C. elegansPAR-3 and PAR-6 are required for apicobasal asymmetries associated with cell adhesion and gastrulation

Abstract

PAR proteins distribute asymmetrically across the anterior-posterior axis of the 1-cell-stage C. elegans embryo, and function to establish subsequent anterior-posterior asymmetries. By the end of the 4-cell stage,anteriorly localized PAR proteins, such as PAR-3 and PAR-6, redistribute to the outer, apical surfaces of cells, whereas posteriorly localized PAR proteins, such as PAR-1 and PAR-2, redistribute to the inner, basolateral surfaces. Because PAR proteins are provided maternally, distinguishing apicobasal from earlier anterior-posterior functions requires a method that selectively prevents PAR activity after the 1-cell stage. In the present study we generated hybrid PAR proteins that are targeted for degradation after the 1-cell stage. Embryos containing the hybrid PAR proteins had normal anterior-posterior polarity, but showed defects in apicobasal asymmetries associated with gastrulation. Ectopic separations appeared between lateral surfaces of cells that are normally tightly adherent, cells that ingress during gastrulation failed to accumulate nonmuscle myosin at their apical surfaces and ingression was slowed. Thus, PAR proteins function in both apicobasal and anterior-posterior asymmetry during the first few cell cycles of embryogenesis.

Cytoskeletal Symmetry Breaking and Chirality: From Reconstituted Systems to Animal Development

“…Following A/P polarization, chiral cortical actomyosin activity patterns the D/V and L/R axes [187,188,191,192,197] (see above), and cortical contractility drives cell internalization and most likely also cell sorting during gastrulation [197,[262][263][264][265][266][267]. The central inductive cue(s) that drives non-muscle myosin II activation during gastrulation is constituted by Wnt signaling [200,265].…”

Analysis of centriole elimination duringC. elegansoogenesis

“…The following genotypes were used: sas-6(ok2554) (Kitagawa et al, 2011), zyg-1(it25) (Kemp et al, 2007), spd-2(oj29) (O'Connell et al, 1998), sas-5(t2033) , sas-5(gk400) (http://www.wormbase.org), sas-4(tm3951) (Kitagawa et al, 2011), cki-2(ok2105) (Buck et al, 2009), fog-1(q253) (Barton and Kimble, 1990) (shifted to the restrictive temperature of 25°C as L1/L2), fog-2(q71) (Schedl and Kimble, 1988), fog-3(q470) (Ellis and Kimble, 1994), tra-1(e1076) (Schedl et al, 1989), her-1(hv1y101) unc-42 and her-1(hv1y101) unc-42 dpy-11;lon-2 (Francis et al, 1995b), analyzed as described (Bean et al, 2004), mog-1(q233) (Graham and Kimble, 1993), fem-3(q96gf) (Barton et al, 1987), cgh-1(ok492) (Audhya et al, 2005), glo-1(zu391) (Hermann et al, 2005), rrf-1(pk1417) (Sijen et al, 2001), GFP-SAS-4 (Kirkham et al, 2003), GFP-SAS-5 , GFP-SAS-6 , GFP-SPD-2 (Kemp et al, 2004), GFP-TBG-1 (Oegema et al, 2001), GFP -TAC-1 (Bellanger and Gönczy, 2003), VIT-2-GFP (Grant and Hirsh, 1999), NMY-2-GFP (Nance et al, 2003).…”

MEX-5 asymmetry in one-cellC. elegansembryos requires PAR-4-and PAR-1-dependent phosphorylation

“…LGI: gsk-3(nr2047); LGII: fzr-1(ok380), mex-6(pk440) (Schubert et al, 2000), vrk-1(ok1181), zyg-1(b1) (Wood et al, 1980);LGIII: kin-19(ok602), par-2(it5ts) (Kemphues et al, 1988), unc-119(ed3) (Maduro and Pilgrim, 1995); LGIV: mex-5(zu199) (Schubert et al, 2000), mbk-2(ne992) (Pang et al, 2004), par-5(it55) (Morton et al, 2002); LGV: par-1(b274), par-1(e2012), par-1(it51), par-1(it60) (Guo and Kemphues, 1995), par-4(it33), par-4(it47ts), par-4(it75) (Watts et al, 2000); and transgene zuIs45 (nmy-2:NMY-2:GFP) (Nance et al, 2003).…”

“…All washes were done in . Dilutions were as follows: αMEX-5(pS458), 1:1000; αMEX-5, 1:50 (Schubert et al, 2000); αGFP, 1:2000 (Abcam ab6556); αPAR-3, 1:20 (Nance et al, 2003); αPIE-1, 1:20 (Tenenhaus et al, 1998). Incubations were at room temperature for two hours , αGFP] or at 4°C overnight.…”