Description

The Role of Ephrins in Neural Patterning in Planarians. Signaling mediated by Eph receptors and their Ephrin ligands has broad and diverse functions in animals, especially in the development of the nervous system. For example, Eph/Ephrins are involved in processes like axon guidance, neural patterning, and inhibiting neuroregeneration after CNS injury. While many studies have highlighted the roles of Eph/Ephrins in neurogenesis in mammals, we know very little about their role in planarian nervous system development and regeneration. Our lab uses the freshwater planarian Schmidtea mediterranea as a model to study tissue regeneration. S. mediterranea can regenerate any type of tissue, including the nervous system. This regenerative capacity makes planarians an excellent model organism for studying mechanisms involved in patterning the nervous system. Our previous work revealed that the transcription factor soxB1-2 is crucial for the regeneration and maintenance of a planarian mechanosensory system with a discrete and spatially restricted pattern and that the neurons in this system arise from pou4+ progenitor cells. A genetic screen for genes differentially expressed in pou4+ cells to identify genes downstream of pou4-2 transcriptional regulation identified the planarian homolog of human Ephrin type-A receptor 4 (EphA4) as a candidate factor. EphA4 has been implicated in the regulation of neurogenesis and axon guidance in other animals. Preliminary experiments in our lab showed that disrupting ephA4 function results in ectopic mechanosensory cells, suggesting that ephA4 is required for patterning newly born mechanosensory neurons. My research aims to elucidate the role of ephrin signaling in neural patterning in planarians. To understand how ephA4 inhibition affects mechanosensory system patterning, I will combine RNA interference (RNAi) and whole mount in situ hybridization (WISH) for markers of sensory neuron populations and patterning genes. In addition, other candidate ephs and ephrins will be identified using a planarian single-cell database, and their roles in neural patterning will be examined using RNAi, WISH, and immunolabeling of the nervous system. Elucidating the role of ephrins in neural patterning in planarians will help expand our understanding of how the nervous system is developed and maintained in a regenerative species.