Identification of regulatory elements for MafB expression in the cardiac neural crest.

Cardiac neural crest cells arise in the caudal hindbrain and then migrate to the heart through the pharyngeal arches. These cells contribute to the formation of the heart, including the outflow tract, and are unique to this neural crest population. MafB is a transcription factor expressed specifically in early migrating cardiac neural crest cells as well as in rhombomeres (r) 5 and 6. Here, we identified the regulatory region in the chicken genome controlling the expression of endogenous MafB transcripts and used these essential elements to express MafB in the cardiac neural crest in reporter assays. A reporter driven by this regulatory region was employed to trace the migration of these cells into the pharyngeal arches. This regulatory region demonstrated transcriptional activity in the cardiac neural crest but not in other neural crest cell subpopulations, such as the cranial and trunk cells. This study provides insights into the gene regulatory mechanisms that specify cardiac neural crest cells among neural crest cell populations.