- A molecular signaling molecule that specifies ventral cell fates in the neural tube when in high quantities 
- When in moderate quantities, Shh specifies more median cell fates 
- Involved in cell fate decisions in limb, and gut, as well as the neural tube 

Sonic Hedgehog (Shh) 

- Two molecular signaling molecules that specify dorsal cell fates in the neural tube when in high quantities 

Wnt and BMP 

- 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 

Smith College

- 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 

Cranial 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

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

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