Characterization of thyroid hormones and thyroid hormone receptors during the early development of Pacific bluefin tuna (Thunnus orientalis).
We studied the profiles of 3,5,3'-l-triiodothyronine (T3), thyroxine (T4), and thyroid hormone receptors (TRs) in Pacific bluefin tuna (Thunnus orientalis) during embryonic and post-embryonic development. Both T3 and T4 were detected in embryos just before hatching, and it was found that the levels of both were increased in postflexion fish. The thyroid follicles were increased in both size and number in postflexion fish compared with preflexion fish. A TRbeta cDNA clone was generated by RACE. Two TRalpha cDNA clones were also partially identified and analyzed by real-time RT-PCR in this study. The TR mRNA levels in embryos were determined, and these were found to be lower than those in preflexion fish. Therefore, we considered that thyroid hormones function during early post-embryonic development as well as during embryonic development. Moreover, there was a peak in the TR mRNA level during postflexion stages, as seen during metamorphosis in Japanese flounder and Japanese conger eel. It is possible that thyroid hormones control the early development of scombrid fish through TRs, as they do for Pluronectiformes and Anguilliformes.
Kawakami
Yutaka
Y
Department of Fisheries, Graduate School of Agriculture, Kinki University, Nara 631-8505, Japan. yutakakjp@yahoo.co.jp
Nozaki
Jun
J
Seoka
Manabu
M
Kumai
Hidemi
H
Ohta
Hiromi
H
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary / Q000302:isolation & purification / Q000378:metabolism; D004625:Embryo, Nonmammalian; D018507:Gene Expression Regulation, Developmental; D008018:Life Cycle Stages / Q000235:genetics / Q000502:physiology; D008954:Models, Biological; D008969:Molecular Sequence Data; D010802:Phylogeny; D011988:Receptors, Thyroid Hormone / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D013961:Thyroid Gland / Q000033:anatomy & histology / Q000196:embryology / Q000254:growth & development; D013963:Thyroid Hormones / Q000378:metabolism*; D013997:Time Factors; D014413:Tuna / Q000196:embryology / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism
D018076:DNA, Complementary; D011988:Receptors, Thyroid Hormone; D013963:Thyroid Hormones