- A range of morphogen signaling molecules are used to specify cell identity across the cranial neural tube axis
- This includes Sonic hedgehog (Shh), Wnt, and BMP 

Morphogen Signaling in Cranial Neural Tube 

- Mechanism that precedes/ prepares for neural tube closure
- Changes rectangular epithelial cells into wedge shaped-cells by forcing the cells to contract (via protein actomyosin) 
- Ultimately leads to bending of tissue, creating "hinge points" that are required for neural tube closure 
- While apical constriction is a required prerequisite for neural tube closure, questions remain about whether this process is needed during the act of neural tube closure itself 
- Knowing that many of the processes that drive cranial neural tube closure are unknown, apical constriction is being investigated for its possible role in this process

Apical Constriction 

- 100+ genes are used to facilitate closure of the cranial neural tube 
- Researchers have hypothesized that unique mechanisms for neural tube closure are utilized in this region, since the cranial neural plate region is much wider compared to that of the spinal cord or other regions
- The cranial neural tube also utilizes a range of morphogen (molecular) signaling patterns to differentiate cells into specific identities across its axis 

Smith College

- All vertebrate systems utilize an early embryonic structure known as the dorsal neural tube
- The "head" of this structure will go on to form various subdivisions of the brain   

Development from Dorsal Neural Tube

Brooks, E. R., Islam, M. T., Anderson, K. V., & Zallen, J. A. (2020). Sonic hedgehog signaling directs patterned cell remodeling during cranial neural tube closure. eLife, 9, e60234. https://doi.org/10.7554/eLife.60234

Sonic hedgehog signaling directs patterned cell remodeling during cranial neural tube closure

Neural Tube Library 

- During the early development, the embryo will transform a flat plane of neuroepithelial cells into a closed tube, which will eventually develop/ differentiate into structures of the brain and spinal cord 
-  In order for this to occur, these neuroepithelial cells utilize specific genetic expression patterns to allow for closure across the head to tail axis, and allow for appropriate cell behavior in specific regions 
- There are also certain prerequisite processes that allow neural tube closure to happen, such as apical constriction 

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