FZD2 regulates limb development by mediating β-catenin-dependent and -independent Wnt signaling pathways

Area of Science:

• Developmental Biology
• Genetics
• Molecular Biology

Background:

• Robinow syndrome (RS) and dominant omodysplasia type 2 (OMOD2) are genetic disorders characterized by skeletal abnormalities.
• Heterozygous mutations in the Wnt receptor FZD2 have been linked to RS and OMOD2.
• The exact role of FZD2 in limb development, particularly its activation of canonical and non-canonical Wnt pathways, remains unclear.

Purpose of the Study:

• To investigate the precise functions and mechanisms of FZD2 in limb development.
• To elucidate the role of FZD2 in mediating canonical and non-canonical Wnt signaling during skeletal development.
• To confirm the causative link between pathogenic FZD2 mutations and RS/OMOD2.

Main Methods:

• Generation of Fzd2 mutant mice (Fzd2em1Smill) with a frameshift mutation in the Dishevelled-interacting domain.
• Phenotypic analysis of Fzd2em1Smill mutant mice embryos, focusing on limb development.
• Assessment of canonical Wnt signaling and WNT5A/planar cell polarity (PCP) pathway activity in developing limb mesenchyme.

Main Results:

• Fzd2em1Smill mutant mice exhibited shortened limbs, mirroring human RS and OMOD2 phenotypes.
• Mutant embryos showed reduced canonical Wnt signaling in limb mesenchyme.
• Disruption of digit chondrocyte elongation and orientation, linked to WNT5A/PCP signaling, was observed.

Conclusions:

• FZD2 is essential for normal limb development by mediating both canonical and non-canonical Wnt pathways.
• The study confirms that pathogenic FZD2 mutations cause Robinow syndrome and dominant omodysplasia type 2.
• FZD2's dual role in Wnt signaling provides insight into the pathogenesis of these skeletal disorders.