Hashmi, S. S. | bioRxiv Science

bioRxiv2022

Disruption of fos causes craniofacial anomalies in developing zebrafish

Craniofacial development is a complex and tightly regulated process and disruptions can lead to structural birth defects, the most common being nonsyndromic cleft lip and palate (NSCLP). Previously, we identified FOS as a candidate regulator of NSCLP through family-based association studies, yet its specific contributions to oral and palatal formation are poorly understood. This study investigated the role of fos during zebrafish craniofacial development through genetic disruption and knockdown approaches. Fos was expressed in the periderm, olfactory epithelium and other cell populations in the head. Genetic perturbation of fos produced an abnormal craniofacial phenotype with a hypoplastic oral cavity that showed significant changes in midface dimensions by quantitative facial morphometric analysis. Loss and knockdown of fos caused increased cell apoptosis in the head, followed by a significant reduction in cranial neural crest cells (CNCCs) populating the upper and lower jaws. These changes resulted in abnormalities of cartilage, bone and pharyngeal teeth formation. Periderm cells surrounding the oral cavity showed altered morphology and a subset of cells in the upper and lower lip showed disrupted Wnt/{beta}-catenin activation, consistent with modified inductive interactions between mesenchymal and epithelial cells. Taken together, these findings demonstrate that perturbation of fos has detrimental effects on oral epithelial and CNCC-derived tissues suggesting that it plays a critical role in zebrafish craniofacial development and a potential role in NSCLP. Summary statementPerturbation of fos, a candidate gene associated with nonsyndromic cleft lip and palate in humans, causes a distinctive orofacial phenotype in zebrafish as a result of abnormal development of craniofacial tissues. Disruption of fos in the oral epithelial, cranial neural crest and Wnt responsive cell populations around the oral cavity causes anomalies that suggest a potential role in the etiology of NSCLP.

developmental biology↗

bioRxiv2022

zFACE: Facial Analytics from a Coordinate Extrapolation System for Developing Zebrafish

Facial development requires a complex and coordinated series of cellular events, that when perturbed, can lead to structural birth defects. A standardized quantitative approach to quickly assess morphological changes could address how genetic or environmental inputs lead to differences in facial development. Here we report on a method to rapidly analyze craniofacial development in zebrafish embryos that combines a simple staining and mounting paradigm with Facial Analytics based on a Coordinate Extrapolation system, termed zFACE. Confocal imaging of frontal/rostral mounted embryos generates high-resolution images to capture facial structures and morphometric data is quantified based on a coordinate system that assesses 26 anatomical landmarks present at defined times in development. The semi-automated analysis can be applied to embryos at different stages of development and quantitative morphometric data can detect subtle phenotypic variation. Shape analysis can also be performed with the coordinate data to inform on global changes in facial morphology. We applied this new approach to show that loss of smarca4a in developing zebrafish leads to craniofacial anomalies, microcephaly and alterations in brain morphology. These changes are characteristic of humans with Coffin-Siris syndrome (CSS), a rare genetic disorder associated with mutations in SMARCA4 that is defined by anomalies in head size, intellectual disabilities and craniofacial abnormalities. We observed that smarca4a is expressed in craniofacial tissues and our multivariate analysis facilitated the classification of smarca4a mutants based on changes in specific phenotypic characteristics. Together, our approach provides a way to rapidly and quantitatively assess the impact of genetic alterations on craniofacial development in zebrafish.

developmental biology↗