Hox-mediated endodermal identity patterns the pharyngeal muscle formation in the chordate pharynx

Abstract

The chordate pharynx, possessing gill slits and the endostyle, is a complex of multiple tissues that are highly organized along the anterior-posterior (AP) axis. Although Hox genes show AP coordinated expression in the pharyngeal endoderm, tissue-specific roles of these factors for establishing the regional identities within this tissue have not been demonstrated. Here, we show that Hox1 is essential for the establishment of AP axial identity of the endostyle, a major structure of the pharyngeal endoderm, in the ascidian Ciona intestinalis. We found that knockout of Hox1 causes posterior-toanterior transformation of the endostyle identity, and that Hox1 represses Otx expression and anterior identity, and vice versa. Furthermore, alteration of the regional identity of the endostyle disrupts the formation of body wall muscles, suggesting that the endodermal axial identity is essential for coordinated pharyngeal development. Our results demonstrate an essential role of Hox genes in establishment of the AP regional identity in the pharyngeal endoderm and reveal crosstalk between endoderm and mesoderm during development of chordate pharynx.

A Nearly Complete Genome of Ciona intestinalis Type A (C. robusta) Reveals the Contribution of Inversion to Chromosomal Evolution in the Genus Ciona

“…2002) was originally identified as C. intestinalis . To avoid such confusion, many reports have included two names to identify the species, such as C. intestinalis type A ( C. robusta ) (e.g., Yoshida et al. 2017; Satoh et al.…”

Neural crest and the patterning of vertebrate craniofacial muscles

“…While this review focuses on the outcomes that are NCr‐dependent, in no case does this imply that NCr populations act autonomously. Signals from and cross‐talk between neural crest cells and the brain (Marcucio, Hallgrimsson, & Young, ; Trainor, Ariz‐McNaughton & Krumlauf, ), surface ectoderm (Couly, Creuzet, Bennaceur, Vincent, & Le Douarin, ; Hu & Marcucio, ; Hu, Marcucio, & Helms, ), and pharyngeal endoderm (Abu‐Issa, Smyth, Smoak, Yamamura, & Meyers, ; Billmyre & Lingensmith, ; Creuzet, Couly, & Le Douarin, ; Couly et al, ; Depew, Simpson, Morasso, & Rubenstein, ; Frisdal & Trainor, ; Graham & Richardson, ; Piotrowski & Nüsslein‐Volhard, ; Vietch et al, 1999; Yoshida et al, ), as well as with adjacent mesoderm are necessary participants in this process. We make no attempt to distinguish whether NCr cells act as instructors or messengers facilitating these interactions.…”

An atlas of anteriorhoxgene expression in the embryonic sea lamprey head:hox-code evolution in vertebrates

“…8B). In urochordates, Hox1 genes have been implicated in endostyle patterning (Canestro et al, 2008; Yoshida et al, 2017), while Hox3 genes are required for normal thyroid development in mice (Manley and Capecchi, 1995; Manley and Capecchi, 1998). This suggests that there may be similar requirements for Hox genes in patterning these endoderm-derived pharyngeal organs across chordates.…”