%0 Journal Article
%T The eggshell is required for meiotic fidelity, polar-body extrusion and polarization of the C. elegans embryo
%A Wendy L Johnston
%A Aldis Krizus
%A James W Dennis
%J BMC Biology
%D 2006
%I BioMed Central
%R 10.1186/1741-7007-4-35
%X We show that the GLD (Germline differentiation abnormal)-1-regulated hexosamine pathway enzyme, glucosamine-6-phosphate N-acetyltransferase (GNA)-2, is required for synthesis of uridine diphosphate-N-acetylglucosamine (UDP-GlcNAc), the substrate for eggshell chitin synthesis by chitin synthase-1 (CHS-1). Furthermore, while chs-1(RNAi) or combined RNAi with the chitin-binding proteins, CEJ-1 and B0280.5, does not interfere with normal meiotic timing, lagging chromosomes are observed at meiosis, and polar-body extrusion fails. We also demonstrate that chitin, and either CEJ-1 or B0280.5, are essential for the osmotic/permeability barrier and for movement of the sperm pronucleus/centrosome complex to the cortex, which is associated with the initiation of polarization.Our results indicate that the eggshell is required in single-cell C. elegans development, playing an essential role in multiple actin-dependent early events. Furthermore, the earliest meiotic roles precede osmotic barrier formation, indicating that the role of the eggshell is not limited to generation of the osmotic barrier.During oocyte development, inhibition of mitogen-activated protein kinase (MAPK) signaling causes arrest at meiotic prophase I. Subsequent maturation, which results in breakdown of the germinal vesicle (nuclear envelope) and assembly of the meiotic spindle, requires relief of MAPK inhibition. In Caenorhabditis elegans, this relief is provided by major sperm protein (MSP), budded off from sperm stored in the spermatheca [1,2]. MSP displaces ephrin bound to oocyte VAB-1 receptors, resulting in MAPK activation and oocyte maturation. MSP also binds non-VAB receptors on oocyte and gonadal sheath cell membranes, inducing ovulation of the mature oocyte into the spermatheca, the site of fertilization. Fertilization activates the anaphase-promoting complex/cyclosome (APC/C), triggering progression past anaphase I [3]. Concomitantly, fertilization signals the rapid assembly of a chitinous eggshel
%U http://www.biomedcentral.com/1741-7007/4/35