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標題: | 神經調節素1基因的變異對小鼠腦室下區及感覺皮質神經細胞新生的影響 Effects of Neuregulin1 Gene Mutation on Neurogenesis of Mouse Subventricular Zone and Somatosensory Cortex |
作者: | Li-Hsin Peng 彭立欣 |
指導教授: | 尹相姝(Hsiang-Shu Yin) |
關鍵字: | Nrg1,背外側腦室下區,紋狀體腦室下區,BrdU,DCX, Neuregulin1 (Nrg1),subventricular zone (SVZ),dorsolateral SVZ (DLSVZ),striatal SVZ (SSVZ), |
出版年 : | 2013 |
學位: | 碩士 |
摘要: | 已知出生後哺乳動物的腦室下區 (Subventricular zone, SVZ)可以持續進行神經細胞新生。當腦組織受傷,SVZ新生的神經細胞可能會取代受損的細胞。SVZ的細胞會表現Neuregulin1 (神經生長素, Nrg1)及它的受體ErbB4,顯示Nrg1可能影響SVZ神經細胞的生長及遷移等。故本論文探討Nrg1基因變異對發育中小鼠SVZ細胞的增生與分化的影響。
本實驗使用年輕(出生後四週)和成熟(出生後八週)的野生型 (wild type, WT)及Nrg1基因變異小鼠 (Exon9 mutant, 129S1-Nrg1tm1Lex)進行實驗。開放空間行為顯示,成熟Nrg1變異小鼠在中央停留時間比野生型小鼠多66%,在周邊行走距離比野生型小鼠少11%。此結果指出變異小鼠可能較遲鈍,不夠警覺。 形態方面,我們使用免疫染色法 (immunohistochemistry)觀察SVZ細胞增生及分化的情形。將小鼠連續三天,一天一次注射Bromodeoxyuridine (BrdU),150 mg/Kg,第四天 (D4)及第十天 (D10) 將小鼠灌流犧牲,並將其腦部以石蠟包埋並製備冠狀切片,以供Nissl及免疫染色。根據圖譜,將小鼠額葉 (frontal region)分成前段 (anterior)、中段 (middle)及後段 (posterior)。SVZ則分成背外側腦室下區 (dorsolateral SVZ, DLSVZ)及紋狀體腦室下區 (striatal SVZ, SSVZ)。 我們發現,第四天的年輕Nrg1變異小鼠,額葉前段與中段的DLSVZ,BrdU細胞數目比野生型小鼠少30%與32%,後段卻比野生型小鼠多59%。但是第十天的變異小鼠SVZ的BrdU細胞數目類似野生型小鼠。第四天的成熟變異小鼠額葉前、中與後段的 DLSVZ,BrdU細胞數目比野生型小鼠少 34%、 49%和 36%;額葉前、中與後段的SSVZ,BrdU細胞數目也比野生型小鼠少 40%、32%和38%。第十天的成熟變異小鼠的SVZ,BrdU細胞數目類似野生型小鼠。此外,成熟變異小鼠在額葉前段的第十天新生細胞數量佔第四天的百分比為DLSVZ 72.85%和SSVZ 101.52%,比野生型小鼠41.04%和66.05%多,在額葉中段DLSVZ 64.51%也比野生型小鼠 38.38%多。 BrdU注射後第四天或第十天的年輕Nrg1變異小鼠,在胼胝體 (Corpus callosum, CC)的BrdU細胞數目類似野生型小鼠。第四天的成熟Nrg1變異小鼠,額葉體感覺皮質下方的胼胝體新生細胞數量比野生型小鼠多65%~81%,顯示Nrg1變異可能降低成熟小鼠從SVZ遷移至胼胝體的新生細胞數量。 我們使用Doublecortin (DCX),存在於神經母細胞內的一種細胞骨架蛋白,的抗體標誌未成熟的神經母細胞。年輕Nrg1變異小鼠額葉前與中段的DLSVZ的DCX染色強度 (optical density, OD)值,比野生型小鼠低約12%和13%。成熟變異小鼠額葉前與中段的DLSVZ和SSVZ的DCX OD值,也比野生型小鼠低11%~19%。 使用免疫組織化學雙重染色法發現,在SVZ,不論年輕或成熟的變異或野生型小鼠,BrdU細胞表現DCX或Glial fibrillary acidic protein (GFAP, 星狀細胞)的標誌蛋白,但是沒有表現腦室細胞的特定蛋白質(S100-β)。 年輕Nrg1變異小鼠前後肢體感覺皮質 (Hind- and Forelimb cortex)的第四層,DCX細胞數目比野生型小鼠多53%,成熟變異小鼠的前後肢體感覺皮質與桶狀皮質(Barrel cortex)的第四層,DCX細胞數也比野生型小鼠多106%和89%。這些結果顯示Nrg1變異使得此區出現更多神經母細胞,這些細胞的來源可能是SVZ,此區內的血管,或其它。使用雙重染色法發現,不論年輕或成熟的變異或野生型小鼠,在體感覺皮質,有些DCX細胞也表現GAD67蛋白質。 Nrg1變異導致小鼠在開放空間行為表現異常,指出Nrg1可能影響小鼠的焦慮情緒。變異小鼠SVZ和胼胝體的新生細胞數量減少,指出SVZ細胞的增生與遷移可能受到Nrg1變異的影響,其影響似乎隨動物年紀不同而有差異。體感覺皮質的神經母細胞數目反而在變異小鼠上升 It is known that the subventricular zone (SVZ) of postnatal mammalian animals can keep on undergoing neurogenesis. The newborn neurons generated in SVZ may replace injured cells in nervous tissue. The cells of SVZ can express neuregulin 1 (Nrg1), a key growth factor in neural development, and its receptor ErbB4, indicating roles of Nrg1 in the growth and migration of newly formed cells of SVZ. Thus, this study aimed to examine the effects of Nrg1 gene mutation on the neurogenesis of SVZ. The postnatal 4 week (young) and 8 week (adult) old wild type and Nrg1 gene mutated (Exon9 mutant, 129S1-Nrg1tm1Lex)mice were used for the experiments. Open field behavioral observation revealed that adult Nrg1 mutant mice stayed for a relatively longer period of time in the center area than WT mice, and had less moving distance in the peripheral area. This points to that the mutant mice may be less anxious and alert than that of WT mice. The proliferation of cells in SVZ was studied by injecting bromodeoxyuridine (BrdU) to mice and detecting the newly formed cells using immunohistochemistry with the anti-BrdU antibody. BrdU was intraperitoneally injected to the mice, at 150 mg/kg, once each day for 3 days and the mice were sacrificed on day 4 (D4) and day 10 (D10). Coronal paraffin sections of the brains were prepared. On D4, the numbers of BrdU-immunopositive cells were decreased by 30% and 32% in the anterior and posterior frontal portions, while increased 59% in the posterior portion of the dorsal lateral SVZ (DLSVZ) of the young mutant mice, compared with respective areas of WT mice. For adult mutant mice, on D4, decreases in the numbers of BrdU cells were in the DLSVZ, 34%, 49%, and 36% in the anterior, middle and posterior frontal portions, and 40%, 32% and 38% in the three portions of SSVZ. On D10, the numbers of BrdU cells were similar in the mutant SVZ to that of WT of both ages. Higher percentages of D4 cells remained on D10 anterior DLSVZ 72.85%, SSVZ 101.52%, and middle DLSVZ 64.51% in the adult mutant mice than WT 41.04%, 66.05%, and 38.38%, implying a lower migration rate of the cells in the mutant. On D4, the mature mutant mice had 65~81% lower numbers of BrdU cells in the corpus callosum beneath the somatosensory cortex in the different portions of frontal lobe, compared to WT. This implicates that mutation of Nrg1 gene may lower the number of newborn cells in the corpus callosum that were probably migrated from SVZ. The staining levels of doublecortin (DCX) were decreased by 11-19% in anterior and middle DLSVZ of young mutant mice, and anterior and middle DLSVZ and SSVZ of adult mice. It is likely that the reduced level of DCX in the neuroblasts could indicate a decreased ability of the cells to undergo migration. Double immunostaining showed that BrdU cells expressed DCX or glial fibrillary acidic protein (GFAP), but not S100-beta, a specific marker of ependymal cells. In the young mutant mice, the number of DCX-positive cells was 53% higher in the layer 4 of hind and forelimb somatosensory cortex (SSC), compared to that of WT. The numbers of DCX cells were also increased by 106% and 89% in the layer 4 of hind-forelimb SSC and barrel cortex in the adult mutant mice. It appears that the Nrg1 gene mutation increased the number of neuroblasts in SSC, but the source of the increased cells remains unknown, although they may come from SVZ, local blood vessels or other sources. A number of DCX-cells also expressed GAD67 in layers of SSC of both Mut and WT. The Nrg1 gene mutation induced abnormality of the mice in the open field behavior and thus may affect the state of anxiety of the animals. The newly formed cells were generally decreased in number in SVZ and corpus callosum, implying age-dependently altered proliferation and migration of the progenitors in SVZ. By contrast, the number of neuroblasts was increased in mutant SSC. These morphological changes may play certain roles in the manifestation of the abnormal behavior, because the neurogenesis of SVZ is closely associated with the physiology of olfactory bulb, SSC and striatum, the emotional limbic structures. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/60677 |
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