PT - JOURNAL ARTICLE AU - Alison Heffer AU - Felicia A Gilels AU - Amy E Kiernan TI - Deletion of <em>Notch1</em> during cochlear maturation leads to rapid supporting cell death and profound deafness AID - 10.1523/JNEUROSCI.1090-22.2022 DP - 2022 Nov 23 TA - The Journal of Neuroscience PG - JN-RM-1090-22 4099 - http://www.jneurosci.org/content/early/2022/11/23/JNEUROSCI.1090-22.2022.short 4100 - http://www.jneurosci.org/content/early/2022/11/23/JNEUROSCI.1090-22.2022.full AB - The sensory region of the mammalian hearing organ contains two main cell types, hair cells and supporting cells. During development, Notch signaling plays an important role in the decision to become either a hair cell or supporting cell, by mediating lateral inhibition. However, once the cell fate decisions have been determined, little is understood about the role Notch plays in cochlear maturation. Here we report that deletion of Notch1 from the early postnatal mouse cochlea in both male and female animals resulted in profound deafness at 6 weeks of age. Histological analyses at 6 weeks revealed significant hair cell and supporting cell loss throughout the Notch1-deficient cochlea. Early analyses revealed a reduction in supporting cells in the outer hair cell region between P2-P6, without a comparable increase in outer hair cell number, suggesting a mechanism other than lateral inhibition. Consistent with this, we found apoptotic cells in the outer supporting cell region of the cochlea at P1 and P2, indicating that Notch1 is required for outer supporting cell survival during early cochlear maturation. Interestingly, inner supporting cell types were not lost after Notch1 deletion. Surprisingly, we do not detect outer hair cell loss in Notch1 mutants until after the onset of hearing, around P14, suggesting that hair cell loss is caused by loss of the supporting cells. Together, these results demonstrate that Notch1 is required for supporting cell survival during early maturation and that loss of these cells causes later loss of the hair cells and cochlear dysfunction.SIGNIFICANCE STATEMENT:During development, Notch signaling has been shown to be critical in regulating the cell fate choices between hair cells and supporting cells. However, little is known how Notch functions after those cell fate choices are made. Here, we examine the role of Notch1 in the maturing cochlea. We demonstrate that deletion of Notch1 results in profound deafness by 6 weeks of age. Histological analyses revealed rapid supporting cell death shortly after Notch1 deletion, followed by eventual loss of the hair cells. These results reveal an unexpected role for Notch in supporting cell survival during cochlear maturation.