Project description:MicroPoly(A)Pure kits (Ambion) were used to prepare mRNA from P. salmonis-infected and control Atlantic salmon head kidney. Head kidney mRNA samples were prepared from pooled (n = 10) infected or control kidney. Approximately 200 ng of infected or control head kidney mRNA was used as template in aRNA synthesis reactions. Two infected head kidney samples were pooled to yield 8.9 ug of aRNA, and a single control head kidney sample contained 8.4 ug of aRNA. Infected and control head kidney aRNA samples were visualized on agarose gels to check quality and quantity (data not shown). Except for the amounts of aRNA and reverse transcription (RT) primer used, head kidney target labeling reactions and microarray hybridizations were identical. Head kidney target syntheses used 2 ug of aRNA and 2 ug of random primers (Roche). RT primers were mixed with aRNA samples, and nuclease-free H2O (Invitrogen) was added to make 10 ul total volume. Samples were incubated at 70 degrees C for 4 min, then placed on ice. RT reactions included 50 mM Tris HCl pH 8.3, 75 mM KCl, 3 mM MgCl2, 10 mM DTT, 0.5 mM each dATP, dCTP, and dGTP, 0.2 mM dTTP, 0.05 mM Cy3-dUTP or Cy5-dUTP (Amersham), 40U RNAguard ribonuclease inhibitor (Amersham), and 400U Superscript II Rnase H- reverse transcriptase (Invitrogen). RT reactions were incubated at 42 degrees C for 2.5 h, followed by addition of 0.025U RNase A (Sigma) and 1.5U RNase H (New England BioLabs) and incubation at 37 degrees C for 30 min. Labeled targets were cleaned using the Qiaquick PCR purification kit (Qiagen) and precipitated, with 300 mM sodium acetate, 1 ul of 20 ug/ul glycogen (Invitrogen), and 2.5 volumes of 100% ethanol, at -20 degrees C overnight. Each labeled target was recovered by centrifugation (14,000 rpm, 4 degrees C, 1 h), washed in 70% ethanol, air-dried, and resuspended in 60 ul of hybridization buffer: 50% deionized formamide, 5X SSC, 0.1% SDS, 5 ul of 5 ug/ul oligo dT (5’T18[Q-N]3’), 5 ul of 2 ug/ul BSA (Pierce), and 2 ul of 10 ug/ul sonicated human placental DNA (Sigma). Targets were incubated at 96 degrees C for 3 min, and then at 65 degrees C until applied to microarrays. Microarrays were prepared for hybridization by washing 2 X 5 min in 0.1% SDS, washing 5 X 1 min in MilliQ H2O, immersing 3 min in 95 degrees C MilliQ H2O, and drying by centrifugation (2000 rpm, 5 min, in 50 ml conical tube). Microarray hybridizations were run in the dark under HybriSlips hybridization covers (Grace Biolabs) in slide hybridization chambers (Corning) submerged in a 45 degrees C water bath for 16 h. Coverslips were floated off in 45 degrees C (1X SSC, 0.2% SDS), and arrays were washed 1 X 10 min in 45 degrees C (1X SSC, 0.2% SDS), 3 X 4 min in room temperature (0.1X SSC, 0.1% SDS), and 4 X 4 min in room temperature 0.1X SSC. Slides were dried by centrifugation as before. Fluorescent images of hybridized arrays were acquired immediately at 10 um resolution using ScanArray Express (PerkinElmer). The Cy3 and Cy5 cyanine fluors were excited at 543 nm and 633 nm respectively, and the same laser power (90%) and photomultiplier tube (PMT) settings were used for all slides in a study (PMT 75 Cy3, PMT 63 or 64 Cy5 for head kidney study). Fluorescent intensity data were extracted from TIF images using Imagene 5.5 software (Biodiscovery). Keywords: other
2004-02-11 | GSE1031 | GEO
