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Address

Tsukada Laboratory,
Department of Biomolecular Science,
Faculty of Science,
Toho University

Miyama2-2-1, Funabashi,
Chiba, 274-8510 Japan

Lab Overview

 

Eel serum toxin

 Anguilliformes including Japanese eels, conger eels, moray eels, have toxin in their serum. Eating uncooked eel meat causes diarrhea, vomiting, dermatitis in human. The toxin has been named ichthyohemotoxin (Latin: ichthyo: fish, hemo: blood, toxin: poison) and the research has a long history. However, the gene encoding eel serum toxin has not been found. Recently, our research group discovered an eel serum toxin gene. Our laboratory is studying the various physiological effects of eel serum toxin, in future, we are planning to expand our research on eel serum toxin to drug discovery research.

Appetite research

Yellow eels are the top predator eating small fish and insects in rivers, but once they migrate to the ocean, their teeth and digestive tracts degenerate (giving up eating and using abdominal space for gonadal development), and they swim over 2,500 km for spawning. On the other hand, cultured eels actively feed in fishponds, but when they are treated with cold water for shipping, their appetite is completely suppressed for several months or more. Cultured eels raised in our laboratory endured fasting for up to one year and seven months, and during the fasting period, they survived only on nutrients stored in the muscle. Thus, eels can be a new experimental model for stress, appetite, and metabolism research. We are aiming practical applications in eating disorders and dieting from research of eel’s unique appetite.

Tissue remodeling in eel

Japanese eel, Anguilla japonica, can survive both in freshwater and seawater (called ‘Euryhaline fish’). This fish has special ability that remodels their tissues when they encounter the different salinity environments. For example, when freshwater eels face seawater, eels destroy their freshwater-type tissues and re-construct seawater-type tissues within 2 weeks (i.e. They become seawater fish from freshwater fish within 2 weeks!). In nature, eel alters their tissues during metamorphosis and sexual maturation, we think that tissue remodeling is also associated with these processes. Our laboratory is studying molecular mechanisms underlying tissue remodeling in eel. Tissue breakdown is seen in many pathological conditions in human, but, unlike eel, most destroyed tissues can not be fully regenerable. Outstanding regenerative capacity in eel will contribute to understanding of disease and to regenerative medicine.
Tissue remodeling

C-type natriuretic peptides in eel

C-type natriuretic peptide is a hormone expressed strongly in the brain. However, the brain function of CNP has not been revealed since its discovery in 1990. Our laboratory is focusing on evolutionary evidence that CNP molecules have been diversified and conserved in teleost (in other words, CNP molecules are important in teleost), and is studying functions of CNP in fish brain. Our final goal is to decipher essential CNP function in verteberate including human from an evolutionary point of view.
(Top) C-type natriuretic peptides among vertebrates: CNP has been diversified after teleost lineage. However, some CNP molecules have been erased in mammals during the process of evolution.
(Bottom) Expression of CNP3 in eel pituitary: CNP3 expression is higher in freshwater-acclimated eel than that in seawater-acclimated eel, suggesting that CNP3 is important regulator in freshwater environment.