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Microarray Comparison Using Normal Human Colonic Mucosa

ABSTRACT: This series represents a group of five samples (from sigmoid colon biopsies of clinically normal Patients A-E) profiled by a publicly available cDNA-based platform (GPL284) and a commercial oligonucleotide-based platform (GPL91). Sample RNA extraction: Biopsies taken during endoscopic analysis were immediately snap-frozen in liquid nitrogen and at no time prior to or during subsequent sample manipulation were the samples allowed to thaw. Standard laboratory procedures to eliminate the presence of RNases, including the use of RNase free plastic-ware, heat baked glassware, molecular biology grade chemicals and DEPC-treated solutions, were adopted. Frozen biopsies were crushed to a fine powder under liquid nitrogen using a manual crusher with a teflon head (Omnilab) and total RNA was isolated using the RNeasy Mini Kit (Qiagen) according to the manufacturers protocol, with minor modifications that improved RNA yields and purity in our hands. In brief, crushed biopsy samples were lysed in an appropriate volume of Buffer RLT (typically 600 µL/20 mg tissue). To facilitate complete lysis, samples were allowed to stand at room temperature for 5-10 min before vortexing. The lysate was homogenized by addition to a QIA shredder column (Qiagen) and centrifuged at 14,000 rpm for 2 min. The resulting supernatant was centrifuged at 14,000 rpm for 3 min to pellet any cell debris. One volume of 70% ethanol was added to the cleared lysate, added to the RNeasy column and centrifuged at 10,000 rpm for 15 sec. Bound RNA was washed with the addition of RW1 buffer to the column and allowed to stand at room temperature for 10 min followed by centrifugation at 10,000 rpm for 15 sec. DNase 1 incubation mix (Stock: 273 kunits; RNase-free DNase Set, Qiagen) was added directly to the spin column membrane and digestion of any contaminating genomic DNA was carried out at room temperature for 30 min. The column was washed with RWI buffer and the DNase treatment step was repeated. The bound RNA was washed with RW1 buffer and centrifuged at 10,000 rpm for 15 sec three times, followed by two additional wash and centrifugation steps with RPE buffer. Finally, purified RNA was eluted off the column with RNase-free water. RNA concentration and purity was determined spectrophotometrically at A260/A280 and was determined to be intact as assessed by formaldehyde gel electrophoresis. The presence of genomic DNA contamination was assessed by PCR amplification of GAPDH using standard PCR conditions and the following primers: GAPDH_F2-5’- ACCCACTCCTCCACCTTTGAC-3’, GAPDH_R2- 5’-CTGTTGCTGTAGCCAAATTCGT-3’. RNA was re-treated with DNase if necessary. Upon confirming the quality of the RNA (intact and free of genomic DNA), 15 µg of total RNA from each of the five biological replicates was used for expression screening on either the Affymetrix or the clone-based filter platform. Keywords: parallel sample

ORGANISM(S): Homo sapiens

PROVIDER: GSE405 | GEO | 2003/12/14

SECONDARY ACCESSION(S): PRJNA84951

REPOSITORIES: GEO

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Project description:Proteomic analysis Epilepsy was induced using perforant pathway stimulation (PPS) in rats as described (Norwood BA, et al. (2010) Classic hippocampal sclerosis and hippocampal-onset epilepsy produced by a single "cryptic" episode of focal hippocampal excitation in awake rats. J Comp 803 Neurol 518(16):3381-3407). Rats were killed under deep anesthesia (xylazine+ketamine) by transcardial perfusion with ice-cold 0.9 % NaCl solution at the following time points: 1 h, 24 h, 72 h, 10 d and 16 d after PPS (epileptogenesis); within 1 d of first spontaneous seizure (early epilepsy); 1 month after first spontaneous seizure (chronic epilepsy). Control rats were killed on day 17 after surgery (corresponding to day 10 after PPS). Hippocampi were removed and snap frozen at -80°C. Frozen rat hippocampi were resuspended in 200 ul lysis buffer (6M GdmCl, 10mM TCEP, Complete protease inhibitor cocktail, PhosSTOP inhibitor, 100 mM TEAB, benzonase) and dounced 30 times on ice. Samples were boiled for 5 min, sonicated on ice for 2min and centrifuged at 13000 rpm for 3 min. The supernatant was added chloroacetamide to a final concentration of 20 mM followed by incubation in the dark for 30 min at room temperature (RT). Proteins were digested with LysC for 30 min at RT and then diluting 10x— using 100 mM TEAB followed by adding trypsin and incubating overnight at 37°C with shaking. LysC and trypsin were added in a LysC/trypsin:protein ratio of 1:100. Samples were centrifuged at 13000 rpm for 5 min and from the supernatant a volume corresponding to 50 ug peptide was transferred to a new eppendorff tube. Sets of 6 samples were labelled using the TMTsixplex isobaric label reagent. (ThermoFisher Scientific). The labeling reagent was prepared using the manufactures instructions to first equilibrate to RT, then dissolving the labeling reagent in 41 ul anhydrous acetonitrile. The labeling reagent was added to each sample and incubated for 1 hour at RT. The reaction was quenched by incubating with 0.76 M lysine for 15 min. A small amount was taken from each sample, mixed and tested by mass spectrometry for labeling efficiency and mixing ratio. Remaining samples were mixed in a 1:1 ratio. The Stage-tips for the high-pH reverse phase fractionation were prepared by placing first two C18 disks in a p200 pipette tip, then adding a slurry of C18 beads (ReproSil-Pur, 3 um) in methanol and adding one additional C18 disk in the top. The column was activated and equilibrated by washing one time in 150 ul buffer B (50% buffer A, 50% ACN) and then two times in 150 ul buffer A (20mM Ammonium hydroxide, pH 10). The labeled peptide sample was adjusted to pH 10 using buffer A and then loaded onto the activated and equilibrated stage-tip by spinning the sample through the column and collecting 26 the flow-through. The column was washed 2 times with 150 ul buffer 585 A and the washes were collected and combined with the flow-through. Next, peptides were eluted stepwise in 17 fractions by spinning 150 ul of buffer A containing increasing amounts of ACN for each step (3.5%, 4.5%, 6%, 8%, 10%, 10.5%, 11.5%, 13.5%, 15%, 16%, 17.5%, 18.5%, 19.5%, 21%, 27%, 50%, 80%) through the column. After collection, the liquid was evaporated completely in a Concentrator Plus (Eppendorf) and prepared for MS by resuspending in buffer A* (2% ACN, 0.1% TFA). Samples were analyzed using an Easy-nLC system coupled online to a Q Exactive HF mass spectrometer (Thermo Scientific) equipped with a nanoelectrospray ion source (Proxeon/Thermo Scientific). The peptides were eluted into the mass spectrometer during a chromatographic separation from a fused silica column packed in-house with 3 um C18 beads (Reprosil, Dr. Maisch) using a 120 min gradient of buffer B (80% ACN, 0.5% acetic acid) with a flow rate of 250 nL/min. The Q Exactive HF was operated in positive ion mode with a top 12 data-dependent acquisition method where ions were fragmented by higher-energy collisional dissociation (HCD) using a normalized collisional energy (NCE)/ stepped NCE of 28 and 32. The resolution was set to 60,000 (at 400m/z), with a scan range of 300-1700 m/z and an AGC target of 3e6 for the MS survey. MS/MS was performed at a scan range of 100 - 2000 m/z using a resolution of 30,000 (at 400 m/z), an AGC target of 1e5, an intensity threshold of 1e5 and an isolation window of 1.2 m/z. Further parameters included an exclusion time of 45 sec and a maximum injection time for survey and MS/MS of 15 ms and 45 ms respectively.

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Microarray Comparison Using Normal Human Colonic Mucosa

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