|Differentiation state-specific mitochondrial dynamic regulatory networks are revealed by global transcriptional analysis of the developing chicken lens. |
Chauss, D; Basu, S; Rajakaruna, S; Ma, Z; Gau, V; Anastas, S; Brennan, LA; Hejtmancik, JF; Menko, AS; Kantorow, M
G3 (Bethesda, Md.)
The mature eye lens contains a surface layer of epithelial cells called the lens epithelium that requires a functional mitochondrial population to maintain the homeostasis and transparency of the entire lens. The lens epithelium overlies a core of terminally differentiated fiber cells that must degrade their mitochondria to achieve lens transparency. These distinct mitochondrial populations make the lens a useful model system to identify those genes that regulate the balance between mitochondrial homeostasis and elimination. Here we used an RNA sequencing and bioinformatics approach to identify the transcript levels of all genes expressed by distinct regions of the lens epithelium and maturing fiber cells of the embryonic Gallus gallus (chicken) lens. Our analysis detected more than 15,000 unique transcripts expressed by the embryonic chicken lens. Of these, more than 3000 transcripts exhibited significant differences in expression between lens epithelial cells and fiber cells. Multiple transcripts coding for separate mitochondrial homeostatic and degradation mechanisms were identified to exhibit preferred patterns of expression in lens epithelial cells that require mitochondria relative to lens fiber cells that require mitochondrial elimination. These included differences in the expression levels of metabolic (DUT, PDK1, SNPH), autophagy (ATG3, ATG4B, BECN1, FYCO1, WIPI1), and mitophagy (BNIP3L/NIX, BNIP3, PARK2, p62/SQSTM1) transcripts between lens epithelial cells and lens fiber cells. These data provide a comprehensive window into all genes transcribed by the lens and those mitochondrial regulatory and degradation pathways that function to maintain mitochondrial populations in the lens epithelium and to eliminate mitochondria in maturing lens fiber cells.
|Hypoxia induced upregulation and function of the thiamine transporter, SLC19A3 in a breast cancer cell line. |
Rebecca Sweet,Amber Paul,Jason Zastre
Cancer biology & therapy
Adaptive responses within hypoxic tumor microenvironments require the altered expression of Solute Carrier (SLC) transporters to maintain nutrient uptake in support of cellular metabolism and biosynthesis. Using a real time PCR array strategy to further characterize changes in transporter expression within a chronic hypoxia breast cancer cell line model (BT474), we have found a 31 fold increase in the expression of the thiamine transporter, SLC19A3. Thus, further investigations into the expression changes of the thiamine transporters, SLC19A2 and SLC19A3, and the role of hypoxia inducible factor-1 alpha (HIF-1α) regulating their expression were conducted. Chronic culturing of BT474 cells in 1% O2 up to 142 days consistently demonstrated a high level of SLC19A3 expression with a mean of approximately 40 fold with no change in SLC19A2. A corresponding 2 fold increase in thiamine uptake over 15 min was measured in chronic hypoxic BT474 cells compared to normoxia. Acute 1% O2 exposure of BT474 cells up to 72 h demonstrated a 7.5 fold increase in SLC19A3 expression. The chemical hypoxia mimetic deferoxamine, resulted in an approximately 70 fold increase in SLC19A3 expression. Stable shRNA knockdown of HIF-1α reduced hypoxia mediated SLC19A3 up-regulation by approximately 3 fold compared to scrambled construct. In conclusion, SLC19A3 transporter expression was observed to be up-regulated under acute, chronic and DFO induced hypoxia. The attenuated increase in SLC19A3 expression after HIF-1α knockdown suggests a role for HIF-1α mediated pathways regulating SLC19A3 gene expression.