Tj expression and tissue organization in the wild-type GSC niche.

(A) Schematic drawing of the GSC niche. (B-C) Cap cells can form a symmetric (B) or asymmetric cluster (C) as indicated by arrows. A broad gap is visible between the cluster of tightly packed cap cell nuclei and the nuclei of escort cells (EsC), as indicated by a dashed line. Lamin C (LamC) staining of the nuclear envelope (green) is strong in TF cells, weak in cap cells (and surrounding ovariole sheath cells (OS)), and not detectable in escort cells. (D) GSCs, marked by Vasa (blue) form protrusions (arrowheads) around the cap cell cluster (yellow). A transition cell (TC) connects the cap cell cluster to the TF (green). Nuclei of escort cells (EsC, orange) sit posterior to the GSCs. Tj staining (red) is very strong in escort cells, strong in cap cells, weak in the transition cell, and not detectable in the TF. Bab2 (green) is stronger expressed in cap cells than in other somatic cells. (E-F') GSCs have plasma membrane protrusions, marked by GAP43-mEos (arrowheads in E',F') that partially envelop the Tj-positive (red) cap cells (arrows in E,F). Spectrosomes (Sp) of GSCs are highlighted by Hu li tai shao (Hts) (white). (F,F') A GSC is connected to its daughter cystoblast via an open ring canal. CB, pre-cystoblast/cystoblast. Anterior is up. Scale bars: 10 μm.