Biology subjects

Larrieu, D.

Publications and source records attributed to Larrieu, D..

6 recordsLinked to original sources

bioRxiv2025

Patching up the nucleus: a novel role for PMLII in nuclear envelope rupture repair

The nuclear envelope (NE) is important for cellular health as it protects and organizes the genome. NE dynamics is important for various cellular processes including cell growth, migration and removal of defective NE components. In extreme cases, the NE can rupture leading to exchange of material between the nuclear interior and the cytoplasm. Rapid repair of the NE is initiated to minimize the effect on the genome. While our understanding of the machinery involved in this repair process is increasing, a lot is still unknown about this process including events leading up to NE rupture. Interestingly, biomolecular condensates have recently been found to play important roles in membrane repair and remodelling in cells. Here, we found that promyelocytic leukemia protein isoform II (PMLII), a protein involved in nuclear PML body formation, forms condensates at the NE. These condensates specifically form at sites where the lamina is disrupted. We show that NE rupture often occurs at these sites and that PMLII stays present until rupture repair is initiated suggesting a role in stabilization of the site for effective repair.

cell biology↗

bioRxiv2024

Targeting the acetyltransferase NAT10 corrects pathologies in human frontotemporal neurons and extends lifespan in an in vivo Drosophila tauopathy model

Disruption of the neuronal nuclear membrane and perturbation of nucleocytoplasmic transport are features of neurodegenerative diseases, including Alzheimers disease, that involve the microtubule-associated protein tau (MAPT). We previously identified that missense and splicing mutations in the MAPT gene, causal for frontotemporal dementia, result in nuclear envelope deformation and disrupted nucleocytoplasmic transport in human neurons. This is most likely due to microtubule mechanical stress, similar to that observed in Hutchinson-Gilford Progeria Syndrome (HGPS). A small molecule inhibitor of the acetyltransferase NAT10 has been shown to correct nuclear membrane defects in HGPS by modulating microtubule dynamics. We report here that NAT10 inhibition alters microtubule dynamics and corrects nuclear lamina defects and aberrant nucleocytoplasmic transport in human iPSC-derived FTD-MAPT neurons. Similarly, NAT10 inhibition and haploinsufficiency correct neuronal nuclear shape defects and extend lifespan in vivo in a Drosophila model of tauopathy. Our results show that NAT10 mediates neuronal pathologies in tauopathies and is a promising new therapeutic target in these diseases.

neuroscience↗

bioRxiv2023

A Novel Role for CSA in the Regulation of Nuclear Envelope Integrity: Uncovering a Non-Canonical Function

Cockayne syndrome (CS) is an autosomal recessive premature ageing condition mainly characterized by microcephaly, growth failure, and neurodegeneration. It is caused by mutations in ERCC6 or ERCC8 genes which encode for Cockayne Syndrome B (CSB) and Cockayne Syndrome A (CSA) proteins, respectively. CSA and CSB have well-characterised roles in transcription-coupled nucleotide excision repair (TC-NER), responsible for the removal of bulky DNA lesions, including those caused by UV irradiation. Here, we report that CSA knockout cells and CSA patient cells (CS-A) carrying a loss-of-function mutation in the ERCC8 gene exhibit defects in nuclear envelope (NE) integrity. NE dysfunction is a characteristic phenotype of cells from progeroid disorders caused by mutation in NE proteins, such as Hutchinson-Gilford Progeria Syndrome (HGPS). However, it has never been reported in Cockayne Syndrome. We observed that CS-A cells displayed reduced levels of LAP2-emerin-MAN1 (LEM)-domain 2 (LEMD2) at the NE resulting in decreased formation of LEMD2-lamin A/C complexes. In addition, loss of CSA function caused increased actin stress fibers that contributed to enhanced mechanical stress to the NE. Altogether, these led to NE blebbing and ruptures in interphase, causing activation of the innate/immune cGAS/STING signaling pathway. Disrupting the linker of the nucleoskeleton and cytoskeleton (LINC) complex that is responsible for anchoring the cytoskeleton to the NE, rescued the NE phenotypes and reduced the activation of cGAS/STING pathway. This work has revealed a previously uncharacterized role for CSA in regulating NE integrity and shed light on mechanisms that may further explain some of the clinical phenotypes observed in CS patients such as neuroinflammation. This is to our knowledge, the first study showing NE dysfunction in a progeroid syndrome caused by mutations in a DNA damage repair protein, reinforcing the connection between NE deregulation and ageing.

cell biology↗

bioRxiv2022

A multiparametric anti-aging CRISPR screen uncovers a role for BAF in protein translation

Progeria syndromes are very rare, incurable premature aging conditions recapitulating most aging features. Here, we report the first whole genome, multiparametric CRISPR anti-aging screen, identifying 43 new genes that can reverse multiple aging phenotypes in progeria. The screen was implemented in fibroblasts from Nestor- Guillermo Progeria Syndrome (NGPS) patients, carrying a homozygous p.Ala12Thr mutation in barrier-to-autointegration factor (BAF A12T). The hits were enriched for genes involved in protein translation, protein and RNA transport and osteoclast formation. We further confirmed that BAF A12T drives increased protein translation and translational errors that could directly contribute to premature aging in patients. This work has highlighted the power of multiparametric whole genome synthetic rescue screens to identify new anti-aging genes and uncover novel biology behind progeria-associated cellular dysfunction. One-Sentence SummaryA whole genome multiparametric screen in progeria identifies new pathways that can reverse cellular aging phenotypes.

molecular biology↗

bioRxiv2022

The BAF A12T mutation reduces BAF affinity to lamin A/C, preventing its recruitment to nuclear ruptures in Nestor Guillermo Progeria Syndrome cells.

The premature aging disorder Nestor Guillermo Progeria Syndrome (NGPS) is caused by a homozygous Alanine to Threonine mutation at position 12 (A12T) in Barrier-to- Autointegration Factor (BAF). BAF is a small essential protein that binds to DNA and nuclear envelope proteins. It contributes to important cellular processes including transcription regulation and nuclear envelope reformation after mitosis. More recently, BAF was identified as an important factor for nuclear envelope repair upon rupture in interphase. However, the mechanism by which the BAF A12T mutation causes NGPS has remained unclear. To investigate the effects of this mutation on nuclear envelope integrity, we used NGPS-derived patient cells and engineered an isogenic cell line by reversing the BAF A12T homozygous mutation using CRISPR/Cas9. Using a combination of cellular models, structural data and in vitro assays, we identified that the A12T mutation reduces the affinity of BAF for lamin A/C by tenfold. As a result, BAF A12T is unable to recruit lamin A/C to sites of nuclear envelope rupture. This leads to persistent lamin A/C gaps at sites of ruptures, and contributes to nuclear fragility in NGPS patient cells, which show increased frequency of nuclear envelope re- rupturing. Overexpression of wild-type BAF in a NGPS context rescues lamin A/C recruitment to sites of nuclear rupture, which could explain why the heterozygous A12T mutation does not cause premature aging.

cell biology↗

bioRxiv2018

Abnormal microtubule dynamics disrupt nucleocytoplasmic transport in tau-mediated frontotemporal dementia

The neuronal microtubule-associated protein tau (MAPT) is central to the pathogenesis of many dementias, including Alzheimers disease. Autosomal dominant mutations in MAPT cause inherited frontotemporal dementia (FTD), but the underlying pathogenic mechanisms are unclear. Using human stem cell models of FTD due to MAPT mutations, we find that tau becomes hyperphosphorylated and mislocalises to neuronal cell bodies and dendrites in cortical neurons, recapitulating a key early event in FTD. Mislocalised tau in the cell body leads to abnormal microtubule dynamics in FTD-MAPT neurons that grossly deform the nuclear membrane, resulting in defective nucleocytoplasmic transport. Neurons in the post-mortem human FTD-MAPT cortex have a high incidence of nuclear deformation, indicating that tau-mediated nuclear membrane dysfunction is an important pathogenic process in FTD. Defects in nucleocytoplasmic transport in FTD point to important commonalities in the pathogenic mechanisms of both tau-mediated dementias and ALS-FTD due to TDP-43 and C9orf72 mutations.

neuroscience↗