Vision requires vascular balance
During postnatal eye development, an embryonic network of hyaloid blood vessels regresses in a process that requires precise timing to allow mice to develop high-acuity vision.
The researchers demonstrate that eye development depends on light responses in the retina that are controlled by Opsin 5, a protein expressed in a subset of retinal ganglion cells. Opsin 5 and the neurotransmitter dopamine—which promotes blood vessel regression—work in unison to regulate vascular development.
The team developed a line of OPN5 knockout mice to show its effect. Without Opsin 5, dopamine levels rose within the vitreous (the clear, gel-like substance in the eye). This caused hyaloid blood vessels to regress very quickly, hindering normal eye development.
Light therapy restored the balance
The researchers also showed that 380-nanometer violet-colored light normally activates signaling via Opsin 5. This suppressed dopamine levels and produced other molecular changes in the eye that produced normal timing and appropriately balanced vascular development.
"From an evolutionary perspective, it may not be surprising that biological pathways use 380 nm light, because it is present in the natural sunlight spectrum,” Nguyen says. “However, artificial lighting systems that do not produce this wavelength may be insufficiently activating this response."
Lang says more preclinical study is required before these mouse-based findings can be evaluated in a human clinical trial.
Nguyen MT, Vemaraju S, Nayak G, Odaka Y, Buhr ED, Alonzo N, Tran U, Batie M, Upton BA, Darvas M, Kozmik Z, Rao S, Hegde RS, Iuvone PM, Van Gelder RN, Lang RA. An opsin 5-dopamine pathway mediates light-dependent vascular development in the eye. Nat Cell Biol. 2019 Apr;21(4):420-429.