神經中間絲蛋白α-internexin在雞視網膜的表現

Abstract

α-internexin 是一種神經元中間絲蛋白。在過去的研究中，它在發育中的囓齒類動物視網膜的表現經常和神經中間絲蛋白三合體(neurofilament triplet proteins)一起做比較。 α-internexin在發育中的小鼠視網膜會短暫地表現在無軸突細胞(amacrine cells)。在成體中，只會分布在視神經(optic nerve fibers)和水平細胞(horizontal cells)中。資料顯示α-internexin可能與發育中視網膜內神經連結可塑性有有關。由於α-internexin過去在雞視網膜中的表現尚未被探討，本研究主要目的在瞭解雞視網膜發育過程中，α-internexin和神經元中間絲蛋白在時間和空間的變化分布。

本論文利用即時定量聚合酶連鎖反應、西方墨點轉漬與免疫組織化學染色等方法研究α-internexin核酸表現與蛋白質表現量與分布。在雞胚時期第八天，α-internexin分布在神經節細胞(ganglion cell)上，接著在雞胚時期第十四天開始分布在無軸突細胞和水平細胞，並持續表達到胚胎時期第二十天。α-internexin在成體中則主要分布在視神經和無軸突細胞。除此之外，低分子量神經元中間絲蛋白與高分子量神經元中間絲蛋白在胚胎時期會和α-internexin共同出現在神經節細胞及視神經與無軸突細胞，成體時期更會分布在水平細胞上，顯示神經元中間絲蛋白可部分彌補α-internexin的功能。

本論文的結果顯示α-internexin會表現在發育中的雞視網膜，並且隨著時間的推衍而分布在不同的神經細胞中。我們認為α-internexin未來可以應用成為研究視網膜中神經細胞的特定標記物。

α-internexin is one of the neuronal intermediate filament proteins, together with neurofilament (NF) triplet proteins have been studied in developing rodent retina. α-internexin displayed transient expression in amacrine cells during development, and mainly localized in the optic nerve fibers, horizontal cell processes of adult mice. It has been suggested that α-internexin may play a role in neuroplasticity during development. Since the distribution of α-internexin in chicken retina has not yet been investigated, we aimed to discover the spatial and temporal distribution patterns of α-internexin and neurofilament NFL/NFH in developing chicken retina. The RNA expression of α-internexin and NFH was examined by Real-Time Quantitative PCR. The proteins levels of α-internexin, NFL and NFH in developing retina was examined by Western blot. And the distribution of α-internexin together with NFL, NFH, parvalbumin and NeuN in chicken retina were examined by immunohistochemistry. The immunoreactivity of α-internexin was detected in ganglions cell at embryonic day 8 (E8), then appeared in soma and processes of amacrine cells as well as horizontal cells E14 onward. In adult, the immunoreactivity of α-internexin was detected mainly in the optic nerve fibers, soma and processes of amacrine cells, yet the immunoreactivity in horizontal cells could not be detected. Besides, neurofilament proteins were observed to co-localize with α-internexin in ganglion cells and amacrine cells in developing retina, and were found to appear in outer plexiform layer of adult chicken retina. This result might point to the replacement of α-internexin with neurofilament proteins in adult chicken retina. Our result revealed that differential distribution patterns of α-internexin could be found in the neurons of developing chicken retina. We suggest that α-internexin could be one of good neuronal markers in the study of chicken retina.