A392V and R945X mutations cause orofacial clefts via impairing PTCH1 function

Area of Science:

• Developmental Biology
• Genetics
• Molecular Biology

Background:

• Hedgehog (HH) signaling is crucial for embryonic development and organogenesis.
• Dysregulation of HH signaling contributes to human birth defects, including orofacial cleft (OFC).
• PTCH1 variants are implicated in OFC, but their functional impact remains largely uncharacterized.

Purpose of the Study:

• To functionally validate two PTCH1 variants (A392V and R945X) identified in families with hereditary OFC.
• To elucidate the molecular mechanisms by which these PTCH1 variants contribute to OFC pathogenesis.

Main Methods:

• Zebrafish embryo microinjection with wild-type and mutant PTCH1 mRNA.
• Mammalian cell culture to assess PTCH1 function and signaling.
• Biochemical assays to determine protein stability and localization.

Main Results:

• Zebrafish embryos injected with A392V and R945X PTCH1 mRNA exhibited milder craniofacial defects compared to wild-type.
• Mutant PTCH1 proteins showed reduced ability to inhibit HH signaling in mammalian cells.
• A392V and R945X mutations decreased PTCH1 protein stability and altered its cellular localization.

Conclusions:

• The A392V and R945X PTCH1 variants function as loss-of-function mutations.
• These variants disrupt PTCH1 stability and localization, leading to HH signaling dysregulation.
• This study provides mechanistic insights into the role of PTCH1 variants in OFC development.