Quality assessment of cross-species hybridization of CHO transcriptome on a mouse DNA oligo microarray

DNA microarray technology has been widely utilized for species with extensive genome sequence information available. Given the limited genomic information pertaining to Chinese hamster ovary (CHO) cell line, crossspecies hybridization using mouse microarrays provides a viable alternative. In this study, the utility of mouse Affymetrix microarrays for transcriptome profiling in CHO cells was assessed by hybridizing identical sets of cRNA samples from CHO cells on both mouse and CHO Affymetrix microarrays. Expression level measured by probe sets for orthologous transcripts on the two microarrays was compared. Only a fraction of the orthologous probes which detected expression calls in same species hybridization were similarly called present in cross species hybridization. In further analysis at the 25-mer probe level, it was revealed that specific hybridization signals were detectable by the subset of mouse probes that have a high degree of homology to the corresponding CHO sequences. The feasibility of cross species hybridization for quantifying the extent of differential expression was assessed by comparing transcript levels of CHO cells cultivated with and without sodium butyrate. While same species hybridization gave consistent degree of differential expression calls in replicated runs, a much inferior ability in quantifying differential expression was seen with cross species hybridization. Our results demonstrate that through detailed analysis of homology at the probe pair level, a subset of probes on existing mouse Affymetrix oligo-array can be used successfully for transcriptome profiling of CHO cells.