The Vacuolar-ATPase Complex Regulates Retinoblast Proliferation and Survival, Photoreceptor Morphogenesis and Pigmentation in the Zebrafish Eye
Richard John Nuckels 1,
Anthony Ng 1,
Tristan Darland 2,
and
Jeffrey M. Gross 3*
1 Molecular Cell and Developmental Biology, University of Texas at Austin, Austin, Texas, United States
2 Biology, University of North Dakota, Grand Forks, North Dakota, United States
3 Molecular Cell and Developmental Biology, University of Texas at Austin, Box C0930, Austin, Texas, 78712, United States
* To whom correspondence should be addressed. E-mail: jmgross{at}mail.utexas.edu.
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Abstract |
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Purpose: The vacuolar-ATPase (v-ATPase) complex is a key regulator of the acidification of endosomes, lysosomes and the lumenal compartments of several cell types, tissues and organs; however, little is know about the in vivo function of the v-ATPase complex or its roles during eye development. Here, we report the characterization of ocular defects in five zebrafish mutants in which core components of the v-ATPase complex are affected (atp6v1h, atp6v1f, atp6v1e1, atp6v0c and atp6v0d1), as well as a sixth mutant in which a v-ATPase associated protein (atp6ap1) is affected.
Methods: v-ATPase mutants were characterized using histological, molecular and ultrastructural analyses.
Results: v-ATPase mutants are oculocutaneous albinos and present with defects in the formation and/or survival of melanosomes, and with malformations in the retinal pigmented epithelium (RPE) that compromise melanosome distribution. v-ATPase mutants are microphthalmic and BrdU incorporation assays indicate that retinoblast cell cycle exit and maintained proliferation in the ciliary marginal zone (CMZ) are compromised. v-ATPase mutants also possess elevated levels of apoptotic neurons within their retinas and brains. Photoreceptor outer segment morphology is abnormal in the mutant eye with rosette structures forming adjacent to affected regions of the RPE. Ultrastructural analyses indicate that RPE cells in v-ATPase mutants possess numerous membrane-bounded vacuoles containing undigested outer segment material. In situ hybridization analyses localized v-ATPase subunit transcripts within the RPE.
Conclusions: These results demonstrate that the v-ATPase complex plays a number of critical roles during vertebrate eye development and maintenance, and they suggest that defects in v-ATPase complex function could possibly underlie human ocular disorders that affect the RPE.
Key Words:
albinism, retinal development, retinal pigment epithelium, photoreceptor morphology
