1 INTRODUCTION

The history of International Xenopus conferences for worldwide Xenopus researchers started in 1984 in Virginia, USA. Conferences have been held biennially, and the new 20th International Xenopus Conference is scheduled for 2025 in Portsmouth, UK. Past host countries have been concentrated in North America and Europe, except the 11th International Xenopus Conference held in 2006 in Japan. As the need for exchange and collaboration among Xenopus researchers in the Asian region has emerged, the demand for the Asian International Xenopus Conference has increased. The 1st Asian Xenopus Conference was the very first international meeting for Asian Xenopus researchers. The first day of the conference was held in Senri Life Science Center, Science Hall, and the second and third days were held in Nambu Yoichiro Hall at Osaka University, Toyonaka Campus. This conference had seven sessions, two keynote lectures, one luncheon seminar, and a poster session. Thirty-two presenters presented their research; 6 postdoctoral researchers and 3 graduate students were included. For the poster presentation, 26 posters participated in it (Table 1, Figure 1). The program is available online at (https://2024.xenopus-asia.org/program/). Approximately 100 participants from the Republic of Korea and Japan attended this conference. This conference was an excellent opportunity to discuss research topics with other researchers and allowed us to view research from different perspectives across various fields.

A common research focus among the participants of this conference, Xenopus, was first introduced in experimental studies in the 1930s as a biological tool for pregnancy tests, also known as the Hogben test. Lancelot Hogben discovered that injecting a pregnant woman's urine into a female Xenopus laevis caused the laying of eggs (Elkan, 1938). Then, in the mid-twentieth century, scientists began using Xenopus as a laboratory model organism. Xenopus undergoes external fertilization, and owing to the large size of its embryos, it is easy to observe the developmental process. In vitro fertilization also allows for the simultaneous obtaining of many embryos at the same developmental stage. Furthermore, by utilizing microinjection techniques with morpholinos and the clustered regularly interspaced short palindromic repeats (CRISPR) system, along with advancements in fate mapping, gene expression can be precisely manipulated in specific target cells. These advantages have led to the widespread use of Xenopus as a research model organism in various fields (De Robertis & Gurdon, 2021). Thus, the conference covered a wide range of biological topics, including developmental biology, genetics, signaling pathways, regenerative medicine, epigenetics, and molecular cellular biology, all through Xenopus.

2 KEYNOTE LECTURES

In the keynote lectures, the meeting organizers invited the global experts in Xenopus research, Prof. Ken W. Y. Cho (University of California, USA) and Prof. John B. Wallingford (University of Texas at Austin, USA). Prof. Ken W. Y. Cho lectured about the ectoderm specification revealed by genomic approaches. The pluripotency of blastula ectodermal cells allows them to differentiate into various cell types. However, it is lost by the early gastrula stage as ectodermal specification progresses. He demonstrated that the ectodermal lineage is directed by maternally localized transcription factors, which bind cis-regulatory modules in the naïve genome before zygotic genome activation. These transcription factors function as master regulators of ectoderm differentiation by modulating gene expression and shaping the epigenetic landscape of the embryonic genome. He discussed his approach in delineating the gene-regulatory program that controls this process during early embryogenesis. Prof. John B. Wallingford showed the history of planar cell polarity and convergent extension. He emphasized that understanding the cell biology of developing embryos is a crucial challenge in biology because the defects in the individual cells’ behavior are a key cause of human congenital disabilities. He focused on understanding the collective cell behaviors, such as convergent extension (CE), that elongate the body axis in vertebrate embryos. He discussed his work illuminating the nexus between tissue-specific developmental signaling systems that govern cell movements and the ubiquitous cell biological machinery that executes them.

3 LUNCHEON SEMINAR

At the 1st Asian Xenopus Conference, organizers and committees prepared the luncheon seminar for trainee students to support learning how to write scientific papers by inviting technical editor Dr. Steven D. Aird. His seminar presented the principles and procedures necessary to write a well-composed scientific narrative and how to write it. The methods presented make scientific writing more straightforward and effective for trainee students.

4 SESSION LECTURE I

This conference consisted of seven sessions covering various fields of biological science, featuring presentations by professors, postdoctoral researchers, and students. Owing to space limitations, this meeting report cannot cover all sessions, so only a portion of the seven sessions has been selected and summarized. The author subjectively chose the selection criteria and tried to introduce research in various fields. Prof. Mikiko Tanaka (Institute of Science Tokyo, Japan) presented research on the role of environmental oxygen in tetrapod limb development (Cordeiro et al., 2019). She demonstrated that oxygen availability influences reactive oxygen species (ROS) levels, which regulate interdigital cell death (ICD) in tetrapod limb development. Increasing the environmental oxygen around amphibian limbs can induce ICD, indicating that oxygen availability plays a crucial role in limb patterning and evolution. The findings demonstrate that BMP signaling enhances the production of ROS by regulating ROS-related enzymes, which in turn promotes ICD in the interdigital region. This work provides novel insights into the regulatory mechanisms underlying limb development and highlights the evolutionary significance of oxygen and BMP signaling in shaping the tetrapod limb. Dr. Hyun-Kyung Lee (Kyungpook National University, Republic of Korea) reported the role of cytoplasmic liker-associated protein 1 (Clasp1) during ciliogenesis. She identified that Clasp1 is explicitly expressed in multi-ciliated cells of the Xenopus epidermis. She observed that it partially colocalizes with the ciliary adhesion component and appears to link basal bodies with actin/microtubules. Clasp1 initially resides deeper within the cell and migrates along with basal bodies to the cell surface during early ciliogenesis, suggesting its involvement in the apical migration of basal bodies. Her findings highlighted the essential role of Clasp1 in ciliogenesis by mediating interactions between basal bodies and cytoskeletal elements.

5 SESSION LECTURE II

Prof. Yuta Tanizaki (The University of Tokyo, Japan) introduced his recent work focused on the role of thyroid hormone in erythropoiesis during metamorphosis by using Xenopus with a double knockout of both thyroid hormone (T3) receptors (TR) α and β. He determined that the liver of TR-deficient tadpoles exhibited significant developmental defects with excessive iron accumulation in the river during metamorphosis, indicating a disruption in iron metabolism (Tanizaki et al., 2023). His findings suggested that T3 is essential for liver development, iron metabolism, and the transition to adult erythrocytes, highlighting its role in iron recycling via liver macrophages during metamorphosis. Dr. Hyo Jung Sim (Ulsan National Institute of Science and Technology, Republic of Korea) presented the investigation of R-loops in development and disease. R-loops, structures formed by RNA invading the DNA duplex, have roles in both genomic instability and physiological processes. Using Xenopus embryos, she found R-loops enriched in telomeres, suggesting a link to telomere elongation. In addition, she observed that, in pathological contexts, R-loop analysis in DDX41 mutant cells associated with leukemia identified genes linked to the disease, and ongoing studies aim to validate a Xenopus leukemia model and identify R-loop binding proteins. Her research highlighted the roles of R-loops in both development and disease.

6 SESSION LECTURE III

Prof. Yusuke Mii (Kyoto University, Japan) presented research on Wnt11's role in planar cell polarity (PCP) regulation. He demonstrated that Wnt11 regulates PCP in Xenopus embryos independently of concentration gradients, showing a polarized distribution that colocalizes with core PCP components. Mutual regulation was observed in which the polarization of Wnt11 is dependent on core planar cell polarity (PCP) components, while Wnt11 itself also induces the polarization of these components, creating regulatory loops. This study emphasizes the significance of local interactions between Wnt11 and PCP components in establishing PCP and proposes a mechanism for PCP formation independent of gradients. Dr. Hyeyoon Lee (Deutsches Krebsforschungszentrum, Germany) presented her findings on the role of R-Spondin 2 (Rspo2) in left–right symmetry breaking during Xenopus development (Lee et al., 2024). She discovered that Rspo2 is a symmetrically expressed initializing signal in the left–right organizer (LRO). She demonstrated that Rspo2 acts downstream of leftward fluid flow but upstream of the gene dand5 and antagonizes FGF receptors by promoting their endocytosis. Her research showed that Rspo2 establishes an FGF signaling gradient, with higher levels on the right side, which is critical for LR symmetry breaking.

7 SESSION LECTURE IV (FRIENDS OF Xenopus)

Prof. Jun-Yeong Lee (Kyungpook National University, Republic of Korea) and Prof. Akane Kawaguchi (National Institute of Genetics, Japan) lectured in the “Friends of Xenopus” session. It was an excellent opportunity to learn about how other animal models are utilized in research, their advantages, and the various animal models used in studies beyond Xenopus. Prof. Jun-Yeong Lee lectured about research on the conservation of CpG islands (CGIs)-mediated dual-mode gene regulation across multicellular eukaryotes (Lee et al., 2021). He observed that CGI⁺ genes are localized at the nuclear center and engage in long-range interactions, while CGI⁻ genes, associated with heterochromatin, move to the center of nuclear upon activation. His comparative epigenomic analyses showed that this dual-mode regulation is conserved in various eukaryotes, including those lacking CGIs. He highlighted that invertebrates without DNA methylation, such as fruit flies and nematodes, exhibit gene regulation divergence, providing insights into the evolutionary aspects of gene expression regulation across species. Prof. Akane Kawaguchi investigated the epigenetic mechanisms underlying salamander limb regeneration (Kawaguchi et al., 2024). She identified histone H3K27me3 as a key positional marker at limb homeoprotein gene loci, encoding segment-specific identities in connective tissue cells. During regeneration, she observed that regeneration-specific regulatory elements activate before developmental elements, enabling genes such as HoxA13 in the hand to bypass the upper limb program. Her findings also underscored a conserved set of transcription factors shared across regenerative species, pointing to an ancient and universal regeneration program.

8 SESSION LECTURE V

Prof. Masanori Taira (Chuo University, Japan) explored the mechanism of heterochronic pyloric sphincter formation during Xenopus laevis metamorphosis. He discovered that sphincter formation begins unexpectedly at the flexure in the middle of the pylorus, later repositioning to the posterior end of the stomach as the posterior pylorus shortens (Nagura et al., 2025). His analyses revealed that sphincter-related genes such as bmp4, gata3, and sox9 are expressed in the pylorus region before metamorphosis, indicating that their presence alone does not trigger sphincter formation. Multi-regional RNA-seq identified additional transcription factors (isl1, nkx2-3, and pdx1) expressed during metamorphosis. His study suggests that retinoic acid suppresses sphincter formation in herbivorous tadpoles and is released during metamorphosis to initiate this process. Dr. Hongchan Lee (Kyungpook National University, Republic of Korea) investigated the noncanonical functions of cathepsin K (CTSK) in Xenopus development. He revealed that ctsk is expressed in Xenopus embryos’ head, branchial region, and notochord. Knockdown of ctsk led to phenotypes resembling pycnodysostosis (PYCD), such as dwarfism, spondylolysis, and small jaw. Remarkably, protease function-deficient CTSK could rescue these phenotypes, indicating a protease-independent role of CTSK in embryogenesis. In addition, treatment with CTSK inhibitors such as odanacatib and BML-244 did not impact development, reinforcing this novel discovery. This study emphasizes that CTSK plays a role in embryogenesis beyond its conventional protease function.

9 SESSION LECTURE VI

Prof. Tae Joo Park (Ulsan National Institute of Science and Technology, Republic of Korea) discussed the various roles of cilia in cancer. He explained that cilia, microtubule-based organelles crucial for sensing extracellular signals and regulating the cell cycle, are intricately connected to tumor dynamics. Depending on the context, primary cilia can either promote or inhibit the development of various cancers, including medulloblastoma, glioblastoma, and breast cancer. Using Xenopus laevis embryos, he discovered that mebendazole (MBZ) disrupts cilia formation and sensitizes ciliated cancer cells to combine MBZ and anticancer drug treatments (Hong et al., 2024). His work provides novel insights into the role of cilia in cancer and highlights the potential of MBZ in cilia-mediated cancer therapies. Prof. Yuuri Yasuoka (RIKEN IMS, Japan) explored the evolution and roles of keratan sulfate (KS) biosynthesis in vertebrate development. He identified the paralogous genes chst1 and chst3, derived from whole-genome duplication, as key regulators of highly sulfated KS (HSKS) in the otic vesicles and notochord of Xenopus embryos, respectively (Yasuoka, 2023). Loss-of-function studies revealed their subfunctionalization, with chst1 and chst3 crucial for HSKS deposition in otic vesicles and the notochord. In addition, he found KSGal6ST-like gene expression in the notochord of amphioxus embryos, suggesting its ancestral role in chordates, with ongoing studies investigating functional conservation. Prof. Asako Shindo (Osaka University, Japan) presented research on the cellular mechanisms of morphogenesis, focusing on environmental-organ interactions. She demonstrated that thyroid morphogenesis in Xenopus is regulated by nutritional cues, with follicle formation halting in the absence of feeding and resuming upon feeding initiation (Takagishi et al., 2022). Her study revealed that nutritional signals target cell adhesion molecules and cytoskeletal elements, with glycolysis inhibiting cell adhesion and promoting unique cell polarity. She is expanding her research to explore how other organs respond to nutritional factors and environmental cues using three-dimensional (3D) imaging to uncover broader mechanisms of organ morphogenesis influenced by the environment.

10 SESSION LECTURE VII (RESOURCE)

Prof. Taejoon Kwon (Ulsan National Institute of Science and Technology, Republic of Korea) explained an update on the comprehensive genome annotation of Xenopus tropicalis. He introduced the release of version 10 of the genome, which offers high accuracy comparable to major model species such as humans and mice. This update has not undergone a systematic review compared with the previous version. He discussed the integration of three annotation versions (NCBI RefSeq, Ensembl, and the genome consortium version) using multiple evaluation criteria, including gene expression signatures and predicted protein structures. He also highlighted improvements in human-Xenopus orthology through gene family phylogeny and synteny analyses. This updated annotation will reference other amphibian species, including Xenopus borealis and Xenopus petersii.

11 POSTER SESSION

The poster session received 26 submissions from postdoctoral researchers and students. For the presenters, it was a significant opportunity to engage with participants from researchers of various fields, exchange ideas, participate in Q&A sessions, and receive valuable feedback that contributed to refining their research and shaping their future research directions.

12 CONCLUSIONS

The 1st Asian Xenopus Conference, conceived in response to the growing desire for collaboration among Xenopus researchers in the Asian region, was successfully held thanks to many researchers’ keen interest and active participation across Asia. Through this event, Xenopus researchers in the Asian region had the opportunity to network and strengthen their connections while committing to continuing such conferences. The next conference will be held in the Republic of Korea in 2026. We look forward to the continued interest, enthusiasm, and active participation of Xenopus researchers from the Asian region at the 2nd Asian Xenopus conference.

FUNDING INFORMATION

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (RS-2023-00243564; HJ Sim, RS-2023-00250458; DG Jang).