SAT-LB131 Examination of Hepatic Gene Expression Following Developmental Exposure to Dieldrin in Trachemys Scripta and Discovery of a Novel Hepacivirus
Journal of the Endocrine Society
The Massachusetts Military Reservation (MMR) is a Superfund site where ground water has been contaminated by a mixture of pollutants. Exposure to these chemicals is a public health concern and reproductive impairments have been observed in a population of turtles (Chrysemys picta) endemic to this site. We hypothesize that developmental exposure to endocrine disrupting compounds originating from the MMR might lead to abnormalities seen in adult animals. Upon examination of egg yolk from turtles
... yolk from turtles at the impacted site, we found the presence of dieldrin and p,p'-DDE. Turtles from a reference site were also found to have p,p'-DDE present in the yolk. In order to investigate these chemicals in the laboratory we used a closely related turtle (Trachemys scripta) and applied vehicle, dieldrin, or p,p'-DDE to the eggshells. Absorption of p,p'-DDE through the eggshell was limited. Although there were variations in absorbance, we were able to achieve levels of dieldrin in the yolk similar to what was seen in animals from the impacted site. Following in ovo exposure to dieldrin, we used RNAseq to examine hepatic gene expression in neonates and found that several transcripts were repressed at least 1.5-fold in the dieldrin-treated animals. QPCR was carried out to confirm differences in gene expression. We found that hepatic gene expression (fold ± SEM) of Gamma-Butyrobetaine Hydroxylase 1 (Bbox1) was higher in vehicle-treated animals (1 ± 0.60) compared to dieldrin-treated animals (0.29 ± 0.12). Bbox1 catalyzes the last step in the L-carnitine biosynthetic pathway, which is necessary for mitochondrial beta-oxidation. Dieldrin-induced reduction in L-carnitine production may be a critical factor in adult reproductive function. Further, Protein-L-Isoaspartate (D-Aspartate) O-Methyltransferase Domain Containing Protein 1 (Pcmtd1) was higher (1± 0.76) in vehicle-treated animals compared to dieldrin-treated animals (0.13 ± 0.044), and DENN Domain Containing 5B (Dennd5b) was also found to be higher in vehicle-treated (1 ± 0.39) compared to dieldrin-treated (0.28 ± 0.10) turtles. We found that dieldrin exposure did not alter gene expression of Cytochrome p450 1a (Cyp1a) a marker of aryl hydrocarbon receptor signaling, or Vitellogenin 2 (Vtg2) a marker of estrogen signaling. In our RNAseq analysis we unexpectedly discovered a hepacivirus infecting T. scripta. In the dieldrin-treated group, we used QPCR to examine gene expression of potential markers of hepacivirus infection. Neither Interleukin 1 Beta (Il-1β), SMAD Family Member 6 (Smad6), C-C Motif Chemokine Ligand 5 (Ccl5), or TNF Receptor Superfamily Member 9 (Tnfrsf9) was found to differ in turtles carrying the virus, compared to non-infected animals. In conclusion, we found that developmental dieldrin exposure of T. scripta slightly reduces neonatal expression of several gene transcripts which may be correlated to adult reproductive fitness.