Abstract: Most internal organs are built around fluid-filled tubes and control of fluid secretion is essential for their development and function. Defects in fluid secretion have been linked to some of the most prevalent genetic and acquired pathological conditions, including Cystic Fibrosis, Polycystic Kidney Disease and secretory diarrheas. At the cellular level, fluid secretion is driven by directional salt ion transport which is then followed by water. Several key channels and pores responsible for ion and water transport have been identified. However, we still need to understand how fluid secretion functions as a developmental force and how different processes that depend on fluid secretion are coordinated at the whole organism level. To address these fundamental problems I have embarked on a fully integrated approach based on zebrafish genetics and physiology. My focus is on the Cystic Fibrosis Transmembrane conductance Regulator, a chloride channel that is the major regulator of fluid secretion in vertebrates. The proposed research plan will lead to new insights into: (1)how fluid pressure shapes development and (2)the responses elicited at the cellular level by this force;(3)CFTR function and how its activity is regulated in vivo and in real time during development;(4)We will also carry out a forward genetic screen to identify mutations controlling CFTR-dependent and independent fluid secretion. These approaches will establish a new genetic and physiologic model system for studying the functional regulation and developmental potential of fluid secretion and CFTR activity. Public Health Relevance: Changes in the activity of the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) chloride channel is a major factor in the two genetic conditions most prevalent in the US, Cystic Fibrosis and Polycystic Kidney Disease. In addition, uncontrolled activation of the CFTR channel is a key element in the pathopysiology of inherited and infectious secretory diarrheas. The latter constitutes the leading cause of death in the developing world. Understanding the functional regulation of the CFTR channel has been hindered by the lack of a genetic model. The project described here will establish a genetic and model system to study CFTR function and will identify new molecules that may constitute new molecular targets for Cystic Fibrosis and Polycystic Kidney Disease therapy.
