Fruit Fly Study Uncovers Key Mechanisms Behind Collective Cell Migration

By Pooja Toshniwal PahariaReviewed by Frances BriggsJun 26 2025

Researchers have uncovered how two signaling molecules, Plexin A and Semaphorin 1b, control the coordinated movement of muscle cells during Drosophila testis development, offering new insights into organ shaping and potential cancer therapies.

Image Credit: nechaevkon/Shutterstock.com

Published in Science Advances, the study explores how contact-regulated collective cell migration drives organ development in fruit flies. Researchers focused on the testes, where muscle precursor cells, known as myotubes, use Plexin A (PlexA) and Semaphorin 1b (Sema1b) to orchestrate tissue shaping.

While these molecules are best known for their roles in guiding neurons, the study revealed that they also regulate how cells move and organize during organ formation.

This discovery demonstrated that the same signaling systems used in neural development may also shape other organs, including the reproductive system. The findings also offer a potential therapeutic angle; disrupting these pathways could limit cancer cell migration, while better understanding them could improve tissue engineering approaches.

About The Study

Using the TNM system, the researchers examined how muscle precursor cells contribute to organ development in Drosophila fruit flies.

This approach enabled them to conduct large-scale genetic screens to identify potential myotube-specific regulators involved in shaping the testis. To assess PlexA’s role in testis morphogenesis, they applied a combination of gene knockdown techniques and established quantification pipelines to evaluate the severity of related morphological phenotypes.

They further investigated how PlexA ligands affect testis development, particularly looking into potential interactions with Sema1b. Spatial statistical analyses revealed distinct patterns of cell clustering depending on the genetic background, whether involving Sema1b mutations, PlexA loss-of-function, or PlexA overexpression.

To quantify structural gaps in live myotubes, the team used machine learning-based models, while confocal microscopy enabled detailed line scan analysis. They also studied cell adhesion and protrusion by tracking the expression of various architectural protein markers.

In addition, live cell imaging allowed them to observe testis development in real time. They used phalloidin staining to examine muscle coverage and CRISPR/Cas9 knockouts to rule out off-target genetic effects. To better understand how PlexA and Sema1b influence cell-cell adhesion, they performed double knockdowns with N-cadherin and conducted co-immunoprecipitation assays to explore the involvement of GTPases in TNM cell migration.

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Results

The study showed that PlexA is essential for keeping myotube cells linked during collective movement. It helps them migrate as a continuous sheet over the testis, reshaping it from an oval to a spiral. This process involves the R-Ras homolog Ras2 and the GTPase Rap2L, and relies on PlexA’s cytoplasmic domain to manage cell behavior.

When PlexA is knocked down, migration slows, cell junctions become more rigid, and the structure has more epithelial-like properties. Gaps also appear in the muscle layer, particularly at the testis tip, disrupting its regular shaping. In contrast, Sema1b knockdown promotes a looser, more mesenchymal cell arrangement.

Interestingly, overexpressing PlexA causes adhesion defects that resemble those of Sema1b knockdown rather than PlexA deficiency, suggesting Sema1b acts as a counterbalance to PlexA.

Their interaction helps fine-tune each cell's position along the epithelial-mesenchymal spectrum, which is key to coordinated movement in tight spaces. The fact that this same signaling system operates in both testes and the brain indicates that the system could be conserved across different organs.

Conclusion

This study revealed how PlexA and Sema1b work together, and sometimes against each other, to guide group cell migration during organ development.

By understanding how these signals maintain the cohesion and positioning of migrating cells, researchers open the door to new applications in cancer treatment and regenerative medicine. These findings could apply across species, allowing for future studies in vertebrate models and other complex systems. 

Journal Reference

Maik C et. al. (2025). Plexin/Semaphorin antagonism orchestrates collective cell migration and organ sculpting by regulating epithelial-mesenchymal balance. Sci. Adv., 11, eadu3741, DOI: 10.1126/sciadv.adu3741. https://www.science.org/doi/10.1126/sciadv.adu3741