Light exposure vital for developing eye

Developmental Biology

Research published in Nature concludes that light exposure during pregnancy is fundamental for normal eye development in the foetus. Research led by scientists at Cincinnati Children’s Hospital Medical Centre and the University of California, San Franciso (UCSF) , demonstrated that the activation of a newly described light-response pathway must happen during pregnancy to activate the developmental steps that produce a normal, health eye.

“This fundamentally changes our understanding of how the retina develops,” said study co-author Richard Lang from the Division of Paediatric Ophthalmology at CCHMC. “We have identified a light-response pathway that controls the number of retinal neurons. This has downstream effects on developing vasculatures in the eye and is important because several major eye diseases are vascular diseases.”

The team unexpectedly discovered that photons of light activate a protein called melanopsin directly in the foetus – rather than the mother – to help initiate normal development of retinal neurons and blood vessels in the eye.

The researchers conducted several experiments in laboratory mouse models that allowed them to identify the light-response pathway’s specific mechanism and function.

Groups of mice were reared either in the dark or in a normal day-night cycle at the start of late gestation to observe the comparative effects on ocular vascular development. The researchers also mutated a gene called Opn4 that produces melanopsin in another group of mice.

Both the mice reared in the dark and those with mutated Opn4 exhibited abnormal retinal blood vessel growth.

The researchers suggest that one purpose of this light-dependent pathway is to supress blood vessel development in the retina. While these vessels are critical to retinal neurons, which require large amounts of oxygen to form and function correctly, if retinal vessels grow unchecked, this continue expansion can put intense pressure on the developing eye causing damage and blindness in severe cases.

Melanopsin is present in both mice and humans during pregnancy. Lang said the research team will continue to study how the light-response pathway could influence the susceptibility of pre-term infants to retinopathy of prematurity.

Sujata Rao, Christina Chun, Jieqing Fan, J. Matthew Kofron, Michael B. Yang, Rashmi S. Hegde, Napoleone Ferrara, David R. Copenhagen, Richard A. Lang. 2013. A direct and melanopsin-dependent fetal light response regulates mouse eye development.  Nature, 2013; DOI: http://dx.doi.org/10.1038/nature11823