Molecular Genetic Response in Xiphophorus maculatus Skin upon Exposure to Various Wavebands of Light
Authors: Chang Jordan , Lu Yuan , Boswell William , Boswell Mikki , Caballero Kaela , Walter Ronald 
Published: November 2023

Xiphophorus fishes represent a vertebrate model to study the genetics associated with melanoma development. In particular, select interspecies hybrids have been shown to develop melanoma after exposure to ultraviolet B (UVB) light. Recently, RNA‐Seq was utilized to define the global genetic effects UVB (341 nm) and 4,100K “cool white” fluorescent light exposure produced. These findings suggest that fluorescent light elicits a robust response in differentially expressed genes comparable to that observed following UVB exposure. However, the sets of genes found differentially expressed after exposure to either light source were fundamentally different. UVB incited a response in skin defined by genes involved with mounting an inflammatory response while fluorescent light served to suppress large numbers of genes involved with cell cycle progression. Thus, it is imperative to characterize gene sets that may be transcriptionally modulated due to specific wavelengths of light exposure.

We report RNA‐Seq determined global genetic shifts in male Xiphophorus maculatus Jp 163 B fish skin following exposure to 50 nm wavebands from 300 to 600 nm. Differential gene expression (DE) was assessed for each of six 50 nm waveband exposures and the genes affected were functionally clustered. Overall, we observed two specific wavelength regions (350–400 nm and 500–550 nm) produced much greater numbers of transcriptionally modulated genes than all other wavelength regions. Exposure to the 350–400 nm waveband resulted in differential expression of 117 genes, while 500–550 nm exposure led to transcriptional modulation of 378 genes. Genes from both of these wavelength regions showed differential expression in genes involved in circadian rhythm, lipid oxidation, and cell proliferation; however, the manner that genes were modulated within each region suggests that specific wavelengths of light affects transcription via different mechanisms.

To further define transcriptional activity for wavelengths within the 500–550 nm band, X. maculatus were exposed to 10 nm wavelength bands between 500 to 550 nm. Skin exposed to 510–520 nm light exhibited the greatest number of modulated genes (849 genes) and functional clustering of these genes showed similarity to the 500–550 nm exposure, indicating both cellular stress and suppression in cell cycle progression.

These results identify specific wavelength regions within the broad light spectrum that appear to be inducing aberrant gene regulation in fish skin. While this study focuses on narrow 50 nm and 10 nm waveband regions, it suggests that combinatorial effects may result from co‐exposure to different wavelength regions and this presents interesting avenues for further research.

Support or Funding Information

We thank Markita Savage, Natalie Taylor, and the Xiphophorus Genetic Stock Center, Texas State University, for maintaining the pedigreed fish lines, performing interspecies crosses, helping with dissections, and caring for the animals used in this study. The authors would also like to thank Drs. Tzintzuni Garcia, Yingjia Shen, and Kuan Yang for setting up the bioinformatics pipelines used in some of the data analysis presented herein. This work was supported by the National Institutes of Health, Division of Comparative Medicine, R24 OD‐011120 and R24 OD‐018555.