Thomas C. Peeler

MicroRNA expression signature in human abdominal aortic aneurysms

BackgroundAbdominal aortic aneurysm (AAA) is a dilatation of the aorta affecting most frequently elderly men. Histologically AAAs are characterized by inflammation, vascular smooth muscle cell apoptosis, and extracellular matrix degradation. The mechanisms of AAA formation, progression, and rupture are currently poorly understood. A previous mRNA expression study revealed a large number of differentially expressed genes between AAA and non-aneurysmal control aortas. MicroRNAs (miRNAs), small non-coding RNAs that are post-transcriptional regulators of gene expression, could provide a mechanism for the differential expression of genes in AAA.MethodsTo determine differences in miRNA levels between AAA (n = 5) and control (n = 5) infrarenal aortic tissues, a microarray study was carried out. Results were adjusted using Benjamini-Hochberg correction (adjusted p < 0.05). Real-time quantitative RT-PCR (qRT-PCR) assays with an independent set of 36 AAA and seven control tissues were used for validation. Potential gene targets were retrieved from miRNA target prediction databases Pictar, TargetScan, and MiRTarget2. Networks from the target gene set were generated and examined using the network analysis programs, CytoScape® and Ingenuity Pathway Core Analysis®.ResultsA microarray study identified eight miRNAs with significantly different expression levels between AAA and controls (adjusted p < 0.05). Real-time qRT-PCR assays validated the findings for five of the eight miRNAs. A total of 222 predicted miRNA target genes known to be differentially expressed in AAA based on a prior mRNA microarray study were identified. Bioinformatic analyses revealed that several target genes are involved in apoptosis and activation of T cells.ConclusionsOur genome-wide approach revealed several differentially expressed miRNAs in human AAA tissue suggesting that miRNAs play a role in AAA pathogenesis.

The potential role of DNA methylation in abdominal aortic aneurysms.

Abdominal aortic aneurysm (AAA) is a complex disorder that has a significant impact on the aging population. While both genetic and environmental risk factors have been implicated in AAA formation, the precise genetic markers involved and the factors influencing their expression remain an area of ongoing investigation. DNA methylation has been previously used to study gene silencing in other inflammatory disorders and since AAA has an extensive inflammatory component, we sought to examine the genome-wide DNA methylation profiles in mononuclear blood cells of AAA cases and matched non-AAA controls. To this end, we collected blood samples and isolated mononuclear cells for DNA and RNA extraction from four all male groups: AAA smokers (n = 11), AAA non-smokers (n = 9), control smokers (n = 10) and control non-smokers (n = 11). Methylation data were obtained using the Illumina 450k Human Methylation Bead Chip and analyzed using the R language and multiple Bioconductor packages. Principal component analysis and linear analysis of CpG island subsets identified four regions with significant differences in methylation with respect to AAA: kelch-like family member 35 (KLHL35), calponin 2 (CNN2), serpin peptidase inhibitor clade B (ovalbumin) member 9 (SERPINB9), and adenylate cyclase 10 pseudogene 1 (ADCY10P1). Follow-up studies included RT-PCR and immunostaining for CNN2 and SERPINB9. These findings are novel and suggest DNA methylation may play a role in AAA pathobiology.

Metabolic Responses of Plant Cells to Stress

Plants are routinely exposed to a bewildering variety of environmental stresses. Considering the extremes of temperature, salinity, moisture level, etc. that must be overcome, it is perhaps surprising that plant life is distributed as widely as it is. The key to survival lies in the remarkable capacity of many plants to acclimate to changing conditions. Such an acclimation is necessary because the patterns of cellular composition and metabolism favoring productive growth under one set of conditions usually do not suffice under different conditions.

Metabolism of Inositol Phospholipids in Response to Osmotic Stress in Dunaliella Saline

One of the most active areas of animal cell biochemistry deals with the transduction of hormonal and environmental signals across the plasma membrane by a mechanism involving polyphoinositide degradation. Surprisingly little attention has been directed towards identifying an equivalent system in plants. Isolated elements of the transduction pathway have been reported (e.g. Drobak and Ferguson, 1985; McMurray and Irvine, 1988; Morse, et al., 1988), but only preliminary evidence has been established concerning a physiological role for signal transduction by this mechanism. We have characterized such a system which may mediate the acclimation of Dunaliella salina, a halotolerant green alga, to osmotic stress.