Heterotrimeric G protein signaling governs the cortical stability during apical constriction in Drosophila gastrulation

Abstract

During gastrulation in Drosophila melanogaster, coordinated apical constriction of the cellular surface drives invagination of the mesoderm anlage. Forces generated by the cortical cytoskeletal network have a pivotal role in this cellular shape change. Here, we show that the organisation of cortical actin is essential for stabilisation of the cellular surface against contraction. We found that mutation of genes related to heterotrimeric G protein (HGP) signaling, such as Gβ13F, Gγ1, and ric-8, results in formation of blebs on the ventral cellular surface. The formation of blebs is caused by perturbation of cortical actin and induced by local surface contraction. HGP signaling mediated by two Gα subunits, Concertina and G-iα65A, constitutively regulates actin organisation. We propose that the organisation of cortical actin by HGP is required to reinforce the cortex so that the cells can endure hydrostatic stress during tissue folding.

Gprk2 adjusts Fog signaling to organize cell movements in Drosophila gastrulation

“…Since we observed that apical protrusions in LM cells always pointed toward the ventral furrow and that cells close to the furrow extended longer protrusions than cells distant from it, we speculate that the apical protrusion might be induced by the apically constricting neighbors. Indeed, in cta mutant embryos the apical protrusions did not always point toward mid-ventral, but rather frequently pointed toward the slight depressions that were formed at random positions by uncoordinated apical constriction [data not shown; see also figure 4E in Kanesaki et al (Kanesaki et al, 2013)]. One possibility is that mechanical or chemical signals that emanate from apically constricting cells might induce apical protrusions in surrounding cells.…”

“…The antibodies used in this study were anti-Eve, anti-Dl, anti-Dlg, anti-Sxl, anti-DE-Cadherin (obtained from DSHB), anti-β-gal (mouse antibody from Promega; rat antibody kindly provided by T. Isshiki, National Institute of Genetics, Japan), anti-α-Tubulin (Sigma), anti-aPKC (Santa Cruz), anti-Zip (kindly provided by F. Matsuzaki, RIKEN, Japan), anti-Mir (IkeshimaKataoka et al, 1997), anti-Cta (Kanesaki et al, 2013) and anti-Twi (Roth et al, 1989).…”

“…For scanning electron microscopy (SEM), embryos were fixed as previously described (Kanesaki et al, 2013). Ion-coated embryos were observed using a JEOL JSM-7500F scanning electron microscope.…”

“…For immunostaining analysis, embryos were fixed and stained as described (Kanesaki et al, 2013). To acquire images, we mainly used confocal laser scanning microscopy (Carl Zeiss LSM5 Live or Olympus FV10).…”

“…The roles of G protein regulators in development are poorly understood. Ric-8 is a putative guanine nucleotide-exchange factor for G protein (Tall et al, 2003), and Drosophila Ric-8 plays important roles during mesoderm invagination (Kanesaki et al, 2013). GPCR kinase (also known as GRK) is another example of a G protein regulator (Pitcher et al, 1998;Penn et al, 2000).…”