Characterization of UVB Inducible Gene Expression in Xiphophorus Skin




Downs, Kevin P.

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Hybrids between select Xiphophorus species have served as experimental models for UVB induced melanomagenesis. Photobiological responses observed in Xiphophorus UV inducible melanoma models support a role for DNA damage in carcinogenesis. For example, UVB induced melanomas in Xiphophorus backcross hybrids are reduced to near background levels by exposing fish to visible light, presumably to promote photoenzymatic repair (PER) of UV photoproducts. Although this biological endpoint has been well studied, little is known about the initial molecular genetic events of UVB exposure in Xiphophorus skin and how this response may be modulated by photoreactivating light (PRL). Here we report RNAseq results from adult X. maculatus exposed to UVB (6.4 kJ) or UVB plus PRL (2 hrs), where total RNA was isolated from skin after 4 hrs in the dark to allow time for gene expression. Concurrent DNA isolation allowed radioimmunoassay to quantify the major UVB photoproducts, cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts (6-4PDs). Skin RNA was sequenced using the Illumina High-Seq platform (100 bp, PE). RNAseq reads were mapped to an X. maculatus reference transcriptome using Bowtie and relative gene expression levels compared with DESeq. Blast2GO analysis was used to assign genes functional ontology groups. In X. maculatus, genes involved in critical molecular processes such as transcription, DNA repair, and response to cellular stress displayed significantly modulated levels of expression whether PRL was present after UVB exposure or not. These expression patterns, in UVB vs. PRL exposed skin, hallmark wavelength dependent antagonistic regulatory signaling and biochemical pathways.



Xiphophorus, DNA repair, Ultraviolet radiation, Photoreactivating light, RNA sequencing


Downs, K. P. (2013). <i>Characterization of UVB inducible gene expression in Xiphophorus skin</i> (Unpublished thesis). Texas State University-San Marcos, San Marcos, Texas.


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