Expression Atlas of Avian Neural Crest Proteins: Neurulation to Migration

ABSTRACT Neural crest (NC) cells are a dynamic population of embryonic stem cells that create various adult tissues in vertebrate species including craniofacial bone and cartilage and the peripheral and enteric nervous systems. NC development is a conserved and complex process that is controlled by a tightly regulated gene regulatory network (GRN) of morphogens, transcription factors, and cell adhesion proteins. While multiple studies have characterized the expression of several GRN factors in single species, a comprehensive protein analysis that directly compares expression across development is lacking. To address this, we used three closely related avian models, Gallus gallus (chicken), Coturnix japonica (Japanese quail), and Pavo cristatus (Indian peafowl), to compare the localization and timing of four GRN transcription factors, PAX7, SOX9, SNAI2, and SOX10 from the onset of neurulation to migration. While the spatial expression of these factors is largely conserved, we find that quail NC cells express SOX9, SNAI2, and SOX10 proteins at the equivalent of earlier developmental stages than chick and peafowl. In addition, quail NC cells migrate farther and more rapidly than the larger organisms. These data suggest that despite a conservation of NC GRN players, differences in the timing of NC development between species remain a significant frontier to be explored with functional studies. Graphical abstract Comparative analysis of neural crest (NC) protein spatiotemporal localization in quail, chick, and peafowl embryos. Avian embryos were incubated for different lengths of time to achieve the same developmental stage marked by somite number (somite stage, SS) as described by Hamburger and Hamilton (HH) in 1951. (A) Quail, (B) chick, and (C) peafowl embryos were collected for immunohistochemistry (IHC) to define and quantify the timeline of NC protein expression. We specifically focused on the expression of PAX7, SNAI2, SOX9, and SOX10 proteins. We determined that neural crest development as marked by common NC-specific proteins differs between species. Rather than similar, but scaled development, each organism has its own NC developmental timeline. Quail embryos develop much more rapidly than their counterparts, chick and peafowl. Further, chick and peafowl amino acid sequences are more similar to each other than they are to quail.