In both Xiphophorus fishes and humans, males are reported to have a higher incidence of melanoma than females. To better understand sex specific differences in the molecular genetic response to UVB, we performed RNA-Seq experiments in skin of female and male Xiphophorus maculatus Jp 163 B following UVB doses of 8 or 16 kJ/m2 exposure. Male X. maculatus differentially express a significantly larger number of transcripts following exposure to 16 kJ/m2 UVB (1,293 genes) compared to 8 kJ/m2 UVB (324 genes). Female skin showed differential gene expression in a larger number of transcripts following 8 kJ/m2 UVB (765) than did males; however, both females and males showed similar numbers of differentially expressed genes at 16 kJ/m2 UVB (1,167 and1,293, respectively). Although most modulated transcripts after UVB exposure represented the same dominant pathways in both females and males (e.g., DNA repair, circadian rhythm, and fatty acid biosynthesis), we identified genes in several pathways that exhibited opposite modulation in female vs. male skin (e.g., synaptic development, cell differentiation, wound healing, and glucose metabolism). The oppositely modulated genes appear related through uncoupling protein 3 (UCP3) that is involved with regulation of fatty acid oxidation and serves to balance glucose and lipid metabolism. Overall, these results identify gender specific differences in UVB induced genetic profiles in the skin of females and males and show female and male X. maculatus respond to UVB differently through pathways involved in reactive oxygen species, wound healing, and energy homeostasis.

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We optimized a peptide extraction and LC–MS protocol for identification and quantification of antimicrobial peptides (AMPs) in biological samples. Amphipathic AMPs were extracted with various concentrations of ethanol, methanol, acetonitrile, formic acid, acetic acid or trichloroacetic acid in water. Yields were significantly greater for extraction with 66.7% ethanol than other extraction methods. Liquid chromatography was accomplished on a C18 column with a linear gradient of acetonitrile–formic acid, and mass spectrometry detection was performed in the positive electrospray multiple reaction monitoring mode by monitoring the transitions at m/z 385.2/239.2 and m/z 385.2/112.0 (AMP 1018), m/z 418.1/104.1 and m/z 418.1/175.1 (Methionine-1018). This method was shown to be reliable and efficient for the identification and quantification of scorpion AMPs Kn2-7 and its D-isomer dKn2-7 in human serum samples by monitoring the transitions at m/z 558.7/120.2 and m/z 558.7/129.1 (Kn2-7/dKn2-7).

The Ku complex performs multiple functions inside eukaryotic cells, including protection of chromosomal DNA ends from degradation and fusion events, recruitment of telomerase, and repair of double-strand breaks (DSBs). Inactivation of Ku complex genes YKU70 or YKU80 in cells of the yeast S. cerevisiae gives rise to mutants that exhibit shortened telomeres and temperature-sensitive growth. In this study we have investigated the mechanism by which overexpression of telomerase suppresses the temperature sensitivity of yku mutants. Viability of yku cells was restored by overexpression of the Est2 reverse transcriptase and TLC1 RNA template subunits of telomerase, but not the Est1 or Est3 proteins. Overexpression of other telomerase- and telomere-associated proteins (Cdc13, Stn1, Ten1, Rif1, Rif2, Sir3, Sir4) did not suppress the growth defects of yku70 cells. Mechanistic features of suppression were assessed using several TLC1 RNA deletion derivatives and Est2 enzyme mutants. Supraphysiological levels of three catalytically inactive reverse transcriptase mutants (Est2-D530A, Est2-D670A and Est2-D671A) suppressed the loss of viability as efficiently as the wildtype Est2 protein, without inducing cell senescence. Roles of proteins regulating telomere length were also determined. The results support a model in which chromosomes in yku mutants are stabilized via a replication-independent mechanism involving structural reinforcement of protective telomere cap structures.