Sonic hedgehog differentially regulates expression of GLI and GLI3 during limb development

Area of Science:

• Developmental Biology
• Molecular Genetics
• Signal Transduction

Background:

• Sonic hedgehog (Shh) is a secreted factor crucial for patterning the anterior-posterior axis in developing limbs.
• The precise signaling pathway for Shh transduction remains incompletely understood.
• In Drosophila, genes like cubitus interruptus (ci) act downstream of hedgehog (hh), with ci encoding a homolog of vertebrate GLI transcription factors.

Purpose of the Study:

• To investigate the role of GLI family genes in the vertebrate Sonic hedgehog signaling pathway.
• To identify potential downstream targets and regulators within the Shh pathway.
• To elucidate the differential regulation of GLI and GLI3 by Shh during limb development.

Main Methods:

• Isolation of chick GLI and GLI3 genes.
• Analysis of gene expression patterns during embryogenesis.
• Experimental manipulation of Shh signaling in developing limb buds.
• Assessment of Patched gene expression in response to activated GLI.

Main Results:

• Chick GLI and GLI3 expression patterns suggest they are targets of Shh signaling.
• Sonic hedgehog differentially regulates GLI and GLI3 transcription in limb bud mesenchymal cells: GLI is upregulated, while GLI3 is downregulated.
• Activated GLI can induce the expression of Patched, a known Shh target gene.

Conclusions:

• GLI transcription factors are key components of the vertebrate hedgehog signaling pathway.
• GLI and GLI3 likely mediate distinct functions inherited from their Drosophila homolog, cubitus interruptus.
• The findings provide insights into the molecular mechanisms of Shh-mediated limb patterning.