The C. elegans eggshell

Abstract

In all animals, oocytes are surrounded by an extracellular matrix upon fertilization. This matrix serves similar purposes in each animal. It functions to mediate sperm binding, to prevent polyspermy, to control the chemical environment of the embryo, and to provide physical protection to the embryo as it developes. The synthesis of the C. elegans matrix, or eggshell, begins when the oocyte enters the spermatheca and is fertilized by a single sperm. The process of eggshell synthesis is thought to take place during the completion of the maternal meiotic divisions such that the multi-layered eggshell is completed by anaphase II. The synthesis of the eggshell occurs in a hierarchical pattern such that the outermost layers are synthesized first in order to capture and retain the innermost layers as they form. Recent studies have revealed that the lipid-rich permeability barrier is distinct from the outer trilaminar eggshell. These new findings alter our previous understanding of the eggshell. This chapter aims to define each of the eggshell layers and the molecules that are known to play significant roles in their formation.

Embryo integrity regulates maternal proteostasis and stress resilience

“…In contrast, knockdown of genes involved in the formation of the chitin layer of the eggshell did not improve maternal stress resilience, suggesting that the embryo-to-mother pathway is specific to the vitelline layer. In all metazoans, the fertilized egg is coated with an extracellular matrix that provides physical protection to the developing embryo, known as the eggshell in C. elegans (Stein and Golden 2018). The eggshell is composed of six different layers, of which the vitelline layer is established first and is required for the proper assembly of the subsequent layers (Johnston et al 2010).…”

CBD-1 scaffolds two independent complexes required for eggshell vitelline layer formation and egg activation in C. elegans

“…Surprisingly, mCherry-tagged PERM-2 and PERM-4 were found on the surface of oocytes in the gonad before fertilization and the embryonic eggshell after fertilization ( Fig. 2A,B), a pattern consistent with the outermost vitelline layer of the eggshell rather than the innermost permeability barrier (Johnston and Dennis, 2011;Olson et al, 2012;Stein and Golden, 2015). The chitin-binding domain protein CBD-1 similarly localized to unfertilized oocytes in a previous study (Johnston et al, 2010) and is proposed to be a vitelline layer protein (Johnston and Dennis, 2011;Stein and Golden, 2015), so we also investigated its localization following fertilization.…”

Dietary supplementation with PUFAs rescues the eggshell defects caused byseipinmutations inC. elegans

“…The synthesis of this eggshell occurs in a 87 hierarchical pattern, with each layer being sequentially added, starting with the outermost layer 88 first. A lipid-rich layer known as the permeability barrier is the fifth layer of the eggshell to be 89 synthesized and is responsible for preventing osmotic and mechanical stress from harming 90 developing embryos (Johnston and Dennis, 2012;Olson et al, 2012;Stein and Golden, 2018). 91…”