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Published on: January 4, 2017
Chondrocyte-specific Smad4 gene conditional knockout results in hearing loss and inner ear malformation in mice
Shi-ming Yang1, Zhao-hui Hou, Guan Yang
1Department of Otolaryngology, Head and Neck Surgery, Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, China. yangsm301@263.net
Abstract:
Smad4 is the central intracellular mediator of transforming growth factor-beta (TGF-beta) signaling, which plays crucial roles in tissue regeneration, cell differentiation, embryonic development, and regulation of the immune system. Conventional Smad4 gene knockout results in embryonic lethality, precluding its use in studies of the role of Smad4 in inner ear development. We used chondrocyte-specific Smad4 knockout mice (Smad4Co/Co) to investigate the function of Smad4 in inner ear development. Smad4Co/Co mice were characterized by a smaller cochlear volume, bone malformation, and abnormalities of the osseous spiral lamina and basilar membrane. The development of the hair cells was also abnormal, as evidenced by the disorganized stereocilia and reduced density of the neuronal processes beneath the hair cells. Auditory function tests revealed the homozygous Smad4Co/Co mice suffered from severe sensorineural hearing loss. Our results suggest that Smad4 is required for inner ear development and normal auditory function in mammals.
Insights
Smad4 is essential for mammalian inner ear development. Chondrocyte-specific Smad4 knockout mice showed abnormal cochlear structures and severe sensorineural hearing loss, highlighting Smad4's role in auditory function.
Area of Science:
- Developmental Biology
- Genetics
- Otolaryngology
Background:
- Smad4 mediates transforming growth factor-beta (TGF-beta) signaling, vital for development and regeneration.
- Conventional Smad4 knockout causes embryonic lethality, hindering inner ear development studies.
Purpose of the Study:
- Investigate Smad4's function in mammalian inner ear development.
- Determine the role of Smad4 in auditory system formation and function.
Main Methods:
- Utilized chondrocyte-specific Smad4 knockout mice (Smad4Co/Co).
- Analyzed inner ear morphology and hair cell development.
- Conducted auditory function tests.
Main Results:
- Smad4Co/Co mice exhibited smaller cochlear volume and bone malformations.
- Abnormalities observed in the osseous spiral lamina, basilar membrane, and hair cell stereocilia.
- Homozygous Smad4Co/Co mice displayed severe sensorineural hearing loss.
Conclusions:
- Smad4 is indispensable for normal inner ear development.
- Smad4 plays a critical role in establishing and maintaining auditory function.
