[
Cell Calcium,
2011]
IP receptor is a Ca(2+) release channel localized on the endoplasmic reticulum. IP(3) receptor is composed of three isoforms, which are expressed in various cells and tissues, and play variety of roles throughout development. I here describe the role of IP receptor from oogenesis, meiotic maturation and fertilization. I also describe the Ca(2+) signaling at meiosis and mitosis, and especially the role in early embryogenesis to determine dorso-ventral axis formation. Loss of function mutation of type 1 IP receptor in mouse, both by gene targeting and spontaneous mutations shows severe ataxia and other phenotypes. Interestingly, double knockouts of type 1 and type 2 exhibit cardiogenesis arrest and that of type 2 and type 3 results in exocrine secretion deficit. IPR of Drosophila or Caenorhabditis elegans is single gene and mutation results severe phenotype of behavior. All the data described here show that IPRs are essential for life and abnormality of IP(3)Rs results in severe abnormality in its structure and function of organism.
[
Cell Motil Cytoskeleton,
2009]
Intermediate filaments (IFs) make up one of the three major fibrous cytoskeletal systems in metazoans. Numerous IF polypeptides are synthesized in cell type-specific combinations suggesting specialized functions. The review concentrates on IFs in the model organism Caenorhabditis elegans which carries great promise to elucidate the still unresolved mechanisms of IF assembly into complex networks and to determine IF function in a living organism. In contrast to Drosophila melanogaster, which lacks cytoplasmic IFs altogether, the nematode genome contains 11 genes coding for cytoplasmic IFs and only a single gene for a nuclear lamin. Its cytoplasmic IFs are expressed in developmentally and spatially defined patterns. As an example we present the case of the intestinal IFs which are abundant in the mechanically resilient endotube, a prominent feature of the C. elegans intestinal terminal web region. This IF-rich structure brings together all three cytoskeletal filaments that are integrated into a coherent entity by the C. elegans apical junction (CeAJ) thereby completely surrounding and stabilizing the intestinal lumen with its characteristic brush border. Concepts on the developmental establishment of the endotube in relation to polarization and its function for maintenance of epithelial integrity are discussed. Furthermore, possible connections of the cytoplasmic cytoskeleton to the nuclear lamin IFs and the importance of these links for nuclear positioning are summarized.