The expression of nuclear lamins in human liver: an immunohistochemical study

Overview of cellular homeostasis-associated nuclear envelope lamins and associated input signals

With the discovery of the role of the nuclear envelope protein lamin in human genetic diseases, further diverse roles of lamins have been elucidated. The roles of lamins have been addressed in cellular homeostasis including gene regulation, cell cycle, cellular senescence, adipogenesis, bone remodeling as well as modulation of cancer biology. Features of laminopathies line with oxidative stress-associated cellular senescence, differentiation, and longevity and share with downstream of aging-oxidative stress. Thus, in this review, we highlighted various roles of lamin as key molecule of nuclear maintenance, specially lamin-A/C, and mutated LMNA gene clearly reveal aging-related genetic phenotypes, such as enhanced differentiation, adipogenesis, and osteoporosis. The modulatory roles of lamin-A/C in stem cell differentiation, skin, cardiac regulation, and oncology have also been elucidated. In addition to recent advances in laminopathies, we highlighted for the first kinase-dependent nuclear lamin biology and recently developed modulatory mechanisms or effector signals of lamin regulation. Advanced knowledge of the lamin-A/C proteins as diverse signaling modulators might be biological key to unlocking the complex signaling of aging-related human diseases and homeostasis in cellular process.

LMNA functions as an oncogene in hepatocellular carcinoma by regulating the proliferation and migration ability

The role of the LMNA gene in the development and progression of hepatocellular carcinoma (HCC) and the associated molecular mechanism is not yet clear. Therefore, the purpose of this study was to evaluate the relationship between LMNA and HCC. LMNA gene expression in normal tissues and corresponding tumours was evaluated and the Kaplan-Meier survival analysis was performed. Next, the LMNA gene was knocked out in the 293T and HepG2 cell lines using the CRISPR/Cas9 technique. Subsequently, the proliferation, migration and colony formation rate of the two LMNA knockout cell lines were analysed. Finally, the molecular mechanism affecting the tumorigenesis due to the loss of the LMNA gene was evaluated. The results showed that the LMNA gene was abnormally expressed in many tumours, and the survival rate of the HCC patients with a high expression of the LMNA gene was significantly reduced compared with the rate in patients with a low LMNA expression. The knockout of the LMNA gene in the HCC cell line HepG2 resulted in a decreased tumorigenicity, up-regulation of the P16 expression and down-regulation of the CDK1 expression. These findings suggested that LMNA might function as an oncogene in HCC and provided a potential new target for the diagnosis and treatment of HCC.

A Novel Role of Lamins from Genetic Disease to Cancer Biomarkers

Lamins are the key components of the nuclear lamina and by virtue of their interactions with chromatin and binding partners act as regulators of cell proliferation and differentiation. Of late, the diverse roles of lamins in cellular processes have made them the topic of intense debate for their role in cancer progression. The observations about aberrant localization or misexpression of the nuclear lamins in cancerous tissues have often led to the speculative role of lamins as a cancer risk biomarker. Here we discuss the involvement of lamins in several cancer subtypes and their potential role in predicting the tumor progression.

Nuclear lamins: key regulators of nuclear structure and activities

The nuclear lamina is a proteinaceous structure located underneath the inner nuclear membrane (INM), where it associates with the peripheral chromatin. It contains lamins and lamin-associated proteins, including many integral proteins of the INM, chromatin modifying proteins, transcriptional repressors and structural proteins. A fraction of lamins is also present in the nucleoplasm, where it forms stable complexes and is associated with specific nucleoplasmic proteins. The lamins and their associated proteins are required for most nuclear activities, mitosis and for linking the nucleoplasm to all major cytoskeletal networks in the cytoplasm. Mutations in nuclear lamins and their associated proteins cause about 20 different diseases that are collectively called laminopathies'. This review concentrates mainly on lamins, their structure and their roles in DNA replication, chromatin organization, adult stem cell differentiation, aging, tumorogenesis and the lamin mutations leading to laminopathic diseases.

The influence of pharmacogenetics on fatty liver disease in the wistar and kyoto rats: a combined transcriptomic and metabonomic study

Although fatty liver disease is caused by a number of toxicological insults and the metabolic syndrome, the exact mechanisms by which many of these pathophysiological stimulii induce fatty liver are unknown. The rapid and profound steatosis caused by orotic acid, resulting from an impairment in the production of ApoB, has been investigated in the Wistar strain rat using a combined transcriptomic and metabonomic/metabolomic approach. Analysis of liver tissue from rats exposed to orotic acid for 1, 3, and 14 days was performed by DNA microarrays and high resolution 1H NMR spectroscopy based metabonomics of both tissue extracts and intact tissue (n = 3). Data were analyzed using a combination of ANOVA and principal components analysis, used as a data reduction tool to visualize the most perturbed transcripts and metabolites. Orotic acid produced a profound 8-fold increase in total lipids, and in particular increases in resonances associated with polyunsaturated fats (CH=CH and CH2CH=CH groups). This was accompanied by increases in the concentrations of trimethylamine-oxide (TMAO), betaine, choline, and phosphocholine, as well as a relative decrease in glucose and glycogen. At the transcriptional level, perturbations were detected in both oxidative stress and osmoregulation/pH homeostasis. However, this contrasts with a previous transcriptomic/metabolic study of fatty liver disease in a combined data set of Wistar (out-bred) and Kyoto (in-bred) strains of rats, with only 4 transcripts being found to be in common between the two analyses. This emphasizes the need to understand how strain background interacts with a given toxic lesion or genetic modification.

The nuclear pore complex protein ALADIN is mislocalized in triple A syndrome

Triple A syndrome is a human autosomal recessive disorder characterized by an unusual array of tissue-specific defects. Triple A syndrome arises from mutations in a WD-repeat protein of unknown function called ALADIN (also termed Adracalin or AAAS). We showed previously that ALADIN localizes to nuclear pore complexes (NPCs), large multiprotein assemblies that are the sole sites of nucleocytoplasmic transport. Here, we present evidence indicating that NPC targeting is essential for the function of ALADIN. Characterization of mutant ALADIN proteins from triple A patients revealed a striking effect of these mutations on NPC targeting. A variety of disease-associated missense, nonsense, and frameshift mutations failed to localize to NPCs and were found predominantly in the cytoplasm. Microscopic analysis of cells from a triple A patient revealed no morphological abnormalities of the nuclei, nuclear envelopes, or NPCs. Importantly, these findings indicate that defects in NPC function, rather than structure, give rise to triple A syndrome. We propose that ALADIN plays a cell type-specific role in regulating nucleocytoplasmic transport and that this function is essential for the proper maintenance andor development of certain tissues. Our findings provide a foundation for understanding the molecular basis of triple A syndrome and may lead to unique insights into the role of nucleocytoplasmic transport in adrenal function and neurodevelopment.

Analysis of the B cell repertoire against autoantigens in patients with giant cell arteritis and polymyalgia rheumatica

The analysis of the antibody repertoire of patients with giant cell arteritis (GCA) and polymyalgia rheumatica (PMR) might identify target antigens of the autoimmune response with potential relevance to our understanding of the pathogenesis of the disease and to the development of serodiagnostic tests. To detect such antigens, we screened a cDNA library derived from normal human testis for antigens reacting with IgG antibodies in the 1 : 250 diluted sera of three patients with untreated GCA using SEREX, the serological identification of antigens by recombinant cDNA expression cloning. Of 100 000 clones screened with each serum, six, 28 and six clones, respectively, were positive, representing a total of 33 different antigens. Most of the antigens reacted only with the serum used for identification and/or at a similar frequency with normal control sera. However, lamin C and the nuclear antigen of 14 kD reacted specifically with 32% of GCA/PMR, but with none of the control sera, while human cytokeratin 15, mitochondrial cytochrome oxidase subunit II, and a new gene product were detected preferentially, but not exclusively by sera from GCA/PMR patients. We conclude that patients with GCA/PMR develop antibodies against a broad spectrum of human autoantigens. Antibodies against human lamin C, the nuclear autoantigen of 14 kD as well as human cytokeratin 15, mitochondrial cytochrome oxidase subunit II and the product of a new gene should be investigated further to determine their value as tools for the diagnosis and/or the definition of clinical subgroups of patients with GCA/PMR.

Toxicity of chemical mixtures: proteomic analysis of persisting liver and kidney protein alterations induced by repeated exposure of rats to JP-8 jet fuel vapor

Male Sprague-Dawley rats were exposed by whole body inhalation to 1000 mg/m3 +/- 10% JP-8 jet fuel vapor or room air control conditions for 6 h/day, 5 days/week for six consecutive weeks. Following a rest period of 82 days rats were sacrificed, and liver and kidney tissues examined by proteomic methods for both total protein abundance and protein charge modification. Kidney and lung samples were solubilized and separated via large scale, high resolution two-dimensional electrophoresis (2-DE) and gel patterns scanned, digitized and processed for statistical analysis. Through the use of peptide mass fingerprinting, confirmed by sequence tag analysis, three altered proteins were identified and quantified. Numerical, but not significantly different increases were found in total abundance of lamin A (NCBI Accession No. 1346413) in the liver, and of 10-formyltetrahydrofolate dehydrogenase (10-FTHF DH, #1346044) and glutathione-S-transferase (GST; #2393724) in the kidneys of vapor-exposed subjects. Protein charge modification index (CMI) analysis indicated significant alterations (P < 0.001) in expressed lamin A and 10-FTHF DH. These persisting changes in liver and kidney proteins are discussed in terms of possible alterations in the functional capacity of exposed subjects.

Expression of nuclear lamins in human tissues and cancer cell lines and transcription from the promoters of the lamin A/C and B1 genes

We have examined the expression of lamins A, B1, and C in human tissues and cancer cell lines and the function of the lamin A/C and B1 gene promoters in transfected cells. Northern analysis and immunoblotting demonstrated that lamin A/C mRNA and protein were not detectable in some human cell lines whereas lamin B1 was always present. Sequencing of approximately 2.6 kb of the lamin A/C and 1.6 kb of the lamin B1 genes 5' to the translation initiation sites showed that they did not contain typical TATA boxes near the transcription start sites. The lamin B1 and A/C proximal promoter regions were transcribed in transfected HeLa, Raji, and NT2/D1 cell lines even if the cells did not contain detectable endogenous lamin A/C mRNA or protein. These results show that, similar to most cytoplasmic intermediate filament genes, transcriptional regulatory elements in the promoters of the human nuclear lamin A/C and B1 genes do not control their cell type-specific expression in culture lines.