A precise regulation of presenilin expression is required for the sea urchin early development

Presenilins or PSENs homologues are widely expressed across eukaryotes. Two PSEN are expressed in humans where they play a crucial role in Alzheimer's disease (AD). Each PSEN can be part of the γ-secretase complex that has multiple substrates such as Notch or the amyloid precursor protein (AβPP) which gives the Aβ peptides composing the senile plaques during AD. PSENs also interact with various proteins independently of their γ-secretase activity. They can then be involved in numerous cellular functions, which makes their role in a given cell and/or organism complex to decipher. We settled the sea urchin embryo as a new model to study the role of PSEN. PSEN is present in unduplicated form and highly similar to that of humans. Our results suggest that its expression must be precisely tuned to control the course of the first mitotic cycles and the associated Cai transients, gastrulation execution and, probably in association with ciliated cells, the establishment of the pluteus. We suggest that it would be relevant to study the role of PSEN within the GRN deciphered in the sea urchin.