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Importance of thyroid hormone receptors alpha and beta in preimplantation bovine embryo development in vitro

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Title: Importance of thyroid hormone receptors alpha and beta in preimplantation bovine embryo development in vitro
Author: Rho, Na-Young
Department: Department of Biomedical Sciences
Program: Biomedical Sciences
Advisor: King, Wiiliam. Allan
Abstract: Thyroid hormone receptors (THRα and β) mediate the genomic action of thyroid hormones (TH) which play a role in bovine embryo development, however, little is known about the THR in the preimplantation embryo. Therefore, the objective of this study was to investigate the importance of THRs in in vitro preimplantation bovine embryos. To do this, the levels of THR mRNA and protein were monitored in oocytes and developing embryos up to the blastocyst stage. Subsequently, embryos were treated with THs and mRNA levels and developmental rates were determined. Finally, embryonic transcription of THR α and β was inhibited by α-Amanitin and maternal and embryonic transcripts were knocked down by siRNA micro-injection and THR mRNA and protein levels were assessed by RT-PCR and immunoflouresence techniques. TH treatment increased the rate of development but did not affect THR mRNA levels. THR mRNA and protein levels were shown to rise after fertilization in untreated controls but inhibition of transcription and knock-down by siRNA confirmed a significant (p<0.05) level of transcript of the THRs genes from 2-cell stage onwards. THR protein levels was not altered at 2-cell stage, but exhibited a significant (p<0.05) decrease from the 4-cell stage. Inhibition of THR α and β by siRNA led to a significant decrease in the developmental rate, embryo morphology and cell number. It was concluded that THR α and β are transcribed soon after fertilization, before the major activation of the embryonic genome, and that they are essential for bovine embryo development in vitro.
Date: 2013-01
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