Identification of a Novel nkx2.3 Transgenic Reporter Specifically Visualizing Craniofacial Muscle Development in...

Transgenic reporters offer valuable opportunities to investigate the genetic and cellular basis of embryonic development in live organisms. While the specificity of transgenic reporters is essential for their effectiveness in developmental studies, many existing transgenic muscle reporters used for craniofacial muscle development in zebrafish also label trunk skeletal and cardiac muscles, as well as other head tissues. Here, we report the identification of a new transgenic reporter marking craniofacial muscles, Tg(nkx2.3:Alcama-GFP), in zebrafish. This transgenic reporter exhibits Alcama-GFP expression in growing muscle fibers at embryonic stages and in grown muscle fibers at larval stages. However, endogenous nkx2.3 transcripts are barely detected in growing craniofacial muscle fibers by in situ hybridization, and nkx2.3 mutants display fairly normal ventral jaw muscles adjacent to the lower jaw cartilages and extraocular muscles adjacent to the eye. Although an essential role for Nkx2.3 in craniofacial muscle formation remains to be determined, the Tg(nkx2.3:Alcama-GFP) craniofacial muscle reporter provides better opportunities for the precise analysis of craniofacial muscle development at the cellular and genomic levels.