Zebrafish Forkhead Box D5 Plays a Role in Somitogenesis
Date Issued
2007
Date
2007
Author(s)
Lo, Fang-yi
DOI
zh-TW
Abstract
In all germ layers, Forkhead Box (Fox) transcriptional factors play important roles in the determination of cell fates. During somitogenesis, zebrafish FoxD3 is known of maintaining the somitic expression of myf5, and subsequently regulates myogenesis. FoxD5, another gene of the FoxD family, is also expressed in forming somites of the anterior PSM. However, the regulatory function of FoxD5 in somitogenesis is not clear. To address this issue, we microinjected Morpholino Oligonucleotides (MO), which acts as a specific translational inhibitor, into 1-cell stage zebrafish embyos to knockdown the expression of FoxD5. Results showed that the newly forming somites of the FoxD5-MO-injected embryos were malformed both in the stage when the somitogenesis was completed (24-hpf) and in the stage when the somitogenesis was in progress (14-hpf). By whole-mount in situ hybridization, the cyclic patterns of her1 and deltaC in PSM were not altered in the FoxD5 morphants. Nevertheless, the anteroposterior polarity determinants mespa and mespb were both affected: the expression of mespa was downregulated and the expression of mespb was changed from the stripe pattern to the disrupted pattern called “salt and pepper”. In addition, the expression of papc, which is involved in the epithelializtion of somites, was increased from 3 bands of stripes at S-II, S-I, and S0 to 5-6 bands. These observations suggested that FoxD5 dose not take parts in the cyclic pre-pattern of the PSM, but involves in the process of somite formation. Furthermore, myogenesis was not affected in the FoxD5 morphants, owing to the results of myf5 downergulation in somites and myod upregulation due to the knockdown of myf5, and therefore resulted in myogenin normal expression. In addition, FoxD5 was upregulated in the FoxD3-knockdown embryos, suggesting that FoxD5 might compensate the functions of FoxD3 in the PSM. On the other hand, in spite of the severely distorted axis, the FoxD5-overexpressed embryos displayed neither somite nor muscle defects. Based on these results, we speculate that FoxD5 plays different roles in axis and somite formation. During somitogenesis, FoxD5 functions in the maintenance of the anteroposterior polarity of somites, and in turn plays roles in proper formation of somites.
Subjects
斑馬魚
體節
zebrafish
somite
FoxD5
Type
other
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