QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online 16 September 2003
doi: 10.1242/dev.00735

This Article Summary Full Text Full Text (PDF) Movies Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Nance, J. Articles by Priess, J. R. Search for Related Content PubMed PubMed Citation Articles by Nance, J. Articles by Priess, J. R.

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

Jeremy Nance¹, Edwin M. Munro² and James R. Priess^1,*,

¹ Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
² Center for Cell Dynamics and Friday Harbor Labs, Friday Harbor, WA 98250, USA

View larger version (62K): [in a new window]   Fig. 1. Localization and degradation of PAR proteins. (A) Schematic diagram of early stages of embryogenesis; sister cells are linked by short bars. Somatic precursors are indicated by bold outlines, germline precursors are indicated by a yellow asterisk. Germline precursors divide asymmetrically into a somatic precursor and a new germline precursor; the germline daughter has a high level of germline proteins, such as PIE-1, (dark red cells) and the somatic daughter contains a low level of PIE-1 (pink cells) that is degraded within one or two additional cell cycles (white cells). (B) PAR expression in early embryos. Embryos are oriented as in panel A; yellow asterisks mark germline precursors. (a,b) 1-cell embryos expressing either PAR-6GFP (a) or PAR-6ZF1-GFP (b); arrows point to the anterior cortex. (c,d) 4-cell embryos stained for endogenous PAR-3 (c) or PAR-3ZF1-GFP (d); large arrow in c points to the apical cortex of ABp. (d) Large arrow in d indicates the apical cortex of ABp, arrowhead indicates the apical cortex of EMS, and small arrow points to the cortex of the germline precursor. (e,f) 8-cell embryos expressing either PAR-6GFP (e) or PAR-6ZF1-GFP (f); note that PAR-6ZF1-GFP has disappeared from the oldest somatic cells (arrow) but is still detectable in the younger somatic cells (arrowheads). (g,h) 24-cell embryos showing PAR-3 (g) and PAR-3ZF1-GFP (h). (i,j) PAR-3 expression in epithelia of an organogenesis-stage wild-type embryo (i) and a par-3(ZF1) embryo (j); arrowheads point to the apical surfaces of cells forming the digestive tract. (k) Chimeric embryo formed by combining a wild-type embryo with a par-3 mutant embryo; arrowheads indicate former apical surfaces of the wild-type cells that now contact the par-3 mutant cells (p). (l) PAR-3 expression in the chimeric embryo in k; note localization of PAR-3 to the contact-free surface of the wild-type cell (arrows). In all panels, exposures were adjusted to visualize the background fluorescence of cells; the level of fluorescence in the ABa and ABp cells in d was similar to that in par-3 mutant embryos lacking the transgene. Transgene expression was identical in wild-type and par-3 mutant backgrounds; embryos shown are wild-type in a-c,e-g,i and par-3 in d,h,j. Embryos in this and subsequent figures are 50 µm in length. Scale bar: 10 µm.

View larger version (63K): [in a new window]   Fig. 2. Anterior-posterior asymmetry. (A-D) Wild-type, 2-cell embryo in the light microscope (A) after staining for P granules (B, green), and PIE-1 (C, red). DNA is shown in blue. (D) A 24-cell, wild-type embryo with an end-1::gfp transgene; the GFP fluorescence image (green) was superimposed on the light microscope image. The middle and bottom rows show par-mutant embryos (middle) and par(ZF1) embryos (bottom) prepared as above. Embryo genotypes are as follows: par-3(it71) (E,F,H); par-6(zu222) (G); par-3(ZF1) (I,J,L); par-6(ZF1) (K).

View larger version (44K): [in a new window]   Fig. 3. Localization of PAR-2 and HMR-1/E-cadherin. (A-D) Each row shows a single 8-cell embryo, either wild-type or par-3(ZF1), immunostained for both PAR-3 (A,C) and PAR-2 (B,D). (B',D') higher magnifications of the boxed regions in B,D, respectively. The arrow in C points to PAR-3 that remains in a young somatic cell. Note presence of apical PAR-2 in the par-3(ZF1) embryo (arrow in D'). (E) Two cells in an 8-cell par-3(ZF1) embryo immunostained for PAR-3 (red) and HMR-1 (green). PAR-3 is present at the apical cortex (arrow) of one cell only. Note that HMR-1 is present at basolateral surfaces but is not detected at apical surfaces (arrowhead). DNA is stained blue in all panels. Yellow asterisks mark germline precursors. Scale bar: 5 µm.

View larger version (77K): [in a new window]   Fig. 4. Localization of apical PAR proteins. Each row depicts a single embryo immunostained for the protein at the bottom right of each panel. Embryo genotypes are shown above each row. Where visible, the germline precursor is indicated with a yellow asterisk and the youngest somatic precursors are indicated by arrows. Embryos are shown at representative stages; similar results were obtained for other stages. (A-B) An 8-cell embryo. (C-D) A 12-cell embryo. (E-F) A 14-cell embryo. (G-H) A 26-cell embryo. At this stage, PAR-3ZF1-GFP is present only in the three youngest somatic cells (arrows), whereas apical PAR-3 is present in several older somatic cells (arrowheads in H).

View larger version (99K): [in a new window]   Fig. 5. Lateral cell adhesion. (A,B) Surface (A) and internal (B) images of a wild-type embryo viewed by light microscopy. (C,D) Surface (C) and internal (D) views of a par-6(ZF1) embryo. (E) Transmission electron micrograph of a par-3(ZF1) embryo. The arrow indicates abnormal intercellular separations. Opposing arrowheads in E indicate contacts between lateral membranes. n, nucleus. Scale bars: 5 µm in D; 1 µm in E.

View larger version (145K): [in a new window]   Fig. 6. Ingression of the endodermal precursors. (A) Images from video recordings of the ingression of the E daughters, the endodermal precursors. The focal plane is through the center of the embryo. (a) 24-cell stage. The E daughters (nuclei indicated by single asterisks) are present on the surface of the embryo. (b) 28-cell stage. The E daughters have moved toward the interior of the embryo (top). (c) 46-cell stage. The E daughters have entered the body cavity and divided into the E granddaughters (double asterisks indicate the two visible granddaughters). Neighboring cells (triangle) cover the site of ingression. (d-f) Comparable stages of par-3(ZF1) embryos, labeled as above. Note that the E granddaughters remain on the surface of the embryo in f. (B) Confocal images of NMY-2GFP in living embryos during the early stages of ingression, labels as above. The arrowheads in b,e indicate levels of NMY-2GFP in the midbodies of dividing cells; arrows in c and f show the apical surfaces of the E daughters. Time points in minutes are indicated in the lower right-hand corner of each panel; t=0 was the 26-cell stage just after the MS(2) to MS(4) division. Scale bars: 5 µm.