XB-ART-42856Development. April 1, 2011; 138 (7): 1321-7.
RACK1 is a novel interaction partner of PTK7 that is required for neural tube closure.
RACK1 is an evolutionarily conserved intracellular adaptor protein that is involved in a wide range of processes including cell adhesion and migration; however, its role in vertebrate development is largely unknown. Here, we identify RACK1 as a novel interaction partner of PTK7, a regulator of planar cell polarity that is necessary for neural tube closure. RACK1 is likewise required for Xenopus neural tube closure. Further, explant assays suggest that PTK7 and RACK1 are required for neural convergent extension. Mechanistically, RACK1 is necessary for the PTK7-mediated membrane localization of Dishevelled (DSH). RACK1 facilitates the PTK7-DSH interaction by recruiting PKCδ1, a known effector of DSH membrane translocation. These data place RACK1 in a novel signaling cascade that translocates DSH to the plasma membrane and regulates vertebrate neural tube closure.
PubMed ID: 21350015
Article link: Development.
Genes referenced: actl6a dvl2 myc ptk7 rack1
Morpholinos referenced: gnb2l1 MO1 gnb2l1 MO2 ptk7 MO2 ptk7 MO4
Article Images: [+] show captions
|Fig. 2. RACK1 loss of function leads to similar neural tube closure defects as PTK7 loss of function. (A) Time-lapse images of Xenopus embryos injected with 10 ng control MO, RACK1 MO1 or PTK7 MO analyzed at stages 15, 18 and 23 show a similar delay in neural tube closure in the RACK1 and PTK7 morphants and the embryos remain shorter than the control. Embryos were injected at the one-cell stage and images were taken at 30-minute intervals from stage 13 to stage 23. (B) The expression of SOX2 (a pan-neural marker) and PAX3 (a lateral neural plate marker) is expanded in stage 17-18 embryos injected with 10 ng RACK1 MO1 or PTK7 MO compared with control MO. (C,D) Transverse sections of stage 18 embryos injected with 20 ng RACK1 MO or PTK7 MO. Embryos were injected in one blastomere at the two-cell stage; the dashed line demarcates the injected from the control side of the embryo. Phalloidin staining (red) marks the actin cytoskeleton. Actin accumulation, indicating hinge point formation (white arrows), is seen on the injected and control sides. However, the neural plate remains wide on the injected side (yellow arrow), indicating a defect in convergent extension. (E-H) Neural convergent extension was analyzed in ectodermal explants (animal caps) injected with 450 pg XBF-2 RNA. Explant elongation was analyzed when control embryos reached stage 20. (E) Uninjected control caps did not elongate. (F) Explants injected with XBF-2 and 20 ng control MO showed various degrees of elongation. (G) Co-injection of 20 ng RACK1 MO inhibited explant elongation. (H) Co-injection of 20 ng PTK7 MO inhibited elongation of explants. (I) The percentage of elongated explants from the experiments illustrated in E-H. Black indicates a strong elongation, gray a mild elongation. The number of explants is indicated for each condition.|