The researchers said retinas in newborn mice appear perfectly fine without any help from tiny bits of genetic material called microRNAs except the retinas don't work.

Researchers at the University of Florida and the Italian National Research Council say their study is the first to focus on the effects of the absence of microRNAs in the mammalian eye. They said they found a gradual structural decline in retinas that lack microRNAs. That's in sharp contrast to the immediate devastation that occurs in limbs, lungs and other tissues that develop without microRNAs.

"MicroRNAs are behaving differently in the nervous system than they are in other bodily tissues," said University of Florida Assistant Professor Brian Harfe. "Judging by our previous studies in limb development, I was expecting to see lots of immediate cell death in the retina. I was not expecting a normal-looking retina in terms of its form. It would be something like finding a perfectly formed arm at birth that just did not work."

The study is reported in the Journal of Neuroscience.