With the recent explosion of interest in regenerative medicine and stem cell therapies, biologists have reinvested in the study of regeneration with modern molecular techniques that were not available in the field's early years. Conditional mutants and transgenic zebrafish, a teleost fish model research system, are useful tools to study human genetic diseases, development, and mechanisms of adult stem cell activation and regeneration. In fact, zebrafish are used in regeneration research because they have a robust capacity to regenerate the fins, portions of the heart, renal tissue, and importantly the neural retina. Genetic tools facilitate this research because signaling mechanisms controlling regeneration can be explored in the context of an in vivo model system and then be applied to biomedical research in mammalian model systems. In mammalian systems, when the retina is damaged, M|ller glial (MG) cells react to the damage by forming a glial scar and do not restore vision. In contrast, the zebrafish MG act as retinal stem cells to regenerate the lost photoreceptors and restore vision within 2 weeks after the light injury. A microarray analysis of isolated MG from regenerating retinas in the first 36 hours after light damage found similar gene expression changes in MG cells compared with previously published studies of the regenerating heart and fin, including the transcriptional co-repressors TGF2-interacting factor (tgif1) and sine oculis-related homeobox 3b (six3b). This suggests that tgif1 and six3b may be involved in a general regeneration program that is not tissue-specific. Both of these genes repress TGF2 signaling and are associated with congenital forebrain and facial defects in humans. Because tgif1 and six3b have common roles and both increase early in the MG of damaged retina, increased tgif1 and six3b expression may allow for the dedifferentiation and/or mitotic activation of MG stem cells during the early stages of retina regeneration by dynamically regulating TGF2 signaling. The proposed research will provide a comprehensive analysis of the role tgif1 and six3b have in early retina regeneration and develop a new transgenic fish line and retinal explant system to use in future studies of retinal regeneration. This research will inform studies of the mammalian MG following retinal damage by identifying genes that are necessary for induction of MG proliferation and subsequent regeneration, thus providing potential therapeutic targets for regenerative medicine.

Public Health Relevance

The proposed research will help define what changes in gene expression are necessary in the stem cells of the retina, M|ller glia, to regenerate lost photoreceptors after damage and restore eye sight. The results of this study will help determine gene targets for developing therapeutic treatments for blindness and low vision in humans.

National Institute of Health (NIH)
National Eye Institute (NEI)
Postdoctoral Individual National Research Service Award (F32)
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Special Emphasis Panel (ZRG1-F05-A (20))
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Agarwal, Neeraj
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University of Michigan Ann Arbor
Schools of Arts and Sciences
Ann Arbor
United States
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Lenkowski, Jenny R; Raymond, Pamela A (2014) Müller glia: Stem cells for generation and regeneration of retinal neurons in teleost fish. Prog Retin Eye Res 40:94-123
Lenkowski, Jenny R; Qin, Zhao; Sifuentes, Christopher J et al. (2013) Retinal regeneration in adult zebrafish requires regulation of TGF* signaling. Glia 61:1687-97