Nuclear Envelope Proteins Research Articles

EXTH-24. THERAPEUTIC TARGETING OF MISLOCALIZED NUCLEAR ENVELOPE PROTEINS INMYC-DRIVEN GROUP 3 MEDULLOBLASTOMA

Abstract Medulloblastoma (MB) is the most common, malignant pediatric brain tumour comprised of four distinct molecular subgroups (WNT, SHH, Group 3, and Group 4). A subset of Group 3 MB tumors harbors focal amplifications of the MYC oncogene (MYC-G3MB) and are particularly prone to tumour recurrence due to their highly proliferative nature linked to its embryonic stem cell-of-origin and programming. We discovered that LBR, an inner nuclear transmembrane protein, while present in all cells at the nuclear envelope (NE), is aberrantly presented to the cell surface in MYC-G3MBs. Transcriptomic profiling of publicly available datasets identified significant NE protein enrichment in MYC-G3MB compared to normal tissue and high expression during fetal development that dampens postnatally and in adult samples. Immunohistochemistry analysis of LBR on patient tumors was able to significantly prognosticate overall and progression free survival. Flow cytometry analysis identified LBR cell surface expression in MYC-G3MBs with low to no expression in human neural stem cells and other MB subgroups. High resolution microscopy of endogenously tagged LBR revealed cell surface presentation to be linked to ER-like vesicles that directly trafficked to the cell surface in MYC-G3MBs. Transcriptomic analysis of LBR cell surface positive and negative cells identified LBR to be linked to mitotic processes and mislocalization was significantly enriched following exposure to chemotherapy and radiation in vitro and in vivo. Therefore, we demonstrate that LBR is an ideal therapeutic target for patients facing treatment-refractory MB and have generated single domain antibodies (sdAb) to develop LBR-CAR T cells. Validation of LBR sdAbs demonstrate on-target binding and comparable affinity and avidity to commercial LBR antibodies. There is an undeniable paucity of targets for MB patients stemming from the lack of neoantigens and genomic aberrations in pediatric tumors. The preclinical development and validation of novel immunotherapeutic targets such as LBR provides alternative therapies for patients otherwise facing palliation.

A novel role for CSA in the regulation of nuclear envelope integrity: uncovering a non-canonical function.

Cockayne syndrome (CS) is a premature ageing condition characterized by microcephaly, growth failure, and neurodegeneration. It is caused by mutations in ERCC6 or ERCC8 encoding for Cockayne syndrome B (CSB) and A (CSA) proteins, respectively. CSA and CSB have well-characterized roles in transcription-coupled nucleotide excision repair, responsible for removing bulky DNA lesions, including those caused by UV irradiation. Here, we report that CSA dysfunction causes defects in the nuclear envelope (NE) integrity. NE dysfunction is characteristic of progeroid disorders caused by a mutation in NE proteins, such as Hutchinson-Gilford progeria syndrome. However, it has never been reported in Cockayne syndrome. We observed CSA dysfunction affected LEMD2 incorporation at the NE and increased actin stress fibers that contributed to enhanced mechanical stress to the NE. Altogether, these led to NE abnormalities associated with the activation of the cGAS/STING pathway. Targeting the linker of the nucleoskeleton and cytoskeleton complex was sufficient to rescue these phenotypes. This work reveals NE dysfunction in a progeroid syndrome caused by mutations in a DNA damage repair protein, reinforcing the connection between NE deregulation and ageing.

Pnn deficiency alters expressions of calcium handling proteins and impairs nuclear envelope structure in cardiomyocytes

Abstract Pnn is a multi-functional protein playing roles in the regulation of gene transcription, mRNA alternative splicing, as well as cell-cell connection. Previous studies suggested an association between Pnn genetic defects and arrhythmogenic right ventricular cardiomyopathy (ARVC) in human. In this study, we applied an inducible cardiomyocyte-specific Pnn depletion mouse model (Myh6-CreERT2, Pnnflox/flox) to determine the impact of loss of Pnn on cardiac structure and function in mice. Six weeks after inducing Pnn gene disruption, electrocardiographic abnormalities, ventricular dilatation, and reduced left ventricular ejection fraction (LVEF) were observed in mice with loss of Pnn in cardiomyocytes. Histopathological examinations showed that the proliferation of cardiac fibroblasts and expression of α-smooth muscle actin were increased with Pnn depletion, while the cell-cell connection between cardiomyocytes were impaired. In addition to impaired intercalated discs, loss of Pnn also altered the distribution and expression of nuclear envelope proteins and the linker of nucleoskeleton and cytoskeleton (LINC) complex proteins, such as nuclear lamins, Emerin, and SUNs, in cardiomyocytes. Microarray analysis as well as subsequent RT-PCR and Western blots also indicated that loss of Pnn regulated myocardial expressions of genes responsible for calcium handling, such as RYR2, Atp2a2, Slc8a1, and Kcnj3. Furthermore, infiltrations of macrophages and neutrophiles were observed in the myocardium with Pnn depletion, while expression levels of oxidative stress-associated proteins were also significantly regulated by Pnn depletion. In conclusion, Pnn plays an essential role in the maintenance of intercalated disc integrity and nuclear envelope structure of cardiomyocytes, while cardiomyocyte-specific loss of Pnn impairs the calcium handling and leads to arrhythmogenic dilated cardiomyopathy in mice.Cardiac MRI of mice with Pnn depletionMyocardial expression of SUN2 and Emerin

Decitabine Enhances Sorafenib Sensitivity in Renal Cell Carcinoma by Promoting BIN1 and SYNE1 Expressions.

Renal cell carcinoma (RCC), especially clear cell RCC (ccRCC), significantly impacts health, and results in particularly poor outcomes in patients at the advanced stage. Resistance to vascular endothelial growth factor (VEGF) pathway-targeting tyrosine kinase inhibitors (TKIs) is a major barrier in effective ccRCC treatment. Herein, we aim to explore how decitabine mediates bridging integrator 1 (BIN1) and spectrin repeat containing nuclear envelope protein 1 (SYNE1) to impact resistance of ccRCC to sorafenib. Employing bioinformatics on datasets GSE64052 and CancerSea, we identified genes linked to TKI resistance, ultimately focusing on SYNE1. We assessed influences of SYNE1 overexpression and BIN1 knockdown via quantitative real-time PCR (qRT-PCR) and Western blot. Assessment of cell viability and apoptosis was accomplished using cell counting kit-8 (CCK-8) assays and flow cytometry. The investigation into the potential interactions between SYNE1 and BIN1, as well as their impacts on sorafenib sensitivity was accomplished by Co-Immunoprecipitation (Co-IP) and Glutathione-S-transferase (GST) Pull-down. SYNE1 was substantially down-regulated in sorafenib-resistant ccRCC cells, and its overexpression increased sorafenib sensitivity, decreased viability and enhanced apoptosis. Interaction between BIN1 and SYNE1 was confirmed, with BIN1 level lower in resistant cells. BIN1 knockdown reduced the beneficial effects of SYNE1 overexpression on sorafenib sensitivity. Decitabine treatment elevated both SYNE1 and BIN1, while boosting apoptosis and reducing sorafenib resistance. SYNE1 contributes to the modulation of sorafenib resistance in ccRCC cells through interacting with BIN1. Decitabine treatment enhances expressions of these two proteins to improve TKI response, suggesting a potential strategy for counteracting resistance and bettering patient outcomes.

How the Oocyte Nucleolus Is Turned into a Karyosphere: The Role of Heterochromatin and Structural Proteins.

Oocyte meiotic maturation includes large-scale chromatin remodeling as well as cytoskeleton and nuclear envelope rearrangements. This review addresses the dynamics of key cytoskeletal proteins (tubulin, actin, vimentin, and cytokeratins) and nuclear envelope proteins (lamin A/C, lamin B, and the nucleoporin Nup160) in parallel with chromatin reorganization in maturing mouse oocytes. A major feature of this reorganization is the concentration of heterochromatin into a spherical perinucleolar rim called surrounded nucleolus or karyosphere. In early germinal vesicle (GV) oocytes with non-surrounded nucleolus (without karyosphere), lamins and Nup160 are at the nuclear envelope while cytoplasmic cytoskeletal proteins are outside the nucleus. At the beginning of karyosphere formation, lamins and Nup160 follow the heterochromatin relocation assembling a new spherical structure in the GV. In late GV oocytes with surrounded nucleolus (fully formed karyosphere), the nuclear envelope gradually loses its integrity and cytoplasmic cytoskeletal proteins enter the nucleus. At germinal vesicle breakdown, lamin B occupies the karyosphere interior while all the other proteins stay at the karyosphere border or connect to chromatin. In metaphase oocytes, lamin A/C surrounds the spindle, Nup160 localizes to its poles, actin and lamin B are attached to the spindle fibers, and cytoplasmic intermediate filaments associate with both the spindle fibers and the metaphase chromosomes.

LMNA-Cardiomyopathy in Emery-Dreifuss Muscular Dystrophy

Emery-Dreifuss muscular dystrophy is a rare disease resulting from a genetic defect in nuclear envelope proteins, most commonly in emerin and lamin A/C. The disease is characterized by slowly progressing weakness of the scapular-brachial and pelvic-peroneal muscle groups, myodystrophy, primary joint contracture and cardiomyopathy with rhythm disorders and conduction abnormalities. Cardiovascular complications and life-threatening arrhythmias are the main cause of death in such patients at a young age. Depending on the leading symptoms and family history, patients are under the care of different specialists. Unfortunately, neurologists, cardiologists, cardio surgeons and orthopedics are not well informed about this rare condition and thus the disease tends to be not diagnosed in time. This article examines the data of epidemiology, pathophysiology, features of the course, diagnosis, approaches to the management of cardiovascular pathology in progressive Emery-Dreyfus muscular dystrophy with the development of LMNA cardiomyopathy. A clinical case of this disease is also given.

Metastatic organotropism in small cell lung cancer.

Metastasis is the leading cause of cancer-related deaths, yet its regulatory mechanisms are not fully understood. Small-cell lung cancer (SCLC) is the most metastatic form of lung cancer, with most patients presenting with widespread disease, making it an ideal model for studying metastasis. However, the lack of suitable preclinical models has limited such studies. We utilized well-annotated rapid autopsy-derived tumors to develop xenograft models that mimic key features of SCLC, including histopathology, rapid and widespread development of metastasis to the liver, brain, adrenal, bone marrow, and kidneys within weeks, and response to chemotherapy. By integrating in vivo lineage selection with comprehensive transcriptomic and epigenomic analyses, we identified critical cellular programs driving metastatic organotropism to the liver and brain, the most common sites of SCLC metastasis. Our findings reveal the key role of nuclear-cytoskeletal interactions in SCLC liver metastasis. Specifically, the loss of the nuclear envelope protein lamin A/C, encoded by the LMNA gene, increased nuclear deformability and significantly increased the incidence of liver metastasis. Human liver metastases exhibited reduced LMNA expression compared to other metastatic sites, correlating with poorer patient outcomes and increased mortality. This study introduces novel preclinical models for SCLC metastasis and highlights pathways critical for organ-specific metastasis, offering new avenues for the development of targeted therapies to prevent or treat metastatic disease.

Microtubule forces drive nuclear damage in LMNA cardiomyopathy.

Nuclear homeostasis requires a balance of forces between the cytoskeleton and nucleus. Mutations in the LMNA gene, which encodes the nuclear envelope proteins lamin A/C, disrupt this balance by weakening the nuclear lamina. This results in nuclear damage in contractile tissues and ultimately muscle disease. Intriguingly, disrupting the LINC complex that connects the cytoskeleton to the nucleus has emerged as a promising strategy to ameliorate LMNA-associated cardiomyopathy. Yet how LINC complex disruption protects the cardiomyocyte nucleus remains unclear. To address this, we developed an assay to quantify the coupling of cardiomyocyte contraction to nuclear deformation and interrogated its dependence on the nuclear lamina and LINC complex. We found that, surprisingly, the LINC complex was mostly dispensable for transferring contractile strain to the nucleus, and that increased nuclear strain in lamin A/C-deficient cardiomyocytes was not rescued by LINC complex disruption. Instead, LINC complex disruption eliminated the cage of microtubules encircling the nucleus. Disrupting microtubules was sufficient to prevent nuclear damage and rescue cardiac function induced by lamin A/C deficiency. We computationally simulated the stress fields surrounding cardiomyocyte nuclei and show how microtubule forces generate local vulnerabilities that damage lamin A/C-deficient nuclei. Our work pinpoints localized, microtubule-dependent force transmission through the LINC complex as a pathological driver and therapeutic target for LMNA-cardiomyopathy.

A human progeria-associated BAF-1 mutation modulates gene expression and accelerates aging in C. elegans.

Alterations in the nuclear envelope are linked to a variety of rare diseases termed laminopathies. A single amino acid substitution at position 12 (A12T) of the human nuclear envelope protein BAF (Barrier to Autointegration Factor) causes Néstor-Guillermo Progeria Syndrome (NGPS). This premature ageing condition leads to growth retardation and severe skeletal defects, but the underlying mechanisms are unknown. Here, we have generated a novel in vivo model for NGPS by modifying the baf-1 locus in C. elegans to mimic the human NGPS mutation. These baf-1(G12T) mutant worms displayed multiple phenotypes related to fertility, lifespan, and stress resistance. Importantly, nuclear morphology deteriorated faster during aging in baf-1(G12T) compared to wild-type animals, recapitulating an important hallmark of cells from progeria patients. Although localization of BAF-1(G12T) was similar to wild-type BAF-1, lamin accumulation at the nuclear envelope was reduced in mutant worms. Tissue-specific chromatin binding andtranscriptome analyses showed reduced BAF-1 association in most genes deregulated by the baf-1(G12T) mutation, suggesting that altered BAF chromatin association induces NGPS phenotypes via altered gene expression.

Decreased mitochondrial translation confers 3,3′-Diindolylmethane resistance to Schizosaccharomyces pombe

3,3′-Diindolylmethane (DIM), a compound derived from natural fruits and vegetables, is widely recognized for its anti-cancer activity. However, its action mechanisms remain ambiguous. In this study, to study the molecular mechanism of 3,3′-Diindolylmethane, we identified a novel mutation in the gene of mitochondrial translation elongation factor EF-Ts (tsf1+), a key factor in mitochondrial protein translation, that conferred DIM resistance to Schizosaccharomyces pombe. The tsf1Δ also conferred DIM resistance. Decreased mitochondrial translation was found to be responsible for conferring DIM resistance to Schizosaccharomyces pombe, as the cells gained DIM resistance after treatment with chloramphenicol, a specific mitochondrial translation inhibitor. Notably, tsf1Δ conferred DIM resistance in the absence of either autophagy-related protein, Atg7, or nuclear envelope protein, Lem2, two proteins that have been reported to be required for cell survival in the presence of DIM. Overall, this study revealed novel biological functions of DIM and highlighted its potential as an anti-cancer agent.

SUN1 inhibits osteogenesis and promotes adipogenesis of human adipose-derived stem cells by regulating α-tubulin and CD36 expression.

Sad and UNC84 domain 1 (SUN1) is a kind of nuclear envelope protein with established involvement in cellular processes, including nuclear motility and meiosis. SUN1 plays an intriguing role in human adipose-derived stem cells (hASCs) differentiation; however, this role remains largely undefined. This study was undertaken to investigate the role of SUN1 in hASCs differentiation, as well as its underlying mechanisms. Employing siRNAs, we selectively downregulated SUN1 and CD36 expression. Microtubules were depolymerized using nocodazole, and PPARγ was activated using rosiglitazone. Western blotting was performed to quantify SUN1, PPARγ, α-tubulin, CD36, OPN, and adiponectin protein expression levels. Alkaline phosphatase and Oil red O staining were used to assess osteogenesis and adipogenesis, respectively. Downregulated SUN1 expression increased osteogenesis and decreased adipogenesis in hASCs, concomitant with upregulated α-tubulin expression and downregulated CD36 expression, alongside reduced nuclear localization of PPARγ. Microtubule depolymerization increased CD36 expression. Rescue experiments indicated that microtubule depolymerization counteracted the downregulated SUN1-induced phenotypic changes. This study demonstrates that SUN1 influences the differentiation of hASCs towards osteogenic and adipogenic lineages, indicating its essential role in cell fate.

The Arabidopsis KASH protein SINE3 is involved in male and female gametogenesis.

The Arabidopsis KASH protein SINE3 is involved in male and female gametophyte development, likely affecting the first post-meiotic mitosis in both cases, and is required for full seed set. Linker of nucleoskeleton and cytoskeleton (LINC) complexes are protein complexes spanning the inner and outer membranes of the nuclear envelope (NE) and are key players in nuclear movement and positioning. Through their roles in nuclear movement and cytoskeletal reorganization, plant LINC complexes affect processes as diverse as pollen tube rupture and stomatal development and function. KASH proteins are the outer nuclear membrane component of the LINC complex, with conserved C-termini but divergent N-terminal cytoplasmic domains. Of the known Arabidopsis KASH proteins, SUN-INTERACTING NUCLEAR ENVELOPE PROTEIN 3 (SINE3) has not been functionally characterized. Here, we show that SINE3 is expressed at all stages of male and female gametophyte development. It is located at the NE in male and female gametophytes. Loss of SINE3 results in a female-derived seed set defect, with sine3 mutant ovules arresting at stage FG1. Pollen viability is also significantly reduced, with microspores arresting prior to pollen mitosis I. In addition, sine3 mutants have a minor male meiosis defect, with some tetrads containing more than four spores. Together, these results demonstrate that the KASH protein SINE3 plays a crucial role in male and female gametophyte development, likely affecting the first post-meiotic nuclear division in both cases.

Role of lamin A/C on dendritic cell function in antiviral immunity

Dendritic cells (DCs) play a crucial role in orchestrating immune responses, particularly in promoting IFNγ-producing-CD8 cytotoxic T lymphocytes (CTLs) and IFNγ-producing-CD4 T helper 1 (Th1) cells, which are essential for defending against viral infections. Additionally, the nuclear envelope protein lamin A/C has been implicated in T cell immunity. Nevertheless, the intricate interplay between innate and adaptive immunity in response to viral infections, particularly the role of lamin A/C in DC functions within this context, remains poorly understood. In this study, we demonstrate that mice lacking lamin A/C in myeloid LysM promoter-expressing cells exhibit a reduced capacity to induce Th1 and CD8 CTL responses, leading to impaired clearance of acute primary Vaccinia virus (VACV) infection. Remarkably, in vitro-generated granulocyte macrophage colony-stimulating factor bone marrow-derived DCs (GM-CSF BMDCs) show high levels of lamin A/C. Lamin A/C absence on GM-CSF BMDCs does not affect the expression of costimulatory molecules on the cell membrane but it reduces the cellular ability to form immunological synapses with naïve CD4 T cells. Lamin A/C deletion induces alterations in NFκB nuclear localization, thereby influencing NF-κB-dependent transcription. Furthermore, lamin A/C ablation modifies the gene accessibility of BMDCs, predisposing these cells to mount a less effective antiviral response upon TLR stimulation. This study highlights the critical role of DCs in interacting with CD4 T cells during antiviral responses and proposes some mechanisms through which lamin A/C may modulate DC function via gene accessibility and transcriptional regulation.

Clinical and Genetic Heterogeneity of Nuclear Envelopathy Related Muscular Dystrophies in an Indian Cohort.

Nuclear envelopathies occur due to structural and/or functional defects in various nuclear envelope proteins such as lamin A/C and lamin related proteins. This study is the first report on the phenotype-genotype patterns of nuclear envelopathy-related muscular dystrophies from India. In this retrospective study, we have described patients with genetically confirmed muscular dystrophy associated with nuclear envelopathy. Data on clinical, laboratory findings and muscle MRI were collected. Sixteen patients were included with median age at onset of 3 years (range: 1 month - 17 years). Three genes were involved: LMNA (11, 68.75%), EMD (4, 25%) and SYNE1 (1, 6.25%). The 11 patients with LMNA variants were Congenital muscular dystrophy (MDCL)=4, Limb Girdle Muscular Dystrophy (LGMD1B)=4 and Emery-Dreifuss Muscular Dystrophy (EDMD2)=3. On muscle biopsy, one patient from each laminopathy phenotype (n = 3) revealed focal perivascular inflammatory infiltrate. Other notable features were ophthalmoparesis in one and facial weakness in one. None had cardiac involvement. Patients with EDMD1 had both upper (UL) and lower limb (LL) proximo-distal weakness. Cardiac rhythm disturbances such as sick sinus syndrome and atrial arrhythmias were noted in two patients with EDMD1. Only one patient with variant c.654_658dup (EMD) lost ambulation in the 3rd decade, 18 years after disease onset. Two had finger contractures with EMD and SYNE1 variants respectively. All patients with LMNA and SYNE1 variants were ambulant at the time of evaluation. Mean duration of illness (years) was 11.6±13 (MDCL), 3.2±1.0 (EDMD2), 10.4±12.8 (LGMD1B), 11.8±8.4 (EDMD1) and 3 (EDMD4). One patient had a novel SYNE1 mutation (c.22472dupA, exon 123) and presented with UL phenotype and prominent finger and wrist contractures. The salient features included ophthalmoparesis and facial weakness in LMNA, prominent finger contractures in EMD and SYNE1 and upper limb phenotype with the novel pathogenic variant in SYNE1.

The silent protector: Nucleoporin93's role in vascular health.

Nuclear envelope proteins have recently gained traction as novel regulators of endothelial and vascular function. Nuclear pore complexes (NPCs) stand as one of the largest protein complexes found at the nuclear envelope yet the role of component NPC proteins (i.e., nucleoporins) in vascular health remains unclear. In the issue of Aging Cell, Nguyen et al. (2024) identify Nucleoporin93, a major structural protein of the NPC, as an indispensable player in endothelial protection. This discovery raises the possibility that endothelial NPCs are susceptible to risk factors for consequent vascular disease.

Lamin A/C deficiency-mediated ROS elevation contributes to pathogenic phenotypes of dilated cardiomyopathy in iPSC model

Mutations in the nuclear envelope (NE) protein lamin A/C (encoded by LMNA), cause a severe form of dilated cardiomyopathy (DCM) with early-onset life-threatening arrhythmias. However, molecular mechanisms underlying increased arrhythmogenesis in LMNA-related DCM (LMNA-DCM) remain largely unknown. Here we show that a frameshift mutation in LMNA causes abnormal Ca2+ handling, arrhythmias and disformed NE in LMNA-DCM patient-specific iPSC-derived cardiomyocytes (iPSC-CMs). Mechanistically, lamin A interacts with sirtuin 1 (SIRT1) where mutant lamin A/C accelerates degradation of SIRT1, leading to mitochondrial dysfunction and oxidative stress. Elevated reactive oxygen species (ROS) then activates the Ca2+/calmodulin-dependent protein kinase II (CaMKII)-ryanodine receptor 2 (RYR2) pathway and aggravates the accumulation of SUN1 in mutant iPSC-CMs, contributing to arrhythmias and NE deformation, respectively. Taken together, the lamin A/C deficiency-mediated ROS disorder is revealed as central to LMNA-DCM development. Manipulation of impaired SIRT1 activity and excessive oxidative stress is a potential future therapeutic strategy for LMNA-DCM.

Genotype is associated with left ventricular reverse remodelling and early events in recent-onset dilated cardiomyopathy.

Recent-onset dilated cardiomyopathy (RODCM) is characterized by heterogeneous aetiology and diverse clinical outcomes, with scarce data on genotype-phenotype correlates. Our aim was to correlate individual RODCM genotypes with left ventricular reverse remodelling (LVRR) and clinical outcomes. In this prospective study, a total of 386 Czech RODCM patients with symptom duration ≤6months underwent genetic counselling and whole-exome sequencing (WES). The presence of pathogenic (class 5) or likely pathogenic (class 4) variants in a set of 72 cardiomyopathy-related genes was correlated with the occurrence of all-cause death, heart transplantation, or implantation of a ventricular assist device (primary outcome) and/or ventricular arrhythmia event (secondary outcome). LVRR was defined as an improvement of left ventricular ejection fraction to >50% or ≥10% absolute increase, with a left ventricular end-diastolic diameter ≤33mm/m2 or ≥10% relative decrease. Median follow-up was 41months. RODCM was familial in 98 (25%) individuals. Class 4-5 variants of interest (VOIs) were identified in 125 (32%) cases, with 69 (18%) having a single titin-truncating variant (TTNtv) and 56 (14%) having non-titin (non-TTN) VOIs. The presence of class 4-5 non-TTN VOIs, but not of TTNtv, heralded a lower probability of 12-month LVRR and proved to be an independent baseline predictor both of the primary and the secondary outcome. The negative result of genetic testing was a strong protective baseline variable against occurrence of life-threatening ventricular arrhythmias. Detection of class 4-5 VOIs in genes coding nuclear envelope proteins was another independent predictor of both study outcomes at baseline and also of life-threatening ventricular arrhythmias after 12months. Class 4-5 VOIs of genes coding cytoskeleton were associated with an increased risk of life-threatening ventricular arrhythmias after baseline assessment. A positive family history of dilated cardiomyopathy alone only related to a lower probability of LVRR at 12months and at the final follow-up. RODCM patients harbouring class 4-5 non-TTN VOIs are at higher risk of progressive heart failure and life-threatening ventricular arrhythmias. Genotyping may improve their early risk stratification at baseline assessment.

Altered expression and localization of nuclear envelope proteins in a prostate cancer cell system

BackgroundThe nuclear envelope (NE), which is composed of the outer and inner nuclear membranes, the nuclear pore complex and the nuclear lamina, regulates a plethora of cellular processes, including those that restrict cancer development (genomic stability, cell cycle regulation, and cell migration). Thus, impaired NE is functionally related to tumorigenesis, and monitoring of NE alterations is used to diagnose cancer. However, the chronology of NE changes occurring during cancer evolution and the connection between them remained to be precisely defined, due to the lack of appropriate cell models.MethodsThe expression and subcellular localization of NE proteins (lamins A/C and B1 and the inner nuclear membrane proteins emerin and β-dystroglycan [β-DG]) during prostate cancer progression were analyzed, using confocal microscopy and western blot assays, and a prostate cancer cell system comprising RWPE-1 epithelial prostate cells and several prostate cancer cell lines with different invasiveness.ResultsDeformed nuclei and the mislocalization and low expression of lamin A/C, lamin B1, and emerin became more prominent as the invasiveness of the prostate cancer lines increased. Suppression of lamin A/C expression was an early event during prostate cancer evolution, while a more extensive deregulation of NE proteins, including β-DG, occurred in metastatic prostate cells.ConclusionsThe RWPE-1 cell line-based system was found to be suitable for the correlation of NE impairment with prostate cancer invasiveness and determination of the chronology of NE alterations during prostate carcinogenesis. Further study of this cell system would help to identify biomarkers for prostate cancer prognosis and diagnosis.

Quantitative proteome analysis of LAP1-deficient human fibroblasts: A pilot approach for predicting the signaling pathways deregulated in LAP1-associated diseases

Lamina-associated polypeptide 1 (LAP1), a ubiquitously expressed nuclear envelope protein, appears to be essential for the maintenance of cell homeostasis. Although rare, mutations in the human LAP1-encoding TOR1AIP1 gene cause severe diseases and can culminate in the premature death of affected individuals. Despite there is increasing evidence of the pathogenicity of TOR1AIP1 mutations, the current knowledge on LAP1's physiological roles in humans is limited; hence, investigation is required to elucidate the critical functions of this protein, which can be achieved by uncovering the molecular consequences of LAP1 depletion, a topic that remains largely unexplored. In this work, the proteome of patient-derived LAP1-deficient fibroblasts carrying a pathological TOR1AIP1 mutation (LAP1 E482A) was quantitatively analyzed to identify global changes in protein abundance levels relatively to control fibroblasts. An in silico functional enrichment analysis of the mass spectrometry-identified differentially expressed proteins was also performed, along with additional in vitro functional assays, to unveil the biological processes that are potentially dysfunctional in LAP1 E482A fibroblasts. Collectively, our findings suggest that LAP1 deficiency may induce significant alterations in various cellular activities, including DNA repair, messenger RNA degradation/translation, proteostasis and glutathione metabolism/antioxidant response. This study sheds light on possible new functions of human LAP1 and could set the basis for subsequent in-depth mechanistic investigations. Moreover, by identifying deregulated signaling pathways in LAP1-deficient cells, our work may offer valuable molecular targets for future disease-modifying therapies for TOR1AIP1-associated nuclear envelopathies.

SUN5 interacts with nuclear membrane LaminB1 and cytoskeletal GTPase Septin12 mediating the sperm head-and-tail junction.

Acephalic spermatozoa syndrome (ASS) is a severe teratospermia with decaudated, decapitated, and malformed sperm, resulting in male infertility. Nuclear envelope protein SUN5 localizes to the junction between the sperm head and tail. Mutations in the SUN5 gene have been identified most frequently (33-47%) in ASS cases, and its molecular mechanism of action is yet to be explored. In the present study, we generated Sun5 knockout mice, which presented the phenotype of ASS. Nuclear membrane protein LaminB1 and cytoskeletal GTPases Septin12 and Septin2 were identified as potential partners for interacting with SUN5 by immunoprecipitation-mass spectrometry in mouse testis. Further studies demonstrated that SUN5 connected the nucleus by interacting with LaminB1 and connected the proximal centriole by interacting with Septin12. The binding between SUN5 and Septin12 promoted their aggregation together in the sperm neck. The disruption of the LaminB1/SUN5/Septin12 complex by Sun5 deficiency caused separation of the Septin12-proximal centriole from the nucleus, leading to the breakage of the head-to-tail junction. Collectively, these data provide new insights into the pathogenesis of ASS caused by SUN5 deficiency.