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Regulator of inner ear progenitor fate and outer hair cell function

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Question 1
Hollyfield: Regulator of inner ear progenitor fate and outer hair cell function.
Introduction
Located within the mammalian cochlea and critical to hearing function, the organ of Corti is a sensory epithelium, comprised of auditory receptors, called hair cells, and their supporting cells. In avians, hair cells and supporting cells share common progenitors in the auditory epithelia (Fekete et al., 1998; Kirjavainen et al., 2008). During embryonic development it is crucial to have the right number of hair cells and supporting cells from progenitor cells for proper organ function. Loss or even gain of supernumerary hair cells and/or supporting cells can lead to deafness (Chen et al., 2008; Chen and Segil, 1999; Mellado Lagarde et …show more content…

Not only can the loss of inner hair cells lead to deafness, but so can the loss of outer hair cells. In rats, loss of 1/3 of OHCs will cause hearing impairment, and 2/3 loss will lead to deafness (Chen et al., 2008) .
Supporting cells: Within the organ of Corti, there are also five different types of supporting cells with distinct morphologies: Hensen’s cells are cuboidal or slightly oblong, inner phalangeal cells and border cells are columnar, and Deiters’ and pillar cells are elongated and have strong cytoskeletons for large structural demands (Wan et al., 2013). Like hair cells, supporting cells are also precisely arranged in the organ of Corti, by rows from the outer edge to the inner edge of the organ in the order of: Hensen’s cells, Deiters’ cells, pillar cells, inner phalangeal cells, and border cells (Wan et al., 2013). One should note that supporting cells do not just take up space in the auditory epithelium. Loss of Deiters’ and pillar cells enviably leads to a loss of OHCs, causing deafness due lack of amplification (Mellado Lagarde et al., 2013). In addition, supporting cells also provide trophic factors, which are vital to the maintenance of spiral ganglion neurons (Monzack and Cunningham, 2013)
Cell cycle exit and p27kip1
To get the right number of hair cells and supporting cells during development,

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