Approches transcriptomiques dans l’étude de la fibrose kystique
Biotechnical advances have allowed a large number of molecular mechanisms to be identified, and have also underlined the complexity of gene regulation. Nonetheless, we still only have a partial understanding of cellular homeostasis. Even with our current knowledge, molecular dysfunctionality observed in genetic illnesses such as cystic fibrosis remain largely misunderstood, prohibiting us from developing efficient treatments. Cystic fibrosis is caused by a mutation of the CFTR (cystic fibrosis transmembrane conductance regulator) gene which codes for a chloric transmembrane channel. The most frequent mutation (ΔF508) causes the unfolding of the protein and its retention in the endoplasmic reticulum. This absence of a functional CFTR to the membrane has an impact on the ionic homeostasis and the hydration of the respiratory mucus. Consequently, the mucociliary clearance is disrupted, which leads to chronic infection and excessive inflammation - two fundamental factors of CF’s physiopathology. Inflammation plays a key role in the evolution of the illness and despite many studies on this subject, the regulation of the inflammatory process remains a mystery and CFTR’s role is not well established. Additionally, since the physiopathology cannot be explained by mutation alone, several authors suggest the importance of other factors (genetic and/or environmental) which are factors in the clinical picture of the illness. In our study, we use microarray technology to evaluate the transcriptional state of an epithelial lung cell issued from a human with cystic fibrosis. Initially, our analysis identifies 128 inflammatory genes which are over-expressed in the cystic fibrosis cells versus non-cystic fibrosis cells, showing several inflammatory gene families such as cytokines or calgranulins. An analysis of the publications and annotations of these transcripts suggests that their modulations depend upon the cascade of NF-κB and/or signalling pathways associated with interferons (IFN). In other words, their modulations could be associated with epigenetic modifications of their chromosomal loci. Secondly, we study the transcriptional activity of an epithelial lung cell issued from a human with cystic fibrosis in the presence of DMNQ, a cytotoxic molecule. Our goal is to identify the biological processus which are disturbed by the mutation of the CFTR gene in the presence of oxidative stress. Based on a canonical redundancy analysis, we identify 60 genes associated with cell death and their modulation in our study explained by the combined effect of mutation and oxidative stress. By measuring the activity of caspase 3/7, an effector of apoptosis (programmed cell death), we see that the cells containing the mutation ΔF508 could present a problem with apoptosis. Our transcriptomic data suggest that decreased activity of the MAPK cascade and over-expression of anti-apoptotic genes would be a factor in apoptotic imbalance.
ΔF508 inflammation Cystic fibrosis microarray inflammation apoptosis canonical redundancy analysis