- 作者: Che-Yi Lin, Ming-Yuan Tsai, Yu-Hsiu Liu, Yu-Fen Lu, Yi-Chung Chen, Yun-Ren Lai, Hsin-Chi Liao, Huang-Wei Lien, Chung-Hsiang Yang, Chang-Jen Huang and Sheng-Ping L. Hwang
- 作者服務機構: 1. Department of Bioscience and Biotechnology, National Taiwan Ocean University, Keelung, Taiwan 2. Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan 3. Department of Life Science, National Taiwan University, Taipei, Taiwan
- 中文摘要:
- 英文摘要:
Background
Although vertebrates are bilaterally symmetric organisms, their internal organs are distributed asymmetrically along a left-right axis. Disruption of left-right axis asymmetric patterning often occurs in human genetic disorders. In zebrafish embryos, Kupffer’s vesicle, like the mouse node, breaks symmetry by inducing asymmetric expression of the Nodal-related gene, spaw, in the left lateral plate mesoderm (LPM). Spaw then stimulates transcription of itself and downstream genes, including lft1, lft2, and pitx2, specifically in the left side of the diencephalon, heart and LPM. This developmental step is essential to establish subsequent asymmetric organ positioning. In this study, we evaluated the role of krüppel-like factor 8 (klf8) in regulating left-right asymmetric patterning in zebrafish embryos.
Methods
Zebrafish klf8 expression was disrupted by both morpholino antisense oligomer-mediated knockdown and a CRISPR-Cas9 system. Whole-mount in situ hybridization was conducted to evaluate gene expression patterns of Nodal signalling components and the positions of heart and visceral organs. Dorsal forerunner cell number was evaluated in Tg(sox17:gfp) embryos and the length and number of cilia in Kupffer’s vesicle were analyzed by immunocytochemistry using an acetylated tubulin antibody.
Results
Heart jogging, looping and visceral organ positioning were all defective in zebrafish klf8 morphants. At the 18–22 s stages, klf8 morphants showed reduced expression of genes encoding Nodal signalling components (spaw, lft1, lft2, and pitx2) in the left LPM, diencephalon, and heart. Co-injection of klf8 mRNA with klf8 morpholino partially rescued spaw expression. Furthermore, klf8 but not klf8△zf overexpressing embryos showed dysregulated bilateral expression of Nodal signalling components at late somite stages. At the 10s stage, klf8 morphants exhibited reductions in length and number of cilia in Kupffer’s vesicle, while at 75% epiboly, fewer dorsal forerunner cells were observed. Interestingly, klf8 mutant embryos, generated by a CRISPR-Cas9 system, showed bilateral spaw expression in the LPM at late somite stages. This observation may be partly attributed to compensatory upregulation of klf12b, because klf12b knockdown reduced the percentage of klf8 mutants exhibiting bilateral spaw expression.
Conclusions
Our results demonstrate that zebrafish Klf8 regulates left-right asymmetric patterning by modulating both Kupffer’s vesicle morphogenesis and spaw expression in the left LPM. - 中文關鍵字:
- 英文關鍵字: Zebrafish, Klf8, Spaw, L-R patterning, Kupffer’s vesicle