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標題: | 分析Cyp11a1基因剔除對發育中海馬迴神經元樹突型態之影響 Analysis of Dendritic Morphology of Developing Hippocampal Neurons in Cyp11a1 Null Mice |
作者: | Hao-Hua Jiang 姜浩華 |
指導教授: | 胡孟君(Meng-Chun Hu) |
關鍵字: | 神經類固醇,發育,海馬迴,基因剔除小鼠,樹突型態, neurosteroids,development,hippocampus,gene null mice,dendritic morphology, |
出版年 : | 2013 |
學位: | 碩士 |
摘要: | 在神經系統中,神經類固醇可以經由 P450scc 酵素以膽固醇為原料轉換而來。CYP11A1 基因可生成P450scc (P450 side-chain cleavage) 酵素,其在類固醇生成中為第一個酵素且扮演速率決定步驟之關鍵角色。許多研究結果發現神經類固醇參與了許多神經方面的功能,包括神經突起的生長、神經保護、髓鞘之形成、以及神經發育。另外,在一些行為失調和神經退化性疾病上,例如: 壓力、焦慮和記憶,神經類固醇也扮演了重要的角色。目前已有研究發現神經類固醇能夠影響神經樹突的型態。
根據本實驗室先前研究的結果,在出生後五天大的Cyp11a1基因剔除小鼠的海馬迴中,CA1以及CA3腦區的錐狀神經元之樹突大小和其分支複雜度皆有顯著下降的情形。對於神經突觸的形成和成熟而言,出生後十五天是一個關鍵的時期。本篇實驗想更進一步探討於十五大的剔除小鼠中,Cyp11a1基因對於海馬迴中錐狀神經元之樹突形態的影響。 我們先利用給予固醇類荷爾蒙的方式將這些基因剔除小鼠的生命延續至十五天大。再以Golgi-Cox染色法作海馬迴組織染色,檢驗CA1和CA3區域中錐狀神經元的樹突型態。分析結果顯示在十五天大的基因剔除小鼠中,CA1和CA3區域的錐狀細胞之樹突型態在數突總長度和樹突分枝複雜度上都顯著少於野生型小鼠。此外,由分析錐狀神經元上樹突棘數量的結果可知,在十五天大基因剔除小鼠的海馬迴中CA1和CA3腦區的樹突棘密度都有顯著下降的情形。 為了更進一步探討這些因Cyp11a1基因剔除而造成的樹突大小、分枝複雜度以及樹突棘密度下降的情況與哪些分子相關,以西方點墨法分析microtubule-associated protein 2 (MAP2), GAP-43, synapsin I 以及 PSD-95在基因剔除小鼠的海馬迴中之蛋白質表現量。結果顯示,在十五天大之剔除小鼠的海馬迴中,synapsin I 和 PSD-95的蛋白質表現量都有顯著性下降。 由以上實驗結果可知,Cyp11a1基因剔除會影響發育中海馬迴神經元的樹突型態。 Neurosteroids can be de novo synthesized from cholesterol through the P450scc in the nervous system. P450scc, encoded by CYP11A1 gene, is the cholesterol side-chain cleavage enzyme that catalyzes the first and rate-limiting step in the steroidogenesis. Neurosteroids have a variety of neurological functions, such as neurite growth, neuroprotection, myelination, and neurogenesis. They also play roles in many behavioral functions and diseases, including stress, anxiety, seizure disorders, and memory. It has been verified that several neurosteroids such as DHEA, DHEAS, and PREG are able to affect the dendritic morphology through in vitro experiments. Previous study in our lab has revealed that there were significant shrinkage of dendrite size and diminishment of dendritic branching in CA1 and CA3 pyramidal neurons in the hippocampus of Cyp11a1 null mice at the age of postnatal day 5 (P5). In this study, we further explore the dendritic morphology in the developing hippocampal neurons of the Cyp11a1 null mice at the age of P15, which is a critical period for synapse formation and maturation. The lives of knockout mice were maintained to P15 by receiving hormone administration. To reveal the dendritic morphology, Golgi-Cox method was used to stain the CA1 and CA3 pyramidal neurons in the hippocampus. The results showed that the total dendritic length, number of dendritic branchings versus orders, as well as dendritic arborization in the CA1 and CA3 pyramidal neurons are significantly decreased in P15 knockout mice when compared to the wild type. In addition, the result of quantification of dendritic spine revealed that the spine densities were significantly decreased in an overall pattern in CA1 and CA3 pyramidal neuron of P15 knockout mice. To further investigate the molecules related to the Cyp11a1 deficiency induced diminishment of dendrite size and dendritic branching as well as shrinkage of the dendritic spine densities, the neuronal markers including microtubule-associated protein 2 (MAP2), GAP-43, synapsin I and PSD-95 were used to measure the expression levels in the hippocampus of CYP11a1 null mice. The western blot analysis showed that the expression levels of synapsin I and PSD-95 were significantly decreased in the knockout mice compared to which in the wild type at P15. In conclusion, these results suggested that Cyp11a1 deficiency impaired the dendritic morphology in the developing hippocampal pyramidal neurons. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/17270 |
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