title: Identification of the origin and localization of chorion (egg envelope) proteins in an ancient fish, the white sturgeon, Acipenser transmontanus.
abstract: In many modern teleost fish, chorion (egg envelope) glycoproteins are synthesized in the liver of females, and the expression of those genes is controlled by endogenous estrogen released from the ovary during maturation. However, among the classical teleosts, such as salmonid, carp, and zebrafish, the chorion glycoproteins are synthesized in the oocyte, as in higher vertebrates. Sturgeon, which are members of the subclass Chondrostei, represent an ancient lineage of ray-finned fishes that differ from other teleosts in that their sperm possess acrosomes, their eggs have numerous micropyles, and early embryo development is similar to that of amphibians. In order to understand the molecular mechanisms of chorion formation and the phylogenetic relationship between sturgeon and other teleosts, we used specific antibodies directed against the primary components of sturgeon chorion glycoproteins, using immunoblotting and immunocytochemistry approaches. The origin of each chorion glycoprotein was determined through analyses of both liver and ovary, and their localization during ovarian development was investigated. Our data indicate that the origin of the major chorion glycoproteins of sturgeon, ChG1, ChG2, and ChG4, derive not only from the oocyte itself but also from follicle cells in the ovary, as well as from hepatocytes. In the follicle cell layer, granulosa cells were found to be the primary source of ChGs during oogenesis in white sturgeon. The unique origins of chorion glycoproteins in sturgeon suggest that sturgeons are an intermediate form in the evolution of the teleost lineage.
authors.affiliation: Center for Health and the Environment, University of California, Davis, California kmurata@ucdavis.edu.
authors.forename: Kenji
authors.initials: K
authors.lastname: Murata
authors.affiliation: Department of Animal Science, University of California, Davis, California.
authors.forename: Fred S
authors.initials: FS
authors.lastname: Conte
authors.affiliation: Department of Animal Science, University of California, Davis, California.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: McInnis
authors.affiliation: Department of Animal Science, University of California, Davis, California.
authors.forename: Tak Hou
authors.initials: TH
authors.lastname: Fong
authors.affiliation: Bodega Marine Laboratory, University of California, Davis, Bodega Bay, California Departments of Environmental Toxicology and Nutrition, University of California, Davis, California.
authors.forename: Gary N
authors.initials: GN
authors.lastname: Cherr
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002823:Chorion / Q000502:physiology*; D004527:Egg Proteins / Q000096:biosynthesis* / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism; D005260:Female; D005399:Fishes / Q000502:physiology*; D006023:Glycoproteins / Q000096:biosynthesis* / Q000378:metabolism; D007150:Immunohistochemistry; D009108:Mumps Vaccine / Q000378:metabolism; D009865:Oocytes / Q000166:cytology / Q000378:metabolism; D009866:Oogenesis / Q000502:physiology*; D006080:Ovarian Follicle / Q000166:cytology / Q000378:metabolism; D010063:Ovum / Q000166:cytology / Q000378:metabolism; D010802:Phylogeny
chemical_list: D004527:Egg Proteins; D006023:Glycoproteins; D009108:Mumps Vaccine; C015753:chorion proteins
keywords: choriogenin; chorion; chorion proteins; egg envelope; extracellular matrix; fish reproduction; gametogenesis; oocyte development; oogenesis; white sturgeon; zona pellucida