Tietz syndrome ... (Tietz syndrome) - Gen MITF.

Tietz's syndrome is a disorder characterized by a profound hearing loss since birth, white skin and light colored hair. Hearing loss in affected individuals it is caused by abnormalities of the inner ear (sensorineural hearing loss) and is present from birth. Although people with Tietz syndrome are born with white hair and very pale skin, often her hair color darkens with time to blond or red. The skin of the affected people who tan easily, can tan or slightly reddish freckles develop limited exposure to the sun; however, your skin and hair color are still lighter than other family members. This disease also affects the eyes, and the iris of the affected individuals is blue, and retinal pigment epithelial cells lack normal pigment. Changes in the retinal pigment epithelium are usually detectable only by an eye exam. It is unclear whether these changes affect vision.

Tietz's syndrome is due to mutations in the MITF gene, located on the short arm of chromosome 3 (3p14.2-p14.1). This gene encodes a protein called microphthalmia-associated transcription factor that plays a role in the development, survival and function of certain cell types. The molecules of the MITF protein bind together or with other proteins that have similar structures, creating a dimer. The dimer binds to specific areas of DNA and helps control the activity of particular genes. Based on this action, the MITF protein is called a transcription factor. The MITF protein helps control the development and function of melanocytes. Inside these cells, this protein controls the production of melanin, which contributes to the color of hair, eyes and skin. Melanocytes are also found in the inner ear and play an important role in hearing. In addition, the MITF protein regulates the development of the retinal pigment epithelium.

They have identified at least 2 mutations of MITF gene in people with Tietz syndrome. Mutations in this gene, deleted or changed amino acids in an area of the MITF protein known as the basic region. Dimers incorporating the MITF protein abnormal can not be transported to the cell nucleus to bind DNA. As a result, most of the dimers are not available to bind to DNA, which affects the development of melanocytes and melanin production. The resulting reduction or absence of melanocytes in the inner ear, resulting in hearing loss. It has been suggested that Tietz syndrome may represent a severe form of Waardenburg syndrome, which can also be due to mutations MITF gene.

This disease is inherited as an autosomal dominant, which means that a copy of the altered gene in each cell is sufficient for the disease to be expressed. In most cases, an affected person has a parent with the disease.

Tests in IVAMI: in IVAMI perform detection of mutations associated with Tietz syndrome by complete PCR amplification of exons MITF gene, and subsequent sequencing.

Samples recommended: EDTA blood collected for separation of blood leukocytes, or impregnated sample card with dried blood (IVAMI may mail the card to deposit the blood sample).