|
FOR IMMEDIATE
RELEASE
Wednesday, February 7, 2007
 Subscribe |
|
|
CONTACT:
Jennifer Wenger
301-496-7243 (NIDCD office)
240-398-1196 (during meeting)
|
News Advisory
Federally Funded Research on Cochlear
Implants, Genetics of Hearing Loss, Hair Cell Generation
Featured at ARO Conference in Denver
|
| What: |
Current research funded by the National Institute on Deafness
and Other Communication Disorders (NIDCD), one of the National
Institutes of Health, will be featured at the 2007 Midwinter
Meeting of the Association for Research in Otolaryngology (ARO). |
| When: |
February 10-15, 2007 |
| Where: |
Hyatt Regency Denver at Colorado Convention
Center, Denver, CO |
|
Additional Information:
Research conducted by NIDCD scientists include:
Mutation in Gene for Protein Radixin Causes Hearing Loss in
Humans
Radixin is an important protein that makes up the hair-like bundles on
top of sensory cells in the inner ear. Mutations of the gene RDX, which
encodes radixin, have been found to cause deafness in mice. In this study,
NIDCD researchers show evidence that two Pakistani families with mutations
in the RDX gene also exhibit hearing loss that is not associated with other
symptoms. The findings are published in the Jan. 16, 2007, issue of Human
Mutation. Title: Mutations of the RDX Gene Cause Nonsyndromic Hearing Loss
at the DFNB24 Locus (poster); Principal investigator: Thomas Friedman,
Ph.D., NIDCD.
Mutation that Causes Muenke Syndrome Severely Disrupts Inner
Ear Development in Mice
Muenke syndrome, a rare disorder that includes symptoms such as an abnormally
shaped skull, dwarfism, and hearing loss, is caused by a mutation in the
gene that encodes the protein Fgfr3. Fgfr3 is a receptor for fibroblast
growth factors, a protein family that signals nearby cells and kick-starts
activities that play a key role in embryonic development and growth, including
the development of hearing structures. In this study, researchers show
that mice missing the Fgfr3 gene exhibit a broad range of hearing abnormalities,
indicating that Fgfr3 regulates many developmental processes in the inner
ear. Title: Disruption of Fgfr3 Signaling Results in Defects in Cellular
Differentiation, Neuronal Patterning, and Hearing Impairment (poster);
Principal investigator: Matthew Kelley, Ph.D., NIDCD.
Signaling Proteins Help Ear's Sensory Cells "Know" Where to
Grow
The process by which an embryo develops the highly-specialized structures
necessary for hearing is still a mystery to scientists. A cascade of reactions,
kicked off by "signaling" proteins, is critical in directing the activities
of an embryo's ' dividing cells. One such family, the Wnt proteins, is
of particular importance in initiating reactions in a developing organism,
and a disruption of these reactions — caused by a mutation to one
or more Wnt genes — can result in developmental defects, diseases,
and cancer. NIDCD researchers describe how activities of three Wnt proteins
help determine the precise location and orientation of key sensory cells
in the inner ear. Title: Wnt Signaling in the Mammalian Cochlea (symposium
session); Principal investigator: Matthew Kelley, Ph.D., NIDCD.
Form of Cadherin 23 Linked to Deafness in Mouse Model Identified
Cadherin 23 is a large protein that composes sensory structures in both
the inner ear and retina. Researchers have yet to understand why some mutations
to the gene that encodes it, CDH23, cause only deafness while other mutations
cause deafness, blindness, and balance problems, as in Usher syndrome type
1. Cadherin 23 also comes in a variety of forms that may be expressed differently
in the retina and inner ear. NIDCD researchers examined cadherin 23's various
forms and found only one form to be expressed in the cochlea of a mouse
model, suggesting that the loss of function of this form is responsible
for the mouse's deafness. Title: Cadherin 23 Alternative Splice Variants:
Studying the Molecular Basis of Waltzer (poster); Principal investigator:
Thomas Friedman, Ph.D., NIDCD.
'Motor'-Protein-Containing Particles Help Rev Up Our Hearing
Scientists are exploring how tiny sensory structures in our inner ears,
called hair cells, are sensitive to faint sounds. Although all hair cells
help convert sound vibrations to electrical signals, inner hair cells relay
those signals to the brain, while outer hair cells are thought to play
a role in amplifying those signals. With the aid of an atomic force microscope,
NIDCD researchers have found that tiny particles packed inside the cell
membrane of the outer hair cell are composed of prestin, a 'motor' protein
known for causing a cell to change shape in response to an electrical signal.
The findings indicate that the membrane particles play a direct role in
the expansion and contraction of outer hair cells in response to electrical
signals and, most likely, the strengthening of those signals. Title:
Evidence for Prestin in 10 nm Particles in the Lateral Membrane Of Outer
Hair Cells: an Atomic Force Microscopic Study (podium session); Principal
investigator: Kuni Iwasa, Ph.D., NIDCD.
Research conducted by NIDCD-funded scientists include:
Are Two Cochlear Implants Better Than One?
More and more often, children with profound hearing loss are being fitted
with two cochlear implants — one for each ear — in hopes that
the child may better home in on a sound's source and gain a more realistic
listening experience. In this NIDCD-supported study, researchers assess
the sound-localization abilities of children (ages 5 to 14 years) wearing
two cochlear implants in comparison to one. The researchers found that
most of the children in the study located the source of a sound more accurately
when they were wearing two implants as opposed to one. In addition, the
team found that improvement in localization was seen only when the child
used two implants, but not when a single implant was used; also, the more
experienced the child was with two implants, the more adept he or she became
at localizing sound. Litovsky's research team is now investigating the
effects of bilateral implants on word learning and language acquisition
in young-implanted infants and toddlers. Title: Emergence of Localization
Abilities in Children with Sequential Bilateral Cochlear Implants (podium
session); Principal investigator: Ruth Litovsky, Ph.D., University of Wisconsin.
Inner Ear Stem Cells May Help Rewire Hearing
When hair cells are destroyed — by disease, injury, or aging — the
attached nerve cells, or neurons, that relay electrical signals to the
brain are often destroyed as well. In this NIDCD-funded study, scientists
demonstrate that stem cells from the inner ear of a mouse can be grown
into new neurons. Moreover, these neurons can form new connections with
hair cells and carry electrical signals. The findings may one day be used
in combination with other potential technologies for the treatment of hearing
loss, such as hair cell regeneration and more advanced cochlear implants.Title:
Neurons Derived from Inner Ear Stem Cells Form Synapses with De-Afferented
Hair Cells (poster); Principal investigator: Albert Edge, Ph.D., Harvard
Medical School.
Restoring the Sixth Sense
Scientists are currently working to develop an implant for some people
who lose their sense of balance. Just as the cochlear implant converts
sound to electrical signals that stimulate the auditory nerve, a vestibular
implant converts movements of the head into signals that stimulate the
vestibular nerve. Although this technology is still in the early stages
of development, two NIDCD-funded studies describe recent progress. The
first study describes a model that predicts current flow for different
electrode designs and a second study describes adjustments that would reduce
power consumption of an implant in humans. Titles:1)An Anatomically
Precise Finite Element Model Predicts Current Flow in Labyrinths Implanted
with a Multi-Channel Vestibular Prosthesis (poster) and 2)Paired Linear
Accelerometers Emulate Gyros to Reduce Power Consumption and Size for an
Implantable Multi-Channel Vestibular Prosthesis (poster); Principal investigator:
Charles C. Della Santina, M.D., Ph.D., Johns Hopkins School of Medicine.
New Tool Helps Scientists Tinker with the Ear's ‘Motor’
NIDCD-supported researchers have developed a computer model to study how
outer hair cells, sensory structures in the inner ear, help us to hear.
Hair cells convert sound vibrations into electrical signals that are relayed
to the brain. The membrane of the outer hair cell can act as a “motor” that
amplifies inner ear vibrations and improves the electrical signal by causing
the cell to lengthen and contract. If this membrane motor doesn't function,
hearing loss results. The computer model simulates the stretching of a
cell membrane, a lab technique researchers use to study a membrane's properties.
By observing the membrane in more vivid detail, scientists will better
understand the membrane-lodged motor that allows us to hear. Title:
Modeling Membrane-Cytoskeleton Interaction in the Cochlear Outer Hair Cell
Tether Pulling Experiment (poster); Principal investigator: William Brownell,
Ph.D., Baylor College of Medicine.
For more information about the Association for Research in Otolaryngology,
visit their Web site at www.aro.org.
NIDCD supports and conducts research and research training on the
normal and disordered processes of hearing, balance, smell, taste,
voice, speech and language and provides health information, based upon
scientific discovery, to the public. For more information about NIDCD
programs, see the Web site at www.nidcd.nih.gov.
The National Institutes of Health (NIH) — The Nation's Medical
Research Agency — includes 27 Institutes and Centers and is
a component of the U.S. Department of Health and Human Services. It is
the primary federal agency for conducting and supporting basic, clinical
and translational medical research, and it investigates the causes, treatments,
and cures for both common and rare diseases. For more information about
NIH and its programs, visit www.nih.gov.
|
