Alizarin Red perturbs skeletal patterning and biomineralization via catalase inhibition

Alizarin Red S (AZ) is a dye that is commonly used in histological studies and textiles. We find that AZ is teratogenic to Lytechinus variegatus sea urchin larvae. Here, we demonstrate that embryos exposed to AZ have abnormal skeletal patterning and perturbed migration of skeletogenic mesenchyme cells, along with mild ectodermal abnormalities and reduced neural connectivity. Temporal transcriptomics reveal delayed development and implicate wide-reaching changes in gene expression with AZ treatment. Particle image velocimetry experiments show that AZ treatment perturbs the normal pattern of fluid flow away from the larval mouth and inhibits larval feeding. Finally, we show that AZ promotes a significant elevation of reactive oxygen species (ROS) via catalase inhibition. ROS-mediated effects are expected to be broad, in agreement with the broad effects of AZ detected by transcriptomics. Catalase knockdown and hydrogen peroxide treatment are each sufficient to quantitatively phenocopy AZ-mediated skeletal patterning defects, while catalase overexpression is sufficient to rescue the AZ skeletal phenotype. This study is the first to define the teratogenic consequences of AZ exposure on development, skeletal patterning and biomineralization.