GRNHairCell · Understanding the Gene Regulatory Network involved inner ear Hair Cell differentiation

Understanding the Gene Regulatory Network involved inner ear Hair Cell differentiation

• What is the problem/issue being addressed? Understanding the molecular basis for transcription factor (TF) specificity in different developmental contexts is vital to grasp a mindful knowledge of the embryonic development and key for the development of effective regenerative therapies. Our model system is the inner ear hair cell (HC), essential to hearing and balance. Very little is known about the genetic networks regulating HC development. To gain new insights, we developed a new transcriptional programming strategy to promote in vitro HC differentiation, starting from pluripotent stem cells. In vivo Atoh1 is the only TF known to be necessary and sufficient for HC differentiation, but in vitro its overexpression induces neuronal rather than HC differentiation. Previously, we discovered that Atoh1 expression combined with two other TFs (Pou4f3, Gfi1) resulted in efficient HC generation. This work offers a new paradigm to understand the molecular mechanisms governing TF specificity. How do Pou4f3-Gfi1 modulate Atoh1 activity to orchestrate a HC differentiation program? To address these questions, we have interrogated cells undergoing this well-defined transcriptional programming event in order to understand the properties of the gene regulatory network controlling HC differentiation. • Why is it important for society? Hearing loss affects millions of people worldwide and is largely caused by the loss of mechanosensory HCs. There is no cure: HCs do not regenerate in mammals (unlike in other vertebrates) and prosthetic devices poorly substitute for lost HCs. bHLH transcription factor, Atoh1, drives HC specification in development and understanding its role is crucial for future therapeutic strategies. Indeed, much effort is expended on Atoh1 research and it is already the subject of gene therapy trials. However, our mechanistic knowledge is incomplete. For instance, why is Atoh1 unable to drive HC regeneration in mammals? Understanding the mechanism of Atoh1 function and its limitations requires determining its place within the gene regulatory network (GRN) of HC development. This knowledge will have a major impact for novel therapeutic approaches that could restore HCs. • What are the overall objectives? The overall objectives of this project can be divided in 3 general aims containing different sub-aims: 1) Understand how Atoh1 cooperates with Pou4f3 and Gfi1 to implement the HC differentiation program: -Determine the precise gene expression changes triggered by Atoh1, Pou4f3 and Gfi1 during HC differentiation. -Determine the direct target genes of Atoh1, Pou4f3 and Gfi1 during early stage of HC differentiation and identify the main functions of each TF. 2) Understand how Atoh1 function can be modulated to cause a switch from neural to HC fate: -Determine the precise gene expression changes triggered by Atoh1 alone or in combination with other TFs (Gfi1/Pou4f3). -Determine how Atoh1’s direct targets differ between HC and neuronal contexts (i.e. with and without Gfi1/Pou4f3). 3) Generate gene regulatory models (GNR) of HC differentiation: -Test predictions arising from these models in vivo.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз