Evidence for a Role of Hox2 in Atrial Siphon Fusion of the Ascidian Ciona
4 affiliations
- 1Shimoda Marine Research Center University of Tsukuba Shimoda, Shizuoka Japan
- 2Information Biology Laboratory, Division of Bioengineering and Bioinformatics, Faculty of Information Science and Technology Hokkaido University Sapporo Japan
- 3Graduate School of Agriculture, Kyoto University Kyoto Japan
- 4Department of Mathematical and Life Sciences Graduate School of Science, Hiroshima University Hiroshima Japan
Abstract
The hallmark of sessile adult ascidians is a vase‐like shape with a single oral and atrial siphon. Ciona, however, develops two atrial siphons after metamorphosis, which subsequently fuse into one. The mechanisms underlying this fusion are unknown. This study suggests that Hox2 controls this process. Hox2‐knockout animals using Transcription‐Activator‐Like Effector Nuclease (TALEN) retain two atrial siphons throughout their lives. During normal fusion, epidermal cells between the siphons narrow along the anterior–posterior axis. This cellular narrowing does not occur in Hox2‐knockout animals, suggesting that the shape change in the epidermal cells produces tension, allowing the atrial siphon openings to converge at the midline for fusion. Hox2‐knockout animals lack cupular organs, which are suspected hydrodynamic sensors in the internal epithelium of the fused atrial siphon and on the sperm duct. Among several knockout attempts, atrial siphon fusion was reproduced by only one TALEN pair, suggesting that this phenotype is driven by a mutation having a broader effect than those abolishing protein function. Many ascidians, unlike Ciona, develop a single atrial siphon shortly after metamorphosis. Our findings suggest that a phylogenetically conserved gene, Hox2, establishes this group‐specific atrial siphon formation mechanism in Ciona.
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BibTeX
@article{liu2026evidence,
title = {{Evidence for a Role of Hox2 in Atrial Siphon Fusion of the Ascidian Ciona}},
author = {Yurong Liu and Keita Yoshida and Akiko Hozumi and Kosuke Itagaki and Nicholas Treen and Tetsushi Sakuma and Takashi Yamamoto and Toshinori Endo and Yasunori Sasakura},
journal = {Development, Growth \& Differentiation},
year = {2026},
month = oct,
doi = {10.1111/dgd.70073},
url = {https://doi.org/10.1111/dgd.70073},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Evidence for a Role of Hox2 in Atrial Siphon Fusion of the Ascidian Ciona
AU - Yurong Liu
AU - Keita Yoshida
AU - Akiko Hozumi
AU - Kosuke Itagaki
AU - Nicholas Treen
AU - Tetsushi Sakuma
AU - Takashi Yamamoto
AU - Toshinori Endo
AU - Yasunori Sasakura
PY - 2026
DA - 2026/10/01
JO - Development, Growth & Differentiation
DO - 10.1111/dgd.70073
UR - https://doi.org/10.1111/dgd.70073
AB - The hallmark of sessile adult ascidians is a vase‐like shape with a single oral and atrial siphon. Ciona, however, develops two atrial siphons after metamorphosis, which subsequently fuse into one. The mechanisms underlying this fusion are unknown. This study suggests that Hox2 controls this process. Hox2‐knockout animals using Transcription‐Activator‐Like Effector Nuclease (TALEN) retain two atrial siphons throughout their lives. During normal fusion, epidermal cells between the siphons narrow along the anterior–posterior axis. This cellular narrowing does not occur in Hox2‐knockout animals, suggesting that the shape change in the epidermal cells produces tension, allowing the atrial siphon openings to converge at the midline for fusion. Hox2‐knockout animals lack cupular organs, which are suspected hydrodynamic sensors in the internal epithelium of the fused atrial siphon and on the sperm duct. Among several knockout attempts, atrial siphon fusion was reproduced by only one TALEN pair, suggesting that this phenotype is driven by a mutation having a broader effect than those abolishing protein function. Many ascidians, unlike Ciona, develop a single atrial siphon shortly after metamorphosis. Our findings suggest that a phylogenetically conserved gene, Hox2, establishes this group‐specific atrial siphon formation mechanism in Ciona.
SN - 0012-1592
SN - 1440-169X
ER -