PAX3: A Driver of Normal Development and Disease.

PAX3 plays a vital role in regulating proper growth, migration, differentiation, and survival during development of normal tissues, including those derived from the embryonic neural crest. PAX3 is a transcription factor with two separate DNA-binding domains and can positively (and less frequently, negatively) regulate gene expression. The levels of PAX3 can be modified by upstream molecular pathways, and its subsequent downstream functions are regulated through a wide range of protein interactions and posttranscriptional modifications. PAX3 direct downstream target genes are other transcription regulators and factors that modulate cellular proliferation, lineage specificity, migration, and survival. The pathways that PAX3 regulates during development may be recycled and subverted during disease progression, for example, during cancer progression, growth, and metastasis. Indeed, PAX3 is overexpressed in several cancers, including melanoma, neuroblastoma, and rhabdomyosarcoma. While there is still much that is unknown about the mechanisms by which PAX3 controls such a wide array of key cellular functions, a great deal of progress has been made to advance our understanding of this critical and multi-faceted factor.