Beta-Catenin Causes Adrenal Hyperplasia by Blocking Zonal Transdifferentiation

Area of Science:

• Endocrinology
• Molecular Biology
• Oncology

Background:

• Activating mutations in the Wnt/β-catenin pathway drive hyperplasia, a precursor to tumor development, primarily through increased cell proliferation.
• It remains unknown if additional mechanisms contribute to β-catenin-driven hyperplasia in various tissues.

Purpose of the Study:

• To investigate the mechanisms underlying β-catenin gain-of-function (βcat-GOF) induced hyperplasia in the adrenal cortex.
• To determine if β-catenin drives adrenal hyperplasia through proliferation-dependent and/or -independent pathways.

Main Methods:

• Somatic βcat-GOF mutations were targeted to zona glomerulosa (zG) cells in the adrenal cortex.
• Cell proliferation, cell differentiation (transdifferentiation from zG to zF), and gene expression (Pde2a) were analyzed.
• The impact of trophic factors on hyperplasia and organomegaly was assessed.

Main Results:

• Targeting βcat-GOF to zG cells induced progressive hyperplastic expansion without increasing proliferation.
• Hyperplasia resulted from a block in zG cell transdifferentiation into zona fasciculata (zF) cells.
• Upregulation of Pde2a, an inhibitor of zF-specific cAMP/PKA signaling, was observed in zG cells.
• Trophic factor stimulation exacerbated hyperplasia and led to organomegaly.

Conclusions:

• β-catenin drives adrenal hyperplasia through both proliferation-dependent and -independent mechanisms.
• A novel, proliferation-independent mechanism involves the blockage of zG to zF cell transdifferentiation.
• Pde2a upregulation plays a key role in mediating β-catenin-driven hyperplasia in the adrenal cortex.