September 1, 2001;
Differential gene expression of Xenopus Pitx1, Pitx2b and Pitx2c during cement gland, stomodeum and pituitary development.
The members of the Pitx family of homeobox transcription factors have been involved in many aspects of vertebrate embryogenesis, like for example, development of teeth
and limbs. We previously reported expression patterns and function of Pitx2c
in the generation of laterality and asymmetric morphogenesis of heart
and gastro-intestinal tract in mouse, frog and zebrafish (Development 126 (1999) 1225; Mech. Dev. 90 (2000) 41). Here we describe the differential expression of Pitx1
, Pitx2b and Pitx2c
ectodermal pattern formation and differentiation of cement gland, stomodeum and pituitary
in the frog Xenopus laevis.
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Fig. 2. Ectodermal expression of Xenopus Pitx genes at neurula stages. (A–C) Early neurula (stage 13), (D–F) mid-neurula (stage 18), (G–I) late neurula (stage 22). Lines indicate approximate levels of sections. (A*) and (C*–E*) show larger magnifications of sections. Note that Pitx1 and Pitx2c were co-expressed in the primordia of the cement gland (black arrow; A,C,D,F,G,I) and the stomodeum/pituitary (yellow arrow; (A–I)), while Pitx2b was resticted to the deep layer cells fated to become pituitary (B,E,H). Note also that Pitx1 was not expressed in the neuroectoderm, whereas Pitx2b and Pitx2c RNAs were found in neural tissue (red arrows; (F,H,I)).
Fig. 3. Expression of Pitx genes in Xenopus tadpoles. Co-localization of Pitx1 and Pitx2c mRNA was found in the cement gland (black arrow; (A,C,E,G)). All three genes were co-expressed in the pituitary and stomodeum (yellow arrows; (A–C), (E–G)) and in the midbrain (E–G). Exclusive expression of Pitx1 was found in the foregut (blue arrow; (A,D,E,H)), lens (D+E), and posterior lateral plate mesoderm (pLPM). (C) and (G) show the asymmetric expression of Pitx2c in the left LPM and heart anlage, where Pitx1 and Pitx2b were not detected (B,D–F). Lines indicate approximate levels of sections. aLPM, anterior LPM; em, eye muscle; ha, heart anlage; hm, head mesenchyme; le, lens; LPM, lateral plate mesoderm; pLPM, posterior LPM.