Zfp423 Regulates Sonic Hedgehog Signaling via Primary Cilium Function.

Area of Science:

• Developmental biology
• Genetics
• Cell biology

Background:

• Zfp423 is a transcription factor implicated in ciliopathies like Joubert syndrome.
• Its complex expression and nuclear localization present unique mechanistic questions.
• Previous studies proposed various cellular roles for Zfp423 in development.

Purpose of the Study:

• To investigate the cell-intrinsic role of Zfp423 in cerebellar granule cell precursors.
• To elucidate the molecular mechanisms by which Zfp423 loss leads to ciliopathy phenotypes.
• To determine Zfp423's position within developmental signaling pathways.

Main Methods:

• Analysis of Zfp423 expression in cerebellar granule cell precursors.
• CRISPR-Cas9 mediated knockout of Zfp423 in these cells.
• Assessment of cell proliferation, Shh pathway response, and primary cilia function.
• Gene expression analysis and Tulp3 interaction studies.

Main Results:

• Zfp423 loss in precursors reduced proliferation and Shh pathway response.
• Primary cilia showed abnormalities, including altered Smoothened and IFT88 localization.
• Zfp423 deficiency increased Tulp3 expression, a direct binding target.
• Overexpression of Tulp3 in Zfp423-deficient cells partially rescued Smoothened defects.

Conclusions:

• Zfp423 acts upstream of Shh signaling in cerebellar development.
• Zfp423 deficiency is a bona fide ciliopathy with cell-intrinsic effects on granule cell precursors.
• Altered Tulp3 expression contributes to the observed Smoothened translocation defects and cerebellar hypoplasia.