Transcriptional Profiling of Human Familial Longevity Indicates a Role for ASF1A and IL7R

The Leiden Longevity Study consists of families that express extended survival across generations, decreased morbidity in middle-age, and beneficial metabolic profiles. To identify which pathways drive this complex phenotype of familial longevity and healthy aging, we performed a genome-wide gene expression study within this cohort to screen for mRNAs whose expression changes with age and associates with longevity. We first compared gene expression profiles from whole blood samples between 50 nonagenarians and 50 middle-aged controls, resulting in identification of 2,953 probes that associated with age. Next, we determined which of these probes associated with longevity by comparing the offspring of the nonagenarians (50 subjects) and the middle-aged controls. The expression of 360 probes was found to change differentially with age in members of the long-lived families. In a RT-qPCR replication experiment utilizing 312 controls, 332 offspring and 79 nonagenarians, we confirmed a nonagenarian specific expression profile for 21 genes out of 25 tested. Since only some of the offspring will have inherited the beneficial longevity profile from their long-lived parents, the contrast between offspring and controls is expected to be weak. Despite this dilution of the longevity effects, reduced expression levels of two genes, ASF1A and IL7R, involved in maintenance of chromatin structure and the immune system, associated with familial longevity already in middle-age. The size of this association increased when controls were compared to a subfraction of the offspring that had the highest probability to age healthily and become long-lived according to beneficial metabolic parameters. In conclusion, an “aging-signature” formed of 21 genes was identified, of which reduced expression of ASF1A and IL7R marked familial longevity already in middle-age. This indicates that expression changes of genes involved in metabolism, epigenetic control and immune function occur as a function of age, and some of these, like ASF1A and IL7R, represent early features of familial longevity and healthy ageing

Regulated intramembrane proteolysis of the AXL receptor kinase generates an intracellular domain that localizes in the nucleus of cancer cells

Deregulation of the TAM (TYRO3, AXL, and MERTK) family of receptor tyrosine kinases (RTKs) has recently been demonstrated to predominately promote survival and chemoresistance of cancer cells. Intramembrane proteolysis mediated by presenilin/gamma-secretase is known to regulate the homeostasis of some RTKs. In the present study, we demonstrate that AXL, but not TYRO3 or MERTK, is efficiently and sequentially cleaved by alpha-and g-secretases in various types of cancer cell lines. Proteolytic processing of AXL redirected signaling toward a secretase-mediated pathway, away from the classic, well-known, ligand-dependent canonical RTK signaling pathway. TheAXL intracellular domain cleavage product, but not full-length AXL, was further shown to translocate into the nucleus via a nuclear localization sequence that harbored a basic HRRKK motif. Of interest, we found that the g-secretase-uncleavable AXL mutant caused an elevated chemoresistance in non-small-cell lung cancer cells. Altogether, our findings suggest thatAXL can undergo sequential processing mediated by various proteases kept in a homeostatic balance. This newly discovered post-translational processing ofAXL may provide an explanation for the diverse functions of AXL, especially in the context of drug resistance in cancer cells.-Lu, Y., Wan, J., Yang, Z., Lei, X., Niu, Q., Jiang, L., Passtoors, W. M., Zang, A., Fraering, P. C., Wu, F. Regulated intramembrane proteolysis of the AXL receptor kinase generates an intracellular domain that localizes in the nucleus of cancer cells. FASEB J. 31, 1382-1397 (2017). www.fasebj.or

Gene expression analysis of mTOR pathway:Association with human longevity

mTOR signalling is implicated in the development of disease and in lifespan extension in model organisms. This pathway has been associated with human diseases such as diabetes and cancer, but has not been investigated for its impact on longevity per se. Here, we investigated whether transcriptional variation within the mTOR pathway is associated with human longevity using whole-blood samples from the Leiden Longevity Study. This is a unique cohort of Dutch families with extended survival across generations, decreased morbidity and beneficial metabolic profiles in middle-age. By comparing mRNA levels of nonagenarians and middle-aged controls, the mTOR signalling gene set was found to associate with old age (P=4.6×10-7). Single gene analysis showed that seven of 40 mTOR pathway genes had a significant differential expression of at least 5%. Of these, the RPTOR (Raptor) gene was found to be differentially expressed also when the offspring of nonagenarians was compared with their spouses, indicating association with familial longevity in middle-age. This association was not explained by variation between the groups in the prevalence of type 2 diabetes and cancer or glucose levels. Thus, the mTOR pathway not only plays a role in the regulation of disease and aging in animal models, but also in human health and longevity

Expression profiles of 2,953 probes that differed between nonagenarians and middle-aged controls.

<p>Expression intensities of the 2,953 probes were analyzed by one-dimensional hierarchical clustering. Each probe is represented by a row; each subject by a column. Samples are organized left to right by increasing age which is indicated for a few individuals for reference. The largest cluster of probes exhibits reduced expression (transition from red to blue), and another cluster exhibits increased expression (transition from blue to red) in nonagenarians compared to controls. Mean centered expression values of probes are displayed according to the color scale in which red represents above average expression levels and blue below average expression levels. Fold changes of individual probes are given in Supplementary <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0027759#pone.0027759.s002" target="_blank">Table S1</a>.</p

RT-qPCR results.

<p>FC: fold change between groups; a FC above 1 indicates an increase in expression and a FC below 1 indicates a decrease in expression compared to the controls. p: unadjusted p values. Bold indicate p values are below the significant level of 0.05 after Bonferroni correction for multiple testing (threshold p = 0.002).</p

Flowchart of gene expression analyses.

<p>The order of analyses is shown for the explorative analysis (top half of the figure) and the replication analysis (bottom half of the figure). The probes/genes are depicted in the boxes and to the left thereof are the techniques or analyses used.</p