Transcription factors involved in retinogenesis are co-opted by the circadian clock following photoreceptor differentiation

Abstract

The circadian clock is known to regulate a wide range of physiological and cellular processes, yet remarkably little is known about its role during embryo development. Zebrafish offer a unique opportunity to explore this issue, not only because a great deal is known about key developmental events in this species, but also because the clock starts on the very first day of development. In this study, we identified numerous rhythmic genes in zebrafish larvae, including the key transcriptional regulators neurod and cdx1b, which are involved in neuronal and intestinal differentiation, respectively. Rhythmic expression of neurod and several additional transcription factors was only observed in the developing retina. Surprisingly, these rhythms in expression commenced at a stage of development after these transcription factors are known to have played their essential role in photoreceptor differentiation. Furthermore, this circadian regulation was maintained in adult retina. Thus, once mature photoreceptors are formed, multiple retinal transcription factors fall under circadian clock control, at which point they appear to play a new and important role in regulating rhythmic elements in the phototransduction pathway.

Identification and expression analysis of blue light receptor aureochrome in the harmful alga Heterosigma akashiwo (raphidophyceae)

“…DD condition) (Hwang et al, 1996;Laranjeiro and Whitmore, 2014). In the present study, Haaureo1 expression is rhythmic in LD condition, but the rhythmicity disappeared when the cells were transferred to DD condition (Fig.…”

The bHLH Transcription Factor NeuroD Governs Photoreceptor Genesis and Regeneration Through Delta-Notch Signaling

“…The absence of neurod expression from mature cones has been documented in embryonic and adult retinas, 14,39 although recent data indicate rhythmic, circadian expression in mature cones peaking in the light phase and in mature rods peaking in the dark phase. 96 Our data were all collected during the light phase, indicating that loss of neurod from newly regenerated cones results from regenerative mechanisms rather than circadian rhythmicity.…”

Conserved and Exapted Functions of Nuclear Receptors in Animal Development

“…PNR has been shown to interact with Rev-Erb, probably as a heterodimer [172]. Interestingly, PNR has been shown to exhibit circadian regulatory patterns in zebrafish, suggesting an evolutionarily-conserved PNR/Rev-Erb regulatory module associated with neuron differentiation and rhythmic patterns of gene expression [180]. Mutations in human PNR result in inherited retinal degeneration diseases [181].…”