Jun 2026· Brain : a journal of neurology· 0 citations
Medicine
TL;DR
It is demonstrated that RBMX and RBMXL1 share protein and RNA partners and act redundantly in brain development, with RBMXL1 buffering the impact of RBMX deficiency and establishing RBMXL1 as a functional paralog of RBMX that is likely buffering deleterious variation in a context- and dosage-dependent manner.
Abstract
Retrotransposition has generated thousands of intronless gene copies in mammalian genomes, yet their contribution to brain development and evolution remains largely unexplored. RBMX encodes an X-linked RNA-binding protein involved in pre-mRNA splicing. RBMX has highly similar retrocopies, RBMXL1, which arose independently in primates and rodents, suggesting convergent evolutionary pressure and potential functional compensation. We identified individuals with RBMX variants through exome sequencing and GeneMatcher. We combined transcriptomic profiling, protein-protein and protein-RNA interaction studies both in human cellular models and mouse embryonic cortices to assess the functional redundancy between RBMX and its retrocopy RBMXL1. Finally, we use mouse genetics to dissect RBMX function and its compensation by RBMXL1 in corticogenesis. Hemizygous RBMX variants lead to neurodevelopmental disorders characterized by intellectual disability and variable brain, ocular, and genital malformations. N-terminal variants include missense changes and in-frame deletions, whereas truncating variants clustered in the final exon. RBMX pathogenic variants disrupt cortical development through both partial loss-of function (C-terminal variants) and gain-of-function (N-terminal variants) mechanisms. Despite severe phenotypes in humans, Rbmx-deficient mice display only mild cortical abnormalities. We demonstrate that RBMX and RBMXL1 share protein and RNA partners and act redundantly in brain development, with RBMXL1 buffering the impact of RBMX deficiency. Together, these findings establish RBMXL1 as a functional paralog of RBMX that is likely buffering deleterious variation in a context- and dosage-dependent manner. More broadly, these results identify retrocopies as active contributors to neurodevelopmental robustness and suggest that functional retrocopies may have facilitated the evolutionary diversification of the mammalian brain.
ASXL3 patient truncations in neurodevelopmental condition Bainbridge-Ropers syndrome are shown to mediates gain-of-function (GOF) by escaping nonsense-mediated decay and Cullin 4-dependent degradation, resulting in aberrant protein accumulation, widespread transcriptional dysregulation, and altered chromatin accessibility.
Y. Nakamura, T. Nguyen, N. Mor et al.· medRxiv· 0 citations
These results identify POGZ as a G9a/GLP-associated chromatin regulator that protects neurodevelopmental gene domains from heterochromatinization and perinuclear sequestering, preserving 3D architecture and transcription during cortical development.
N. Mariano, Katerina J. Williams, Katie Munechika et al.· bioRxiv· 0 citations
This study describes two patients with neurodevelopmental delay who carry de novo TRIM28 missense variants and demonstrates that these variants result in the loss of the histone mark H3K9me3 over TEs, establishing a link between TRIM28 variants and neurodevelopmental delay.
Laura Castilla-Vallmanya, Ninoslav Pandiloski, Carrie Davis-Hansson et al.· bioRxiv· 0 citations
Abstract Protein-truncating variants caused by stop codons are the most prevalent class of rare variant mutations in neurodevelopmental diseases, with UGA codons being most common. Suppressor transfer RNA (sup-tRNA) has therapeutic potential for premature termination codon (PTC) rescue but has thus far underperformed by traditional AAV delivery platforms, and progress has been hampered by the lack of methods to non-invasively assess in vivo activity in mammalian brain. To fill this material gap, we utilize transcranial in vivo bioluminescence imaging data from a luciferase-UGA mouse model to optimize viral payloads with sup-tRNA genes. These data demonstrate that U6 promoter-driven and single-stranded AAV2/9 constructs show variable and dose-dependent activity, whereas self-complementary AAV2/9 with the tRNA in a minimal 100-bp genomic context provides broad and efficacious PTC rescue. Further, payload tRNA multiplexing and use of tRNA introns enable efficacy of low viral titers and sustained rescue. tRNA sequencing of scAAV-delivered ArgUCA sup-tRNA in brain demonstrates no effects on endogenous tRNA levels, their acylation, or processing, and these features are also maintained in the delivered ArgUCA sup-tRNA. Collectively, this work defines a scalable strategy for precision UGA PTC stop codon suppression, supporting development of durable genetic rescue therapies for neurodevelopmental disorders in the mammalian brain.
Ahmad Al Saneh, Lionel Gissot, Christopher A. Ahern· Nucleic Acids Research· 0 citations
Nonsense-mediated mRNA decay (NMD) is a basic post-transcriptional mechanism ensuring the fidelity of many biological processes including brain development. Together with alternative splicing, it regulates the inclusion of poison exons. NMD is involved in the control of multiple processes during brain development such as neural progenitor proliferation and differentiation, neuronal migration, axonal guidance, and synaptic plasticity. Under physiological conditions, this mechanism safeguards neuronal identity and the functional maturation of the brain. When disrupted, the consequences range from structural cerebral anomalies to cognitive impairment and epilepsy. This review examines NMD-mediated regulatory mechanisms across different stages of brain development. Special emphasis is placed on how dysfunction in NMD pathway components—specifically core degradation factors, the exon junction complex, and neuron-specific splicing regulators—underpins an extensive array of neurodevelopmental disorders (NDDs). Furthermore, we delineate the relationship between the position of a premature termination codon (PTC) within a transcript and the resulting molecular outcome. While the degradation of aberrant mRNAs often leads to haploinsufficiency, their escape from NMD might result in the accumulation of truncated proteins with dominant-negative effects, thereby causing specific clinical phenotypes in affected patients. Elucidating these mechanisms is essential for both the interpretation of variant pathogenicity and the development of targeted therapeutic strategies.
Polina E Anisimova, A. Filat'eva, Victor S Tarabykin et al.· Frontiers in Molecular Biosc...· 0 citations
Functional modelling in zebrafish confirms a loss‑of-function mechanism and highlights species‑dependent differences specifically in the impact of the missense variant on protein function, and provides a cautionary tale about overreliance on animal models as a screening tool for variant classification.
H. Shamseldin, Dana Marafi, Mohammed A Al-Muhaizea et al.· Scientific Reports· 0 citations