Yin and Yang of Hair Cells: The Role of Activin A and Follistatin in Inner Ear Development

Prajapati-DiNubila et al. discovered that the differentiation of sensory hair cells in the inner ear is regulated by the cytokine activin A and its antagonist follistatin through the modulation of the transcription factor ATOH1. They found that activin A promotes the expression of ATOH1, leading to hair cell differentiation, while follistatin decreases ATOH1 expression, thereby reducing the number of inner hair cells. This study highlights the importance of the balance between activin A and follistatin in the development of hair cells in the inner ear.