Project description:Individual organisms age at different rates, however, it remains unclear how aging alters the properties of individual cells. Here we show that zebrafish pancreatic beta-cells exhibit heterogeneity in both gene expression and proliferation with age. Individual beta-cells show marked variability in transcripts involved in endoplasmic reticulum stress, inhibition of growth factor signaling and inflammation, including NF-kB signaling. Using a reporter line, we show that NF-kB signaling is indeed activated heterogeneously with age. Notably, beta-cells with higher NF-kB activity proliferate less compared to neighbors with lower activity. Furthermore, NF-kB-signalinghigh beta-cells from younger islets upregulate socs2, a gene naturally expressed in beta-cells from older islets. In turn, socs2 can inhibit proliferation cell-autonomously. NF-kB activation correlates with the recruitment of tnfα-expressing immune cells, pointing towards a role for the islet microenvironment in this activity. We propose that aging is heterogeneous across individual beta-cells and identify NF-kB signaling as a marker of heterogeneity.
Project description:To address the role of NF-kB in aging in vivo, we utilized a well-characterized system that allows inducible and site-specific inhibition of NF-kB activity in murine skin. The hormone binding domain of the mutant estrogen receptor that is responsive to 4-hydroxytamoxifen (4-OHT) was fused to a mutant of p50 (IDNkB, inducible dominant negative NF-kB) that dimerizes with other NF-kB subunits but is unable to bind DNA, thus dominantly inhibiting NF-kB activity. Expression was driven within the basal layer of murine epidermis by the keratin 14 promoter in transgenic mice. To test whether NF-kB activity is required to maintain age-associated gene expression, we applied topical 4-OHT and ethanol vehicle (EtOH) for two weeks to the right (R) and left (L) dorsal flanks, respectively, of chronologically aged transgenic mice (O, 18-23 months). Young transgenic mice (Y, 1 month) were treated in parallel as control. Skin samples were harvested and analyzed for gene expression using mouse cDNA microarrays containing 35,217 elements, representing 18,880 unique genes. Set of arrays organized by shared biological context, such as organism, tumors types, processes, etc. Keywords: Logical Set Computed
