A combinatory microfluidic and in vivo modeling approach to evaluate collective migration during retinogenesis

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The coordinated migration of groups of cells is a central element of tissue development as well as of stem cell-based repair in the nervous system. In an idealized model, stem-like cells (STLCs) are introduced into a damaged tissue and migrate collectively, as one unit, toward precise injury sites to reestablish neuronal connectivity. In truth, the effects of cues from a cell's genetic makeup and its external environment on collective migration have been only partially explored. The developing retina provides a unique opportunity for quantitative study of collective migration to support the natural development of vision. As the signaling cues that guide retinal development are surprisingly similar among different species, the common fruit fly (Drosophila melanogaster) provides a simple yet excellent model to study this phenomenon. The study of how STLCs naturally migrate to initiate or re-initiate connectivity of the neurons with the retina will greatly deepen our understanding of retinal development and could greatly advance therapies to restore vision. Educational efforts will develop opportunities for undergraduates to teach and mentor summer high school students in retinal research by establishing integrated course modules that engage student teams in device prototyping, design innovation and cell-based laboratory experiments.This project will evaluate the collective migration of STLCs using in vivo genetics to regulate intracellular Fibroblast Growth Factor Receptor (FGF-R) signaling in Drosophila melanogaster (as a model) and microfluidic systems to control extrinsic FGF environments. The study is motived by knowledge that FGF signaling pathways in the Drosophila model are known to mediate the neural migration needed to initiate vision via the optic stalk, but it is not clear if FGF-R regulation alone is sufficient. The system will facilitate genetically-controlled study of FGF-R-mediated chemotaxis with micrometer resolution in tandem with quantitative study of the intercellular signaling needed to preserve spatial cohesion across motile STLC collectives (cell-cell adhesion via innexin-1). The Research Plan is organized under 3 aims. AIM 1 will develop a microfluidic model of the retinal optic stalk (the portion of the developing retina between the Drosophila Brain Lobe and the Eye Imaginal Disc) to generate controlled, extrinsic FGF fields. Experiments will prototype an in vitro system on the scale of the Drosophila retina and develop an analytical model (Finite Element simulation) to describe concentration gradient fields therein. Characteristics of collective in vitro migration will be evaluated by targeted, quantitative parameters. AIM 2 will examine the collective migration of glial and neuronal cells expressing genetically-modified elements of FGF-R, i.e., cells with and without functional receptors. Genetic FGF-R alteration will be used to experimentally determine contribution of FGF-R to the size of motile collectives as well as their neural composition and cell-cell adhesion within the microfluidic system. AIM 3 will evaluate in vivo retinal formation using genetically modified FGF-R glial and neuronal collectives. The specific role for FGF-R during collective migration in vivo will be studied by examining retinogenesis using neural collectives lacking FGF-R function.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.