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DNA Microarray Tool Successfully Identifies Domoic Acid Toxicity in California Sea Lions

Heat map showing clustering of animals according to disease state (DAT - domoic acid toxicity; Lepto - leptospirosis) based on gene expression patterns of a subset of 110 genes (x-axis).  Red indicates a gene is more highly expressed, green indicates a gene is less highly expressed than average.The National Centers for Coastal Ocean Science (NCCOS) has developed a DNA microarray for profiling gene expression patterns in blood to aid in clinical and population level studies of domoic acid exposure on sea lions. There is currently no straightforward way to diagnose domoic acid poisoning due to the highly variable symptoms, the fact that toxin levels are often undetectable, and there is no definitive clinical measurement that distinguishes domoic acid poisoning from other common diseases such as leptospirosis. This DNA microarray starts the process with a long-awaited tool to diagnose current and previous domoic acid poisoning.

Principle components analysis (PCA) plot shows clear differentiation in blood gene expression profiles of domoic acid exposed (purple), leptospirosis infected (green) and healthy control (blue) sea lions.A decade of collaboration between NCCOS and the Marine Mammal Center in Sausalito, CA produced an eight year retrospective analysis of hundreds of California sea lions with acute poisoning and chronic disese. Domoic acid is neurotoxin produced by the diatom Pseudo-nitzschia australis that accumulates in the prey of sea lions and causes lethargy, disorientation, aggression, and seizures.

In this new study of 73 sea lion blood samples to be published in in the April issue of Developmental and Comparative Immunology, the microarray correctly classified domoic acid and leptospirosis infected animals. This tool will be further evaluated in collaboration with the Marine Mammal Center for its utility in screening animals for previous domoic acid exposure.

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