Atrophic thyroid follicles and inner ear defects reminiscent of cochlear hypothyroidism in Slc26a4-related deafness.

Abstract

Thyroid hormone is essential for inner ear development and is required for auditory system maturation. Human mutations in SLC26A4 lead to a syndromic form of deafness with enlargement of the thyroid gland (Pendred syndrome) and non-syndromic deafness (DFNB4). We describe mice with an Slc26a4 mutation, Slc26a4 (loop/loop) , which are profoundly deaf but show a normal sized thyroid gland, mimicking non-syndromic clinical signs. Histological analysis of the thyroid gland revealed defective morphology, with a majority of atrophic microfollicles, while measurable thyroid hormone in blood serum was within the normal range. Characterization of the inner ear showed a spectrum of morphological and molecular defects consistent with inner ear pathology, as seen in hypothyroidism or disrupted thyroid hormone action. The pathological inner ear hallmarks included thicker tectorial membrane with reduced β-tectorin protein expression, the absence of BK channel expression of inner hair cells, and reduced inner ear bone calcification. Our study demonstrates that deafness in Slc26a4 (loop/loop) mice correlates with thyroid pathology, postulating that sub-clinical thyroid morphological defects may be present in some DFNB4 individuals with a normal sized thyroid gland. We propose that insufficient availability of thyroid hormone during inner ear development plays an important role in the mechanism underlying deafness as a result of SLC26A4 mutations.

• Authors: Amiel A Dror, Danielle R Lenz, Shaked Shivatzki, Keren Cohen, Osnat Ashur-Fabian, Karen B Avraham
• Journal: Mammalian genome : official journal of the International Mammalian Genome Society (Mamm Genome) Vol. 25 Issue 7-8 Pg. 304-16 (Aug 2014) ISSN: 1432-1777 [Electronic] United States
• PMID: 24760582 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Anion Transport Proteins
• Large-Conductance Calcium-Activated Potassium Channels
• Slc26a4 protein, mouse
• Sulfate Transporters

Topics

• Animals
• Anion Transport Proteins (metabolism)
• Atrophy
• Cochlea (pathology)
• Deafness (pathology)
• Ear, Inner (pathology, ultrastructure)
• Hair Cells, Auditory, Inner (pathology)
• Humans
• Hyperplasia
• Hypothyroidism (pathology)
• Large-Conductance Calcium-Activated Potassium Channels (metabolism)
• Mice
• Mice, Inbred C3H
• Mice, Mutant Strains
• Models, Biological
• Sulfate Transporters
• Thyroid Gland (abnormalities, pathology)