At 120?hpf, the mRNA levels increased to 23-fold of the normal [Ca2+] group (Fig
At 120?hpf, the mRNA levels increased to 23-fold of the normal [Ca2+] group (Fig.?2e). complex, which exhibits as benign lesions and increases the risk of renal cell carcinoma14. As such, major components of the IIS-PI3K-Akt pathway have targeted as points of therapeutic intervention. A number of assays have been developed, and potent inhibitors for IGF1R/InsR, PI3K, AKT, PTEN, and mTOR have been discovered20, 21. Most, if not all, available assays are molecular target- or cell culture-based platforms. We now understand that there are tremendous complexities in the IIS-PI3K-AKT-mTOR signaling pathway whole animal setting. However, visualization of NaR cells by hybridization and measuring their number manually is not only labor intensive, but also prevent real time analysis of the NaR cell proliferative response. In this study, we have developed a stable zebrafish transgenic line by labeling NaR cell with GFP. These transgenic larvae faithfully report the action of IGF1R-PI3K-Akt signaling and are well suited for high-throughput and real-time cell cycle analysis. Using this platform, the dynamics of NaR cell proliferation in response to low [Ca2+] stress and the distinct roles of Torc1 and Torc2 in this process were elucidated. Results Low [Ca2+] stress induces NaR cell proliferation and a concordant increase in mRNA levels In a previous study, we have reported that mRNA is usually specifically expressed in NaR cells and that whole body mRNA levels are a good GSK1324726A (I-BET726) indicator of NaR cell number in larval zebrafish25. The mRNA is also specifically expressed in NaR cells. In fact, it is considered as a NaR cell marker gene25. We therefore wondered which gene is usually a better indicator of NaR cell number. Moreover, the time-course effects of low [Ca2+] on and expression were not examined and it is unclear whether the low [Ca2+] effects are reversible. To GSK1324726A (I-BET726) answer these questions, wild type zebrafish embryos were raised in embryo rearing solutions made up of various concentrations of [Ca2+] from 0 to 120?hpf. Compared to the larvae raised in normal [Ca2+] (0.2?mM) and high [Ca2+] (2?mM) solution, those raised in 0.02 and 0.001?mM [Ca2+] solutions had many more mRNA- and mRNA-expressing NaR cells (Fig.?1a). The increase was most robust in the 0.001?mM [Ca2+] group (Fig.?1a). Changes in [Ca2+] caused limited changes in the number of HR (H+-ATPase-rich) cells, which was labeled by mRNA expression (Fig.?1a). When analyzed by qPCR, the mRNA levels in the L group (i.e., 0.001?mM [Ca2+]) were 3.5-fold greater than the N group (i.e., 0.2?mM [Ca2+]) (Fig.?1b and c). The levels of mRNA in the L group was 43-fold greater than those of the N group (Fig.?1d). Switching from the normal [Ca2+] to the low [Ca2+] solution (i.e., N??L group) resulted in a 6.3-fold increase in the mRNA levels (Fig.?1d), while it did not change the mRNA levels (Fig.?1c) or the NaR cell density (Fig.?1e). Conversely, switching from the low [Ca2+] to normal [Ca2+] (i.e., L??N group) significantly reduced the mRNA levels (Fig.?1d) but had no effect on mRNA levels (Fig.?1c) or NaR cell density (Fig.?1e). Therefore, while low [Ca2+] stress increases and mRNA levels, the two genes are differentially regulated. Open in a separate window Physique 1 The gene is usually specifically expressed in NaR cells. (a) Wild type zebrafish embryos were raised in embryo rearing solution made up of the indicated [Ca2+] from 0 to 120?hpf (hours post fertilization) and analyzed by whole-mount hybridization using the indicated probes. Images shown are GSK1324726A (I-BET726) the yolk sac region. Scale bar?=?50?m. Unless specified otherwise, all hybridization images shown hereafter are lateral views, anterior to the left and dorsal up. (bCe) The and genes respond differentially to [Ca2+] changes. The experimental design is shown in (b). The mRNA levels of (c) and (d) were measured by qPCR and normalized by the mRNA levels. Data shown are mean??SEM, n?=?3. Different letters indicate significant differences at hybridization using the indicated probes. Representative images are shown. Next, we examined the effect of low [Ca2+] stress in different developmental stages. Low [Ca2+] treatment during the embryonic and early larval stage (i.e., from 0 to 48 and from 0 to 72?hpf) significantly increased the mRNA levels (Supplemental Fig.?S1a), while did not change the mRNA levels and NaR Col3a1 cell number in these stages (Supplemental Fig.?S1b,c). The basal levels of and mRNA increased from 48 to 72?hpf regardless of water [Ca2+], reflecting a developmental increase25. This result suggests that low [Ca2+] stress stimulates expression in both embryonic and larval stages, while it increases expression only in the larval stage. We next mapped the time window of the responsiveness by subjecting the embryos/larvae to low [Ca2+] stress at various time points (Supplemental Fig.?S2a). Low [Ca2+] treatment of all.