LYMPHOCYTE EXPRESSION IN TRANSGENIC TROUT BY MOUSE IMMUNOGLOBULIN PROMOTER ENHANCER/

Two groups of transgenic rainbow trout (Oncorhynchus mykiss, Walbaum) have been produced and compared. One group harbored the reporter gene of chloramphenicol acetyltransferase (CAT) associated with mouse immun oglobulin (Ig) promoter/enhancer (pUCL-CAT-E). The other group carried the same reporter gene under the control of the cytomegalovirus promo ter/enhancer (pCMV-CAT). Slot blot analysis of DNA from blood cells an d other tissues from pUCL-CAT-E fish showed variation of copy number b etween the major tissues but not between red and white blood cells. So uthern blot analysis indicated that multiple copies organized in conca temers were incorporated into the genome. The pCMV-CAT fish had a pron ounced expression of CAT in both white and red blood cells. In contras t, activity of CAT was found in the white blood cells of all pUCL-CAT- E fish but not in their red blood cells. Expression in white blood cel ls was found preferentially in sIg(+) cells, indicating that B cells a re the major expressors. High expression was also found in spleen and kidney, but the activity found in thymocytes was equal to the backgrou nd level. Analysis of some major tissues showed high white blood cell expression associated with low tissue expression, except that liver (k nown to contain lymphoid tissue in fish) was higher. Thus the regulato ry elements of the Ig gene from mouse induce a tissue-specific express ion in fish.