SRA

Per- and polyfluoroalkyl substances (PFAS) are chemicals that are relatively resistant to degradation. While such features are desirable in a variety of consumer and industry products, such as firefighting foams and non-stick cookware coating, some PFAS, including perfluorooctanoic acid (PFOA), are toxic and bioaccumulate. Hexafluoropropylene oxide dimer acid (HFPO-DA) is an emerging PFAS developed to replace PFOA and has not been extensively studied. To evaluate the potential toxicity of HFPO-DA with a cost- and time-efficient approach, we exposed C. elegans larvae to 4×10-9–4 g/L HFPO-DA in liquid media and performed assays measuring developmental, behavioral, locomotor, and transcriptional effects at various exposure levels. After 48 hours of 1.5–4 g/L HFPO-DA exposure, acute developmental toxicity was observed as developmental delay; statistically significantly delayed (p < 0.05) progeny production was observed in worms exposed to 2–4 g/L HFPO-DA. After 48 hours of 4×10-9–0.4 g/L exposure, no significant behavioral or locomotor effect was observed relative to the 0 g/L control group. Statistically significant differential gene expression was identified with over 99% confidence via the R-package NOISeq in all fourteen 48-hour 1.25×10¬-5–4 g/L HFPO-DA exposure groups, except for 6.25×10¬-5 g/L. Among 10298 genes analyzed, 2624 differentially expressed genes (DEGs) were identified in the developmentally delayed 4 g/L group only, and 78 genes were differentially expressed in at least one of the thirteen exposure groups testing 1.25×10¬-5–2 g/L HFPO-DA exposures. Genes encoding for detoxification proteins such as cytochrome P450 enzymes and UDP glucuronosyltransferases are upregulated in 0.25–4 g/L acute exposure groups. In the lower exposure concentration groups, statistically significant gene expression changes were also observed, though these DEGs did not share any biological functions, except for six ribosomal protein-coding genes. While our transcriptional data is insufficient for conclusive mechanistic explanation, the statistically significant gene expression differences detected at 1.25×10¬-5 g/L, the lowest concentration tested for transcriptional changes, is concerning and calls for further targeted analyses that focus on low-dose HFPO-DA exposure effects. Overall design: Gene expression profiling analysis of shallow RNA-seq data for C. elegans 48 hour exposure to hexafluoropropylene oxide dimer acid (HFPO-DA); four replicates of 15 experimental conditions (14 different concentrations of HFPO-DA plus a control) were generated, with each condition containing around 1000 worms