Genomic and biochemical characterization of a bacterial homolog of Selenoprotein N, a selenium-containing protein involved in congenital muscular dystrophy

Abstract

Selenoprotein N (SelenoN) is an endoplasmic reticulum resident transmembrane protein. Mutations in the SELENON gene were linked to different inherited forms of muscular diseases in Humans and the SelenoN protein was shown to be implicated in muscle development and regeneration. However, the catalytic function of SelenoN remains elusive. Bioinformatics search identified a gene homologous to SELENON in one single group of unclassified bacteria, Candidatus Poribacteria. This bacterium is a marine sponge symbiont, yet-to-be cultured. The thesis project has focused on the study of this bacterial ortholog of SELENON. Genomic analysis of different Poribacteria strains identified multicopy of SELENON gene, organized in tandem repeat or in operon with other genes. During my thesis I amplified one form of the SELENON gene and its operon-associated gene, and then expressed and purified the SelenoN protein to be used for functional analyses in the future. In the second part of the project, I studied the abundance and distribution of Poribacteria in the structures of the host sponge, Aplysina aerophoba, using fluorescence in situ hybridization technique, transmission electron microscopy, and immuno-gold labeling. These studies allowed us to get information about the sponge-bacteria interaction and the possible contribution of SelenoN to the symbiosis.