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. 2015 Dec 15;58(1):94–105. doi: 10.1111/dgd.12248

Figure 2.

Figure 2

Schematic of ectodermal endocrine and respiratory primordia in embryos and their specification gene regulatory network. A part of this cartoon is adapted from figure 4 in Sánchez‐Higueras et al. (2014). In each segment, Homeotic genes and Signal Transducers and Activators of Transcription (STAT) induce expression of the early transcription factors. Deformed (Dfd)‐STAT in the maxillary primordium (Mx) and Sex combs reduced (Scr)‐STAT in the labial primordium (Lb) induce ventral veins lacking (vvl) and snail (sna) expression. Spalt (Sal) represses trunk Homeotic gene expression in these primordia, preventing trachealess (trh) expression. The sna‐expressing cells undergo the epithelial‐mesenchymal transition (EMT) and migrate to form the corpora allata (CA) and the prothoracic gland (PG) cells. The corpora cardiaca (CC) cells are separately derived from anterior mesodermal cells. Representative lineage markers are Glass (Gl) in the CC, Seven‐up (Svp) in the CA, and Sal in the PG. These cells make a composite endocrine organ called the ring gland (RG).