Immune related genes in Holothuria glaberrima: Intestinal gene profiling in LPS activation and regeneration.

摘要

The intestine is an opening to the external world. Although its primary function is nutrient absorption, it must serve as a barrier against invading microorganisms and a home for commensal bacteria. Thus, it relies on a complex set of immune reactions that maintains a balance between tolerance and recognition/destruction. The holothurian intestine presents an extra feature, the ability to regenerate following evisceration. Here also, the immune system seems to play a role. Several questions arise from these observations: What molecules compose the immune repertoire of the holothurian? Are these molecules expressed in the intestine? And how are they related to the process of regeneration?;The research presented in this thesis aims at answering these questions. In order to do this, I have used state-of-the-art molecular tools to identify and determine the intestinal expression profiles of immune relevant genes. First, a screening of three cDNA libraries from holothurian normal and regenerating intestines resulted in the identification of 22 putative immune genes. Cells of the immune system, the coelomocytes, were shown to express at least ten of these genes, and five of them were induced by lipopolysaccharides (LPS) challenge. Second, microarray analyses were performed to determine which of the over 7000 sequences were differentially expressed in the intestine of animals challenged with LPS. Fifty sequences were found differentially expressed but only 2 of them were genes associated with immune functions. Third, the differential expression profiles during regeneration were determined for all these immune-relevant sequences. Close to 90% of these genes were found to be differentially expressed during the first week of regeneration.;With this work, I described, for the first time, a group of immune-associated genes in the class Holothuria. I showed that some of them respond differentially to an LPS challenge in coelomocytes and intestines. Finally, I demonstrated that several of these molecules seem to play a role during intestinal regeneration judging by their expression profiles. The discovery and characterization of these holothurian genes will prove useful to determine parallels with similar processes of immune activation and regeneration in other organisms including humans.