Please use this identifier to cite or link to this item:
Molecular Structure of Retinal Photoreceptor Protein Gene of the Common Carp (Cyprinus carpio)
|Publication Year :||1998|
|Abstract:||視紫質蛋白(rhodopsin)是位於視桿細胞(rod cell)上的感光受器，負責弱光中的視覺形成。在脊椎動物視紫質蛋白基因的研究中，絕大部分只有一種視紫質蛋白的cDNA被報告，然而我們在鯉魚(Cyrinus carpio)卻發現有兩種視紫質蛋白的cDNA(Tsai et al., 1994; Lim et al., 1997)。在本研究中，藉由聚合?鍊鎖反應(polymerase chain reaction)以及限制?圖譜分析，證實此兩種視紫質蛋白基因可同時存在於一個鯉魚個體中。在成功選殖並定序第一型視紫質蛋白的染色體基因(genomic gene)後，與第二型相比較，獲知此兩型基因在上游調控區(-3434?+94)只有45.6％的相似度，但卻含有三段相當保守的區域(conserved region)：位於-1262?-614、-539?-419 與-166?＋94，分別具有78.0％、79.3％及92.3％的相似度。另一方面，為了研究魚類視紫質基因的調控，我們在第一型基因的上游調控區域中構築了四種不同長度的DNA片段，分別命名為pDel-6k、pDel-146、pDel-77與pDel-53，依次包含-6k?+66、-146?+94、-77?+94與-53?+94的上游調控區，其後均接上綠色螢光蛋白的cDNA (green fluorescence protein, GFP)為報導基因。將這些片段分別用顯微注射技術轉殖到稻田魚(Oryzias latipes)單一細胞時期(one-cell stage)的受精卵中。結果顯示：除了Del-46片段之外，GFP在視網膜上都有組織專一性表現。由此，我們提出一個假說：調控第一型視紫質基因組織專一性表現的片段，可能位於-77?-53之間。很有趣的是，以這個片段和已知調控陸生脊椎動物視網膜組織專一性的片段相比較，彼此之間的核?酸序列相似度卻很低。至於兩型基因之間調控差異性的研究，則正在進行中。|
Rod opsin, rhodopsin, is one of the photoreceptors but locates at rod cells, which mediates dim-light vision. Only one type of rhodopsin cDNA was reported in most of the species studied. However, two types of rhodopsin cDNA were cloned from the common carp (Cyprinus carpio). They shared 97.2% and 98.6% identities of polynucleotide and amino acid sequences, respectively (Tsai et al., 1994; Lim et al., 1997). Two types of rhodopsin genomic genes were identified in the same individual via PCR and restriction analysis. In addition, a genomic library of the common carp was constructed and the genornic gene of type Ⅰ rhodopsin was isolated and sequenced. Compared to the type Ⅱ rhodopsin gene (Lim, 1996), the type Ⅰ gene shared only 45.6% identity of polynucleotide sequences in the upstream region ranged from nucleotide (nt) position from -3434 to +94. However, there were three conserved segments, which were at nt -1262?-614, -539?-419 and -166?+94, with 78.0 %, 79.3 % and 92.3 % identities, respectively. And the two types of gene were both intronless.
To define the cis-acting DNA elements required for rhociopsin expression, we generated transgenic fish carrying sequences upstream of the type Ⅰ rhodopsin gene fused to the GFP (green fluorescence protein) cDNA as a reporter gene. Upstream sequences extending from -6k to +66 bp, from -146 to +94 bp, and from -77 to +94 bp were able to direct retinal-specific expression, while -53 to +94 bp were not. This suggests that elements which regulate retinal-specific expression may locate within -77?-53. Interestingly, little homology of polynucleotide sequences was shown between the region (-77?-53) and any other known retina-specific protein binding sites of terrestrial animals.
|Appears in Collections:||動物學研究所|
Files in This Item:
There are no files associated with this item.
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.