Can Identities of key amino acids in the ligand binding domain of the AhR be used to predict the sensitivity of endangered sturgeons to dioxins?

Transcription

1 Can Identities of key amino acids in the ligand binding domain of the AhR be used to predict the sensitivity of endangered sturgeons to dioxins? By: Jon Doering

2 Sturgeons Sturgeons have faced population declines due to a variety of anthropogenic causes: Historic Overfishing

3 Sturgeons Sturgeons have faced population declines due to a variety of anthropogenic causes: Historic Overfishing Habitat Alteration

4 Sturgeons Sturgeons have faced population declines due to a variety of anthropogenic causes: Introduced Species Habitat Alteration

5 Sturgeons Sturgeons have faced population declines due to a variety of anthropogenic causes: Introduced Species Pollution

6 Dioxin-like Compounds Includes Dioxins, Furans, and PCBs Extremely persistent in the environment Accumulate in organisms Variety of adverse biological effects Aryl hydrocarbon receptor (AhR) agonists Furans PCBs Dioxins

7 Species Sensitivity Most Sensitive Lake Trout Brook Trout Crucian Carp Mummichog Red Seabream Rainbow Trout Fathead Minnow Channel Catfish Lake Herring Japanese Medakafish White Sucker Northern Pike Zebrafish Pallid Sturgeon Shovelnose Sturgeon Least Sensitive Great differences in species sensitivity: 200-fold difference in embryo-lethality 0 5,000 10,000 15,000 LD50 (pg/g egg)

8 Sturgeons Problem: there are large differences in sensitivity to dioxin-like compounds among species presents a major challenge to risk assessment.

9 Sturgeons Problem: there are large differences in sensitivity to dioxin-like compounds among species presents a major challenge to risk assessment. Solution: develop methods to predict species sensitivity without use of live animals with special interest in predicting the relative sensitivity of sturgeons or other endangered species.

10 Birds

11 Birds

12 Question Lake Trout Brook Trout Crucian Carp Mummichog Red Seabream Rainbow Trout Fathead Minnow Channel Catfish Lake Herring Japanese Medakafish White Sucker Northern Pike Zebrafish Pallid Sturgeon Shovelnose Sturgeon Does the same hold true for fishes? 0 5,000 10,000 15,000 LD50 (pg/g egg)

13 Question Lake Trout Brook Trout Crucian Carp Mummichog Red Seabream Rainbow Trout Fathead Minnow Channel Catfish Lake Herring Japanese Medakafish White Sucker Northern Pike Zebrafish Pallid Sturgeon Shovelnose Sturgeon Can relative sensitivity among species of fishes be predicted based upon relative differences in the molecular initiating event? 0 5,000 10,000 15,000 LD50 (pg/g egg)

14 Sturgeons 3 Main Objectives: 1) Identification of AhR1 and AhR2 amino acid sequences

15 Sturgeons 3 Main Objectives: 1) Identification of AhR1 and AhR2 amino acid sequences 2) Quantification of sensitivity to activation of AhRs by dioxin-like compounds

16 Sturgeons 3 Main Objectives: 1) Identification of AhR1 and AhR2 amino acid sequences 2) Quantification of sensitivity to activation of AhRs by dioxin-like compounds 3) Predict sensitivity of sturgeon of unknown in vivo sensitivity based on other species of fish of known in vivo sensitivity

17 Study Species White Sturgeon (A. transmontanus) Lake Sturgeon (A. fulvescens)

18 AhR1 Comparison - TCDD Luciferase Ratio Ligand Concentration (nm)

19 AhR1 Comparison - TCDD Luciferase Ratio No difference in sensitivity. Ligand Concentration (nm)

20 AhR2 Comparison - TCDD Luciferase Ratio Ligand Concentration (nm)

21 AhR2 Comparison - TCDD Luciferase Ratio 10-fold difference in sensitivity. Ligand Concentration (nm)

22 AhR Structure Do specific amino acid differences in the ligand binding domain of the AhR between species result in differences in affinity of the receptor and differences in sensitivity between species?

23 AhR Ligand binding region of the AhR2 of White and Lake Sturgeon have four amino acid differences.

24 AhR Ligand binding region of the AhR2 of White and Lake Sturgeon have four amino acid differences.

25 AhR2 Structure

26 AhR2 Structure

27 AhR2 Structure

28 AhR2 Structure

29 AhR2 Structure

30 Relative Sensitivity? Lake Trout Brook Trout Crucian Carp Mummichog Red Seabream Rainbow Trout Fathead Minnow Channel Catfish Lake Herring Japanese Medakafish White Sucker Northern Pike Zebrafish Pallid Sturgeon Shovelnose Sturgeon White Sturgeon? 10-fold? Lake Sturgeon? Where do white sturgeon and lake sturgeon fit? 0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 LD50 (pg/g egg)

31 Relative Sensitivity? Lake Trout Brook Trout Crucian Carp Mummichog Red Seabream Rainbow Trout Fathead Minnow Channel Catfish Lake Herring Japanese Medakafish White Sucker Northern Pike Zebrafish Pallid Sturgeon Shovelnose Sturgeon 0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 LD50 (pg/g egg)

32 Diverse Fishes Lake Trout Brook Trout Crucian Carp Mummichog Red Seabream Rainbow Trout Fathead Minnow Channel Catfish Lake Herring Japanese Medakafish White Sucker Northern Pike Zebrafish Pallid Sturgeon Shovelnose Sturgeon Total of 11 species spanning ~70-fold difference in LD50 to embryos 0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 LD50 (pg/g egg)

33 Diverse Fishes Lake Trout Brook Trout Crucian Carp Mummichog Red Seabream Rainbow Trout Fathead Minnow Channel Catfish Lake Herring Japanese Medakafish White Sucker Northern Pike Zebrafish Pallid Sturgeon Shovelnose Sturgeon Total of 10 AhR1s and 15 AhR2s 0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 LD50 (pg/g egg)

34 AhR2 Relatedness tree for AhR2s

35 AhR2 Total of 30 positions with amino acid differences among 17 AhRs from 13 species

36 AhR2 Initial sequence alignment indicates no trends in structure among sensitive vs insensitive fishes

37 AhR2 Can Identities of key amino acids in the ligand binding domain of the AhR be used to predict the sensitivity of endangered sturgeons to dioxins?

38 AhR2 Can Identities of key amino acids in the ligand binding domain of the AhR be used to predict the sensitivity of endangered sturgeons to dioxins? Activation assays Basal expression studies ongoing ongoing

39 Acknowledgements Co-authors: Steve Wiseman Shawn Beitel John Giesy Markus Hecker Co-authors: Reza Farmahin Sean Kennedy Additional Support:

40 Author Contact: Jon Doering Questions??