The EU-funded 'Regulation of ventral otic patterning and integration with general programmes of neurogenesis in the zebrafish embryo' (EM ZF OTIC) project investigated inner ear development. More specifically, scientists studied when and how sensory hair cells, neurons of the inner ear ganglion, and structural cells of the auditory and vestibular (balance) systems develop. For a functioning ear to emerge, the right cells must form at the right time in the right place. Specifically, investigators found that two molecules — fibroblast growth factor (FGF) and retinoic acid (RA) — play critical roles in signalling the emergence of otic neuroblasts, which have the capacity to develop into the sensory neurons of the inner ear. The research also showed that FGF and RA are interconnected in a feedback loop and their combined signalling takes place in the ear tissue itself. Correct signalling is critical for accurate cell specification and differentiation. Studying the relationships between signalling molecules and cell differentiation in a living system has shown that only a few signalling pathways are used over and over again. This finding suggests that the timing and context of a given signal are particularly important for development. This research has improved our knowledge of the genetic mechanisms that establish different cell types in the developing inner ear, and has implications for improving the way that inner ear cells develop in cell culture conditions. Increased knowledge of feedback mechanisms and types of FGF molecules needed for correct cell development has the potential to improve culturing methods. The ability to grow fully functional inner ear hair cells and neurons as cultured cells would be an enormous breakthrough. These cells could then be potentially used as replacements in deaf patients to restore their hearing.
Inner ear, hearing, balance, zebrafish, fibroblast growth factor, retinoic acid, signalling molecules, cell differentiation