Summary
This thesis investigates the roles of melanopsin-expressing cells in zebrafish circadian photoentrainment and direct light responses (masking), finding that retinal ganglion cells contribute to masking independently of opn4xa-driven photosensitivity. Unlike in mammals, neither retinal photoreception nor opn4xa-mediated melanopsin signaling appears necessary for circadian photoentrainment in zebrafish larvae, highlighting fundamental species differences relevant to understanding light-biology pathways.
Key Findings
- opn4xa is expressed in a subpopulation of pineal projection neurons (PNs) in zebrafish, conferring blue and green light sensitivity in LIGHT ON mode
- Retinal ganglion cells (RGCs) are involved in locomotor masking and responses to light transitions, but independently of opn4xa photosensitivity
- opn4xa-/-, lakritz-/- (RGC-absent), and double mutant zebrafish larvae showed no defect in photoentrainment to a white light pulse at the beginning of the night, suggesting retinal and melanopsin-based photoreception are not required for circadian entrainment in larval zebrafish
- Five melanopsin genes exist in zebrafish (versus one in mammals); opn4xa and opn4b are expressed in larval RGCs
Categories
The Science of Light: Investigates melanopsin gene variants (opn4xa, opn4b) and ipRGC-equivalent cells in zebrafish, comparing phototransduction mechanisms across vertebrates including role in circadian entrainment and locomotor masking.
Sleep & Circadian Health: Examines photoentrainment mechanisms and direct light effects on locomotor activity rhythms in a diurnal vertebrate model, with implications for understanding circadian light input pathways.
Author(s)
C Chaigne
Publication Year
2022
Related Publications
The Science of Light
- Phototransduction by retinal ganglion cells that set the circadian clock
- Color appearance models
- The mammalian circadian timing system: organization and coordination of central and peripheral clocks
- Diminished pupillary light reflex at high irradiances in melanopsin-knockout mice
- Melanopsin is required for non-image-forming photic responses in blind mice
Sleep & Circadian Health
- Phototransduction by retinal ganglion cells that set the circadian clock
- The mammalian circadian timing system: organization and coordination of central and peripheral clocks
- The two‐process model of sleep regulation: a reappraisal
- Melanopsin is required for non-image-forming photic responses in blind mice
- Strange vision: ganglion cells as circadian photoreceptors