碩士 / 國立臺灣海洋大學 / 生物科技研究所 / 95 / Abstract
The aryl hydrocarbon receptor (AHR) is a ligand-dependent transcription factor that belongs to the basic helix-loop-helix PAS (bHLH-PAS) protein family. AHR mediates the biological and toxic effects of various environmental pollutants such as dioxin or polycyclic aromatic compounds. The AHR/ARNT complex also regulates numerous genes involved in a variety of physiological process. In mammalian system, a negative regulatory loop of AHR-related signaling pathway is established by AHR repressor (AHRR), which represses AHR mediated genes transcription by competing with AHR for binding to ARNT.
In zebrafish, two forms of ahrr cDNAs have been cloned that encode AHRR1 and AHRR2 with predicted size of 550 and 573 amino acids, respectively. To ascertain the roles of ahrr1 and ahrr2 in embryonic development, we used whole-mount in situ hybridization to analyze the expression pattern of these two genes. In zebrafish embryo, ahrr1 and ahrr2 were expressed mainly in the head region and their transcription reached the highest level at 48hpf, and decreased after then. ahrr2 also expressed in the otic capsule. TCDD did not induce ahrr1 and ahrr2 transcipt significantly. To investigate the regulatory mechanism of ahrr1 and ahrr2 genes, gene-specific antisense morpholino oligonucleotide of ahr2-MO were applied to block AHR2 protein translation. It appears both ahrr1 and ahrr2 were slightly inhibited at 48hpf, but did not have significant changes after hatching, suggesting that ahrr1 and ahrr2 were not regulated by AHR2 signal transduction. To investigate the roles of AHRR1 and AHRR2 in the AHR2 signal transduction pathway, ahrr1-MO and ahrr2-MO were injected into fertilized embryos and found that the expression of cyp1a1 did not changed by TCDD treatment during embryonic stages. The results revealed that induction of cyp1a1 after TCDD treatment was not influeced by AHRR1 and AHRR2.
It was noted that ahrr1 and ahrr2 knockdown results in severe pericardial edema, slow heart rate and increased mortality at 96hpf. Hence, although ahrr1 and ahrr2 were not involved in AHR2 signal transduction pathway, they might play important roles in zebrafish organogenesis, such as cardiogenesis.
| Identifer | oai:union.ndltd.org:TW/095NTOU5111009 |
| Date | January 2007 |
| Creators | Yi-Chih Chen, 陳宜芝 |
| Contributors | Chin-Hwa Hu, 胡清華 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 104 |
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