Thus, genome-wide transcriptional profiling of over 6823 C. neoformans genes identified 476 genes with significant expression changes. Apart from genes involved in ergosterol biosynthesis (e.g. ERG11), genes involved in other important cellular functions,
such as those encoding the sterol homeostasis regulator Sre1 [20] or phospholipase B1 (Plb1) [21], were shown to be induced by FLC treatment. In addition, AFR1 was not found FLC-responsive, suggesting indirectly that this gene is responsible for long-term FLC adaptation in C. neoformans. Methods Strain, growth conditions and RNA isolation C. neoformans var. grubii serotype A strain (H99) was obtained from David S. Perlin [22], kept as 20% glycerol stock at -80°C and sub-cultured, as required, on YEPD (1% yeast extract, 2% peptone, 2% glucose) agar plates at 30°C. For RNA
PSI-7977 order isolation independent overnight cultures were diluted 1:100 in liquid YEPD and grown at 30°C or 37°C with agitation for 3 h to reach a density of 3 × 107 CFU/ml. At this point cultures were equally divided into two aliquots to which either FLC at a concentration of 10 mg/l or distilled water was added, followed by incubation at 30°C or 37°C for 90 min. After this treatment, cultures were centrifuged at 4°C and 5500 × g and total RNA was extracted as previously described [23]. Microarray design and preparation C. neoformans H99 microarrays were designed following the Agilent Belnacasan supplier Array Design guidelines (Earray platform) by first creating two separate sets of 60-base nucleotide probes for each of 6967 open reading frame (ORF) sequences as downloaded from the Broad Institute website http://www.broadinstitute.org/annotation/genome/cryptococcusneoformans/MultiHome.html. The probe selection was performed using the GE Probe Design Tool; probes were filtered following their base composition and distribution, cross-hybridization potential, and melting temperature, to yield final duplicate probes representing 6823 ORFs to cover 97.9% of the whole C. neoformans H99 genome. C. neoformans
custom arrays were manufactured in the 8 × 15k format by Agilent Technologies (Santa Clara, CA, USA). For quality control and normalization either purposes, 157 probes were selected randomly and spotted 10 times throughout each array. Standard controls (Agilent Technologies) were also included. cRNA synthesis, labeling and hybridization RNA sample preparation was performed on three biological triplicates of H99 cells grown at 30°C, as described above. Prior to the labeling/amplification step, purity and integrity of the RNA samples were determined using Agilent RNA 6000 Nano LabChip kit on the Agilent 2100 bioanalyzer (Agilent Technologies). Agilent’s buy BB-94 One-Color Quick Amp Labeling kit (Agilent Technologies) was used to generate fluorescently labeled cRNA probes according to the manufacturer’s instructions.