Scientists at St. Jude Children's Research Hospital have made a groundbreaking discovery regarding the role of cytonemes in neural development. Cytonemes, thin hair-like projections on cells, have long been recognized as important in facilitating direct communication between cells over long distances. However, visualizing and understanding their specific role in mammalian tissue development has posed a challenge.

In a study published in Cell, the researchers developed innovative microscopy techniques and optimized sample preparations to finally capture images of cytonemes in action during mammalian nervous system development. These images revealed that cytonemes act as an "express" system, akin to an express subway, bypassing intervening cells to directly transport signaling molecules to more distant cells.

By investigating cytonemes originating from the notochord, a major station in the nervous system, the scientists observed the transport process of essential signaling proteins. When they blocked these proteins from entering cytonemes, mouse models exhibited disrupted neural development and significant neurological defects.

"This is the first demonstration of these cytoneme-based transport processes occurring during the development of a complex mammalian tissue such as the neural tube," explained corresponding author Dr. Stacey Ogden of the St. Jude Department of Cell and Molecular Biology. "We have shown that when we reduce cytoneme numbers or decrease the ability of cells to load signaling proteins into these structures, we get developmental defects."

The findings shed light on the mechanisms involved in developmental biology, particularly in establishing signaling gradients and transporting critical molecules like sonic hedgehog, a pivotal signaling molecule in neural development. The study also provides evidence supporting the important role of cytoneme signaling in creating morphogen patterns during neural tube patterning.

Dr. Ogden remarked, "It's really exciting to show that cells that are producing morphogen signals are playing an active role in getting them to where they need to go through cytonemes. The signaling cell is not only making the morphogen, but it's also helping to physically deliver the signal."

While the study primarily focused on the role of cytonemes in sonic hedgehog signaling, the researchers suggest that cytonemes may also play a crucial role in transporting other signals during neural tube development.

"This study not only provides valuable insights into the understanding of neural development but also opens up new avenues for research in the field of developmental biology," concluded the researchers.

The study was supported by grants from the National Institutes of Health, the National Cancer Institute, and ALSAC, the fundraising and awareness organization of St. Jude.

This groundbreaking research by St. Jude scientists is a significant step forward in unraveling the complexities of neural development and highlights the crucial role of cytonemes in this intricate process.