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

Trends Genet. 2026 Mar 31:S0168-9525(26)00038-7. doi: 10.1016/j.tig.2026.02.003. Online ahead of print. ABSTRACT The human ASXL gene family consists of ASXL1, ASXL2, and ASXL3, first described as the additional sex combs (Asx) in Drosophila. The encoded proteins scaffold BAP1-mediated histone H2A deubiquitination. ASXL genes are implicated in pre-cancerous, cancerous, and neurodevelopmental conditions. Truncating mutations predominate and were originally predicted to result in protein loss of function (LOF); however, mounting evidence from population genetics and in vitro studies supports gain-of-function (GOF) mechanisms. Sequence analysis suggests that such mechanisms require both escape from nonsense-mediated mRNA decay and removal of a putative C-terminal degron signal within ASXL proteins. We propose GOF as a generalized mechanism for ASXL mutations, resulting in increased protein stability and altered histone modifications, with implications for diagnosis and therapy for these medical conditions. PMID:41925445 | DOI:10.1016/j.tig.2026.02.003

Genet Med. 2026 Mar 16:102551. doi: 10.1016/j.gim.2026.102551. Online ahead of print. ABSTRACT PURPOSE: Biallelic DIAPH1 pathogenic variants cause a neurodevelopmental syndrome occasionally associated with immunodeficiency. This study aims to define the clinical and immunological spectrum of DIAPH1-related neuroimmunological syndrome and explore the gene’s developmental role using vertebrate models. METHODS: 53 individuals with biallelic DIAPH1 variants, including 33 previously unreported patients were studied. Clinical features were analysed and functional studies were conducted using knockout models in Danio rerio and Xenopus tropicalis. RESULTS: Clinical features included developmental delay, intellectual disability, progressive microcephaly, cortical visual impairment or blindness, epilepsy, and frequent occipital-predominant brain abnormalities. Almost half suffered from infections, mainly affecting their respiratory tract related to epilepsy and aspiration. Although the majority had normal lymphocyte subsets and serum immunoglobulins, T-cell receptor excision circles and naïve T-lymphocyte counts were consistently low. The Xenopus model mirrored growth and eye defects seen in humans, while zebrafish exhibited no overt malformations but showed seizure-like behaviour in Phenothiazine assays. CONCLUSIONS: DIAPH1 is critical for neurodevelopment, immune regulation, and DNA repair. The DNA repair defect may influence susceptibility to infection, lymphoma, or treatment-related toxicity. Although absolute T-cell numbers are not consistent with SCID, impaired T-cell maturation suggests these patients could be identified by TREC newborn screening before neurological symptoms develop. PMID:41860019 | DOI:10.1016/j.gim.2026.102551