A dermatologist sees a patient with
Gorlin Syndrome, noting multiple basal cell carcinomas and jaw keratocysts.
Genetic testing shows mutations in PTCH, part of the Hedgehog signalling
pathway.

Which explanation best accounts for
the development of basal cell carcinomas in these patients?

Question

A dermatologist sees a patient with
Gorlin Syndrome, noting multiple basal cell carcinomas and jaw keratocysts.
Genetic testing shows mutations in PTCH, part of the Hedgehog signalling
pathway.

Which explanation best accounts for
the development of basal cell carcinomas in these patients?

Accepted Answer

In
the absence of ligand, PTCH normally inhibits Smoothened; loss of PTCH function
removes this inhibition, allowing uncontrolled Hedgehog pathway activation

Answer

In the absence of ligand, 
 PTCH mutations reduce Hedgehog signalling, leading to compensatory
overgrowth of basal cells

Answer

In the absence of ligand, 
 PTCH gain-of-function mutations directly activate p53-mediated apoptosis,
increasing tumorigenesis

Answer

In the absence of ligand, 
 PTCH mutations increase the patient’s sensitivity to UV-light, directly
causing basal cell carcinoma

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A dermatologist sees a patient with Gorlin Syndrome, noting multiple basal cell...

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