Lowered expression levels of a tumor suppressor gene — Caveolin-1 within dysregulated gene networks of Fanconi anemia

GWAS contribution to atrial fibrillation and atrial fibrillation-related stroke: pathophysiological implications

Atrial fibrillation (AF) and stroke are included in a group of complex traits that have been approached regarding of their study by susceptibility genetic determinants. Since 2007, several genome-wide association studies (GWAS) aiming to identify genetic variants modulating AF risk have been conducted. Thus, 11 GWAS have identified 26 SNPs (p < 5 × 10^-2), of which 19 reached genome-wide significance (p < 5 × 10^-8). From those variants, seven were also associated with cardioembolic stroke and three reached genome-wide significance in stroke GWAS. These associations may shed a light on putative shared etiologic mechanisms between AF and cardioembolic stroke. Additionally, some of these identified variants have been incorporated in genetic risk scores in order to elucidate new approaches of stroke prediction, prevention and treatment.

Nitric oxide promotes cancer cell dedifferentiation by disrupting an Oct4:caveolin-1 complex: A new regulatory mechanism for cancer stem cell formation

Cancer stem cells (CSCs) are unique populations of cells that can self-renew and generate different cancer cell lineages. Although CSCs are believed to be a promising target for novel therapies, the specific mechanisms by which these putative therapeutics could intervene are less clear. Nitric oxide (NO) is a biological mediator frequently up-regulated in tumors and has been linked to cancer aggressiveness. Here, we search for targets of NO that could explain its activity. We find that it directly affects the stability and function of octamer-binding transcription factor 4 (Oct4), known to drive the stemness of lung cancer cells. We demonstrated that NO promotes the CSC-regulatory activity of Oct4 through a mechanism that involves complex formation between Oct4 and the scaffolding protein caveolin-1 (Cav-1). In the absence of NO, Oct4 forms a molecular complex with Cav-1, which promotes the ubiquitin-mediated proteasomal degradation of Oct4. NO promotes Akt-dependent phosphorylation of Cav-1 at tyrosine 14, disrupting the Cav-1:Oct4 complex. Site-directed mutagenesis and computational modeling studies revealed that the hydroxyl moiety at tyrosine 14 of Cav-1 is crucial for its interaction with Oct4. Both removal of the hydroxyl via mutation to phenylalanine and phosphorylation lead to an increase in binding free energy (ΔG_bind) between Oct4 and Cav-1, destabilizing the complex. Together, these results unveiled a novel mechanism of CSC regulation through NO-mediated stabilization of Oct4, a key stem cell transcription factor, and point to new opportunities to design CSC-related therapeutics.

Expression Profiling of Differentially Regulated Genes in Fanconi Anemia

Gene expression analysis mainly helps to study gene quantification methods by using various downstream detection approaches like imaging, amplification, probe hybridization, or sequencing. With respect to DNA, which is less static, mRNA levels vary over time, between cell types under divergent conditions. Gene expression analysis is principally focused on determination of mRNA levels transcribed from DNA. DNA microarrays are one of the robust and powerful tools to detect changes in multiple transcripts in larger cohorts in parallel. The basic principle of DNA microarray hybridization is complementary base pairing of single-stranded nucleic-acid sequences. On a microarray platform (also called a chip), known sequences called targets are attached at fixed locations (spots) to a solid surface such as glass using robotic spotting. Since a large number of samples (variables) are used in a typical hybridization experiment, which often leads to impreciseness for example, target mRNA transcribed from the same source should be identical every time. In such cases, developing an optimized protocol for microarray platform to study the expression profiling of differentially regulated genes is a challenging task. Thus genome-wide expression array analysis yields data about candidate genes that may be involved in disease acquisition progression, and helps in better understanding the pathophysiology of the disease. In this chapter we describe in detail the microarray technique, a well-accepted method for understanding the development and progression of Fanconi anemia (FA), a genetic disorder which is characterized by progressive bone marrow failure and a predisposition to cancer.

Scaffold-free and scaffold-assisted 3D culture enhances differentiation of bone marrow stromal cells

3D cultures of stem cells can preserve differentiation potential or increase the efficiency of methods that induce differentiation. Mouse bone marrow-derived stromal cells (BMSCs) were cultured in 3D as scaffold-free spheroids or "mesoid bodies" (MBs) and as aggregates on poly(lactic) acid microspheres (MB/MS). 3D cultures demonstrated viable cells, interaction on multiple planes, altered cell morphology, and the formation of structures similar to epithelial cell bridges. Cell proliferation was limited in suspension cultures of MB and MB/MS; however, cells regained proliferative capacity when transferred to flat substrates of tissue culture plates (TCPs). Expanded as monolayer, cells retained expression of Sca-1 and CD44 stem cell markers. 3D cultures demonstrated enhanced potential for adipogenic and osteogenic differentiation showing higher triglyceride accumulation and robust mineralization in comparison with TCP cultures. Enhanced and efficient adipogenesis was also observed in 3D cultures generated in a rotating cell culture system. Preservation of multilineage potential of BMSC was demonstrated in 5-azacytidine treatment of 3D cultures and TCP by expression of cardiac markers GATA4 and ACTA1 although functioning cardiomyocytes were not derived.

Genetic variants associated with risk of atrial fibrillation regulate expression of PITX2, CAV1, MYOZ1, C9orf3 and FANCC

Genome-wide association studies (GWAS) have identified genetic variants in a number of chromosomal regions that are associated with atrial fibrillation (AF). The mechanisms underlying these associations are unknown, but are likely to involve effects of the risk haplotypes on expression of neighbouring genes. To investigate the association between genetic variants at AF-associated loci and expression of nearby candidate genes in human atrial tissue and peripheral blood. Right atrial appendage (RAA) samples were collected from 122 patients undergoing cardiac surgery, of these, 12 patients also had left atrial appendage samples taken. 22 patients had a history of AF. Peripheral blood samples were collected from 405 patients undergoing diagnostic cardiac catheterisation. In order to tag genetic variation at each of nine loci, a total of 367 single nucleotide polymorphisms (SNPs) were genotyped using the Sequenom platform. Total expression of 16 candidate genes in the nine AF-associated regions was measured by quantitative PCR. The relative expression of each allele of the candidate genes was measured on the Sequenom platform using one or more transcribed SNPs to distinguish between alleles in heterozygotes. We tested association between the SNPs of interest and gene expression using total gene expression (integrating cis and trans acting sources of variation), and allelic expression ratios (specific for cis acting influences), in atrial tissue and peripheral blood. We adjusted for multiple comparisons using a Bonferroni approach. In subsidiary analyses, we compared the expression of candidate genes between patients with and without a history of AF. Total expression of 15 transcripts of 14 genes and allelic expression ratio of 14 transcripts of 14 genes in genomic regions associated with AF were measured in right atrial appendage tissue. 8 of these transcripts were also expressed in peripheral blood. Risk alleles at AF-associated SNPs were associated in cis with an increased expression of PITX2a (2.01-fold, p=6.5×10(-4)); and with decreased expression of MYOZ1 (0.39 fold; p=5.5×10(-15)), CAV1 (0.89 fold; p=5.9×10(-8)), C9orf3 (0.91 fold; 1.5×10(-5)), and FANCC (0.94-fold; p=8.9×10(-8)) in right atrial appendage. Of these five genes, only CAV1 was expressed in peripheral blood; association between the same AF risk alleles and lower expression of CAV1 was confirmed (0.91 fold decrease; p=4.2×10(-5)). A history of AF was also associated with a decrease in expression of CAV1 in both right and left atria (0.84 and 0.85 fold, respectively; p=0.03), congruent with the magnitude of the effect of the risk SNP on expression, and independent of genotype. The analyses in peripheral blood showed association between AF risk SNPs and decreased expression of KCNN3 (0.85-fold; p=2.1×10(-4)); and increased expression of SYNE2 (1.12-fold; p=7.5×10(-24)); however, these associations were not detectable in atrial tissue. We identified novel cis-acting associations in atrial tissue between AF risk SNPs and increased expression of PITX2a/b; and decreased expression of CAV1 (an association also seen in peripheral blood), C9orf3 and FANCC. We also confirmed a previously described association between AF risk variants and MYOZ1 expression. Analyses of peripheral blood illustrated tissue-specificity of cardiac eQTLs and highlight the need for larger-scale genome-wide eQTL studies in cardiac tissue. Our results suggest novel aetiological roles for genes in four AF-associated genomic regions.

A simplified protocol for the isolation and culture of cardiomyocytes and progenitor cells from neonatal mouse ventricles

The neonatal heart is a very useful tool for the study of biochemical pathways and properties of cardiomyocytes and as it has the potential to regenerate for a brief period of time from birth; it is also useful to study cardiac regeneration. However, as the heart matures, this proficiency for regeneration is reduced. This regenerative potential may be influenced by the microenvironment of the heart in the early stages of postnatal development and therefore, cell cultures derived at this stage may contain functional cardiomyocytes and progenitor cells. The aim of this study was to identify key steps in the isolation and culture of such early stage-neonatal mouse hearts to allow maximum migration of cardiomyocytes from the explant and their maintenance as functional, long term cultures. Explant cultures of mouse ventricles preserved 3-dimensional structure and generated migrating layers of cardiomyocytes that expressed alpha sarcomeric actin which could be further sub-cultured by enzymatic dissociation. Western blotting demonstrated expression of c-KIT, GATA4, alpha sarcomeric actin and connexin43 proteins after 20 days of explant culture. ACTA1, GATA4, and CX43 continued to express in five weeks old explant cultures while the c-KIT protein was expressed up to two passages during sub-culture. Real time PCR and SQRT PCR also demonstrated gene expression of cardiomyocyte markers in long term cultures. Migrating cells from the explants assembled into contracting spheroids after subculture and expressed the c-KIT protein. Progenitor markers CD44, CD90, and extracellular proteins, periostin and vimentin demonstrated the preservation of cellular heterogeneity in such cultures. Supplementation with Hydrocortisone maintained a cardioprotective environment and reduced the non-myocyte population. This is an optimized and efficient method for the generation of neonatal heart cultures that is not labor intensive and does not require supplementation with cytokines.

ROMO1 regulates RedOx states and serves as an inducer of NF-κB-driven EMT factors in Fanconi anemia

Fanconi anemia (FA) is a rare genetic disorder associated with a bone-marrow failure, genome instability, hypersensitivity to DNA crosslinking agents and a predisposition to cancer. Mutations have been documented in 16 FA genes that participate in the FA-BRCA DNA repair pathway, a fundamental pathway in the development of the disease and the presentation of its symptoms. Besides the well-established role of FA genes in DNA damage and repair pathways, recent reports have revealed an overproduction of epithelial to mesenchymal transition (EMT) factors via a NF-κB-dependent mechanism that results in the proliferation of neighboring tumor cells and FA cells have also been shown to possess damaged mitochondria, accompanied by altered RedOx pathways. This study has focused on reactive oxygen species Modulator-1 (ROMO1), an oncomarker and mitochondrial membrane protein, which is known to be associated with cancer growth and in the modulation of RedOx states in some cancer models. Here, we reveal the role of ROMO1 and demonstrate its link in regulating RedOx states and in the activation of NF-κB-dependent EMT factors in FA.

Cardiogel: a nano-matrix scaffold with potential application in cardiac regeneration using mesenchymal stem cells

3-Dimensional conditions for the culture of Bone Marrow-derived Stromal/Stem Cells (BMSCs) can be generated with scaffolds of biological origin. Cardiogel, a cardiac fibroblast-derived Extracellular Matrix (ECM) has been previously shown to promote cardiomyogenic differentiation of BMSCs and provide protection against oxidative stress. To determine the matrix composition and identify significant proteins in cardiogel, we investigated the differences in the composition of this nanomatrix and a BMSC-derived ECM scaffold, termed as ‘mesogel’. An optimized protocol was developed that resulted in efficient decellularization while providing the maximum yield of ECM. The proteins were sequentially solubilized using acetic acid, Sodium Dodecyl Sulfate (SDS) and Dithiothreitol (DTT). These proteins were then analyzed using surfactant-assisted in-solution digestion followed by nano-liquid chromatography and tandem mass spectrometry (nLC-MS/MS). The results of these analyses revealed significant differences in their respective compositions and 17 significant ECM/matricellular proteins were differentially identified between cardiogel and mesogel. We observed that cardiogel also promoted cell proliferation, adhesion and migration while enhancing cardiomyogenic differentiation and angiogenesis. In conclusion, we developed a reproducible method for efficient extraction and solubilization of in vitro cultured cell-derived extracellular matrix. We report several important proteins differentially identified between cardiogel and mesogel, which can explain the biological properties of cardiogel. We also demonstrated the cardiomyogenic differentiation and angiogenic potential of cardiogel even in the absence of any external growth factors. The transplantation of Bone Marrow derived Stromal/Stem Cells (BMSCs) cultured on such a nanomatrix has potential applications in regenerative therapy for Myocardial Infarction (MI).

IL-6, IL-8, MMP-2, MMP-9 are overexpressed in Fanconi anemia cells through a NF-κB/TNF-α dependent mechanism

Fanconi anemia (FA) is a rare autosomal recessive genetic disorder associated with a bone-marrow failure, genome instability, hypersensitivity to DNA crosslinking agents and a predisposition to cancer. Mutations have been documented in 16 FA genes that participate in the FA-BRCA DNA repair pathway, a fundamental pathway in the development of the disease and the presentation of its symptoms. FA cells have been characterized by an overproduction of cytokines, MAPKs, and Interleukins. Through this study we have identified the overexpression of additional secretory factors such as IL-6, IL-8, MMP-2, and MMP-9 in FA cells and in cells depleted of FANCA or FANCC and proved that their expression is under the control of NF-κB/TNF-α signaling pathways. We also demonstrated that these overexpressed secretory factors were effective in promoting the proliferation, migration, and invasion of surrounding tumor cells a fundamental event in the process of epithelial mesenchymal transition (EMT) and that they also modulated the expression of EMT markers such as E-cadherin and SNAIL. Overall our data suggest that the upregulation of EMT promoting factors in FA may contribute to predisposing FA patients to cancer, thereby providing new insights into possible therapeutic interventions.