Researchers Uncover Key Protein in Tadpole Tail Regeneration

Researchers from the University of Tokyo have made significant strides in understanding how tadpoles regenerate their tails. Their study reveals that the protein c1qtnf3, secreted by muscle stem cells, plays a crucial role in directing macrophages from immune responses to regenerative functions. This discovery offers new insights into the regenerative abilities of certain species and opens avenues for future applications in mammals. The findings were published in the Proceedings of the National Academy of Sciences on November 17, 2025.

Understanding Tadpole Regeneration

Tadpoles of the African clawed frog, Xenopus laevis, possess remarkable regenerative capabilities, allowing them to regrow fully functional tails, including spinal cord and muscle. This complex process relies heavily on the activation of stem cells. However, studying these early regenerative stages has posed challenges due to the limited number of stem cells present.

Taro Fukazawa, one of the leading researchers, noted the difficulty in observing these cells, stating, “We have previously established a method for efficiently enriching tissue stem cells. Building on this technique, we planned to clarify the behavior of tissue stem cells during tail regeneration by examining genes specifically expressed in the tissue stem cells.” This led to the use of single-cell RNA sequencing to identify active genes in individual cells.

Through this advanced technique, the team identified various cell types and focused their attention on putative muscle stem cells. They discovered that these cells exhibited a higher expression of c1qtnf3 compared to other cell types. To delve deeper into the role of this gene in regeneration, the researchers performed “knockdown” experiments that blocked its expression.

The Role of Macrophages in Regeneration

The results were illuminating. The knockdown of c1qtnf3 led to impaired tail regeneration, indicating its essential function in the process. Moreover, the researchers observed a significant reduction in the number of macrophages present at the tail stump of the knocked-down tadpoles, suggesting that macrophage activity might be compromised.

This observation prompted the hypothesis that macrophages, which are known for their immune functions, could be redirected towards aiding regeneration through the influence of muscle stem cells and c1qtnf3. To test this theory, the researchers activated macrophages using another gene, neutrophil cytosolic factor 1, which is involved in macrophage function.

Kato expressed excitement at the findings, stating, “When I found that forced expression of the gene, and consequently rising macrophage numbers, rescued tail regeneration in tadpoles, it felt like the dots connected.” The proposed mechanism involves putative muscle stem cells secreting c1qtnf3, which leads to an accumulation of macrophages at the tail stump, thereby promoting regeneration.

Looking ahead, the team aims to further explore how macrophages facilitate regeneration under the influence of c1qtnf3 and to uncover the precise cellular and molecular mechanisms involved in regenerating tissues. This research not only enhances our understanding of biological regeneration but also holds potential implications for regenerative medicine in humans.