Noncanonical Hedgehog signaling

Area of Science:

• Molecular Biology
• Cell Signaling
• Developmental Biology

Background:

• The canonical hedgehog (Hh) signaling pathway is crucial for embryonic development and tissue homeostasis.
• Canonical Hh signaling involves transcriptional regulation mediated by the Gli family of transcription factors.
• Emerging evidence suggests Hh signaling can exert effects independent of Gli-mediated transcription, termed noncanonical signaling.

Purpose of the Study:

• To review recent findings supporting the existence and mechanisms of noncanonical hedgehog signaling in mammals.
• To highlight the roles of Patched1 and Smoothened (Smo) in Gli-independent cellular processes.
• To acknowledge preliminary evidence of noncanonical Hh signaling in Drosophila.

Main Methods:

• Review of recent scientific literature and experimental findings.
• Analysis of studies investigating Patched1 and Smoothened (Smo) functions.
• Examination of cellular and tissue responses to Hh isoforms.

Main Results:

• Patched1 demonstrates the ability to regulate cell proliferation and apoptosis independently of Smoothened (Smo) and Gli.
• Smoothened (Smo) modulates actin cytoskeleton-dependent processes, including fibroblast migration and endothelial cell tubulogenesis.
• These Smo-mediated effects occur through diverse mechanisms that do not involve Gli-dependent transcription.

Conclusions:

• Noncanonical hedgehog (Hh) signaling represents a significant mode of Hh pathway activity in mammals.
• Patched1 and Smoothened (Smo) play critical roles in noncanonical Hh signaling, impacting fundamental cellular behaviors.
• Further research is warranted to fully elucidate the scope and mechanisms of noncanonical Hh signaling.