Meeting Abstract
99.6 Wednesday, Jan. 7 Expression of Sea Lamprey, Petromyzon marinus, Deiodinase Type II Throughout Metamorphosis and Following a Thyroid Challenge. STILBORN, S.S.M*; MANZON, L.A.; SCHAUENBERG, J.D.; MANZON, R.G.; Univ. of Regina, Biology; Univ. of Regina, Biology; Univ. of Regina, Biology; Univ. of Regina, Biology stilborn@uregina.ca
Thyroid hormones (TH) are crucial for major developmental events in all vertebrates studied to date. Most notable is their involvement in vertebrate metamorphosis. However, lampreys appear to be an exception; natural and induced metamorphoses seem to require decreased serum TH levels. We isolated a 1.8kb fragment, including the full-length coding region, of the 10-11kb sea lamprey deiodinase type II (D2) mRNA transcript. The predicted amino acid sequence has 47% identity and 60% similarity to human D2 and includes the selenocysteine characteristic of selenoproteins. However, we have yet to identify the selenocysteine insertion sequence (SECIS) in the 3′ UTR. Real-time PCR detected D2 mRNA in all tissues examined, including intestine, liver, kidney, and brain. In the intestine, liver, and kidney (included gonad and nephrogenic tissue) D2 mRNA levels were highest in immediately premetamorphic larvae through metamorphic stage-2. Thereafter, transcript levels decreased significantly in stages 3 and 4, and remained low into the parasitic phase. D2 is responsible for cellular activation of TH, thus decreased D2 mRNA levels during metamorphosis is consistent with other data showing thyroid axis suppression coincides with, and/or induces, lamprey metamorphosis. Finally, to determine if lamprey D2 levels are regulated by changes in thyroid status, as is the case in most other vertebrates, larval sea lamprey were treated with 50M T3 or 200nM T4 for 3-12-days, or 0.05% KClO4 for 6-24-days. Data on mRNA transcript levels in several tissues will be presented and discussed in the context of the lamprey thyroid axis and its regulation. Funded by NSERC.
