AUTHOR=Drago Laura , Pennati Alessandro , Rothbächer Ute , Ashita Ryuji , Hashimoto Seika , Saito Ryota , Fujiwara Shigeki , Ballarin Loriano 

TITLE=Stress granule-related genes during embryogenesis of an invertebrate chordate

JOURNAL=Frontiers in Cell and Developmental Biology

VOLUME=Volume 12 - 2024

YEAR=2024

URL=https://www.frontiersin.org/journals/cell-and-developmental-biology/articles/10.3389/fcell.2024.1414759

DOI=10.3389/fcell.2024.1414759

ISSN=2296-634X

ABSTRACT=Controlling global protein synthesis through the assembly of stress granules represents a strategy adopted by eukaryotic cells to face various stress conditions. TIA 1-related nucleolysin (TIAR), tristetraprolin (TTP), and Ras-GTPase-activating protein SH3-domain-binding protein (G3BP) are key components of stress granules, allowing the regulation of mRNA stability, and thus controlling not only stress responses but also cell proliferation and differentiation. 
In this study, we aimed at investigating the roles of tiar, ttp, and g3bp during embryogenesis of the solitary ascidian Ciona robusta under both physiological and stress conditions. We carried out CRISPR/Cas9 to evaluate the effects of gene knockout on normal embryonic development, and gene reporter assay to study the time and tissue specificity of gene transcription, together with whole-mount in situ hybridization and quantitative real time PCR. To induce acute stress conditions, we used iron and cadmium as “essential” and “non-essential” metals, respectively. 
Our results highlight, for the first time, the importance of tiar, ttp, and g3bp in controlling the development of mesendodermal tissue derivatives during embryogenesis of an invertebrate chordate.

Scope statement
Tunicates occupy the key phylogenetic position of vertebrate sister group: this justifies the increasing interested towards these marine invertebrates which can contribute to a better understanding of biological processes difficult to study in vertebrates. Ascidians are sessile tunicates present in all the seas and oceans. In previous studies, we demonstrated the presence of tiar, ttp, and g3bp, three genes involved in stress granules formation, in both solitary and colonial ascidians. In the colonial species B. schlosseri and B. primigenus, we also demonstrated their involvement in non-embryonic development. With the present study, we investigated the transcriptional activity of the above genes during embryogenesis of the solitary ascidian Ciona robusta under both physiological and stress conditions. Using CRISPR/Cas9, we evaluated the effects of the gene knockout on embryonic development. In addition, we used gene reporter assay, whole-mount in situ hybridization and quantitative real time PCR to study time and tissue specificity and to quantify gene transcription. Results can help us to add new information on the evolution of stress granules in chordates.