Mechanisms of nematode molting

Project Summary In this MIRA proposal we will gain insight into how biological timers control development and how the apical extracellular matrix (aECM) is constructed and remodeled. How biological timers control human development is only beginning to be understood. Animal development requires precise temporal synchronization of a broad range of events controlled by developmental clocks. In contrast to the circadian clocks that enable animals to anticipate daily cycles of light, temperature, and other environmental variables, the properties, components, and wiring of these developmental timers is only beginning to emerge. Examples of these timers include the clocks that control somite formation and hair follicle cycling. We use C. elegans as a model to understand developmental timers function. Two independent but interconnected biological timers drive progression through C. elegans development. The heterochronic pathway is a linear timer that controls the serial progression of stage-specific cellular events. A cyclical molting timer coordinates apical extracellular matrix regeneration and shedding of the old cuticle. Understanding these timers will inform how animals transition from juveniles to adults, how cell fate and cell divisions are coordinated with linear developmental progression, and how a dynamic aECM is built during development. Aberrant aECM function has been implicated in a variety of human diseases and defects can impact hearing, wound healing, the skin barrier, and cardiovascular and renal function. Despite extensive study of aECMs in many organisms, we know little about their molecular organization. C. elegans is an ideal model system in which to address these knowledge gaps because it is transparent with a new aECM being built each larval stage over a course of 8-10 hours making it possible to perform real time imaging of aECM formation. In addition to informing human biology, we are also interested in nematode-specific biology, as it offers an intervention point to combat parasitic nematode infections. As a group, these animals afflict an estimated 1.5 billion people worldwide, comprising approximately 85% of global neglected tropical diseases. They also threaten food security by infecting crops and livestock. Our long-term goal is to define the mechanisms that ensure faithful molting at the molecular, cellular, and organismal level in C. elegans and then extend our work into parasitic nematode models with the goal of uncovering vulnerable processes for future therapeutic targeting This work involves three projects. In the first 1 we will determine how biological timers control development, focusing on NHR-23, LIN-42, and KIN-20. In the second project, we will test whether NHR-23 is ligand regulated to control molting. In the third project we will determine how the aECM is formed and remodeled during development, focusing on the role of proteases and protease inhibitors. Our hypothesis is that each protease inhibitor has a cognate protease that it regulates to ensure that the protease is only active at a specific time and location.