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. Author manuscript; available in PMC: 2013 Oct 1.
Published in final edited form as: Birth Defects Res A Clin Mol Teratol. 2012 Aug 3;94(10):804–816. doi: 10.1002/bdra.23052

Figure 9. Summary depicting the role of BMP-polarity interactions in HP formation.

Figure 9

Active BMP signaling induces SMAD1, 5, 8 phosphorylation, increasing pSMAD 1,5,8 interactions with the tight-junction associated PAR complex. These interactions stabilize the tight junction and thus neural epithelial organization. BMP blockade decreases the phosphorylation of SMAD1, 5, 8, reducing their interactions with the PAR complex. The partial loss of polarity modulates the junctional complexes sufficiently so that cells are more flexible and can undergo cell-shape changes required for HP formation and neural tube closure. Cyclic BMP signaling permits the dynamic modulation of polarity, but ensures that cells can change shapes without delaminating from the neural epithelium.