Project description:A mouse hepatoma cell line (Hepa1-6 cells, ATCC) was grown in T-25 tissue culture flasks (Corning) at 37ºC in 5% CO2 under two conditions. The first condition was the control, which contained DMEM medium (Gibco BRL) with 25 mM glucose, 4 mM glutamine, 1% penicillin-streptomycin (Sigma), and 10% CPSR-3 (Sigma). The second condition was identical to the first, however the glutamine concentration was altered periodically. Once the cells had grown to confluency, the experiment began at 9:30 PM by exchanging the medium in all flasks. The control flasks received the same medium, containing 4 mM glutamine, while the experimental flasks received identical medium with no glutamine. Twenty-four hours later, the medium was exchanged again, however this time all flasks received medium containing 4 mM glutamine. The first medium exchange was repeated at 48 hours into the experiment, while the second was repeated at 72 hours into the experiment. Hence the glutamine concentration of the experimental flasks oscillated between 0 mM and 4 mM glutamine over 96 hours, while the glutamine concentration of the control flasks remained constant at 4 mM glutamine. At regular intervals, the flasks were sampled. Total RNA was isolated, medium samples were retained, and isotopic measurements were performed from flasks fed different labelled compounds. All samples taken during the experiment were analyzed. The total RNA harvested was labeled and hybridized to DNA microarrays to measure the abundance of transcripts present. Total RNA control samples were labeled using Cy3 dCTP (Perkin-Elmer), and total RNA experimental samples were labeled using Cy5 dCTP (Perkin-Elmer) during reverse transcription. For reverse transcription 10 ug of total RNA was aliquoted into a 6 uL volume. If concentration of the RNA was necessary, this was conducted using a speed vacufuge (Eppendorf) at 60ºC for 10 minutes. The RNA sample was then mixed with 2 uL of 10X Cy-labeled dCTP, 2 uL of 100 mM DTT (Invitrogen), 4 uL of 5X First Strand Buffer (Invitrogen), 2 uL of a dNTP mixture containing 5 mM dGTP, dATP, dTTP and 2 mM dCTP (Invitrogen), 2 uL of 0.5 mg/ mL oligo-dT18-20 (Invitrogen), and 2 uL of Superscript II reverse transcriptase (Invitrogen). This reaction mixture was incubated at 42ºC for approximately two hours. Following the reverse transcription reaction, the RNA template was degraded by addition of 2 uL of 1 N NaOH and incubation at 65 ºC for 10 minutes. The alkaline conditions were then neutralized by addition of 2 uL of 1 N HCl. Samples from identical time points that were to be compared on DNA microarrays were then mixed. The combined sample was cleaned to remove extra primers and nucleotides using a QIAquick Nucleotide Removal kit as described by the manufacturer's instructions. Once cleaned, the sample was concentrated using a speed vacufuge (Eppendorf) for 20 minutes at 65ºC. Following concentration, the sample was resuspended in 32 uL of prewarmed hybridization buffer (Clontech Laboratories), 1 uL was removed for quantitation, and hybridized to prepared oligonucleotide microarrays. Hybridization occurred overnight at 55 ºC using Corning hybridization chambers. The following day the arrays were washed in Glass Hybridization Wash Solution (Clontech Laboratories), and then in 1X SSC, and finally 0.1X SSC. Each wash step was conducted for 20 minutes under high agitation. The arrays were dried by centrifugation and scanned using GenePix 4000B scanner (Axon Instruments). The resulting data was downloaded and formatted in Excel (Microsoft), and then analyzed using Matlab (The MathWorks, Inc.). The arrays used for hybridization were prepared using GAPS glass slides (Corning), and a Virtek arrayer (Bio-Rad). These arrays contained 17,280 features, printed from a synthesized oligonucleotide mouse library (Operon). Briefly, the library was resuspended in 3X SSC, centrifuged, and loaded into the arrayer. Arrays were printed using 32 pins (Telechem), at approximately 50% humidity. Once printed, the probes were crosslinked to the glass slides using a UV Stratalinker (Stratagene). The slides were then blocked for 15 minutes in a 250 mL mixture containing 15.7 g/ L succinic anhydride, 239 mL 1-methyl-2-pyrrolidinone, and 10.7 mL of 1 M boric acid, pH 8.0. They were cleaned by rinsing in 250 mL of milli-Q water (X2), followed by 250 mL of 95% ethanol. They were finally dried using filtered air and stored in the dark at room temperature. Keywords = mouse, liver, hepatoma, cell culture, glutamine, carbon metabolism
2010-06-05 | E-GEOD-404 | biostudies-arrayexpress
