XB-ART-11857Mech Dev. January 1, 2000; 90 (1): 41-51.
During vertebrate left-right development the homeobox gene Pitx2 serves as a mediator between transient nodal signaling in the left lateral plate mesoderm (l-LPM) and asymmetric organ morphogenesis. Misexpression of Pitx2 in chick and frog led to alteration of organ situs. Here we report the presence of different Pitx2 isoforms in mouse and frog. Pitx2c but not Pitx2a or Pitx2b was asymmetrically expressed in the l-LPM, heart and gut, and was specifically induced by nodal in Xenopus animal cap explant cultures and whole embryos. Pitx2c induced its own transcription, suggesting a maintenance mechanism following the down-regulation of nodal in the l-LPM. Pitx2c thus represents the left-specific isoform involved in vertebrate left-right asymmetry.
PubMed ID: 10585561
Article link: Mech Dev.
Genes referenced: nodal nodal1 pitx2
Article Images: [+] show captions
|Fig. 3. Expression of Pitx2c but not Pitx2b during development of left right asymmetries in the frog Xenopus. Embryos were analyzed by wholemount in situ hybridization for the expression of Pitx2 using probes speci for isoform c (A, I) and isoform b (E, M). Lines indicate the approximate levels of transverse sections. (A) At stage 30 both isoforms were co-expressed in the brain (B,F). Pitx2c mRNA was found in the left myocardium (C) and in the l-LPM (D). No speci staining was detectable in the heart and LPM with a probe speci for Pitx2b (G,H). (I) Coexpression of isoforms in the brain presists at stage 38 (J,N). Speci expression of Pitx2c was found on the left side of the looping stomach (st, K) and intestine (i, L), while a Pitx2b probe did not reveal speci signals.|