8. doi: 10.1038/s41586-026-10334-9. Online ahead of print. ABSTRACT Recently, de novo variants in an 18-nucleotide region in the centre of RNU4-2 were shown to cause ReNU syndrome, a syndromic neurodevelopmental disorder that is predicted to affect tens of thousands of individuals worldwide^1,2. RNU4-2 is a non-protein-coding gene that is transcribed into the U4 small nuclear RNA component of the major spliceosome³. ReNU syndrome variants disrupt spliceosome function and alter 5′ splice site selection^1,4. Here we performed saturation genome editing (SGE) of RNU4-2 to identify the functional and clinical impact of variants across the entire gene. The resulting SGE function scores, derived from variants’ effects on cell fitness, discriminate ReNU syndrome variants from those observed in the population and markedly outperform in silico variant effect prediction. Using these data, we redefine the ReNU syndrome critical region at single-nucleotide resolution, resolve variant pathogenicity for variants of uncertain significance and show that SGE function scores delineate variants by phenotypic severity and the extent of observed splicing disruption. Furthermore, we identify variants affecting function in regions of RNU4-2 that are critical for interactions with other spliceosome components. We show that these variants cause a new recessive neurodevelopmental disorder that is distinct from ReNU syndrome. Together, this work defines the landscape of variant function across RNU4-2, providing critical insights for both diagnosis and therapeutic development. PMID:41951737 | DOI:10.1038/s41586-026-10334-9

Exp Mol Med. 2026 Apr 8. doi: 10.1038/s12276-024-01331-x. Online ahead of print. ABSTRACT Brain somatic mosaicism (BSM) refers to genome variation within brain cells that results from accumulated postzygotic mutations. These mutations can be used to understand cell lineage, molecular dynamics and disease processes. Unlike most other organs, brain cells are mostly fixed in position and not replaced throughout life. Thus, assessing mosaic variants (MVs) within the brain, including their spread and cell type-specific distributions and correlations with aging and cellular health, can reveal insights into neurodevelopmental, neuropsychiatric and neurodegenerative diseases. Extracting genetic material from human surgical brain resections, pregnancy remnants, or postmortem samples can reveal the origins of brain cells and uncover the effects of aging and disease on genomic integrity. Technological advances combining high-read-depth bulk sequencing, isolation of specific brain cell types, and single-cell multiomics can both detect and quantify MVs with good precision and recall. Research exploiting brain MVs is revolutionizing the understanding of the origins, mechanisms and potential treatments for brain conditions. PMID:41951903 | DOI:10.1038/s12276-024-01331-x

Nat Genet. 2026 Mar 30. doi: 10.1038/s41588-026-02547-5. Online ahead of print. ABSTRACT Small nuclear RNAs (snRNAs) are essential components of the spliceosome. De novo variants in snRNA genes RNU4-2 (ReNU syndrome), RNU5B-1 and RNU2-2 have been linked to dominant neurodevelopmental disorders (NDDs), revealing a large unexpected contribution of noncoding RNA genes to genetic diseases. Here, through international collaborations, we analyze systematically 200 potentially functional snRNA genes in a French cohort of 34,329 people with rare disorders. We report RNU2-2 variants in 141 individuals, including 35 with recurrent dominant pathogenic variants and 91 affected members from 73 families with biallelic variants. Recessive RNU2-2 NDD is at least twice as frequent as the dominant form and often involves a de novo variant in trans with an inherited allele, consistent with the high mutability of snRNA genes. Dominant and recessive RNU2-2 NDDs share overlapping clinical features, with frequent epilepsy. Blood transcriptomics and DNA methylation analyses revealed subtle, variant-specific effects on splicing and episignatures. Our results support a gradient-of-impact model bridging dominant and recessive inheritance, and establish RNU2-2 variants as a principal contributor to NDDs, nearly as prevalent as ReNU syndrome. PMID:41912934 | DOI:10.1038/s41588-026-02547-5

Nature. 2026 Apr 1. doi: 10.1038/s41586-026-10313-0. Online ahead of print. ABSTRACT The neural crest generates a broad spectrum of cell types that migrate across the body plan to populate multiple tissues¹. However, the relationship between lineages of neural crest derivatives remains unclear, and the extent to which neural crest cells delaminated from the neural tube have specified fates remains debated. Here, leveraging CRISPR barcoding in mice and mosaic variant barcode analysis in humans, we demonstrate robust bilateral progenitor clonal spread of neural crest progenitors along the rostrocaudal axis but limited clonal overlap between sensory and sympathetic lineages. Computational modelling of mosaic variants suggests that most neural crest cells show strong fate restriction before delamination. Real-time imaging of quail embryos further shows a fibroblast-growth-factor-dependent rostrocaudal dispersion of neural crest cells across multiple axial levels. These findings support a model in which neural crest fate bias predominantly emerges within the neural tube, with only a minor subset of delaminated progenitors retaining multipotency to generate both sensory and sympathetic derivatives. PMID:41922758 | DOI:10.1038/s41586-026-10313-0