Mapping the locations of barx1-expressing prechondrogenic condensation domains in the posterior arches during ceratobranchial cartilage formation in zebrafish

초록

During the evolution of vertebrate heads, the emergence of dorso-ventrally segmented facial skeletal elements in the jaw and branchial basket structures is a key feature invented in jawed fish. The segmental development begins from the two distinct prechondrogenic condensations in the dorsal and ventral regions of the respective pharyngeal arches in facial skeletal formation. Interestingly, in zebrafish, a single barx1-expressing prechondrogenic condensation occurs in the posterior arches, in which the ventral ceratobranchial cartilages of the branchial basket form. While the single condensation is expected to cover the ventral regions in the posterior arches for the development of the ventral cartilage, the location of the condensation domain in the arches has not been evaluated yet. Here, we mapped the location of the barx1-expressing condensation domain in the arches through comparative gene expression analyses. The single barx1-expressing condensation domain occupied the whole ventral area and expanded to the middle region of the intermediate area of the respective arches. From the dorsal regions of the condensation domain, the sox9a-expressing chondrocytes for the ventral ceratobranchial cartilages initially arose, with the sox9a expression sustained in the dorsal ends of the developed ceratobranchial cartilages. Our results suggest that the single condensation domain covers not only the ventral but also intermediate regions of the arches, consequently resulting in the dorsal areas of the ventral ceratobranchial cartilages probably originating from the intermediate regions of the arches.

키워드