Altered gene expression associated with epizootic shell disease in the American lobster, Homarus americanus

Epizootic shell disease is a poorly understood condition that has significantly affected the American lobster fishery in New England (northeastern US) since the 1990s. Here we present the results of a study to identify changes in gene expression in lobsters exhibiting symptoms of epizootic shell disease. Suppressive subtractive hybridization (SSH) was used to compare gene expression between cDNA pools from diseased (symptomatic) and apparently healthy (asymptomatic) lobsters. Subsequently, quantitative real-time polymerase chain reaction (qPCR) was used to measure expression of nine genes that were differentially-expressed in the SSH analysis, in seven tissues (muscle, gill, heart, hepatopancreas, brain, branchiostegite, gonad) dissected from individual symptomatic and asymptomatic lobsters. Expression of arginine kinase (involved in cellular energetics) was significantly decreased in muscle of symptomatic lobsters. Expression of hemocyanin (a respiratory hemolymph protein involved in oxygen transport) was highest in hepatopancreas and showed highly variable expression with a trend toward higher expression in asymptomatic individuals. Alpha-2 macroglobulin (involved in the innate immune system) was most highly expressed in the ovary, particularly of symptomatic lobsters. The ESTs produced through this study add to the fledgling field of crustacean genomics and revealed three genes that could be further evaluated in lobsters of varying shell disease severity, molt stage, and reproductive condition, for possible implication in epizootic shell disease.