A quantitative in vivo assay for craniofacial developmental toxicity of histone deacetylases

Many bony features of the face develop from endochondral ossification of preexisting collagen-rich cartilage structures. The proper development of these cartilage structures is essential to the morphological formation of the face. The developmental programs governing the formation of the pre-bone facial cartilages are sensitive to chemical compounds that disturb histone acetylation patterns and chromatin structure. We have taken advantage of this fact to develop a quantitative morphological assay of craniofacial developmental toxicity based on the distortion and deterioration of facial cartilage structures in zebrafish larvae upon exposure to increasing concentrations of several well-described histone deacetylase inhibitors. In this assay, we measure the angle formed by the developing ceratohyal bone as a precise, sensitive and quantitative proxy for the overall developmental status of facial cartilages. Using the well-established developmental toxicant and histone deacetylase-inhibiting compound valproic acid along with 12 structurally related compounds, we demonstrate the applicability of the ceratohyal angle assay to investigate structure-activity relationships. (C) 2021 The Author(s). Published by Elsevier B.V.

Automated summary

Many facial bony features develop from preexisting collagen-rich cartilage structures through endochondral ossification. The proper development of these cartilage structures is crucial for facial morphological formation, which is sensitive to compounds that disturb histone acetylation patterns. A quantitative morphological assay using zebrafish larvae exposed to histone deacetylase inhibitors has been developed to measure the ceratohyal bone angle, providing a precise and sensitive proxy for overall facial cartilage development. This assay has been demonstrated to be applicable for investigating structure-activity relationships using valproic acid and related compounds.