Temperature-dependent expression of melanopsin (opn4) reveals a non-canonical response in adult zebrafish ( Danio rerio )

This is the authors' abstract. We don't add key points for this paper.

Zebrafish (Danio rerio) experience daily temperature variations that align with light–dark cycles. Opsins mediate vision and light perception and can also act as thermosensors. We examined whether low temperature (23°C) modulates melanopsin gene expression in light-exposed and non-exposed organs. At 23°C, the brain showed strong upregulation (~10×) of opn4x1 and opn4x2 during the light phase, and widespread downregulation (~6×) of almost all melanopsin genes during the dark phase. In the eye, opn4m1, opn4m2, and opn4m3 were reduced (~3×) during light phase. Liver melanopsins displayed different expression patterns at 23°C, with up- and downregulation (~10×). All five muscle melanopsins were downregulated (2–10×) at 23°C during the light phase, and opn4m3, opn4x1, and opn4x2 during the dark phase (2–5×). In addition to the photoperiod, we concluded that low temperature also affects melanopsin expression in adult D. rerio, in an organ- and daily time-dependent manner.