Researchers discover elusive gene that causes form of blindness from birth

Researchers from the Massachusetts Eye and Ear Infirmary, The Children's Hospital of Philadelphia, Loyola University Chicago Health Sciences Division and their collaborators have isolated an elusive human gene that causes a common form of Leber congenital amaurosis (LCA), a relatively rare but devastating form of early-onset blindness.  The new LCA gene is called NMNAT1.  Finding the specific gene mutated in patients with LCA is the first step towards developing sight-saving gene therapy.

LCA is an inherited retinal degenerative disease characterised by reduced vision in infancy. Within the first few months of life, parents usually notice a lack of visual responsiveness and unusual roving eye movements known as nystagmus.   LCA typically involves only vision problems, but can be accompanied by disease in other organ systems in a minority of patients. LCA is a common reason children are enrolled in schools for the blind.

''The immediate benefit of this discovery is that affected patients with mutations in this new LCA gene now know the cause of their condition,'' said Eric Pierce, M.D., Ph.D., co-senior author and director of the Ocular Genomics Institute at Mass. Eye and Ear. "Scientists now have another piece to the puzzle as to why some children are born with LCA and decreased vision. The long-term goal of our research is to develop therapies to limit or prevent vision loss from these disorders."

NMNAT1 is the 18th identified LCA gene. The gene resides in a region that was known to harbor an LCA gene since 2003, but the specific disease gene has been undiscovered until now. These findings will be published on July 29 in the online edition of Nature Genetics.

To identify NMNAT1, scientists performed whole exome sequencing of the family of two siblings who initially presented for evaluation of LCA but who had no mutations in any of the known LCA genes.  Being seen by a multi-disciplinary team that took the case from careful clinical characterization to genetic testing to the research laboratory was an essential ingredient for success.

"By using whole exome sequencing, we found a mutation in a gene that no one could have predicted would be associated with LCA," said Dr. Pierce.