A molecular survey of programmed cell death in rainbow trout: Structural and functional specifications of apoptotic key molecules

Abstract Apoptosis is an integral part of homeostasis and supports multiple physiological processes such as development and immune defense, thereby directly targeting damaged or unwanted cells without affecting neighbor cells. In the present study, we characterized the apoptotic key factors caspase-3, −7, and − 8 as well as regulator protein TPT1 (translationally-controlled tumor protein 1) from rainbow trout ( Oncorhynchus mykiss ). We identified multiple single-nucleotide changes in their coding sequences and showed that the CASP3 gene is present in at least three variants. Caspase genes were clustered to their orthologs in bony fish and human by using evolutionary analysis. Expression profiling in seven tissues of unchallenged adult fish revealed predominant transcript levels in the head kidney ( CASP3 , 7 , and 8 ) or brain ( TPT1 ). Further, we analyzed the expression of a more comprehensive panel of 16 trout genes encoding pro- and anti-apoptotic factors and associated proteins during development and upon stress exposure ( in vitro temperature and staurosporine treatment). Previously published transcriptome data suggested that the induction of apoptotic processes is mirrored on the transcript level, but this could not be confirmed by the present gene-profiling study. Yet on the protein level, treatment of trout cell line RT-gill-W1 with 1 μM staurosporine for up to 120 min led to a significant increase of CASP3/7 activity. Moreover, a meta-analysis on published data showed that stress-related expression could only be detected sporadically for apoptotic key factors. In conclusion, there seems to be no reliable pattern or marker representing the stress-related induction of apoptosis in salmonids.