NATIONAL INSTITUTES OF HEALTH FOR IMMEDIATE RELEASE July, 1998
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Contact: Gail Blatt (301) 496-7243 (301) 402-0252 (TTY) blattg@nidcd.nih.gov |
Gene Identified for a Disorder that Causes Deafness and Blindness
Scientists have identified a gene that causes Usher syndrome (US) type IIa,
the most common condition that involves disorders of both hearing and vision.
This finding is reported in the June 12, 1998, issue of the journal Science, by Dr. William J.
Kimberling, an investigator supported by the National Institute on Deafness
and Other Communication Disorders (NIDCD), and a team of scientists from
around the world.
The scientists described three different mutations in a gene called USIIa.
This gene was previously mapped to a location on chromosome 1 and is
associated with the syndrome. The three mutations were found in families
from three distinct geographic areas.
"In addition to potential treatment strategies, discovery of this gene may
provide insight into links between the auditory and visual developmental
pathways," stated Dr. James F. Battey, Jr., Director, NIDCD.
There are three types of Usher syndrome: Usher
syndrome type I (USI); Usher syndrome type II (USII); and, Usher syndrome
type III (USIII). USI and USII are the most common types of Usher syndrome. Together, they account for approximately ten percent of all cases of children who are born deaf. So far, at least nine different genetic locations have been identified as causing all types of Usher syndrome.
People with USI are profoundly deaf from birth and have severe balance
problems. Many of these individuals obtain little or no benefit from hearing
aids. All individuals born with USII have moderate to severe hearing
impairment and normal balance. Not all families with USII, however, have
the same gene for Usher syndrome. USIIb refers to USII families who do not
have this gene for Usher syndrome, but are born with moderate to severe
hearing impairment and normal balance. Although the severity of hearing
impairment varies, most children with USIIb perform well in traditional
classrooms and can benefit from hearing aids. Some children use speech to
communicate and depend, at least to some degree, on lip reading. Others use
sign language to communicate.
The vision problem associated with US, retinitis pigmentosa, is a
degeneration of the retina, the part of the eye that receives images. This
disorder is characterized by blind spots that begin to appear shortly after
the teenage years and progresses to blindness. This loss increases the
disability for individuals who depend heavily upon vision for communication.
The current emphasis in Usher syndrome research is to locate all of the genes
that cause the syndrome and identify the function of those genes. Locating
US genes and discovering the role they play will ultimately permit early
diagnosis, allow for genetic counseling to occur and may, eventually, provide
treatment options.
As the nation's focal point for research in human communication, the NIDCD
conducts and supports biomedical and behavioral research and research
training on normal mechanisms as well as diseases and disorders of hearing,
balance, smell, taste, voice, speech and language that affect 46 million
Americans.
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