Functional analysis of ribosome heterogeneity during zebrafish embryogenesis
The process of embryogenesis involves coordinated changes in gene expression at both transcriptional and translational levels. In zebrafish, translation at early stages of embryo development relies on maternal, oocyte-derived ribosomes which are completely replaced by newly synthesized somatic ribosomes within 5 days after fertilization. Strikingly, preliminary data obtained in the Pauli lab suggest that maternal and somatic ribosomes diverge not only in rRNA content but also in protein composition and structure. Despite their heterogeneity, potential differences in the function of maternal and somatic ribosomes remain unknown. The dual ribosomal system present in zebrafish embryos thus provides a unique, powerful tool to address the controversial idea regarding the existence of ‘specialized ribosomes’ having distinct functions in translation.

In the proposed research project, I will investigate the regulatory potential of maternal and somatic ribosomes during zebrafish embryogenesis. To this end, I will analyze the translational activities of maternal and somatic ribosomes by determining substrate specificity, preferred mRNA features (sequence and length) and kinetics of translation. In addition, I will study the regulation of ribosomal degradation during embryogenesis in order to understand how and why the maternal ribosomal machinery is turned-over despite the high energy cost associated with making a new set of ribosomes. To accomplish these aims, I will combine diverse state-of-the-art methodologies, including in vivo and in vitro translation assays, biochemical ribosome purification techniques, SLAM-seq, and molecular and genetic studies in zebrafish. The results obtained have the potential to reveal novel regulatory mechanisms acting during vertebrate embryogenesis and will help to pinpoint the functional significance of heterogeneous ribosomes.