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Andrew J. Griffith, Ph.D., M.D.

Andrew J. Griffith, M.D., Ph.D.

Otolaryngology Branch

Molecular Biology and Genetics Section
Otolaryngology Branch

5 Research Court, 1A-13
Rockville, MD 20850
Phone: (301) 496-1960
Fax: (301) 402-7580

Dr. Griffith received M.D. and Ph.D. degrees from Yale University.  He completed an Otolaryngology-Head and Neck Surgery residency at the University of Michigan, where he also received fellowship training in the laboratory of Dr. Miriam Meisler in the Department of Human Genetics.

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Otolaryngology Branch

Dr. Griffith and Anne Madeo examine a CT scan.

Dr. Griffith examines a CT scan

Basic molecular biology and genetic research is carried out in the Molecular Biology and Genetics Section. Audiology Unit research activities include audiological and vestibular assessment of human subjects participating in clinical research protocols of the Otolaryngology Branch, the NIDCD, or other NIH Institutes and Centers.

Dr. Hung Jeff Kim is responsible for Neuro-Otology evaluations, treatment, and research. Ms. Julie Muskett is the Genetic Counselor for the NIDCD. Her responsibilities include coordinating clinical research protocols in the Otolaryngology Branch and the Laboratory of Molecular Genetics, and genetic counseling of subjects participating in NIDCD research studies.

Subjects Needed for Research Studies

The Otolaryngology Branch is seeking research subjects from families to participate in research studies in the following areas:

MRI images of the right temporal bone.

Axial T2-weighted fast spin echo MRI images of the right temporal bone showing enlargement of the endolymphatic system (known as EVA) when visualized on CT scans.


Hung Jeff Kim, M.D., Staff Neuro-Otologist (Send e-mail | View photo)
Julie Muskett, M.S., Genetic Counselor (Send e-mail | View photo)
Zelia Pulliam, Office Manager (Send e-mail | View photo)


Molecular Biology and Genetics Section

Illustration: View of the mammalian auditory system showing: cochlea, vestibular apparatus, inner hair cell, scala media, tectorial membrane, outer hair cells, cochlear ganglion, organ of Corti, basilar membrane, and stria vasicularis.

Schematic illustration of the mammalian auditory system (from Griffith and Friedman, Nature Genetics, 1999). View larger image.

Research Statement

Our laboratory identifies and characterizes genes, molecules, and mechanisms underlying hearing and hereditary hearing loss. We use molecular biologic and genetic approaches, human and mouse models, as well as heterologous cell culture expression systems. A variety of techniques—including in situ hybridization, immunohistochemistry, RT-PCR, Western and Northern blotting, and immunoprecipitation—are used to analyze gene and protein expression, function, and interactions.

Current Areas of Interest

We identified a novel gene, TMC1, which underlies dominant DFNA36 and recessive DFNB7/B11 deafness in humans. Dominant and recessive mutations in the mouse Tmc1 gene underlie deafness in the Beethoven (Bth) and deafness (dn) mouse mutants, respectively, which exhibit rapid degeneration of the neurosensory hair cells of the cochleae. TMC1 protein has no sequence similarities to proteins or domains of known function, but has six transmembrane domains whose topologic organization suggests a role as an ion channel or transporter. There are seven other members of the mammalian TMC gene family, and we are using mutant mouse models to identify the function(s) of Tmc1 and these other Tmc genes.

Illustration of the TMC1 gene

Schematic illustration of TMC1 showing predicted transmembrane topology and human and mouse mutations causing deafness. View larger image.

A second project is the molecular genetic analysis of human hearing loss associated with enlargement of the vestibular aqueduct (EVA). EVA is the most commonly observed inner ear malformation in children with hearing loss. In many cases EVA is associated with mutations in the Pendred syndrome gene PDS/SLC26A4, which encodes an integral membrane protein that is thought to transport or exchange chloride, iodide, bicarbonate, or other bases in the inner ear. Some cases of EVA are caused by other genetic or environmental factors, alone or in combination with a single SLC26A4 mutation. We are attempting to identify those other factors as well as the molecular basis for observed SLC26A4 genotype-phenotype correlations.

A third project is positional cloning of the mouse Twirler mutation, which causes inner ear malformations in heterozygous Tw/+ mice, and cleft lip and palate in homozygous Tw/Tw mice. Tw/+ mice exhibit circling behavior and hearing loss due to disruption of the vestibular and auditory functions of the inner ear.

Lab Personnel

Yoshiyuki Kawashima, M.D., Visiting Scientist (Send e-mail | View photo)
Kiyoto Kurima, Ph.D., Staff Scientist (Send e-mail | View photo)
Valentina Labay, Ph.D., Visiting Fellow (Send e-mail | View photo)
Xing Li, Ph.D., IRTA Fellow (Send e-mail | View photo)
Kelly Monahan, B.S., Postbaccalaureate IRTA Fellow (Send e-mail | View photo)

Lab Photos

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Audiology Unit

Research Statement

The primary research interest of the Audiology Unit is the pathogenesis and manifestations of hereditary hearing and balance disorders, and the correlation of distinctive auditory and vestibular phenotypes with underlying molecular genotypes. Additional activities include studies of hearing loss associated with noise or other ototoxins, and inflammatory, neoplastic or infectious processes. We use a comprehensive battery of auditory and vestibular measures that includes otoacoustic emissions, wideband acoustic reflectance, auditory processing evaluation, psychoacoustic measures of pitch perception, auditory and vestibular evoked potentials, videonystagmography, rotary vestibular chair testing, and computerized dynamic platform posturography.

Current Areas of Interest

The Audiology Unit is studying the hearing and balance manifestations of several different forms of syndromic and nonsyndromic human hereditary hearing loss, and correlating clinical features with underlying gene mutations. Many of our studies are part of NICHD, NCI, NIAMS, NINDS, and NHGRI clinical research protocols on a variety of chromosomal and syndromic disorders affecting hearing and balance.

Additional projects include: (1) hearing safety during clinical and research procedures such as magnetic resonance imaging and transcranial magnetic stimulation that involve exposure to high noise levels; (2) effectiveness of various types of hearing protection and the cumulative impact of repeated exposure associated with these procedures; (3) heritability of auditory processing skills, in conjunction with the Laboratory of Molecular Genetics, NIDCD.


Carmen Brewer, Ph.D., Chief of Audiology (Send e-mail | View photo)
Kelly King, B.A., Research Assistant (Send e-mail | View photo)
Christopher Zalewski, M.S., Staff Audiologist (Send e-mail | View photo)


Selected Publications









National Institute on Deafness and Other Communication Disorders. Celebrating 20 years of research: 1988 to 2008