CONCLUSIONS AND FUTURE DIRECTIONS

ERDC TN-DOER-R4

September 2004

CdCl2, B[a]P, and TCE, respectively. Results showed a similar decrease in the numbers of genes

that responded in a consistent manner across all doses, with 18 consistent genes for TCDD, 2 for

PCBs, and 14 for PAHs. There was no overlap between the consistently responding genes for the

three compounds/mixtures tested; gene ID, dose-related responses, and statistical data can be

found in Appendix B. The existence of these unique genes whose expression is consistently

affected by exposure to contaminants provides support for the hypothesis that gene expression

can be used to detect and identify chemical classes of contaminants by their MOAs as evidenced

by gene expression in environmental samples.

CONCLUSIONS AND FUTURE DIRECTIONS: Gene expression profiles for the tested

contaminants and contaminant mixtures appear to be characteristic of the test compounds and

consistent over a large dose range, and thus may be useful for toxicant identification in field

samples. However, confirmation of the gene responses via a secondary methodology such as RT-

PCR is necessary. Additionally, in order to make this approach useful in simultaneously

detecting multiple contaminants in environmental samples, testing chemical mixtures with mixed

MOAs (e.g. combined exposure to PAHs and TCDD) is needed to determine whether the

fingerprints are additive, and whether interactions between the contaminant classes alter the

contaminant-specific responses observed and reported herein.

The number of potentially unique, dose-responsive genes is small enough to allow for the

generation of a smaller customized array, or development of more rapid/less expensive methods

for quantifying them (RT-PCR, glass arrays, etc.). If the expression fingerprints remain intact in

exposures to the more complex mixtures found in environmental samples, it may be possible to

rapidly assess the presence of multiple contaminants in a single assay (presence of unique

expression fingerprint), as well as to assess the severity of the contamination (intensity of

alterations in gene expression).

POINTS OF CONTACT: For additional information, contact one of the authors, Dr. Laura S.

Inouye, (601) 634-2910, ; or Dr. Victor A. McFarland,

(601) 634-3721, , or the Manager of the Dredging

Operations and Environmental Research Program, Dr. Robert M. Engler, (601) 634-3624,

This technical note should be cited as follows:

Inouye, L. S., Ang, C. Y., and McFarland, V. A. (2004). "Development of gene

expression fingerprints for identification of environmental contaminants using DCNA

arrays," DOER Technical Notes Collection (ERDC TN-DOER-R4), U.S. Army Engineer

Research and Development Center, Vicksburg, MS. www.wes.army.mil/el/dots/doer.

REFERENCES

Ang, C. Y., Inouye, L. S., McCant, D. D., and McFarland, V. A. (2000). "Protocols for a rapid

clean-up/extraction procedure and an improved P450RGS dioxin screening assay for sediments,"

DOER Technical Notes Collection (ERDC TN-DOER C10), U.S. Army Engineer Research and

Development Center, Vicksburg, MS. www.wes.army.mil/el/dots/doer.