Differential gene expression in the brain of channel catfish ( Ictalurus punctatus) in response to cold acclimation

Aquatic ectotherms can adapt to a wide range of temperature changes, but the molecular mechanisms that underlie this adaptability are not well understood. We identified genes that are differentially expressed in the catfish ( Ictalurus punctatus) brain using a cDNA microarray approach to gain an initial understanding of adaptation to low temperature. Among 660 genes analyzed, 61 were differentially expressed when compared at 12 degrees C and 24 degrees C. Gene induction was rapid, occurring within 2 h of the temperature shift. The major categories of differentially expressed genes included (1) genes for chaperones such as Hsp70 and Hsp70/Hsp90 organizing protein; (2) genes for transcription factors and gene products involved in signal transduction pathways such as zinc-finger proteins, calmodulin kinase inhibitor, the nuclear autoantigen SG2NA, interferon regulatory factor 3, and inorganic pyrophosphatase; (3) genes involved in lipid metabolism such as TB2 and acyl CoA binding protein; and (4) genes involved in the translational machinery such as ribosomal proteins. Some genes were induced transiently, whereas others were induced in an enduring fashion. Several genes, primarily ribosomal protein genes, were down regulated, indicating reduced metabolic activities after extended incubation at the low temperature. Thus channel catfish respond to low temperature by adjusting expression of a large number of genes. The rapid induction of proteins involved in signal transductions and chaperones suggests that both de novo synthesis of cold-induced proteins and modification of existing proteins are required for adaptation and tolerance of catfish to low environmental temperature.