Abstract
The role of a neural crest developmental transcriptional program, which critically involves Sox10 upregulation, is a key conserved aspect of melanoma initiation in both humans and zebrafish, yet transcriptional regulation of sox10 expression is incompletely understood. Here we used ATAC-Seq analysis of multiple zebrafish melanoma tumors to identify recurrently open chromatin domains as putative melanoma-specific sox10 enhancers. Screening in vivo with EGFP reporter constructs revealed 9 of 11 putative sox10 enhancers with embryonic activity in zebrafish. Focusing on the most active enhancer region in melanoma, we identified a region 23 kilobases upstream of sox10, termed peak5, that drives EGFP reporter expression in a subset of neural crest cells, Kolmer-Agduhr neurons, and early melanoma patches and tumors with high specificity. A ~200 base pair region, conserved in Cyprinidae, within peak5 is required for transgenic reporter activity in neural crest and melanoma. This region contains dimeric SoxE/Sox10 dimeric binding sites essential for peak5 neural crest and melanoma activity. We show that deletion of the endogenous peak5 conserved genomic locus decreases embryonic sox10 expression and disrupts adult stripe patterning in our melanoma model background. Our work demonstrates the power of linking developmental and cancer models to better understand neural crest identity in melanoma.
Highlights
The role of a neural crest developmental transcriptional program, which critically involves Sox[10] upregulation, is a key conserved aspect of melanoma initiation in both humans and zebrafish, yet transcriptional regulation of sox[10] expression is incompletely understood
The transgenic BRAFV600E/p53−/− zebrafish has been established as a powerful melanoma model that is highly reflective of the human disease and can be utilized to study early stages of melanoma initiation[6]
To identify putative regulatory elements surrounding the sox[10] locus in melanoma, ATAC-Seq was performed on bulk melanoma tumors isolated from Tg(BRAFV600E;crestin:EGFP);p53−/− zebrafish (Fig. 1a)
Summary
The role of a neural crest developmental transcriptional program, which critically involves Sox[10] upregulation, is a key conserved aspect of melanoma initiation in both humans and zebrafish, yet transcriptional regulation of sox[10] expression is incompletely understood. Focusing on the most active enhancer region in melanoma, we identified a region 23 kilobases upstream of sox[10], termed peak[5], that drives EGFP reporter expression in a subset of neural crest cells, Kolmer-Agduhr neurons, and early melanoma patches and tumors with high specificity. The transgenic BRAFV600E/p53−/− zebrafish has been established as a powerful melanoma model that is highly reflective of the human disease and can be utilized to study early stages of melanoma initiation[6]. In this model, the human BRAFV600E oncogene is expressed under the control of the mitfa promoter, a melanocyte-specific promoter. Melanoma cells can exhibit neural crest-like behavior after transplantation into chick embryos, demonstrating their plasticity and connection to their developmental origins[13]
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