Transcriptional Regionalization of the Fruit Fly’s Airway Epithelium

Abstract

Although airway epithelia are primarily devoted to gas exchange, they have to fulfil a number of different tasks including organ maintenance and the epithelial immune response to fight airborne pathogens. These different tasks are at least partially accomplished by specialized cell types in the epithelium. In addition, a proximal to distal gradient mirroring the transition from airflow conduction to real gas exchange, is also operative. We analysed the airway system of larval Drosophila melanogaster with respect to region-specific expression in the proximal to distal axis. The larval airway system is made of epithelial cells only. We found differential expression between major trunks of the airways and more distal ones comprising primary, secondary and terminal ones. A more detailed analysis was performed using DNA-microarray analysis to identify cohorts of genes that are either predominantly expressed in the dorsal trunks or in the primary/secondary/terminal branches of the airways. Among these differentially expressed genes are especially those involved in signal transduction. Wnt-signalling associated genes for example are predominantly found in secondary/terminal airways. In addition, some G-protein coupled receptors are differentially expressed between both regions of the airways, exemplified by those activated by octopamine or tyramine, the invertebrate counterparts of epinephrine and norepinephrine. Whereas the OAMB is predominantly found in terminal airway regions, the oct3βR has higher expression levels in dorsal trunks. In addition, we observed a significant association of both, genes predominantly expressed in dorsal trunks or in primary to terminal branches branches with those regulated by hypoxia. Taken together, this observed differential expression is indicative for a proximal to distal transcriptional regionalization presumably reflecting functional differences in these parts of the fly’s airway system.

Testis single-cell RNA-seq reveals the dynamics of de novo gene transcription and germline mutational bias in Drosophila

“…We confirmed that the top 50 most highly enriched genes in cell clusters from each cell type (Supplementary file 1) were consistent with previous knowledge of marker genes. For instance, cup genes were biased toward late spermatids (Barreau et al, 2008), and Hsp23 and MtnA were highly expressed in the epithelial cells (Faisal et al, 2014; Michaud et al, 1997). Cell clusters from each developmental stage in the t-SNE map are near each other, suggesting that cell progression through spermatogenesis is a continuous process.…”

Expression analysis of octopamine and tyramine receptors in Drosophila

“…The differential expression of these receptors in different parts of the tracheal system is of great interest. Whereas Oamb is present in the terminal cells of the system, the TyrR expression is more pronounced in the primary branches that are more involved in gas transport rather than in gas exchange (Faisal et al 2014).…”

“…Tracheal expression in larvae is confined to the terminal cells that are closely attached to their respective target organs. Thus, they might have escaped manual preparation, because manual removal of the tracheal system is only possible for the larger parts, such as the dorsal trunks, primary and secondary branches (Faisal et al 2014). Distinct Oamb expression was also seen in the larval CNS ( Fig.…”

THE OCTOPAMINE RECEPTOR octß2R IS ESSENTIAL FOR OVULATION AND FERTILIZATION IN THE FRUIT FLY Drosophila melanogaster

“…The isolated RNA was free from contaminating DNA. cDNA‐synthesis, and PCR was essentially performed as already described (Faisal et al., ). In brief, cDNA‐synthesis was performed at 50°C for 60 min using a conventional oligo(dT) primer and SuperScript III reverse transcriptase (Life technologies, Darmstadt, Germany).…”