Identification of autophagy genes in Ciona intestinalis: a new experimental model to study autophagy mechanism

Programmed cell death (PCD) is a mechanism implicated in many physiological and pathological processes. Until recently, apoptosis (self-killing) was the most largely studied mechanism of PCD but a growing number of laboratories are now interested in autophagy (self-eating). In the past few years data showing a tight link between both pathways has accumulated. Until now our laboratory used Ciona intestinalis, a chordate model in which in vivo experiments are possible, to study apoptosis. Recently, we showed that autophagy also occurs in the development of Ciona intestinalis and that the specific markers of both types of death are found in the same tissues and/or in the same cells. These results drove us to postulate that Ciona intestinalis can be a good model to study the link between apoptosis and autophagy. In this article, we conducted an in silico study of autophagy genes. We explored the genomes of Ciona intestinalis, of the second ascidian Ciona savignyi, and those of the classical biological models (Saccharomyces cerevisiae, Drosophila melanogaster, Caenorhabditis elegans and Homo sapiens) to extract and compare autophagy gene sequences. This genomic study was completed by an analysis of: (i) mRNA profile expression during development and (ii) the localization of Beclin protein by immunofluorescent staining in the Ciona intestinalis larvae. Taken together, the results allowed us to conclude that a complex autophagic machinery is present in Ciona intestinalis. Actually, the number of autophagy genes in Ciona intestinalis is comparable to the number of autophagy genes in human.