Fig. 1. Identification of cell types within the germarium. (A) A representation of
the germarium. The germline stem cells (GSCs) reside at the anterior tip of
the germarium and divide asymmetrically such that one daughter becomes a
cystoblast (CB) while the other daughter remains a GSC. GSCs are associated
with terminal filament (TF) and cap cells (both somatic cells, dark blue). All
GSCs and CBs contain spectrosomes (green dot) and express
Dad-lacZ (blue dot). The CBs undergo four rounds of mitotic
division with incomplete cytokinesis to produce 2, 4 and 8 germline cell cysts
(CC) in Region 1 and 16 CC in Region 2A. All cyst cells are interconnected by
a fusome (green lines). Germ cells are associated with inner sheath cells
(ISCs) in Regions 1 and 2A of the germarium. In Region 2B, one cell of the 16
CC becomes specified as an oocyte (purple), and cysts become enveloped by
follicle cells (light blue), derived from somatic stem cells (SSC). In Region
3, a stage 1 egg chamber buds off from the germarium. (B-I) Confocal
projections of morphologically wild-type germaria or ovarioles. Arrow
indicates position of terminal filament. (B) Germarium of female carrying a
Nos-Myc transgene, showing low expression in GSCs and CBs (bracket), absence
from two- to eight-cell cysts, and high expression in 16-cell cysts
(anti-spectrin, green; anti-Myc, red). Germarium (C,E,F) and whole ovariole
(G) of females of genotype
P{lacZ}DadP1883/TM3,Sb. (C,E,G)
Anti-lacZ (green), anti-Hts (red). Bracket in G indicates region 2 of
the germarium.(F) Anti-lacZ (green). Dad-lacZ
expression in the germline is present at high levels in GSCs (asterisk) and at
lower levels in CBs (circles in E and F), but expression of
Dad-lacZ is observed in cap cells and ISCs (arrowheads). (D)
Germarium of a female of genotype P{ptc-GAL4} P{UAS-GFP} (anti-GFP,
green; anti-Hts, red). GFP is expressed in ISCs (arrowheads). (H) Distribution
of EGFP-VAS fusion protein in flies carrying a P{vas-egfp::vas}
transgene(anti-GFP, green; anti-Hts, red). Bracket in H indicates region 2 of
the germarium. (I) Ovariole of female of genotype P{vas-GAL4}/+;
P{UAS.p-TkvAct} P{lacZ}DadP1883/+ + (anti-GFP, green;
anti-Hts, red). Note lacZ expression in germ cells at anterior tip of
the germarium (top asterisk) and in egg chambers (bottom asterisks), but not
in developing egg cysts in regions 2 and 3 of the germarium (bracket). (J)
Summary of expression pattern of germline markers. Spec, spectrosome; Fus,
fusome.