Molecular Response to Ultraviolet Radiation Exposure in Fish Embryos: Implications for Survival and Morphological Development

Abstract

UVR exposure is known to cause developmental defects in a variety of organisms including aquatic species but little is known about the underlying molecular mechanisms. In this work we used zebrafish (Danio rerio) embryos as a model system to characterize the UVR effects on fish species. Larval viability was measured for embryos exposed to several UVR spectral treatments by using a solar simulator lamp and an array of UV cutoff filters under controlled conditions in the laboratory. Survival rate and occurrence of development abnormalities, mainly caudal (posterior) notochord bending/torsion, were seriously affected in UV-exposed larvae reaching values of 53% and 72%, respectively, compared with non-UV-exposed larvae after 6 days postfertilization (dpf). In order to elucidate the molecular mechanisms involved, a matricellular glycoprotein named osteonectin and the expression of a DNA-repair related gene, p53, were studied in relation to UVR exposure. The results indicate that osteonectin and p53 expression were increased under UVR exposure due to wavelengths shorter than 335 nm (i.e. mainly UVB) and 350 nm (i.e. short UVA and UVB), respectively. Furthermore, parallel experiments with microinjections of osteonectin-capped RNA showed that malformations induced by osteonectin overexpression were similar to those observed after a UVR exposure. Consequently this study shows a potential role of osteonectin in morphological deformities induced by solar UV radiation in zebrafish embryos.

Co‐exposure of ZnO nanoparticles and UV radiation to Daphnia magna and Danio rerio: Combined effects rather than protection

“…Embryos exposed to UV radiation followed a dosedependent relationship, with the number of dead embryos increasing as the UV radiation dose increased. A well-noticed effect of UV radiation on D. rerio embryos development was the occurrence of tail malformations, also observed in other studies [35,36]. This specific effect can be linked with the position of the embryos at the time of exposure to the UV radiation light.…”

“…Nevertheless, the increased expression of the p53 gene can also lead to cell apoptosis, which in turn will cause the abnormal development of the embryo. Another finding of the study of Nuñez et al was the expression of the matricellular osteonectin protein increase under UV radiation exposure. This protein has a strong activity during embryogenesis, and it, too, has been linked to the formation of skin tumors in response to UV radiation .…”

“…Another finding of the study of Nuñez et al was the expression of the matricellular osteonectin protein increase under UV radiation exposure. This protein has a strong activity during embryogenesis, and it, too, has been linked to the formation of skin tumors in response to UV radiation . Ultraviolet radiation also decreases the capacity of fish to escape from predators, as demonstrated for cod larvae by Fukunishi et al .…”

“…The thinner side of the blastoderm will be the future dorsal surface; therefore, this malformation can be expected to occur . Nuñez et al observed an increase in the expression of the p53 gene after exposing zebrafish embryos to UV radiation, indicating the occurrence of DNA damage, because this gene's functions include repairing DNA. Nevertheless, the increased expression of the p53 gene can also lead to cell apoptosis, which in turn will cause the abnormal development of the embryo.…”

Matricellular protein SPARC/osteonectin expression is regulated by DNA methylation in its core promoter region

“…Specifically, we showed that sparc is a modulator of lineage‐specific transcription factor gata 1 expression levels or activity. Furthermore, we demonstrated a UV exposure‐dependent increase in the expression of the matricellular protein osteonectin in zebrafish embryos (Torres‐Núñez et al, ). Therefore, because of its spatially and temporally regulated expression during development and its multifunctional role, sparc gene is expected to be tightly regulated.…”