Summary
This doctoral thesis characterizes brain photoreceptors in the marine annelid Platynereis dumerilii, revealing conserved ciliary photoreceptor lineages that regulate circadian locomotor activity through melatonin release — a mechanism with deep evolutionary roots in Bilateria. The findings illuminate ancestral functions of opsin-based phototransduction and melatonin signaling relevant to understanding how light-dark cycles entrain circadian clocks across animal species, including humans.
Key Findings
- Ciliary photoreceptors in the Platynereis brain express c-opsin1, bmal, and hiomt (melatonin synthesis marker), indicating these cells form a circadian center homologous to the vertebrate pineal complex.
- Larval ciliary locomotion follows a circadian rhythm with higher speeds during daytime and lower speeds at night, consistent with melatonin mediating nighttime suppression of locomotor activity.
- Melatonin receptors are exclusively expressed in prototroch ciliated locomotor cells, and melatonin specifically decreases prototroch cell activity, linking photoreceptor output directly to behavioral circadian rhythms.
- Knockdown of the transcription factor Rx resulted in complete loss of ciliary photoreceptors and extensive brain developmental disruption, establishing Rx as a conserved regulator of photoreceptor lineage identity.
- Hierarchical clustering showed that Platynereis serotoninergic ciliary photoreceptors and canonical ciliary photoreceptors are the cell types most similar to vertebrate pineal and retinal photoreceptors, respectively, supporting conserved evolutionary origins.
Categories
The Science of Light: Investigates the molecular biology, evolutionary origins, and functional roles of ciliary-type photoreceptors expressing c-opsin and melatonin synthesis markers in brain circadian centers.
Sleep & Circadian Health: Demonstrates that brain photoreceptors drive circadian rhythms in locomotor activity via melatonin signaling, with phototransduction resetting the clock output.
Author(s)
MA Tosches
Publication Year
2013
Number of Citations
2
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