This studied is designed to discover the genes that cause hearing impairment. More
precisely, this study aims to map and clone genes that are important for the development and
maintenance of the anatomy and physiology related to hearing (auditory system).
The study will begin by finding large families who have members with hearing impairment.
Once families are found, members with and without hearing impairment will be evaluated by an
audiologist and a clinician (doctor). An audiologist, is a person trained in evaluating,
habilitating, and rehabilitating people with disorders of hearing function. The clinician's
responsibility is to examine the patients and check for other signs and symptoms related to
Finding the gene for hearing impairment requires:
1. <TAB>DNA samples of hearing impaired family members, taken from standard blood samples.
2. <TAB>DNA samples of members of the family without hearing impairment, taken from
standard blood samples.
3. <TAB>Results of hearing tests conducted by the audiologist for all participants.
Once all members of the family are evaluated researchers can create a pedigree. A pedigree
is like a family tree that charts members of a family with a genetic disorder, like hearing
impairment. Pedigrees are used to determine the mode of inheritance of the gene responsible
for a particular condition.
Finally, researcher intend on using all the information gathered as well as methods for
genetic analysis to map out the location of the gene. Patients participating in this study
will not directly benefit from its research, but scientific understanding achieved may help
researchers better understand the auditory system and someday prevent deafness.<TAB>
The objective of this research project is to map and clone genes that are important for the
normal development or maintenance of the auditory system. One strategy for identifying some
of the genes important for auditory processes is to ascertain large families each with
several hearing impaired individuals. Initial contact will be made by family physicians,
audiologist, supervisors in schools for the hearing impaired, and directly by the principal
investigators during surveys of schools for the deaf and visits with hearing impairment
self-help groups. Members of a family will be evaluated by an audiologist, and instances of
hearing impairment will be documented and categorized. A clinician would then examine
hearing impaired and unaffected members of the family for the presence of other clinical
features so as to distinguish between nonsyndromic and syndromic forms of hearing
impairment. Pedigrees of these families will be analyzed to determine the mode of
inheritance of the hereditary hearing impairment segregating in each family. Families will
be ascertained through audiologists and other clinicians, genetics clinics, schools for the
hearing impaired and through linguists and medical anthropologists who study unique sign
languages and the sociology of communities with a high proportion of hearing impaired
individuals. The mutated gene will then be genetically mapped by a linkage or association
based strategy, using DNA typing of highly polymorphic genetic markers distributed across
the human genome.
- INCLUSION CRITERIA:
It is anticipated that, in most cases, patients will be recruited whose disorders do not
appear to be syndromic (i.e. are not associated with extra-auditory or extra-vestibular
We seek subjects who are members of large families with multiple individuals affected with
a hearing disorder. Sporadic cases will occasionally be included when the phenotype has
features suggestive of mutations in one or a few particular candidate genes, since
autosomal or X-linked recessive inheritance can appear to be sporadic.
If there is evidence of genetic homogeneity, small families can be pooled for linkage
analysis, or a combination of large and small families can be pooled.
Subjects of any ethnic background, gender, age, sexual orientation, or health status will
Patients will be excluded when their hearing or vestibular dysfunction are known to be
caused by a nongenetic etiology such as trauma, infection, metabolic or immunologic
disorders, or exposure to ototoxic agents such as noise or aminoglycoside antibiotics.