Role of visual and non-visual opsins in blue light-induced neurodegeneration in Drosophila melanogaster

Light plays a key role in regulating circadian rhythms and downstream physiological and behavioural functions. However, excessive exposure to artificial blue light (450-500 nm) can disrupt sleep, metabolism and neural integrity. Visual opsins mediate light-dependent signalling, but organisms also express non-visual opsins whose roles in blue-light-induced neural stress are not well understood.

We used Drosophila melanogaster knockout lines lacking either visual rhodopsin 1 (Rh1¹) or non-visual rhodopsin 7 (Rh7¹), alongside wild-type (w¹¹¹⁸) controls. Flies were continuously exposed to 488 nm blue light (1,320 lux; 1,120 μW·cm^-2) from egg deposition until they were 20 days old. DNA damage (γ-H2Av immunostaining) and vacuole formation were quantified in brain regions associated with sensory processing and neurotransmission.

Rh1¹ flies exhibited the highest levels of DNA damage and vacuolisation compared to the w¹¹¹⁸ and Rh7¹ lines. These effects were most pronounced in neuropils linked to sensory integration and synaptic activity.

Our findings demonstrate that the visual opsin Rh1 plays a predominant role in blue-light-induced DNA damage and neurodegeneration in the Drosophila central nervous system. This suggests that it is visual, rather than non-visual, opsins that mediate the neurotoxic effects of exposure to artificial light.