The study, led by assistant professor Kang Zhang, M.D., Ph.D., identified mutations in the PITX3 gene as a significant cause for congenital posterior polar cataracts in four unrelated families from three ethnic groups. According to Zhang, there are only two other gene mutations that have been identified for this type of cataract. Cataracts, or a clouding of the lens of the eye, are the most common cause of blindness in the world. In children, they can cause permanent damage and blindness if not treated appropriately.

While Zhang admits the surgery to remove cataracts in adults and children has become highly refined with low rates of complication, the best option he says is still prevention-especially outside of the United States.

"Cataract surgery has come a long way in the past 20 years. But, they are still the leading cause of blindness for every age group outside of the United States. In addition, surgery for this type of cataract has a much higher rate of complications. Identifying these gene mutations responsible for inherited cataracts could eventually save the vision of tens of thousands of children around the world," he said.

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"This finding is likely to be applicable to humans," Dr. Brinster said. He added that the same growth factors needed to culture the mouse stem cells would likely foster the growth of human spermatogonial cells as well as the cells of other mammals.

Currently, males who undergo chemotherapy that renders them infertile can store their semen so that it can be used at a later date, should they wish to father children. However, this approach results in a less than 50 percent success rate. Boys who are too young to provide a semen sample but who also need such chemotherapy treatments could also be helped by the new technique. Their spermatogonial stem cells could be cultured to increase their numbers, frozen, and reimplanted at a later date, restoring their fertility.

Moreover, the new culture technique would allow researchers to further investigate the potential of spermatogonial stem cells as a source for more versatile adult stem cells to replace diseased or injured tissue. The replacement tissue might be used to help patients with spinal cord injury, or disorders like Parkinson's disease or heart disease.

To conduct their study, Dr. Kubota and his colleagues began with mice that had been genetically altered to express green fluorescent protein, or GFP, which gives off a green light in the presence of a certain wavelength of light. During key stages of the experiment, tissue from the donor mice gave off a green light.

At the first step, the researchers could distinguish spermatogonial stem cells from the cells used to nurture them in lab cultures by the green light the spermatogonial stem cells gave off.

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