Sonic hedgehog

Definition

Sonic hedgehog (Shh) is a signaling molecule that plays a crucial role in embryonic development, particularly in neural induction and neurogenesis. It is part of the Hedgehog signaling pathway, which regulates cell growth, differentiation, and patterning during development. Sonic hedgehog is essential for the proper formation of structures in the brain and spinal cord, influencing the fate of neural precursor cells and promoting the development of various neural tissues.

5 Must Know Facts For Your Next Test

1. Sonic hedgehog is produced by the notochord and floor plate of the developing embryo, influencing nearby neural cells through a gradient concentration.
2. The expression of sonic hedgehog is critical for the formation of motor neurons in the spinal cord and plays a role in forebrain development.
3. Mutations in the sonic hedgehog gene can lead to developmental disorders such as holoprosencephaly, where the forebrain fails to properly divide into two hemispheres.
4. Sonic hedgehog acts as a morphogen, meaning its concentration influences cell fate decisions during neural development.
5. The Hedgehog signaling pathway, which includes sonic hedgehog, is implicated in various diseases, including cancer, due to its role in cell growth regulation.

Review Questions

• How does sonic hedgehog influence the fate of neural precursor cells during development?
  • Sonic hedgehog influences the fate of neural precursor cells by providing crucial signaling that helps determine their differentiation into specific types of neurons or glial cells. The presence of sonic hedgehog creates a concentration gradient that directs these precursor cells' development based on their location relative to the source of the signal. This process ensures that the right types of neurons are formed in appropriate locations within the developing nervous system.
• Discuss the implications of sonic hedgehog signaling in developmental disorders and how it can affect brain formation.
  • Sonic hedgehog signaling is vital for proper brain formation; disruptions in its pathway can lead to developmental disorders such as holoprosencephaly. When mutations occur in the sonic hedgehog gene or its signaling components, it can cause improper neural patterning and result in severe malformations in brain structure. Understanding these implications not only helps elucidate basic developmental biology but also provides insights into potential therapeutic targets for related disorders.
• Evaluate the broader significance of sonic hedgehog signaling beyond embryonic development, particularly in adult tissue homeostasis and disease.
  • Beyond embryonic development, sonic hedgehog signaling plays a role in adult tissue homeostasis and has been implicated in various diseases, including cancers. In adults, this pathway is involved in maintaining stem cell populations and regulating tissue repair mechanisms. However, aberrant activation of sonic hedgehog signaling has been linked to tumorigenesis in several cancers, highlighting its dual role as both a crucial developmental signal and a potential target for cancer therapies. This duality underscores the importance of understanding sonic hedgehog’s functions across different biological contexts.

Related terms

Hedgehog signaling pathway: A fundamental pathway that controls various developmental processes, including cell differentiation, tissue patterning, and organogenesis.

Neural precursor cells: Cells that have the potential to differentiate into various types of neurons and glial cells during the development of the nervous system.

Morphogen: A substance that governs the pattern of tissue development in the process of morphogenesis by providing positional information to cells.