Lrrk2 modulation of Wnt signaling during zebrafish development

Area of Science:

• Neuroscience
• Genetics
• Developmental Biology

Background:

• Mutations in leucine-rich repeat kinase 2 (LRRK2) are a leading genetic cause of Parkinson's disease.
• The precise pathogenic mechanisms of LRRK2 variants are complex due to LRRK2's multifaceted cellular roles.

Purpose of the Study:

• To investigate the developmental roles of LRRK2 using a zebrafish allelic series.
• To dissect the functional importance of LRRK2's distinct domains (GTPase, kinase, scaffolding) in cellular processes.

Main Methods:

• Generation of zebrafish lrrk2 mutants lacking specific functional domains.
• Assessment of Wnt signaling using whole mount RNA in situ hybridization and a transgenic Wnt reporter.
• Analysis of Wnt target gene expression in mutant lines.

Main Results:

• All generated lrrk2 mutant zebrafish lines were viable and exhibited normal morphology and locomotion.
• While Wnt signaling domains were generally preserved, Wnt pathway activation was attenuated in the lrrk2 mutant lacking both scaffolding and catalytic domains (lrrk2^{sbu304/sbu304}).
• This attenuation was not observed in mutants lacking only the GTPase/kinase or only the kinase domain.

Conclusions:

• LRRK2's scaffolding functions, rather than its catalytic kinase activity, appear critical for promoting canonical Wnt signaling in a context-dependent manner during zebrafish embryogenesis.
• These findings provide insights into the complex role of LRRK2 in both Parkinson's disease pathogenesis and normal developmental signaling pathways.