Cohesin protein Smc3 influences kinocilial structure and function.

Cohesinopathies and ciliopathies are congenital disorders affecting overlapping body systems. The extent to which these syndromes may be linked remains largely untested. Recently, reduced expression of a cohesin core subunit, Smc3, was found to result in abnormal otolith development in zebrafish embryos. This finding suggests that Smc3 may contribute to kinociliary development and function, which would represent a novel role for Smc3. Using hair cells found in neuromasts of the posterior lateral line, we found that Smc3 knockdown resulted in reduced kinociliary length. To address the role of Smc3 in kinocilial function, we monitored neomycin resistance of neuromasts (associated with several cilial gene mutants) and FM1-43X uptake in hair cells (associated with mechanotransduction). We found that Smc3 knockdown indeed led to neomycin resistance of the posterior lateral line neuromasts, suggesting impaired kinocilium function. However, neuromast hair cells did not have defects in FM1-43X uptake. We further demonstrated that hair cell number is reduced within neuromasts. This study suggests a significant influence of cohesin subunit Smc3 in ciliary structure and function and provides a preliminary link between cohesinopathy and ciliopathy etiologies.