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Lamin A/C loss promotes R-loop-mediated genomic instability and poor survival in small-cell lung cancer.

Lamin A/C (LMNA), a key component of the nuclear envelope, is essential for maintaining nuclear integrity and genome organization [W. Xie et al., Curr. Biol. 26, 2651-2658 (2016)]. While LMNA dysregulation has been implicated in genomic instability across cancer and aging, the underlying mechanisms remain poorly understood [S. Graziano et al., Nucleus 9, 258-275 (2018)]. Here, we define a mechanistic role for LMNA in preserving genome stability in small-cell lung cancer (SCLC), a malignancy marked by extreme genomic instability [N. Takahashi et al., Cancer Res. Commun. 2, 503-517 (2022)]. LMNA depletion promotes R-loop accumulation, transcription-replication conflicts, replication stress, DNA breaks, and micronuclei formation. Mechanistically, LMNA deficiency disrupts nuclear pore complex organization, specifically reducing phenylalanine-glycine (FG)-nucleoporin incorporation, resulting in impaired RNA export and nuclear retention of RNA. LMNA expression is repressed by EZH2 and reexpressed during SCLC differentiation from neuroendocrine (NE) to non-NE states, and low LMNA levels correlate with poor clinical outcomes. These findings establish LMNA as a key regulator of nuclear transport and genome integrity, linking nuclear architecture to SCLC progression and therapeutic vulnerability.

Lamin Type A

Lamin A/C Deficiency Drives Genomic Instability and Poor Survival in Small-Cell Lung Cancer through Increased R-loop Accumulation.

Lamin A/C (LMNA), a key component of the nuclear envelope, is essential for maintaining nuclear integrity and genome organization [1]. While LMNA dysregulation has been implicated in genomic instability across cancer and aging, the underlying mechanisms remain poorly understood [2]. Here, we investigate LMNA's role in small-cell lung cancer (SCLC), a highly aggressive malignancy characterized by extreme genomic instability [3, 4]. We demonstrate that LMNA depletion promotes R-loop accumulation, transcription-replication conflicts, replication stress, DNA breaks, and micronuclei formation. Mechanistically, LMNA loss disrupts nuclear pore complex distribution, reducing phenylalanine-glycine (FG)-nucleoporin incorporation and impairing RNA export efficiency. Furthermore, we show that LMNA expression is epigenetically repressed by EZH2 during SCLC differentiation from neuroendocrine (NE) to non-NE states. Clinically, low LMNA levels correlate with significantly worse survival in SCLC patients. These findings uncover a novel role for LMNA in safeguarding genome integrity and shaping tumor heterogeneity, with broad implications for cancer and aging.

Biological Sciences

Cardiovascular prognostic impact of missense vs nonmissense lamin A/C variants: A systematic review and meta-analysis.

BACKGROUND: Variants in the LMNA gene, responsible for laminopathies, are associated with severe cardiovascular outcomes, including arrhythmias and heart failure (HF). However, the differential prognostic impact of missense vs nonmissense variants remains unclear. OBJECTIVE: The primary end point of this systematic review and meta-analysis was to compare the cardiovascular outcome defined as combined malignant ventricular arrhythmias (MVAs) and HF among patients with missense vs nonmissense variants in the LMNA gene. Secondary outcomes included a comparison of MVAs and HF-related events analyzed separately. METHODS: A systematic search of PubMed, Ovid MEDLINE, and Cochrane Library was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Meta-analyses were performed using fixed or random effects models, depending on heterogeneity. PROSPERO identifier: CRD42024584721. RESULTS: 12 studies comprising 1818 participants were included. Of these, 969 had missense variants, and 849 had nonmissense variants. The nonmissense group showed a significantly higher rate of cardiovascular events (30.5% vs 21.3%; odds ratio [OR] 2.22; P < .001). MVAs were more frequent in nonmissense carriers (25.5% vs 18.9%; OR 2.37; P < .001). Although limited by the small number of studies (n = 5) and single-study bias, the incidence of HF-related severe events seemed similar between the groups (18.2% vs 23.9%; OR 0.956; P = .801). CONCLUSION: Nonmissense LMNA variants are associated with worse cardiovascular outcomes, particularly arrhythmic events, whereas HF-related events seem comparable between nonmissense and missense variants.

Humans

Participation of the purinergic P2X7 receptor in molecular complexes in the nucleus of human chondrocytes.

In addition to the purinergic receptor P2X7R's known activity as a sensor of damage-associated molecular patterns (DAMPs), evidences support its role in maintaining tissue homeostasis. Its presence in cellular compartments other than its usual transmembrane localization suggests its involvement in specific signaling pathways. This study aimed to analyze P2X7R in the nucleus of human chondrocytes and search for potential interacting partners. Through co-immunoprecipitation and proximity ligation assay we discovered that, independent of extracellular ATP levels, P2X7R is abundantly present in both the nuclear membrane and in the nucleoplasm, where it is found in close proximity to lamin A/C (a component of the nuclear lamina), emerin (a protein involved in the assembly and disassembly of the nuclear envelope), and SUN2 (an inner nuclear membrane protein that facilitates the transmission of mechanical forces). Furthermore, chromatin immunoprecipitation revealed the participation of P2X7R in molecular complexes located in the promoter of specific genes including Sox9, TRPS1, FOXO3a, integrin &#x3b2;2 and connective tissue growth factor. Overall, this evidence reveals for the first time novel partners of P2X7R that place it in an intricate network that influences nuclear structure, mechanosensitivity, chromatin organization, and gene expression. Specifically, on the one hand, a close association between P2X7R and nuclear proteins participating in the LINC (Linker of Nucleoskeleton and Cytoskeleton) complex (lamin A/C, emerin, and SUN2) places it among the factors involved in mechanosignaling and the maintenance of nuclear integrity; on the other, its recruitment to specific gene promoters suggests that it may act as a transcription regulator.

Humans

Vitamin D Pathway Activation Reduces Cardiomyocyte DNA Damage and Improves Cardiac Contractility in Preclinical Models.

BACKGROUND: In heart failure (HF), DNA damage caused by various external stressors contributes to cardiac dysfunction through the activation of DNA damage response pathways. To date, no clinical strategies have been established to restore cardiac function by reducing accumulated DNA damage. We previously found that vitamin D improved contractility in lamin A/C (LMNA) p.Q353R-mutant induced pluripotent stem (iPS) cell-derived cardiomyocytes (iPSCMs), but whether this effect extends to other LMNA variants and in vivo models remained uncertain. OBJECTIVES: The objective of the study was to evaluate the association of vitamin D pathway activation with cardiomyocyte phosphorylated histone H2AX (&#x3b3;H2AX) foci and contractile phenotypes in patient-derived iPSCMs and mouse models of HF. METHODS: iPS cell lines were generated from dilated cardiomyopathy patients carrying the LMNA p.R225X mutation, and the effects of vitamin D treatment on &#x3b3;H2AX foci and cardiomyocyte contractility were evaluated. In addition, the effects of the vitamin D analog paricalcitol were evaluated in Lmna p.R225X mice and in a pressure overload mouse model of HF. RESULTS: Consistent with previous findings, vitamin D treatment reduced &#x3b3;H2AX foci in cardiomyocytes derived from LMNA p.R225X mutant iPS cells through upregulating the expression of DNA repair factors, and improved contractility in these iPSCMs. Furthermore, paricalcitol reduced &#x3b3;H2AX foci and attenuated cardiac dysfunction in both Lmna p.R225X mice and pressure overload HF model mice. CONCLUSIONS: Vitamin D pathway activation improved contractile phenotypes across complementary preclinical models and was accompanied by reduced &#x3b3;H2AX foci or related transcriptional changes. These findings support further mechanistic and preclinical investigation.

DNA damage

Lamin-ating the genome: quantitative gatekeeping of replication initiation.

Discovered in the 1970s, nuclear lamins control chromatin organization and are linked to many diseases. Zhang et al. now find that lamin A/C quantitatively constrains DNA replication initiation by limiting chromatin accessibility and sequestering proliferating cell nuclear antigen, extending lamin's long-known role in replication to the control of origin firing.

Journal Article

CK2&#x3b1; restriction of STING accumulation underlies systemic aging.

Chronic activation of the cGAS-STING pathway drives inflammaging and cellular senescence. Although nuclear envelope (NE) barrier failure leading to cytoplasmic chromatin leakage is a key trigger, the molecular mechanisms governing STING activity at the NE during aging remain poorly understood. Here, we identify lamin A/C (LMNA) as a critical NE scaffold that orchestrates STING regulation by recruiting both STING and Casein Kinase 2 (CK2&#x3b1;). We demonstrate that LMNA facilitates the phosphorylation of STING at Ser366 by CK2&#x3b1;, which promotes STING turnover and restricts its accumulation, thereby attenuating pathway activation and mitigating senescence in myeloid cells as well as systemic aging. Strikingly, pharmacologic STING inhibition in vivo robustly rescues progeroid phenotypes-including loss of bone density and multi-tissue senescence-and extends lifespan in progeroid mouse models. Moreover, H-151 treatment also ameliorates the premature aging phenotypes induced by myeloid-specific CK2&#x3b1; ablation. In contrast, constitutive STING ablation yields limited survival benefits, revealing that controlled attenuation of STING signaling, rather than complete elimination, drives therapeutic efficacy. Our findings establish the LMNA-CK2-STING axis as a key biochemical mechanism that suppresses innate immune activation at the NE, offering a promising strategy for ameliorating aging and progeroid pathologies.

Animals

Epigenetic Regulation in Dilated Cardiomyopathy.

Dilated cardiomyopathy (DCM) is a nonischemic heart muscle disease characterized by impaired contractility, cardiac dilation, and heart failure, with both genetic and nongenetic causes. Emerging evidence highlights epigenetic mechanisms, including deoxyribonucleic acid methylation, histone modifications, chromatin remodeling, and noncoding RNAs, as critical regulators of gene expression in DCM pathogenesis. This article explores familial DCM linked to pathogenic variants in genes like lamin A/C and titin, as well as nongenetic forms such as diabetic and autoimmune DCM. By summarizing recent discoveries, it highlights the epigenetic factors in bridging genetic and environmental influences, offering potential biomarkers and therapeutic targets for improved DCM management.

Humans

In Vivo Base Editing Partially Rescues Bone Dysplasia in a Mouse Model of Hutchinson-Gilford Progeria Syndrome.

Hutchinson-Gilford progeria syndrome (HGPS) is a premature aging disorder affecting tissues of mesenchymal origin. Most patients harbor a c.1824C>T/p.G608= variant, commonly described as G608G, in exon 11 of LMNA that leads to aberrant splicing and production of the toxic progerin protein. In addition to cardiovascular, dermal, and adipose tissue deterioration, HGPS mouse models also develop progressive bone dysplasia that occurs in patients. Here we characterize the efficacy of in&#xa0;vivo mutation correction with an adenine base editor (ABE) to rescue structural and functional defects in HGPS transgenic murine bone tissue. Treatment of double-copy transgenic osteoblast cultures with a lentiviral-delivered CRISPR-Cas9 ABE achieved nearly 40% gene correction in&#xa0;vitro, resulting in significant reduction of progerin transcripts and protein, in the absence of selective agents. Furthermore, gene correction improved progeroid osteoblasts' capacity to deposit and mineralize extracellular matrix compared to untreated cultures. In&#xa0;vivo, a single intravenous dose of AAV9-delivered ABE corrected the mutation, achieving ~14%, ~22%, ~10% and <&#x2009;1% correction in bone by six months of age when administered at P3, P14, 1 and 4&#x2009;months of age, respectively. Partially rescued bone structural and physical parameters were observed in P14-treated mice with concomitant normalization of gene transcriptional programs and intracellular signaling pathways involved in bone remodeling. This work demonstrates in&#xa0;vivo delivery of a locus-specific DNA base editor to bone tissue, delineates the timing of treatment required for maximum efficacy, and suggests that this system might be tailored for application to other monogenic bone disorders.

Animals