一般認為脊椎動物演化過程中，發生了數次大片段或全基因體之複製，導致一個原始基因在脊椎動物體中常常有數個副本基因（duplicated gene）。硬骨魚類又有一次大規模的基因體複製，造成魚類中特有的副本基因。麩胺酸（glutamate）是中樞神經系統中一種主要的興奮性神經傳導物質，麩胺酸所引發之神經傳導訊息由一群麩胺酸受器（glutamate receptor）負責傳導。離子通道型麩胺酸受器（ionotropic glutamate receptor） 依據藥理學可細分為AMPA受器、kinate受器以及NMDA受器。GluR2 是AMPA 受器的次單元，斑馬魚有兩個GluR2副本基因 (paralogue)，分別為GluR2α和GluR2β。NR1是NMDA受器的次單元，斑馬魚有兩個NR1副本基因，分別為NR1.1以及NR1.2。目前針對副本基因保存有許多假設，其中一種所謂DDC模式（duplication-degeneration-complementation model），此種模式預期複製後的副本基因在不同調節片段可能發生失去功能的突變，導致副本基因彼此之間必須相互彌補另一副本基因缺少的功能，因而二個基因都必須被保留。若DCC機制也涉及魚類GluR2及NR1副本基因之保留，則副本基因彼此的表現區域也會不同。我們以全覆式RNA原位雜合染色技術（Whole-mount in situ hybridization）分析GluR2及NR1這兩對副本基因表現區域，發現斑馬魚胚體在視網膜細胞中GluR2β的表現於受精後二至三日間開始顯著增加，而同時間GluR2α在視網膜細胞的表現則只微幅增加。成熟魚腦中端腦（Tel, telencephalon）、視頂蓋（TeO, tectum opticum）及小腦體（CCe, corpus cerebelli）等部位GluR2β表現皆高於GluR2α。成熟魚腦NR1.1以及NR1.2這對副本基因在視頂蓋、小腦體及小腦尾葉（LCA, lobus caudalis cerebelli）等部位有互補性之區域表現。基因表現研究顯示DCC機制也參與演化上保留斑馬魚離子通道型麩胺酸受器基因GluR2及NR1副本基因。

Partial or complete genomic duplications have occurred several times during the evolution of vertebrates, resulting in several duplicated genes derived from a common ancestral gene. Ionotropic glutamate receptors (iGluRs) mediate excitatory synaptic transmission in the vertebrate central nervous system. The ionotropic glutamate receptors are classified into three major subtypes, the AMPA-, kainite-, and NMDA-preferring receptors. Zebrafish expresses two duplicated GluR2 genes, GluR2α and GluR2β, as well as two duplicated NR1 genes, NR1.1 and NR1.2. Duplication-degeneration complementation (DDC) is a model hypothesized to preserve duplicated genes. If DDC is involved in the preservation of duplicated genes, the expression patterns of the paralogous genes are expected to be different and compensatory. In this thesis, whole-mount in situ hybridization was employed to study the expression patterns of GluR2 and NR1 duplicated genes. Experimental results showed that the expression of GluR2β increased significantly in the retina of zebrafish between 2 to 3 day postfertilization; however the expression of GluR2α in the retina increased only mildly over the same peroid. The expression of GluR2β in the telencephalon, tectum opticum and corpus cerebelli are higher than that of GluR2α. The expressions of NR1.1 and NR1.2 are complementary in the regions of telencephalon, corpus cerebelli and lobus caudalis cerebelli. These results showed that DDC may be involved in the preservation of duplicated genes of GluR2 and NR1 during evolution.

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