Lipodystrophic Laminopathies: From Dunnigan Disease to Progeroid Syndromes.

Lipodystrophic laminopathies are a group of ultra-rare disorders characterised by the presence of pathogenic variants in the same gene (LMNA) and other related genes, along with an impaired adipose tissue pattern and other features that are specific of each of these disorders. The most fascinating traits include their complex genotype-phenotype associations and clinical heterogeneity, ranging from Dunnigan disease, in which the most relevant feature is precisely adipose tissue dysfunction and lipodystrophy, to the other laminopathies affecting adipose tissue, which are also characterised by the presence of signs of premature ageing (Hutchinson Gilford-progeria syndrome, LMNA-atypical progeroid syndrome, mandibuloacral dysplasia types A and B, Nestor-Guillermo progeria syndrome, LMNA-associated cardiocutaneous progeria). This raises several questions when it comes to understanding how variants in the same gene can lead to similar adipose tissue disturbances and, at the same time, to such heterogeneous phenotypes and variable degrees of metabolic abnormalities. The present review aims to gather the molecular basis of adipose tissue impairment in lipodystrophic laminopathies, their main clinical aspects and recent therapeutic strategies. In addition, it also summarises the key aspects for their differential diagnosis.

Targeting Caspases 3/6 and Cathepsins L/B May Decrease Laminopathy-Induced Apoptosis in Alzheimer's Disease.

Background: Laminopathy is a pathological manifestation observed in Alzheimer's disease (AD), leading to neuronal apoptosis. Objective: Our objective was to assess inhibitors of enzymes involved in laminopathy. Methods: The mRNA expression of the cathepsins L and B, caspases 3 and 6, lamins b1 and b2, granzymes A and B, and lamins A and C were extracted and analyzed from GSE5281 and GSE28146 datasets. A total of 145 ligands were selected for molecular docking. Subsequently, 10 ns and 100 ns atomistic molecular dynamics (MD) and Martini 3 were performed with NAMD for two selected ligands (PubChem id: 608841 and ChEMBL id: 550872). Results: The mRNA expression level highlighted caspase 6 and lamin A/C upregulation in the hippocampus of the AD samples, in contrast to cathepsin B, lamin b2, and caspase 3. Moreover, there was a strong correlation between the expression level of cathepsin B, lamin A/C, and caspase 6 in the AD group. The MD results suggested molecule with ChEMBL id of 550872 had higher free binding energy, while in longer simulation the molecule with PubChem id of 608841 was suggested to be more stable in complex with the receptor. Conclusions: Our findings suggest that lamins A/C, cathepsins B/L, caspase 6, and lamin B2 are associated with laminopathy as potential factors contributing to apoptosis in AD. We propose that simultaneous inhibition of caspases 6 and cathepsins L may decrease the rate of apoptosis triggered by lamin degradation. Nevertheless, further studies are required to confirm these observations due to the lack of in vivo findings.

Navigating Lipodystrophy: Insights from Laminopathies and Beyond.

Recent research into laminopathic lipodystrophies-rare genetic disorders caused by mutations in the LMNA gene-has greatly expanded our knowledge of their complex pathology and metabolic implications. These disorders, including Hutchinson-Gilford progeria syndrome (HGPS), Mandibuloacral Dysplasia (MAD), and Familial Partial Lipodystrophy (FPLD), serve as crucial models for studying accelerated aging and metabolic dysfunction, enhancing our understanding of the cellular and molecular mechanisms involved. Research on laminopathies has highlighted how LMNA mutations disrupt adipose tissue function and metabolic regulation, leading to altered fat distribution and metabolic pathway dysfunctions. Such insights improve our understanding of the pathophysiological interactions between genetic anomalies and metabolic processes. This review merges current knowledge on the phenotypic classifications of these diseases and their associated metabolic complications, such as insulin resistance, hypertriglyceridemia, hepatic steatosis, and metabolic syndrome, all of which elevate the risk of cardiovascular disease, stroke, and diabetes. Additionally, a range of published therapeutic strategies, including gene editing, antisense oligonucleotides, and novel pharmacological interventions aimed at addressing defective adipocyte differentiation and lipid metabolism, will be explored. These therapies target the core dysfunctional lamin A protein, aiming to mitigate symptoms and provide a foundation for addressing similar metabolic and genetic disorders.

Genetic and Pathophysiological Basis of Cardiac and Skeletal Muscle Laminopathies.

Nuclear lamins, a type V intermediate filament, are crucial components of the nuclear envelope's inner layer, maintaining nuclear integrity and mediating interactions between the nucleus and cytoplasm. Research on human iPSC-derived cells and animal models has demonstrated the importance of lamins in cardiac and skeletal muscle development and function. Mutations in lamins result in laminopathies, a group of diseases including muscular dystrophies, Hutchison-Gilford progeria syndrome, and cardiomyopathies with conduction defects. These conditions have been linked to disrupted autophagy, mTOR, Nrf2-Keap, and proteostasis signaling pathways, indicating complex interactions between the nucleus and cytoplasm. Despite progress in understanding these pathways, many questions remain about the mechanisms driving lamin-induced pathologies, leading to limited therapeutic options. This review examines the current literature on dysregulated pathways in cardiac and skeletal muscle laminopathies and explores potential therapeutic strategies for these conditions.

Recent insights in striated muscle laminopathies.

PURPOSE OF REVIEW: To highlight recent insights in different aspects of striated muscle laminopathies (SMLs) related to LMNA mutations. RECENT FINDINGS: Clinical and genetic studies allow better patient management and diagnosis, with confirmation of ventricular tachyarrhythmias (VTA) risk prediction score to help with ICD implantation and development of models to help with classification of LMNA variants of uncertain significance. From a pathophysiology perspective, characterization of lamin interactomes in different contexts revealed new lamin A/C partners. Expression or function modulation of these partners evidenced them as potential therapeutic targets. After a positive phase 2, the first phase 3 clinical trial, testing a p38 inhibitor targeting the life-threatening cardiac disease of SML, has been recently stopped, thus highlighting the need for new therapeutic approaches together with new animal and cell models. SUMMARY: Since the first LMNA mutation report in 1999, lamin A/C structure and functions have been actively explored to understand the SML pathophysiology. The latest discoveries of partners and altered pathways, highlight the importance of lamin A/C at the nuclear periphery and in the nucleoplasm. Modulation of altered pathways allowed some benefits, especially for cardiac involvement. However, additional studies are still needed to fully assess treatment efficacy and safety.

Creatine and L-carnitine attenuate muscular laminopathy in the LMNA mutation transgenic zebrafish.

Lamin A/C gene (LMNA) mutations contribute to severe striated muscle laminopathies, affecting cardiac and skeletal muscles, with limited treatment options. In this study, we delve into the investigations of five distinct LMNA mutations, including three novel variants and two pathogenic variants identified in patients with muscular laminopathy. Our approach employs zebrafish models to comprehensively study these variants. Transgenic zebrafish expressing wild-type LMNA and each mutation undergo extensive morphological profiling, swimming behavior assessments, muscle endurance evaluations, heartbeat measurement, and histopathological analysis of skeletal muscles. Additionally, these models serve as platform for focused drug screening. We explore the transcriptomic landscape through qPCR and RNAseq to unveil altered gene expression profiles in muscle tissues. Larvae of LMNA(L35P), LMNA(E358K), and LMNA(R453W) transgenic fish exhibit reduced swim speed compared to LMNA(WT) measured by DanioVision. All LMNA transgenic adult fish exhibit reduced swim speed compared to LMNA(WT) in T-maze. Moreover, all LMNA transgenic adult fish, except LMNA(E358K), display weaker muscle endurance than LMNA(WT) measured by swimming tunnel. Histochemical staining reveals decreased fiber size in all LMNA mutations transgenic fish, excluding LMNA(WT) fish. Interestingly, LMNA(A539V) and LMNA(E358K) exhibited elevated heartbeats. We recognize potential limitations with transgene overexpression and conducted association calculations to explore its effects on zebrafish phenotypes. Our results suggest lamin A/C overexpression may not directly impact mutant phenotypes, such as impaired swim speed, increased heart rates, or decreased muscle fiber diameter. Utilizing LMNA zebrafish models for drug screening, we identify L-carnitine treatment rescuing muscle endurance in LMNA(L35P) and creatine treatment reversing muscle endurance in LMNA(R453W) zebrafish models. Creatine activates AMPK and mTOR pathways, improving muscle endurance and swim speed in LMNA(R453W) fish. Transcriptomic profiling reveals upstream regulators and affected genes contributing to motor dysfunction, cardiac anomalies, and ion flux dysregulation in LMNA mutant transgenic fish. These findings faithfully mimic clinical manifestations of muscular laminopathies, including dysmorphism, early mortality, decreased fiber size, and muscle dysfunction in zebrafish. Furthermore, our drug screening results suggest L-carnitine and creatine treatments as potential rescuers of muscle endurance in LMNA(L35P) and LMNA(R453W) zebrafish models. Our study offers valuable insights into the future development of potential treatments for LMNA-related muscular laminopathy.

Epidemiological characteristics of patients with Hutchinson-Gilford progeria syndrome and progeroid laminopathies in China.

BACKGROUND: Hutchinson-Gilford progeria syndrome (HGPS) and progeroid laminopathies (PL) are extremely rare genetic diseases with extremely poor prognoses. This study aims to investigate the epidemiological and genotypic characteristics of patients with HGPS/PL in China. METHODS: Using a cross-sectional study design, general characteristics and genotypic data of 46 patients with HGPS/PL from 17 provinces in China were analyzed. RESULTS: Among the 46 patients with HGPS/PL, 20 patients are HGPS, and the rest are PL; the identified total prevalence of HGPS/PL is 1/23 million. Among 42 patients with gene reports, 3 carried compound heterozygous mutations in the ZMPSTE24 while the other 39 carried LMNA mutations. Among PL, LMNA c.1579 C > T homozygous mutation was the most common. The onset of classic genotype HGPS is skin sclerosis in the first month after birth. The primary clinical manifestations of PL patients include skin abnormalities, growth retardation, and joint stiffness. The median age of onset for PL was 12 (6,12) months. CONCLUSIONS: In China, the identified total prevalence of HGPS/PL is 1/23 million. 92.8% of the genetic mutations of HGPS/PL were located in LMNA, and the rest in ZMPSTE24. Most patients of HGPS/PL have skin abnormalities as the earliest manifestation. Compared to PL, the classic genotype HGPS starts earlier. IMPACT STATEMENT: Hutchinson-Gilford progeria syndrome (HGPS) and progeroid laminopathies (PL) are extremely rare genetic diseases with extremely poor prognoses. To date, there is a paucity of epidemiological data related to HGPS/PL in China. This study first examined the genotypic, phenotypic, and prevalence characteristics of 40-50% of the cases of HGPS/PL in mainland China through a collaborative international registry effort. In China, the identified total prevalence of HGPS/PL is 1/23 million. 92.8% of the genetic mutations of HGPS/PL are located in LMNA. LMNA c.1579 C > T homozygous mutations are the most common form of gene mutations among the Chinese PL population.

A Clinical Diagnosis of Laminopathy without Systolic Dysfunction: When Does Nuclei Malformation Start?

Nuclear shape abnormalities in laminopathy are well known to occur in patients with cardiac systolic dysfunction. However, those in patients without systolic dysfunction are still unclear. We herein report a 42-year-old man who presented with advanced atrioventricular block without systolic dysfunction. Genetic testing identified a laminopathic mutation, c.497G>C, and an endocardial biopsy was performed. The hyperperfine structure on electron microscopy showed malformation of the nuclei, euchromatic nucleoplasm, and partial existence of heterochromatin clumps. Intrusion of heterochromatin into the nuclear fibrous lamina was observed. Cardiomyocyte nuclear shape abnormalities were observed before the progression of systolic dysfunction.

LMNA-related muscular dystrophy involving myoblast proliferation and apoptosis through the FOXO1/GADD45A pathway.

LMNA-related muscular dystrophy is a major disease phenotype causing mortality and morbidity in laminopathies, but its pathogenesis is still unclear. To explore the molecular pathogenesis, a knock-in mouse harbouring the Lmna-W520R mutation was modelled. Morphological and motor functional analyses showed that homozygous mutant mice revealed severe muscular atrophy, profound motor dysfunction, and shortened lifespan, while heterozygotes showed a variant arrangement of muscle bundles and mildly reduced motor capacity. Mechanistically, the FOXO1/GADD45A pathway involving muscle atrophy processes was found to be altered in vitro and in vivo assays. The expression levels of FOXO1 and its downstream regulatory molecule GADD45A significantly increased in atrophic muscle tissue. The elevated expression of FOXO1 was associated with decreased H3K27me3 in its gene promotor region. Overexpression of GADD45A induced apoptosis and cell cycle arrest of myoblasts in vitro, and it could be partially restored by the FOXO1 inhibitor AS1842856, which also slowed the muscle atrophy process with improved motor function and prolonged survival time of homozygous mutant mice in vivo. Notably, the inhibitor also partly rescued the apoptosis and cell cycle arrest of hiPSC-derived myoblasts harbouring the LMNA-W520R mutation. Together, these data suggest that the activation of the FOXO1/GADD45A pathway contributes to the pathogenesis of LMNA-related muscle atrophy, and it might serve as a potential therapeutic target for laminopathies.

How nuclear envelope dynamics can direct laminopathy phenotypes.

The nuclear envelope separates the genome from the cytoplasmic environment. However, the nuclear envelope is also physically associated with the genome and exerts influence on gene expression and genome modification. The nucleus is dynamic, changing shape and responding to cell movement, disassembling and assembling during cell division, and undergoing rupture and repair. These dynamics can be impacted by genetic disease, leading to a family of diseases called laminopathies. Their disparate phenotypes suggest that multiple processes are affected. We highlight three such processes here, which we believe can be used to classify most of the laminopathies. While much still needs to be learned, some commonalities between these processes, such as proteins involved in nuclear envelope formation and rupture repair, may drive a variety of laminopathies. Here we review the latest information regarding nuclear dynamics and its role in laminopathies related to mutations in the nuclear lamina and linker of nucleoskeleton and cytoskeleton complex (LINC) proteins.

Caenorhabditis elegans models for striated muscle disorders caused by missense variants of human LMNA.

Striated muscle laminopathies caused by missense mutations in the nuclear lamin gene LMNA are characterized by cardiac dysfunction and often skeletal muscle defects. Attempts to predict which LMNA variants are pathogenic and to understand their physiological effects lag behind variant discovery. We created Caenorhabditis elegans models for striated muscle laminopathies by introducing pathogenic human LMNA variants and variants of unknown significance at conserved residues within the lmn-1 gene. Severe missense variants reduced fertility and/or motility in C. elegans. Nuclear morphology defects were evident in the hypodermal nuclei of many lamin variant strains, indicating a loss of nuclear envelope integrity. Phenotypic severity varied within the two classes of missense mutations involved in striated muscle disease, but overall, variants associated with both skeletal and cardiac muscle defects in humans lead to more severe phenotypes in our model than variants predicted to disrupt cardiac function alone. We also identified a separation of function allele, lmn-1(R204W), that exhibited normal viability and swimming behavior but had a severe nuclear migration defect. Thus, we established C. elegans avatars for striated muscle laminopathies and identified LMNA variants that offer insight into lamin mechanisms during normal development.

Nuclear proteostasis imbalance in laminopathy-associated premature aging diseases.

Laminopathies are a group of rare genetic disorders with heterogeneous clinical phenotypes such as premature aging, cardiomyopathy, lipodystrophy, muscular dystrophy, microcephaly, epilepsy, and so on. The cellular phenomena associated with laminopathy invariably show disruption of nucleoskeleton of lamina due to deregulated expression, localization, function, and interaction of mutant lamin proteins. Impaired spatial and temporal tethering of lamin proteins to the lamina or nucleoplasmic aggregation of lamins are the primary molecular events that can trigger nuclear proteotoxicity by modulating differential protein-protein interactions, sequestering quality control proteins, and initiating a cascade of abnormal post-translational modifications. Clearly, laminopathic cells exhibit moderate to high nuclear proteotoxicity, raising the question of whether an imbalance in nuclear proteostasis is involved in laminopathic diseases, particularly in diseases of early aging such as HGPS and laminopathy-associated premature aging. Here, we review nuclear proteostasis and its deregulation in the context of lamin proteins and laminopathies.

A subtype of laminopathies: Generalized lipodystrophy-associated progeroid syndrome caused by LMNA gene c.29C>T mutation.

The term laminopathies refers to a group of congenital diseases characterized by accelerated degeneration of human tissues. Mutations in LMNA, LMNB, ZMPSTE24, and other genes lead to structural and functional abnormalities associated with lamins. One subtype of laminopathy is the generalized lipodystrophy-associated progeroid syndrome (GLPS), which occurs in patients with heterozygous mutations of the LMNA gene c.29C>T(p.T10I). This paper reports the first case of GLPS in China and compares the clinical features of other GLPS patients with literature reports. A 16-year-old male patient was treated for diabetic ketoacidosis, presenting with premature aging appearance, systemic lipodystrophy, severe fatty liver, and decreased bone density. After peripheral blood DNA extraction and second-generation sequencing, a heterozygous mutation of exon 1 of the LMNA gene c.29C>T(p.T10I) was detected. This case of GLPS may provide a diagnostic and therapeutic basis for potential patients.

The Interplay between Oxidative Stress and the Nuclear Lamina Contributes to Laminopathies and Age-Related Diseases.

Oxidative stress is a physiological condition that arises when there is an imbalance between the production of reactive oxygen species (ROS) and the ability of cells to neutralize them. ROS can damage cellular macromolecules, including lipids, proteins, and DNA, leading to cellular senescence and physiological aging. The nuclear lamina (NL) is a meshwork of intermediate filaments that provides structural support to the nucleus and plays crucial roles in various nuclear functions, such as DNA replication and transcription. Emerging evidence suggests that oxidative stress disrupts the integrity and function of the NL, leading to dysregulation of gene expression, DNA damage, and cellular senescence. This review highlights the current understanding of the interplay between oxidative stress and the NL, along with its implications for human health. Specifically, elucidation of the mechanisms underlying the interplay between oxidative stress and the NL is essential for the development of effective treatments for laminopathies and age-related diseases.

The role of lamin B2 in human diseases.

Lamin B2 (LMNB2), on the inner side of the nuclear envelope, constitutes the nuclear skeleton by connecting with other nuclear proteins. LMNB2 is involved in a wide range of nuclear functions, including DNA replication and stability, regulation of chromatin, and nuclear stiffness. Moreover, LMNB2 regulates several cellular processes, such as tissue development, cell cycle, cellular proliferation and apoptosis, chromatin localization and stability, and DNA methylation. Besides, the influence of abnormal expression and mutations of LMNB2 has been gradually discovered in cancers and laminopathies. Therefore, this review summarizes the recent advances of LMNB2-associated biological roles in physiological or pathological conditions, with a particular emphasis on cancers and laminopathies, as well as the potential mechanism of LMNB2 in related cancers.

Disease progression rate is a strong predictor of ventricular arrhythmias in patients with cardiac laminopathies: a primary prevention cohort study.

AIMS: Cardiac disease progression prior to first ventricular arrhythmia (VA) in LMNA genotype-positive patients is not described. METHODS AND RESULTS: We performed a primary prevention cohort study, including consecutive LMNA genotype-positive patients from our centre. Patients underwent repeated clinical, electrocardiographic, and echocardiographic examinations. Electrocardiographic and echocardiographic disease progression as a predictor of first-time VA was evaluated by generalized estimation equation analyses. Threshold values at transition to an arrhythmic phenotype were assessed by threshold regression analyses. We included 94 LMNA genotype-positive patients without previous VA (age 38 ± 15 years, 32% probands, 53% females). Nineteen (20%) patients experienced VA during 4.6 (interquartile range 2.1-7.3) years follow up, at mean age 50 ± 11 years. We analysed 536 echocardiographic and 261 electrocardiogram examinations. Individual patient disease progression was associated with VA [left ventricular ejection fraction (LVEF) odds ratio (OR) 1.4, 95% confidence interval (CI) 1.2-1.6 per 5% reduction, left ventricular end-diastolic volume index (LVEDVi) OR 1.2 (95% CI 1.1-1.3) per 5 mL/m2 increase, PR interval OR 1.2 (95% CI 1.1-1.4) per 10 ms increase]. Threshold values for transition to an arrhythmic phenotype were LVEF 44%, LVEDVi 77 mL/m2, and PR interval 280 ms. CONCLUSIONS: Incidence of first-time VA was 20% during 4.6 years follow up in LMNA genotype-positive patients. Individual patient disease progression by ECG and echocardiography were strong predictors of VA, indicating that disease progression rate may have additional value to absolute measurements when considering primary preventive ICD. Threshold values of LVEF <44%, LVEDVi >77 mL/m2, and PR interval >280 ms indicated transition to a more arrhythmogenic phenotype.

Nesprin-1 LINC complexes recruit microtubule cytoskeleton proteins and drive pathology in Lmna-mutant striated muscle.

Mutations in LMNA, the gene encoding A-type lamins, cause laminopathies-diseases of striated muscle and other tissues. The aetiology of laminopathies has been attributed to perturbation of chromatin organization or structural weakening of the nuclear envelope (NE) such that the nucleus becomes more prone to mechanical damage. The latter model requires a conduit for force transmission to the nucleus. NE-associated Linker of Nucleoskeleton and Cytoskeleton (LINC) complexes are one such pathway. Using clustered regularly interspaced short palindromic repeats to disrupt the Nesprin-1 KASH (Klarsicht, ANC-1, Syne Homology) domain, we identified this LINC complex protein as the predominant NE anchor for microtubule cytoskeleton components, including nucleation activities and motor complexes, in mouse cardiomyocytes. Loss of Nesprin-1 LINC complexes resulted in loss of microtubule cytoskeleton proteins at the nucleus and changes in nuclear morphology and positioning in striated muscle cells, but with no overt physiological defects. Disrupting the KASH domain of Nesprin-1 suppresses Lmna-linked cardiac pathology, likely by reducing microtubule cytoskeleton activities at the nucleus. Nesprin-1 LINC complexes thus represent a potential therapeutic target for striated muscle laminopathies.