Myf5和MyoD在斑馬魚頭部發育上扮演不同的角色

Myf5 and MyoD Play Distinct Roles in Craniofacial Development of Zebrafish

楊榮峯(Rong-Feng Yung)

指導教授 ： 蔡懷楨

國立臺灣大學/生命科學院/分子與細胞生物學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.10440

摘要

Myf5和MyoD屬於肌肉發育調控因子，其為肌肉細胞命運決定所必需。然而過去對於Myf5及MyoD的研究，主要著重在軀幹肌肉的發育；對於Myf5和MyoD在頭部肌肉發育時扮演的角色，則很少探討。因此我首先利用whole mount in situ hybridization的方式，來觀察myf5和myoD在斑馬魚頭部肌肉表現的情形。結果顯示myf5表現於兩組斜肌(superior oblique & inferior oblique)、側直肌(lateral rectus)以及咽弧肌肉(pharyngeal arch muscles)的前驅細胞。相較於myf5表現於有限的肌肉前驅細胞，myoD則在所有的頭部肌肉前驅細胞均會表現。抑制myf5轉譯的實驗則顯示，兩組斜肌、側直肌、胸骨舌骨肌(sternohyoideus)以及所有的咽弧肌的形成需要myf5的功能；並且這幾條肌肉的myoD及myogenin表現亦需要myf5的功能。然而抑制myoD轉譯的實驗則顯示，四組直肌(superior rectus, inferior rectus, medial rectus & lateral rectus)以及腹側的咽弧肌的形成需要myoD的功能；而這幾條肌肉的myogenin表現亦需要myoD的功能。此外，由於在whole mount in situ hybridization的實驗中，觀察到表現myf5的上斜肌和下斜肌前驅細胞，有從後端往前端遷移的跡象，我便利用myf5上游調控片段驅動綠螢光蛋白的基因轉殖魚，在活體進行追蹤上斜肌和下斜肌的前驅細胞，結果更證實這些細胞具有遷移行為。抑制myf5轉譯的實驗則顯示，上斜肌和下斜肌的前驅細胞其遷移需要myf5的功能。另外，抑制myf5的轉譯，亦會導致頭形異常、頭部咽弧軟骨減少、頭部神經嵴細胞減少以及頭部大量細胞凋亡，而抑制myoD轉譯則無此現象。故綜合以上結果，在斑馬魚，myf5和myoD在頭部肌肉及軟骨發育時，其扮演的角色不同。

關鍵字

肌肉 ； 肌肉發育 ； 軟骨 ； 頭部神經嵴肌肉發育調控因子

並列摘要

The myogenic regulatory factors Myf5 and MyoD are essential for muscle cell fate specification. The function of Myf5 and MyoD are known on the trunk myogenesis. However, the roles of Myf5 and MyoD during head myogenesis are largely unknown. In this study, I used whole mount in situ hybridization to observe the expression patterns of myf5 and myoD in the head of zebrafish. Results showed that myf5 was expressed in the precursors of two obliques, lateral rectus and pharyngeal muscles. On contrast, myoD transcripts were detected in all of the head muscle precursors. Specifically knockdown of myf5 revealed that myf5 was required for the formation of two obliques, lateral rectus, sternohyoideus and all of the pharyngeal muscle. Myf5 was also required for the expressions of myoD and myogenin in these muscles. However, specifically knockdown of myoD revealed that myoD was required for the formation of the superior rectus, inferior rectus, medial rectus and ventral pharyngeal muscles. MyoD was also required for the expression of myogenin in these muscles. In addition, we also observed that the two myf5-positive oblique precursors migrated from posterior to anterior by whole mount in situ hybridization experiment. This observation was also supported by using myf5:EGFP transgenic zebrafish that carries the reporter EGFP driven by the upstream regulatory fragment of myf5. Since the myf5-expressing cells with GFP can be traced in vivo, the migration of two egfp-positive oblique precursors were observed. Loss-of-function experiments also revealed that myf5 was required for superior oblique and inferior oblique migration. Furthermore, we found that inhibition of myf5 translation result in abnormal head and reduction of the number in cranial neural crest cells and cartilage, and induce apoptosis in the head cells. But these defectives did not occur in the myoD-morpholino-injected embryos. Taken together, our results revealed that myf5 and myoD play distinct roles during head myogenesis and cartilage formation in zebrafish.

並列關鍵字

muscle ； myogenesis ； cartilage ； cranial neural crest ； myf5 ； myoD

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