module: dmel_eggshell_structural_proteins
title: Eggshell structural proteins in Drosophila melanogaster
label: Eggshell structural proteins
module_type: BIOLOGICAL_PROCESS
description: >-
  The Drosophila eggshell is secreted by the somatic follicle cells that
  surround the oocyte during late oogenesis. The vitelline membrane, the
  innermost layer, is laid down first from vitelline membrane proteins
  (Vm26Aa, Vm26Ab, Vm26Ac, Vm32E, Vm34Ca and Vml) that are cross-linked into an
  insoluble layer. The chorion is secreted afterwards and is built from chorion
  proteins encoded mainly by two clusters: an X-linked cluster at 7F (Cp36,
  Cp38 and Cp7Fa-c) and an autosomal cluster at 66D (Cp15, Cp16, Cp18 and
  Cp19). The chorion gene clusters are amplified in follicle cells by
  developmentally regulated DNA re-replication, which allows the large and
  rapid synthesis of chorion proteins.
summary: >-
  Follicle-cell secreted vitelline membrane and chorion proteins that build the
  two main layers of the eggshell.
concepts:
  - {id: GO:0007304, label: chorion-containing eggshell formation}
parts:
  - id: vitelline_membrane_proteins
    label: Vitelline membrane proteins
    role: inner eggshell layer
    module_type: CELLULAR_COMPONENT
    group: VMP
    function: {id: GO:0008316, label: structural constituent of vitelline membrane}
    locations:
      - {id: GO:0060388, label: vitelline envelope}
  - id: chorion_proteins
    label: Chorion proteins
    role: outer eggshell layer
    module_type: CELLULAR_COMPONENT
    function: {id: GO:0005213, label: structural constituent of egg chorion}
    locations:
      - {id: GO:0042600, label: egg chorion}
    parts:
      - id: chorion_cluster_7f
        label: X-linked chorion cluster at 7F
        role: X-linked chorion proteins
        module_type: CELLULAR_COMPONENT
        genes: [Cp36, Cp38, Cp7Fa, Cp7Fb, Cp7Fc]
        function: {id: GO:0005213, label: structural constituent of egg chorion}
        locations:
          - {id: GO:0042600, label: egg chorion}
      - id: chorion_cluster_66d
        label: Third-chromosome chorion cluster at 66D
        role: autosomal chorion proteins
        module_type: CELLULAR_COMPONENT
        genes: [Cp15, Cp16, Cp18, Cp19]
        function: {id: GO:0005213, label: structural constituent of egg chorion}
        locations:
          - {id: GO:0042600, label: egg chorion}
connections:
  - source: vitelline_membrane_proteins
    target: chorion_proteins
    connection_type: PRECEDES
    description: Vitelline membrane proteins are secreted before the chorion proteins.
notes: >-
  Each protein is a separate annoton (complex false): the eggshell layers are
  cross-linked extracellular structures, not defined stoichiometric complexes.
  Vitelline membrane proteins are assigned to the vitelline envelope GO
  component. Several eggshell components outside the two FlyBase groups (for
  example the dec-1 proteins, and peroxidases and other enzymes that
  cross-link the layers) are not modelled. The structural-constituent functions
  of most chorion and vitelline membrane proteins rest on their localization and
  curator inference rather than gene-by-gene mutant analysis.