Immortal and mortal clonal lymphocyte lines from channel catfish: comparison of telomere length, telomerase activity, tumor suppressor and heat shockprotein expression

Channel catfish autonomous (immortal) and nonautonomous (mortal) leukocyte lines were phenotyped with respect to telomere length and the expression of telomerase, Hsp70 and p53, potentially important factors in cellular immor talization. The autonomous cells constitutively expressed telomerase wherea s the nonautonomous cells expressed this activity only transiently. This ob servation, coupled with the low telomerase activity level seen in freshly i solated leukocytes, suggests that telomerase expression in catfish leukocyt es is activation induced. In contrast both types of cell lines exhibited qu ite similar patterns of significantly shortened telomeres, suggesting that telomerase does not stabilize catfish telomeres until a critical short leng th is reached. Northern analyses indicated that, like telomerase, Hsp70 gen e expression was constitutive in autonomous cells and transient in nonauton omous cells. In contrast, p53 mRNA levels appeared similarly low and noncyc ling in both longterm cultured types of catfish cells, regardless of the cu lture situation. Furthermore it was noted, by Western analyses, that both t ypes of cells display multiple sized forms of p53 proteins. This latter obs ervation implies that truncation of p53 protein is probably not directly in volved in the in vitro immortalization process of channel catfish leukocyte s. (C) 2001 Elsevier Science Ltd. All rights reserved.