Dynamic expression of the genes GADD34 and CReP in zebrafish embryos

The unfolded protein response (UPR) is a complex cellular signaling pathway activated by the buildup of misfolded proteins in the endoplasmic reticulum. One specific branch of the UPR is the PERK pathway. When activated PERK promotes the phosphorylation of eIF2ɑ, leading to inhibition of global protein synthesis, preventing the cell from accumulating more misfolded proteins. Our project focuses on two genes which inhibit the PERK pathway, GADD34 and CReP. Both GADD34 and CReP bind to Protein Phosphatase 1 (PP1) to dephosphorylate eIF2ɑ and restore protein synthesis. For our experiments we utilizes zebrafish with loss-of-function mutations for either GADD34 or CReP. Either mutant or wild-type embryos were then subjected to pharmacological agents that induce ER stress such as thapsigargin. We then collected these embryos and subjected them to in situ hybridization, to analyze gene expression for GADD34, CReP or BIP. BIP serves as a positive control, a gene that is known to increase following ER stress. Previous studies in the lab have also demonstrated that both GADD34 and CReP increase in expression following stress induction. Understanding how these two similar genes are expressed following stress induction is critical to understanding the UPR. In our project we seek to determine if there is genetic compensation between GADD34 and CReP. For example, does GADD34 expression increase if CReP is mutated? These findings suggest that CreP and Gadd34 play distinct roles in stress response, with potential implications for understanding gene regulation under physiological stress.