Roadkill attenuates Hedgehog responses through degradation of Cubitus interruptus

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• Hedgehog (Hh) signaling is crucial for development and disease.
• Post-translational regulation of transcription factor Cubitus interruptus (Ci) is key to Hh signal transduction.
• Ci protein levels are tightly controlled by degradation pathways influenced by Hh levels.

Purpose of the Study:

• To identify novel regulators of Ci protein stability and Hh signaling.
• To characterize the function of the newly identified roadkill (rdx) gene in Hh pathway regulation.
• To investigate the role of Rdx in cellular organization and survival within the context of Hh signaling.

Main Methods:

• Gene expression analysis to identify Hh-responsive genes.
• Protein biochemistry to determine Rdx function as a substrate adaptor for Cullin3-mediated ubiquitylation.
• Genetic manipulation (overexpression and loss-of-function) of rdx in vivo.
• Phenotypic analysis of Hh pathway-related processes, including cell organization and survival.

Main Results:

• The roadkill (rdx) gene is upregulated in response to Hh.
• Rdx functions as a substrate adaptor for Cullin3-mediated ubiquitylation, targeting Ci for degradation.
• Overexpression of rdx decreases Ci levels and attenuates both transcriptional activation and repression by Ci.
• Loss of rdx leads to excessive Ci accumulation.
• Rdx manipulation impacts pigment and cone cell organization and survival in the eye, revealing a novel Hh function.

Conclusions:

• Rdx acts as a limiting factor in a negative feedback loop that attenuates Hh pathway responses by reducing Ci levels.
• This feedback mechanism is critical for fine-tuning Hh signaling.
• The discovery of Rdx and its role in Hh signaling has implications for understanding human development and disease, given the existence of human orthologs.