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Results for “Lamin Type A”

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At least 19 recordsLinked to original sources

PubMed2025

The molecular basis of lamin-specific chromatin interactions.

In the cell nucleus, chromatin is anchored to the nuclear lamina, a network of lamin filaments and binding proteins that underly the inner nuclear membrane. The nuclear lamina is involved in chromatin organization through the interaction of lamina-associated domains within the densely packed heterochromatin regions. Using cryo-focused ion beam milling in conjunction with cryo-electron tomography, we analyzed the distribution of nucleosomes at the lamin-chromatin interface at the nanometer scale. Depletion of lamins A and C reduced nucleosome concentration at the nuclear periphery, while B-type lamin depletion contributed to nucleosome density in proximity to the lamina but not further away. We then investigated whether specific lamins can mediate direct interactions with chromatin. Using cryo-electron microscopy, we identified a specific binding motif of the lamin A tail domain that interacts with nucleosomes, distinguishing it from the other lamin isoforms. Furthermore, we examined chromatin structure dynamics using a genome-wide analysis that revealed lamin-dependent macroscopic-scale alterations in gene expression and chromatin remodeling. Our findings provide detailed insights into the dynamic and structural interplay between lamin isoforms and chromatin, molecular interactions that shape chromatin architecture and epigenetic regulation.

Nucleosomes↗

PubMed2025

Nuclear-lamin-guided plastic positioning and folding of the human genome.

The human genome exhibits a highly ordered hierarchical architecture, yet the mechanisms governing its large-scale organization remain poorly understood. Here, we generate lamin single-, double-, and triple-knockout human embryonic and mesenchymal stem cells (hESCs and hMSCs) to investigate the role of lamins in the spatial organization of the human genome. Complete lamin depletion in hMSCs triggers extensive genome repositioning, disrupts chromosome territories, and dissolves long-range compartment clustering and mega-loops. Lamin loss affects both the nuclear periphery and interior, causing partial inversion and dispersion of nuclear speckles, accompanied by reduced global transcription and impaired stem cell homeostasis. Re-expression of wild-type lamin A, which interacts with the speckle scaffold protein SON, partially restores the organizational and transcriptional defects, while the disease-associated E161K mutant disrupts SON binding and shows limited recovery. Our results elucidate the multifaceted roles of lamins in nuclear organization and link their dysfunction to the pathogenesis of laminopathies.

Humans↗

PubMed1979

[Three cases of brain injury due to windshield impact (author's transl)].

Three cases of brain injury due to windshield impact (tempered windshield) were reported. In the case of brain injury, multitude of small cracks injured the frontal lobe through the orbital roof with facial injuries due to windshield impact. Though we are apt to misdiagnose because of very small wounds, the diagnosis can be made easily from the plain film. The craniotomy, with complete removal of glass fragments and dural plasty, must be performed for the purpose of preventing infection and cerebrospinal fluid rhinorrhea. We believe that the use of seat belt and H.P.R. type laminated windshield is the best precaution against the windshield impact.

Accidents, Traffic↗

PubMed1992

Regulation of the expression of lamins A and C is post-transcriptional in P19 embryonal carcinoma cells.

The polypeptide composition of the nuclear lamina can display important variations: undifferentiated cells express only lamin B and they acquire lamins A and C only after differentiation. We have analyzed the expression of lamins A and C in P19 pluripotent mouse embryonal carcinoma cells. Undifferentiated P19 cells are completely devoid of lamins A and C. We show that undifferentiated P19 cells contain low, but detectable steady-state levels of RNAs for lamins A and C that begin to increase by 24 h of retinoic acid-induced differentiation. However, the rate of transcription of the lamin A and C gene(s), analyzed by run-on transcription assays, remains unchanged during the differentiation process. These results demonstrate that, at least in P19 embryonal carcinoma cells, regulation of the expression of lamins A and C is a post-transcriptional event.

Animals↗

PubMed1992

Induction of nuclear lamins A/C during in vitro-induced differentiation of F9 and P19 embryonal carcinoma cells.

Lamin B is the major constituent of the nuclear lamina of undifferentiated mouse embryonal carcinoma cells. The full complement of the three major lamins A, B, and C, found in somatic mammalian cells, is acquired after induction of differentiation in vitro by certain drugs. In this study we have examined the time course of lamin A/C expression in the two embryonal carcinoma cell lines F9 and P19. We show here that lamins A/C are detectable in these cell lines, at the mRNA level and at the protein level, after 3 days of growth in media containing retinoic acid or retinoic acid + 3-isobutyl-1-methylxanthine. The data reported here indicate that the expression of lamins A/C is mainly regulated at the transcriptional level and occurs when the cells, by morphological and functional criteria, have differentiated along their developmental pathway.

1-Methyl-3-isobutylxanthine↗

PubMed1976

Concentric laminated bodies. Ultrastructural demonstration of muscle fiber type specificity.

Concentric laminated bodies were identified in the skeletal muscle of 3 children affected by muscle weakness and hypotonia with probable cerebral involvement. The mean Z-line and M-line widths from each of 11 muscle fibers containing the concentric laminated bodies were calculated. The mean Z-line widths were 61-81 nm and the mean M-line widths from 7 out of 11 fibers were 54-65 nm. According to our present system of fiber typing, the majority of these fibers would be classified as subtype IIB. The possible pathogenesis and fiber type specificity of the concentric laminated body is discussed.

Child, Preschool↗

PubMed1992

Autoantibodies to nuclear lamin C in the eosinophilia-myalgia syndrome associated with L-tryptophan ingestion.

OBJECTIVE: To examine the autoantibodies (antinuclear antibodies [ANA]) present in serum from a patient with eosinophilia-myalgia syndrome (EMS). METHODS: Sera obtained during the early phase of EMS and following therapy with prednisone were screened by indirect immunofluorescence on HEp-2 cells, and ANA were characterized by immunoblotting on a purified nuclear lamin fraction. RESULTS: ANA with a ring-like pattern of nuclear staining were identified at high titer by immunofluorescence, and immunoblotting experiments showed them to be directed against lamin C. The antibody titer declined dramatically after discontinuation of L-tryptophan and therapy with prednisone. CONCLUSION: This is the first characterization of an antigen/autoantibody system associated with EMS. The findings indicate that this EMS-associated autoantibody recognizes epitopes localized in the carboxyterminal region of lamin C. The occurrence of anti-lamin C autoantibodies in one EMS patient expands the spectrum of clinical conditions associated with these antibodies, and provides evidence for an autoimmune response in EMS.

Administration, Oral↗

PubMed2026

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↗

PubMed2026

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 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 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 vivo, a single intravenous dose of AAV9-delivered ABE corrected the mutation, achieving ~14%, ~22%, ~10% and < 1% correction in bone by six months of age when administered at P3, P14, 1 and 4 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 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↗

PubMed2025

Precise progerin targeting using RfxCas13d: A therapeutic avenue for Hutchinson-Gilford progeria syndrome.

Hutchinson-Gilford progeria syndrome (HGPS), an extremely rare progressive genetic disorder, is caused by a point mutation in LMNA that induces progerin production, which disrupts cellular function and triggers premature aging and mortality. Despite extensive efforts, HPGS remains incurable. We successfully implemented a strategy using RfxCas13d to selectively target progerin mRNA at specific junction regions, without unintended cleavage and reduce its expression. This technique discriminated between normal lamin A and progerin, thus providing a safe and targeted therapeutic avenue to treat HGPS. Our approach effectively restored aberrant gene expression and progerin-induced cellular phenotypes, including senescence, mitochondrial dysfunction, and DNA damage in cells with HGPS and LMNAG608G/G608G mice. Notably, LMNAG608G/G608G mice exhibited improved progeroid phenotypes, suggesting a potential therapeutic application of this approach for other diseases resulting from abnormal RNA splicing.

Progeria↗

PubMed2026

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 β2 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↗

PubMed2025

Somatic and germinal mosaicism of a canonical splicing variant causing limb-girdle muscular dystrophy type 1B.

Limb-girdle muscular dystrophy type 1B is one of several muscular dystrophies caused by pathogenic variants in the LMNA gene. In this study, we investigated the clinical, pathological, and genetic findings of an LGMD1B family. Genetic sequencing identified the proband and her younger brother both carried the canonical splicing c.513 + 1G > A variant in the LMNA gene. The variant was absent in the proband's mother, and a certain percentage of the LMNA variant was identified in the venous blood, urine, and semen sample of the proband's father by pyrophosphate sequencing. Further cDNA analysis demonstrated that the canonical splicing c.513 + 1G > A variant in intron 2 induced retention of the first 45 bp of intron 2, resulting in an in-frame insertion of 15 amino acids. Our study directly confirmed the presence of somatic and germinal mosaicism in the LGMD1B family and the pathogenicity of the canonical splicing variant in the LMNA gene.

Humans↗

PubMed2025

Co-morbid monogenic disorders at chromosome region 1q2: LMNA- and FLG-related disorders in a patient referred for assessment of joint hypermobility.

The phenotypic similarities and genetic heterogeneity occurring in diverse forms of Ehlers Danlos Syndrome (EDS) subtypes and many heritable connective tissue disorders can pose a diagnostic challenge. In the wake of the growing applications of next-generation sequencing technologies including exome and genome sequencing, opportunities for achieving definitive genetic diagnosis are increasingly arising. We present a 46-year-old man with joint laxity, recurrent joint subluxations, pelvic floor dysfunction, and postural orthostatic tachycardia syndrome (POTS), who was referred for EDS assessment. His medical history included morbid obesity requiring gastric bypass surgery, hearing loss, asthma, retinopathy, myopia, atrial septal defect, narcolepsy with cataplexy, polyneuropathy, folliculitis, lichen simplex chronicus, atopic dermatitis, and hypogonadism. His family history was significant for multiple first- and second-degree relatives who died from cardiac diseases including cases of childhood deaths. Physical examination showed joint laxity with Beighton score of 3/9, bilateral pes planus, hearing loss and macrocephaly. Exome sequencing revealed heterozygous variants LMNA c.1262 T > C p.L421P [classified as likely pathogenic], FLG c.2282_2285del p. S761Cfs*36 [classified as pathogenic], and FLG c.1501 C > T p. R501* [classified as pathogenic]. Mitochondria sequencing revealed a variant of uncertain significance (VUS), MT-ND2 m.5047 T > C p.V193A that is present at 9% heteroplasmy in blood. These findings show co-occurrence of pathogenic sequence variants in neighboring genes located in chromosome 1q2 region [LMNA and FLG] in a patient with features of hereditary connective tissue disorders. Our study highlights the capability of exome sequencing in achieving some actionable diagnosis in cases of co-morbid genetic disorders with overlapping and non-specific symptoms.

Humans↗

PubMed2026

Generation of two homozygous iPSC lines carrying variants of uncertain significance in LMNA associated with cardiomyopathy.

Variants of uncertain significance (VUS) in the LMNA gene represent a major challenge in clinical genetics, as insufficient functional evidence limits their interpretation and clinical decision-making in laminopathies, including dilated cardiomyopathy (DCM). Here, we generated two isogenic induced pluripotent stem cell (iPSC) lines carrying homozygous LMNA variants, c.293A > G (p.Glu98Gly) and c.439G > A (p.Ala147Thr) by prime editing of a healthy donor iPSC line. Both variants are located within Coil 1B domain of lamin A. The edited iPSC lines retain normal morphology, pluripotency, genomic integrity, and trilineage differentiation capacity, providing a valuable platform for functional characterization and potential clinical reclassification of LMNA VUS.

Humans↗

PubMed2026

CK2α 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 (CK2α). We demonstrate that LMNA facilitates the phosphorylation of STING at Ser366 by CK2α, 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 CK2α 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↗

PubMed2025

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↗

PubMed2025

Radiation symptoms resemble laminopathies and the physical underlying cause may sit at the lamin A C-terminus.

Ionizing radiation causes three divergent effects in the human body: On one side, tissue death (= deterministic effects) sets on, on the other side, mutations and cancer growth (= stochastic effects) can occur. In recent years, the additional phenomenon of accelerated aging has come to light. In the following, we argue that these seemingly contradictory radiation responses namely: (i) increased cancer growth, (ii) ablation of cancer tissue or (iii) deterministic senescence, share an underlying cause from damage at the lamin A C-terminus. In other words, besides the typically described genomic radiation impact, we propose an additional destabilization pathway via oxidation at the nuclear envelope. We propose five concrete hypotheses that draw a direct mechanistic model from radiation damage and cellular oxidative stress, to micronuclei and clinical symptoms. In conjunction with lamin B compensation, we might be able to explain why deterministic or stochastic responses dominate. If our model holds true, a novel target for radiotherapeutics and radiooncology arises, and a rationale to closer connect laminopathy and radioprotection research.

Animals↗

PubMed1992

Identification of a short nuclear lamin protein selectively expressed during meiotic stages of rat spermatogenesis.

The nuclear lamina is a karyoskeletal structure located at the nuclear periphery and intimately associated with the inner nuclear membrane. It is composed of a multigene family of proteins, the lamins, which show a conspicuous cell type-specific expression pattern. The functional role of lamins has not been definitively established but available information indicates that they are involved in the organization of nuclear envelope and interphase chromatin. Spermatogenesis is characterized, among other features, by stage-specific changes in chromatin organization and function. These changes are accompanied by modifications in the organization and composition of the nuclear lamina. In previous experiments we have determined that rat spermatogenic cells express a lamin closely related, if not identical, to lamin B1 of somatic cells; whereas rat somatic lamins A, C, D and E were not detected. Considering that chromatin reorganizations during spermatogenesis may be directly or indirectly related to changes of the nuclear lamina we have decided to further investigate lamin expression during this process. Here we report on the identification of a 52 kDa protein of the rat which, according to immunocytochemical and biochemical data, appears to be a novel nuclear lamin. Using meiotic stage-specific markers, we have also demonstrated that this short lamin is selectively expressed during meiotic stages of spermatogenesis.

Animals↗