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Updated: Jun 3, 2026
Quantitative PCR-based Assay to Measure Sonic Hedgehog Signaling in Cellular Model of Ciliogenesis
Published on: January 31, 2025
Human and mouse mutations in WDR35 cause short-rib polydactyly syndromes due to abnormal ciliogenesis
Pleasantine Mill1, Paul J Lockhart, Elizabeth Fitzpatrick
1Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, Western General Hospital, Edinburgh EH4 2XU, UK. pleasantine.mill@hgu.mrc.ac.uk
Abstract:
Defects in cilia formation and function result in a range of human skeletal and visceral abnormalities. Mutations in several genes have been identified to cause a proportion of these disorders, some of which display genetic (locus) heterogeneity. Mouse models are valuable for dissecting the function of these genes, as well as for more detailed analysis of the underlying developmental defects. The short-rib polydactyly (SRP) group of disorders are among the most severe human phenotypes caused by cilia dysfunction. We mapped the disease locus from two siblings affected by a severe form of SRP to 2p24, where we identified an in-frame homozygous deletion of exon 5 in WDR35. We subsequently found compound heterozygous missense and nonsense mutations in WDR35 in an independent second case with a similar, severe SRP phenotype. In a mouse mutation screen for developmental phenotypes, we identified a mutation in Wdr35 as the cause of midgestation lethality, with abnormalities characteristic of defects in the Hedgehog signaling pathway. We show that endogenous WDR35 localizes to cilia and centrosomes throughout the developing embryo and that human and mouse fibroblasts lacking the protein fail to produce cilia. Through structural modeling, we show that WDR35 has strong homology to the COPI coatamers involved in vesicular trafficking and that human SRP mutations affect key structural elements in WDR35. Our report expands, and sheds new light on, the pathogenesis of the SRP spectrum of ciliopathies.
Insights
Mutations in the WDR35 gene cause severe short-rib polydactyly (SRP) disorders by disrupting cilia formation and function. This study identifies WDR35 defects in human SRP cases and mouse models, revealing its critical role in cilia development and Hedgehog signaling.
Area of Science:
- Genetics
- Developmental Biology
- Cell Biology
Background:
- Cilia defects cause skeletal and visceral abnormalities, including severe short-rib polydactyly (SRP) disorders.
- Genetic mutations in cilia-related genes are known causes, but locus heterogeneity exists.
- Mouse models are crucial for understanding cilia gene function and developmental defects.
Purpose of the Study:
- To identify the genetic cause of a severe form of short-rib polydactyly (SRP).
- To investigate the role of the WDR35 gene in cilia formation and function.
- To elucidate the pathogenesis of SRP spectrum ciliopathies.
Main Methods:
- Positional cloning and genetic sequencing to identify mutations in WDR35 in human SRP patients.
- Generation and analysis of a Wdr35 mutant mouse model.
- Immunofluorescence to determine WDR35 localization in cilia and centrosomes.
- Structural modeling to analyze WDR35 homology and mutation impact.
Main Results:
- Identified homozygous deletion and compound heterozygous mutations in WDR35 in SRP patients.
- A Wdr35 mouse mutation caused mid-gestation lethality with Hedgehog pathway defects.
- WDR35 localizes to cilia and centrosomes; its absence prevents cilia formation in human and mouse cells.
- Structural modeling revealed WDR35 homology to COPI coatamers and impact of mutations on structural elements.
Conclusions:
- WDR35 is essential for cilia formation and function, and its defects cause severe SRP ciliopathies.
- Mutations in WDR35 disrupt cilia and Hedgehog signaling, contributing to SRP pathogenesis.
- This study expands the understanding of the genetic basis and molecular mechanisms underlying SRP spectrum disorders.
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