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Bahaar Chawla, William Swain, Brenda L Bohnsack; Retinoic acid is required for maintenance of adult zebrafish ocular and craniofacial structures. Invest. Ophthalmol. Vis. Sci. 201657(12):.
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© 2017 Association for Research in Vision and Ophthalmology.
Retinoic acid (RA),the bioactive metabolite of vitamin A, is critical for retinal function and is also a well-established regulator of eye and craniofacial development. However, it is unknown whether RA is also required for the maintenance of post-embryonic craniofacial structures. In these studies, we use zebrafish to elucidate the role of RA in the adult eye and cranial bones.
Adult zebrafish (1-2 yr old) were exposed to the pan-aldehyde inhibitor, 4-diethylaminobenzaldehyde (DEAB, 10uM) to inhibit RA synthesis, all-trans RA (100nM), or dimethylsulfoxide (DMSO) control for 5 days. Optokinetic reflex (OKR) was used as assessment of functional vision pre- and post-treatment. Fish were sacrificed and craniofacial and ocular structures were analyzed using TUNEL assay and phosphohistone-3 immunostaining.
Exogenous treatment with DEAB or RA showed significant changes in adult zebrafish vision and craniofacial structures. DEAB treatment resulted in inconsistent tracking during OKR testing and poor visual function. Decreased RA (DEAB treatment) also resulted in a prognathic mandible that correlated with both increased proliferation in Meckels cartilage and a unique apoptotic pattern in the mandible. Exogenous RA treatment resulted in complete lack of tracking during OKR testing and no visual function. RA treatment also caused a decreased in head size and increased transparency of the skull that was due to significantly increased apoptosis throughout the craniofacial region.
Tight control of RA levels was required for the maintenance of adult zebrafish craniofacial structures. Both increased and decreased RA levels disrupted retinal function indicating that proper regulation of RA synthesis and degradation in the eye is key for visual function. RA also regulated post-embryonic skull and jaw morphology through the control of cell survival and proliferation. This suggests that RA could be used as a local target in the treatment of disfiguring craniofacial anomalies and diseases.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
Figure 1. Tight regulation of RA was required for maintenance of craniofacial structures. DEAB (B) caused loss of ocular volume (arrow) and prognathic mandible (double arrow) compared to pre-treatment (A) and control (E,F). RA treatment (D) resulted in decreased cranial volume with increased translucency (star).
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