GENE EXPRESSION IN THE MUSCLES OF YOUNG AND MATURE CHANNEL CATFISH (Ictalurus punctatus) AS ANALYZED BY EXPRESSED SEQUENCE TAGS AND GENE FILTERS

Department of Fisheries and Allied Aquacultures, and Program of Cell and Molecular Biosciences, 203 Swingle Hall, Auburn University, Auburn, AL 36849

Expressed sequence tag (EST) analysis was conducted using a cDNA library made from the muscle mRNA of channel catfish (Ictalurus punctatus). This study had three major objectives: first, to generate expressed sequence tags for genomics research involving genetic linkage analysis; second, to examine gene expression profiles in muscles of channel catfish in a non-normalized muscle cDNA library; and third, to demonstrate the feasibility of functional genomics in small laboratories by comparing gene expression in young and mature channel catfish muscles using the EST reagents and gene filters. One hundred and two randomly picked cDNA clones were analyzed from the channel catfish muscle cDNA library. Of the sequences generated, approximately 87% ESTs were identified as known genes by identity comparisons. These clones of known gene products represent transcriptional products of 27 genes. The 15 clones of unknown gene products represent 12 genes. The major transcripts (62.7% of the analyzed ESTs) in the catfish muscle are from several major genes involved in muscle contraction, relaxation, energy metabolism, and calcium binding. These include alpha actin, creatine kinase, parvalbumin, myosin, troponins, and tropomyosins. The parvalbumin complete cDNA was sequenced and its similarity to other parvalbumins was aligned. Gene expression of the unique ESTs was comparatively studied in the young and adult catfish muscle. Significant differences were observed for aldolase and chilling tolerance-related protein. While chilling tolerance-related protein is down-regulated in the mature fish muscle, the aldolase is significantly up-regulated in the mature fish muscle. Although the physiological significance of changes in expression of the two proteins needs to be addressed further, this research demonstrates the feasibility and power of functional genomics in catfish.