臺灣博碩士論文加值系統

Notch signaling高度保留在各物種之間並且對於決定細胞命運調控上扮演重要角色。在神經發育的過程中，Notch signaling活化之後會使得未成熟的神經細胞前驅物無法進行神經分化進而成為成熟的神經細胞。先前文獻指出，Notch signaling會調控脊椎動物後腦分節發育。在神經發育的過程中，脊椎動物的後腦分節構造會給予神經細胞在物理空間結構的提示，讓神經發育正確。 然而，後腦形成的分子機制還尚未被了解透徹。在此，我想研究一群基因稱之Hairy/E(spl) related genes (her genes )，他們是可能受Notch signaling調控的下游目標群。在我的研究裡就以斑馬魚為平台，欲知這些基因在後腦與神經發育上所扮演的角色。首先，我利用所有目前已解開的斑馬魚基因庫來搜尋所有被發現的her genes ，再依in situ hybridization的結果，觀察到當斑馬魚早期胚胎發育過程中，有三個在後腦分節表達her genes ( her6, her8a以及her9 )。接著，再利用微注射的技術來分析這三個her genes的功能進而了解其在後腦與神經發育上所扮演的角色。我們使用notch signal缺陷的mib突變株來了解這三個 her genes是受Notch signaling調控的下游基因。並且，當her6和her8a失去功能後，her9的表達在後腦的完全消失。目前對於這三個her基因所扮演的角色研究仍持續進行中。

The Notch signaling pathway is a highly evolutionarily conserved signal transduction mechanism that has key roles in the regulation of cell fate decisions during embryonic development. The Notch ligand activated Notch signal on its neighboring cells to prevent them from adopting its own fate. Previous studies have shown that in addition to cell fate decision, Notch activation also regulates the segmentation of the vertebrate hindbrain. The hindbrain segmentation structure provides correct spatial/temporal cues for neurogenesis; however, the molecular mechanism of the hindbrain formation is still not clear. In the present study, I use zebrafish as a model to study the function of her (Hairy/E (Spl) related bHLH) genes, the potential downstream targets of Notch signaling in the developing hindbrain. I analyzed her genes expression by in situ hybridization and found zebrafish her6, her8a and her9, the ortholog of mammalian Hes1, are segmentally expressed in the hindbrain but with distinct patterns, suggest these genes have different roles in hindbrain morphogenesis. The expression of her6, her8a and her9 suggests these genes are downregulated in the mib mutant, a notch signal defect mutant. In addition, her9 expression was lost in her6 or her8a knockdown embryos suggest that her8a or her6 is involved in hindbrain segmentation and neurogenesis and need further investigation.

◎Abstract
◎中文摘要
◎Introduction
1. Notch signaling pathway
2. The background and advantages of Zebrafish
3. Hindbrain in vertebrate
◎Aim
◎Approach Overview
◎Result and Discussion
◎Summary and Future work
◎Material and Methods
◎References

1.Cheng, Y. C. et al. Notch activation regulates the segregation and differentiation of rhombomere boundary cells in the zebrafish hindbrain. Dev Cell 6, 539-50 (2004).
2.Elmasri, H. et al. her7 and hey1, but not lunatic fringe show dynamic expression during somitogenesis in medaka (Oryzias latipes). Gene Expr Patterns 4, 553-9 (2004).
3.Sieger, D., Ackermann, B., Winkler, C., Tautz, D. & Gajewski, M. her1 and her13.2 are jointly required for somitic border specification along the entire axis of the fish embryo. Dev Biol 293, 242-51 (2006).
4.Pasini, A., Henrique, D. & Wilkinson, D. G. The zebrafish Hairy/Enhancer-of-split-related gene her6 is segmentally expressed during the early development of hindbrain and somites. Mech Dev 100, 317-21 (2001).
5.Pasini, A., Jiang, Y. J. & Wilkinson, D. G. Two zebrafish Notch-dependent hairy/Enhancer-of-split-related genes, her6 and her4, are required to maintain the coordination of cyclic gene expression in the presomitic mesoderm. Development 131, 1529-41 (2004).
Latimer, A. J., Shin, J. & Appel, B. her9 promotes floor plate development in zebrafish. Dev Dyn 232, 1098-104 (2005).