APOD
Apolipoprotein D precursor (Apo-D) (ApoD)
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Aging is associated with changes in gene expression levels that affect cellular functions and predispose to age-related diseases. The use of candidate genes whose expression remains stable during aging is required to correctly address the age-associated variations in expression levels. Reverse transcription quantitative-polymerase chain reaction (RT-qPCR) has become a powerful approach for sensitive gene expression analysis. Reliable RT-qPCR assays rely on the normalisation of the results to stable reference genes. Taken these data together, here we evaluated the expression stability of eight frequently used reference genes in three aging models: oncogene-induced senescence (OIS), in vitro and in vivo aging. Using NormFinder and geNorm algorithms, we identified that the most stable reference gene pairs were PUM1 and TBP in OIS, GUSB and PUM1 for in vitro aging and GUSB and OAZ1 for in vivo aging. To validate these candidates, we used them to normalise the expression data of CDKN1A, APOD and TFRC genes, whose expression is known to be affected during OIS, in vitro and in vivo aging. This study demonstrates that accurate normalisation of RT-qPCR data is crucial in aging research and provides a specific subset of stable reference genes for future aging studies.
MeSH Terms
- Aging
- Algorithms
- Gene Expression Profiling
- Genes, Essential
- Humans
- Real-Time Polymerase Chain Reaction
- Software
Apolipoprotein D (ApoD) is an ancient member of the lipocalin family with a high degree of sequence conservation from insects to mammals. It is not structurally related to other major apolipoproteins and has been known as a small, soluble carrier protein of lipophilic molecules that is mostly expressed in neurons and glial cells within the central and peripheral nervous system. Recent data indicate that ApoD not only supplies cells with lipophilic molecules, but also controls the fate of these ligands by modulating their stability and oxidation status. Of particular interest is the binding of ApoD to arachidonic acid and its derivatives, which play a central role in healthy brain function. ApoD has been shown to act as a catalyst in the reduction of peroxidized eicosanoids and to attenuate lipid peroxidation in the brain. Manipulating its expression level in fruit flies and mice has demonstrated that ApoD has a favorable effect on both stress resistance and life span. The APOD gene is the gene that is upregulated the most in the aging human brain. Furthermore, ApoD levels in the nervous system are elevated in a large number of neurologic disorders including Alzheimer's disease, schizophrenia, and stroke. There is increasing evidence for a prominent neuroprotective role of ApoD because of its antioxidant and anti-inflammatory activity. ApoD emerges as an evolutionarily conserved anti-stress protein that is induced by oxidative stress and inflammation and may prove to be an effective therapeutic agent against a variety of neuropathologies, and even against aging.
MeSH Terms
- Aging
- Animals
- Anti-Inflammatory Agents
- Antioxidants
- Apolipoproteins D
- Brain
- Catalysis
- Eicosanoids
- Humans
- Lipid Peroxidation
- Neurodegenerative Diseases
- Neuroprotective Agents
- Oxidative Stress
Keywords
- Aging
- Alzheimer's disease
- Apolipoprotein
- Inflammation
- Lipid peroxidation
- Lipocalin
- Neurodegeneration
- Oxidative stress
- Reactive oxygen species
- Schizophrenia
- Stress response
- Stroke
Numerous microarray studies of aging have been conducted, yet given the noisy nature of gene expression changes with age, elucidating the transcriptional features of aging and how these relate to physiological, biochemical and pathological changes remains a critical problem. We performed a meta-analysis of age-related gene expression profiles using 27 datasets from mice, rats and humans. Our results reveal several common signatures of aging, including 56 genes consistently overexpressed with age, the most significant of which was APOD, and 17 genes underexpressed with age. We characterized the biological processes associated with these signatures and found that age-related gene expression changes most notably involve an overexpression of inflammation and immune response genes and of genes associated with the lysosome. An underexpression of collagen genes and of genes associated with energy metabolism, particularly mitochondrial genes, as well as alterations in the expression of genes related to apoptosis, cell cycle and cellular senescence biomarkers, were also observed. By employing a new method that emphasizes sensitivity, our work further reveals previously unknown transcriptional changes with age in many genes, processes and functions. We suggest these molecular signatures reflect a combination of degenerative processes but also transcriptional responses to the process of aging. Overall, our results help to understand how transcriptional changes relate to the process of aging and could serve as targets for future studies. http://genomics.senescence.info/uarrays/signatures.html. Supplementary data are available at Bioinformatics online.
MeSH Terms
- Aging
- Animals
- Gene Expression Profiling
- Humans
- Mice
- Rats
- Transcription, Genetic
The application of gene expression profiling to the study of chronological ageing has the potential to illuminate the molecular mechanisms underlying a complex and active process. For example, ageing of the skin and its constituent organs has myriad phenotypic consequences, and a better understanding of the means by which these changes arise has important corollaries for intervention strategies. We used a transcriptional profiling approach to investigate changes in gene expression associated with ageing of the large vibrissa follicle of the Wistar rat. Follicle mRNA isolated from male Wistar rats at 1 and 18 months of age was hybridized to Clontech Atlas 1.2 Rat cDNA macroarrays. Confirmation of array results was provided by the use of Northern blotting and immunohistochemistry. Seven transcripts displayed at least a 1.6-fold increase in expression with age, of which APOD (2.5-fold), GSTM2 (2.0-fold) and NPY (1.8-fold) showed the greatest increases. Decreased expression was found in 19 transcripts, most notably in ALOX12 (13.3-fold) and GAP43 (12.6-fold) expression. Follicular ageing is characterized by transcriptional changes associated with diverse aspects of keratinocyte metabolism, proliferation and development.
MeSH Terms
- Aging
- Animals
- Blotting, Northern
- Gene Expression Profiling
- Gene Expression Regulation, Developmental
- Hair Follicle
- Immunoenzyme Techniques
- Male
- RNA, Messenger
- Rats
- Rats, Wistar