Live Visualization of Endoplasmic Reticulum Redox Potential in Zebrafish Embryos Reveals Region-Specific...

Area of Science:

• Cellular biology
• Organelle redox biology
• Zebrafish model systems

Background:

• Redox homeostasis is crucial for cellular function and implicated in diseases like diabetes and neurodegeneration.
• Previous research indicated a more oxidizing Endoplasmic Reticulum (ER) environment compared to the reducing cytosol.
• The universality of ER redox potential across different organisms and systems remains largely unexplored.

Purpose of the Study:

• To investigate the physiological redox potential in the ER and cytosol of live zebrafish embryos.
• To determine the conservation and variability of ER redox states in a vertebrate model.
• To characterize ER-targeting signal sequences in zebrafish.

Main Methods:

• Development of transgenic zebrafish lines expressing redox-sensitive green fluorescent protein (roGFP) sensors targeted to the ER and cytosol.
• In vivo imaging and measurement of redox states in developing zebrafish embryos.
• Confirmation of findings using an alternative ER-targeted sensor (roGFPiE) and assessment of ER redox resilience to proteostasis perturbations (tunicamycin, Azetidine-2-carboxylic acid).

Main Results:

• The ER in developing zebrafish embryos displayed a more reduced redox state than anticipated in specific tissue regions, including parts of the brain.
• This redox heterogeneity was confirmed across different transgenic lines and sensor types.
• The ER redox state demonstrated resilience to proteostasis challenges, with only minor alterations observed upon tunicamycin treatment.

Conclusions:

• The study reveals unexpected heterogeneity and reduced redox states within the ER of developing zebrafish.
• These findings challenge the generalized model of a uniformly oxidizing ER environment.
• Further research is needed to redefine biological understanding of ER redox homeostasis and its implications.