SRGP-1
Supplemental material for the following paper:
Zaidel-Bar, R., Joyce, M.J., Lynch, A.M., Witte, K., Audhya, A., and Hardin, J. (2010). The F-BAR domain of SRGP-1 facilitates cell-cell adhesion during C. elegans morphogenesis. J. Cell Biol. 191, 761-9. PubMed
Summary
Robust cell–cell adhesion is critical for tissue integrity and morphogenesis, yet little is known about the molecular mechanisms controlling cell–cell junction architecture and strength. We discovered that SRGP-1 is a novel component of cell–cell junctions in Caenorhabditis elegans, localizing via its F-BAR (Bin1, Amphiphysin, and RVS167) domain and a flanking 200–amino acid sequence. SRGP-1 activity promotes an increase in membrane dynamics at nascent cell–cell contacts and the rapid formation of new junctions; in addition, srgp-1 loss of function is lethal in embryos with compromised cadherin–catenin complexes. Conversely, excess SRGP-1 activity leads to outward bending and projections of junctions. The C-terminal half of SRGP-1 interacts with the N-terminal F-BAR domain and negatively regulates its activity. Significantly, in vivo structure–function analysis establishes a role for the F-BAR domain in promoting rapid and robust cell adhesion during embryonic closure events, independent of the Rho guanosine triphosphatase–activating protein domain. These studies establish a new role for this conserved protein family in modulating cell–cell adhesion.
Video 1 (0.8 Mb). Ventral enclosure in wild-type and srgp-1(RNAi) embryos. HMP-1::GFP dynamics show extensive membrane ruffling (arrows) and rapid junction formation in wild type versus less membrane ruffling and slower junction formation in the srgp- 1(RNAi) embryo. Single focal plane. Frames are shown at 1 min apart. Play rate is nine frames per second.
Download MP4
Video 2 (1.8 Mb). Morphogenetic failure in hmp-1(fe4)/alpha-catenin;srgp-1 double mutant embryos. One Z section from a Nomarski time-lapse video following the development of hmp-1(fe4);srgp-1(RNAi) embryos from the four-cell stage. All embryos fail in gastrulation cleft closure and subsequently rupture from the cleft. Play rate is nine frames per second.
Download MP4
Video 3 (0.6 Mb). Gastrulation cleft closure in wildtype, hmp-2(qm39)/beta-catenin embryo, and hmp-2(qm39)/beta-catenin;srgp-1(RNAi) embryo. Single Z section, 1-min interval time-lapse videos of cleft closure in wild-type (left), hmp-2(qm39) (middle), and hmp- 2(qm39);srgp-1(RNAi) embryos. Note the faster closure in wild-type embryos and the separation of cells that have already made contact in the mutant embryos. Play rate is nine frames per second.
Download MP4
Video 4 (4.1 Mb). Dynamics of SRGP-1::GFP at various developmental stages. Time-lapse videos of SRGP-1::GFP were acquired at 1- min intervals. Each frame is a projection of eight Z sections spaced 0.2 μm apart. On the top left is a dorsal view of epidermal cells after intercalation; on the top right is a ventral view during late gastrulation. On the bottom left is a view of ventral epidermal enclosure, and on the bottom right is epidermal elongation. Play rate is nine frames per second.
Download MP4