Chaperone-Mediated Autophagy (CMA) is a major pathway of lysosomal proteolysis recognized as a key player of the control of intermediary metabolism. To date, this cellular function is presumed to be restricted to mammals and birds, due the absence of an identifiable LAMP2A, a limiting and essential protein for CMA, in phylogenetically earlier species. However, we recently identified the existence of lamp2a in several fish species. In this context, we propose to define for the first time whether or not a CMA (or a CMA-like) process is ancestral to mammalian/bird species and determine the physiological relevance of the newly identified lamp2a homolog in fish with respect to that process. To address this issue, our strategy will be based on two complementary approaches. We will first characterize the repertoire and the expression of genes involved in CMA in a large number of fish species of agronomical, ecological and scientific interest. The growing number of fish species whose genome was completely sequenced as well as our advances in transcriptome analysis allows including in our study a large number of fish species and thus to provide a comprehensive picture of the “genetic structure” of CMA in fish. Secondly, we will decipher the physiological role of the newly identified lamp2a homolog in fish. Recently, we have generated knockout medaka (Oryzias latipes) for the corresponding lamp2a splice variant of the lamp2 gene, by using the genome-editing tool CRISPR-Cas9. We will therefore perform an exhaustive phenotyping of the lamp2a mutant medaka (at both histological, biochemical and molecular levels) in order to determine the metabolic changes induced by the deletion of lamp2a and the possible existence of a CMA activity in medaka. This project gathers two partners (UMR1419 NuMeA and UR1037 LPGP) with highly complementary expertise and skills in autophagy, fish genomics, gene editing technology and fish metabolism. A major aim of the team members is to put together and mutually benefit from complementary scientific as well as technical expertise of each one of the scientists involved in this project. The present consortium has thus the required complementarity and added value to successfully carry out the present project. The involvement of a PhD student in the present project will also strengthen the cohesion of the consortium. Overall this project, which does not present any particular risk, will demonstrate the existence of a CMA activity - not yet suspected - in fish. Addressing the role of lamp2a and the possible existence of CMA activity in fish will represent a major breakthrough in our understanding of the mechanisms involved in the control of metabolism in these species and provide the necessary fundamental knowledge to cope with the challenges of aquaculture. Moreover, the comparative functional genomics approach across phylogenetical distant species will provide an entirely new aspect of the autophagy research by exploring the extent to which the CMA network has diverged during vertebrate evolution. Finally, the national and international partnership network of the members involved in this project will guarantee an effective dissemination of the obtained results to both the aquaculture industry and the academic partners.