Caenorhabditis elegans Embryogenesis: Genetic Analysis of Cell Specification

Abstract

Cell fate in some early embryonic blastomeres of C. elegans is specified cell autonomously (mosaic development), by proteins localized by cytoskeletal machinery controlled by the par gene products, and in others by cell‐to‐cell signalling (regulative development), using either the APX‐1–GLP‐1 (Notch‐like) or the Wnt signalling pathway.

Keywords: C. elegans; embryogenesis; cell fate specification; regulative development; cell‐autonomous development; Wnt signalling; Notch‐like signalling

Figure 1.

The early lineage of the C. elegans embryo. Tissues produced by each of the founder cells (MS, E, C, D, P4) and by the four AB granddaughters are listed.

Figure 2.

Localization of P granules (small black dots) and spindle orientations in wild‐type and par mutants. (a) Distribution of P granules and PAR‐1 and PAR‐2 (blue) and PAR‐3 and PAR‐6 (red) proteins in the zygote. (b) Pattern after first cleavage and spindle orientations set up for the second cleavage. P granules are mislocalized in the mutant embryos.

Figure 3.

Distribution of the SKN‐1 (blue), PIE‐1 (red), and PAL‐1 (green) proteins in the first three cleavage stages. (a) Two‐cell embryo: maternal SKN‐1 protein is much higher in the P1 nucleus than in AB, and maternal PIE‐1 protein is localized in P1. (b) Four‐cell embryo: SKN‐1 is high in both the P2 and EMS nuclei; PIE‐1 is present in both the cytoplasm and nucleus of P2, and newly translated PAL‐1 protein appears in the P2 and EMS nuclei. (c) Eight‐cell embryo: SKN‐1 is disappearing from all nuclei; PIE‐1 is confined to the P3 nucleus; and PAL‐1 is present in all four posterior nuclei although it functions only in C and D (see text).

Figure 4.

Two signalling pathways set the AB and E blastomere fates by the 12‐cell stage. (a) At the four‐cell stage, P2 signals to AB.p through the APX‐1–GLP‐1 pathway, and also to EMS using the Wnt pathway. The localization of GLP‐1 (green) and APX‐1 (red) proteins is indicated. (b) Ventral view. At the 12‐cell stage, MS signals to AB.alp and AB.ara, the two AB cells that contribute to the pharynx, to differentiate them from their sister cells, again through the GLP‐1 pathway. The Wnt signal that polarizes EMS has inhibited POP‐1 translation in E, with the result that intestinal‐specific genes are activated there but inhibited by high POP‐1 in MS. POP‐1 blue; GLP‐1, green; APX‐1, red. Vertebrate and Drosophila homologues are listed in parentheses.

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Further Reading

Han M (1997) Gut reaction to Wnt signalling in worms. Cell 90: 581–584.

Kemphues KJ and Strome S (1997) Fertilization and establishment of polarity in the embryo. In: Riddle DL, Blumenthal T, Meyer BJ and Priess JR (eds) C. elegans II, pp. 335–360. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press.

Meneghini MD, Ishitani T, Carter JC et al. (1999) MAP kinase and Wnt pathways converge to down regulate an HMG‐domain repressor in Caenorhaditis elegans. Nature 399: 793–797.

Roush W (1996) Divide and confer: how worm embryo cells specialize. Science 272: 1871.

Schnabel R and Priess JR (1997) Specification of cell fates in the early embryo. In: Riddle DL, Blumenthal T, Meyer BJ and Priess JR (eds) C. elegans II, pp. 361–382. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press.

Sulston JE, Schierenberg E, White JG and Thomson JN (1983) The embryonic cell lineage of the nematode Caenorhabditis elegans. Developmental Biology 100: 64–119.

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How to Cite close
Edgar, Lois G(Mar 2003) Caenorhabditis elegans Embryogenesis: Genetic Analysis of Cell Specification. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0001505]