Abstract
Tributyltin-binding proteins (TBT-bps), members of the lipocalin family, bind TBT in fish blood and are presumed to contribute to detoxification of TBT. Recent studies have shown that many fish species have TBT-bp genes, and that these genes are induced by stresses such as exposure to chemicals or fish pathogenic bacteria. However, the function of TBT-bps, and the mechanisms of their induction and detoxification activity are still unclear. Here, towards elucidating the functions of TBT-bp2, we produced a TBT-bp2 knockout (TBT-bp2−/−) strain of Japanese medaka, Oryzias latipes, by using the CRISPR/Cas9 system. Gene expression of the mutated TBT-bp2 was reduced, and the cDNA sequencing and predicted protein structure suggested possible loss of function. However, the fish could be grown under normal conditions. Exposure of the TBT-bp2−/− strain of medaka to various stresses in future experiments is expected to contribute to our understanding of this novel detoxification system in aquatic organisms.
Highlights
Tributyltin-binding proteins (TBT-bps) bind TBT, a typical endocrine disruptor, and are presumed to be involved in detoxification of accumulated TBT (Satone et al, 2008; Shimasaki et al, 2002)
TBT-bps were first discovered in Japanese flounder, Paralichthys olivaceus (Shimasaki et al, 2002), but later studies have shown that these proteins and/or genes, and their homologs are widely expressed in many fish species: e.g., tiger puffer, Takifugu rubripes (Oba et al, 2011); European eel, Anguilla anguilla L. (Nogueira et al, 2009), and Japanese medaka, Oryzias latipes (Hashiguchi et al, 2015; Nassef et al, 2011a)
Response of TBT-bps to chemicals and bacteria has been reported in many fish species: e.g., 5pentachlorobiphenyl (PCB126) and a PCB mixture (Kanechlor-400, KC-400) in Japanese medaka (Nakayama et al, 2008); 7,12-dimethylbenz [a] anthracene (DMBA) in European eel (Nogueira et al, 2009); and pathogenic bacteria Edwardsiella tarda and Aeromonas hydrophila in marine medaka (O. melastigma) (Dong et al, 2017) and carp (Labeo rohita) (Robinson et al, 2014), respectively
Summary
Tributyltin-binding proteins (TBT-bps) bind TBT, a typical endocrine disruptor, and are presumed to be involved in detoxification of accumulated TBT (Satone et al, 2008; Shimasaki et al, 2002). As such, they may bind xenobiotics in a novel detoxification pathway. The mechanisms of the induction response and detoxification of TBT by TBT-bps, and its original role (i.e., before man-made chemicals and pathogenic bacteria) remain to be elucidated
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