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. 2006 Jun;43(6):e25.
doi: 10.1136/jmg.2005.034397.

CRYM mutations cause deafness through thyroid hormone binding properties in the fibrocytes of the cochlea

A Oshima, S Suzuki, Y Takumi, K Hashizume, S Abe, S Usami

CRYM mutations cause deafness through thyroid hormone binding properties in the fibrocytes of the cochlea

A Oshima et al. J Med Genet. 2006 Jun.

Abstract

Background: In a search for mutations of mu-crystallin (CRYM), a taxion specific crystalline which is also known as an NADP regulated thyroid hormone binding protein, two mutations were found at the C-terminus in patients with non-syndromic deafness.

Objective: To investigate the mechanism of hearing loss caused by CRYM mutations

Methods: T3 binding activity of mutant mu-crystallin was compared with that of wild-type mu-crystallin, because mu-crystallin is known to be identical to T3 binding protein. To explore the sites within the cochlea where mu-crystallin is functioning, its localisation in the mouse cochlea was investigated immunocytochemically using a specific antibody.

Results: One mutant was shown to have no binding capacity for T3, indicating that CRYM mutations cause auditory dysfunction through thyroid hormone binding properties. Immunocytochemical results indicated that mu-crystallin was distributed within type II fibrocytes of the lateral wall, which are known to contain Na,K-ATPase.

Conclusions: CRYM mutations may cause auditory dysfunction through thyroid hormone binding effects on the fibrocytes of the cochlea. mu-Crystallin may be involved in the potassium ion recycling system together with Na,K-ATPase. Future animal experiments will be necessary to confirm a causal relation between Na,K-ATPase, T3, and deafness.

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Conflict of interest statement

Conflicts of interest: none declared

References

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