Tissue-enriched expression profiles in Aedes aegypti identify hemocyte-specific transcriptome responses to infection

We present a microarray study of hemocyte-enriched transcriptome in Aedes aegypti. We directed our efforts to critically assess the transcriptomic features distinctive of hemocytes, and discussed our findings in relation to infection-responsive genes and immune-relate gene families. Specifically, our analysis examined how tissue-enriched expression patterns change with the immune status of the host, and resolved patterns of transcriptional change unique to hemocytes from those that are likely shared by other immune responsive tissues. We profiled the transcriptome of circulating hemocytes and the remaining carcass in both naïve and bacteria-challenged adult female mosquitoes. To examine transcriptional changes associated with hemocoelic infection in distinct tissue samples, we adopted a linear model-based framework for analyzing dual-channel hybridizations (i.e., two-color microarrays) as separate single-channels (Smyth, 2004). The biological and technical dye-swap replicates of the 2×3 experimental conditions consisted of forty separate single-channel intensity profiles. For each biological replication, hemolymph perfusate and the remaining carcass were collected as paired samples at 24 hours post intra-hemocoelic injection of either Escherichia coli or Micrococcus luteus overnight culture (0.5 µl) in parallel with an age-matched naïve group from the same cohort. Concomitantly-collected hemocyte and carcass samples were co-hybridized on microarrays. Material for each experimental condition was generated from three (bacterial challenge) or four (naïve) separate generations of mosquitoes, and four separate microarray hybridizations using carcass and hemocyte material were performed. The first hybridization compared naïve and E. coli-challenged conditions, the second compared naïve and M. luteus-challenged conditions, and the third and fourth compared all three conditions.