Understanding the World of Silence

     In the beginning of the semester, Dr. Wei-Ming Yu presented the concepts of Hepsin- which is an important transmembrane serine protease, TMPRSS1, that is crucial for the proper functioning of the cochlea and tectorial membrane. To be better prepared for this presentation, we had to read the article "Critical role of hepsin/TMPRSS1 in hearing and tectorial membrane morphogenesis: Insights from transgenic mouse models" by Yang, Ting-Hua et al. This article first started by introducing that mutations in a type II membrane serine protease in family members are highly associated with a non-syndrome hearing loss although some of those mechanisms are still unclear to be understood.  

First and most importantly, Dr. Yu explained the different mechanisms of how sound is produced by vibrations that create particles in a surrounding medium such as air.  This in turn result in a wave of vibrations that travel through air to the eardrum. When sound enters the ear, a series of hair cells activate in which fluid waves bend hair cells called cilia inside the cochlea. Vibrations travel through the ear canal then press against the eardrum, causing it to oscillate, or move back and forth in a rhythm., The movement of fluid bends the cilia in the cochlea which converts mechanical energy into electrical signals that are processed as sound perception via the brain.

Dr. Yu explained in depth at the molecular level that the proper technique of the tectorial membrane is important for accurate the stimulation of these cilia. This reveals that hepsin/TMPRSS1 plays a key in how we hear sounds. In transgenic mouse models lacking hepsin, the tectorial membrane was abnormally shaped and detached from the hair cell leading to severe hearing impairment. This proved that hepsin is necessary for maintaining the correct composition and structure of the tectorial membrane through processing of some specific extracellular matrix proteins.

In the article “Noise Exposures Causing Hearing Loss Generate Proteotoxic Stress and Activate the Proteostasis Network” by Ramirez et al. describes how exposure to loud sounds damage to the inner ear and imbalances the cochlea. They experienced on rats by exposing them to different levels of sound: moderate, loud and very loud studying the biological effects of noise induced hearing loss. The results were that they found loud levels of sound causes protein in the cochlea to unfold and become damaged. 

Even though both articles are different from one another, they explain concepts at the molecular level of hearing loss providing evidence of how environmental and genetic factors produce sound. 

 

1.     Noise Exposures Causing Hearing Loss Generate Proteotoxic Stress and Activate the Proteostasis Network

Jongkamonwiwat, Nopporn et al. Cell Reports, Volume 33, Issue 8, 108431

2.     Yang, T. H., Hsu, Y. C., Yeh, P., Hung, C. J., Tsai, Y. F., Fang, M. C., Yen, A. C. C., Chen, L. F., Pan, J. Y., Wu, C. C., Liu, T. C., Chung, F. L., Yu, W. M., & Lin, S. W. (2024). Critical role of hepsin/TMPRSS1 in hearing and tectorial membrane morphogenesis: Insights from transgenic mouse models. Hearing research, 453, 109134. https://doi.org/10.1016/j.heares.2024.109134