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Fig. 1. Components of the Jak/Stat pathway are expressed in the GSC niche.
(A) Schematic of a Drosophila germarium. Terminal filament
cells (TFCs), cap cells (CpCs), escort stem cells (ESCs) and escort cells
(ECs) are of somatic origin. Germline stem cells (GSCs) are in close contact
with CpCs and contain apical spectrosomes that evolve into `exclamation mark'
figures in post-mitotic GSCs. Cystoblasts (CB) also contain spectrosomes, but
these do not maintain an apical localisation. CBs undergo four incomplete
rounds of division giving rise to cysts of two, four, eight and sixteen cells
interconnected by branched fusomes. (B) Wild-type germarium double
stained to visualise spectrosomes and fusomes (anti-Hts, red) and the Upd
ligand (anti-Upd, green). The accumulation of Upd protein is clearly visible
in TFCs and CpCs. In addition, a weaker, speckled distribution is present in
more-posterior cells, possibly corresponding to ESCs and ECs, cell types in
which the Jak/Stat pathway is active
(Decotto and Spradling, 2005 ).
(C) Stat92E06346 germarium double stained to
visualise Hts (red) and β-gal (green). Stat92E directs
lacZ expression in TFCs, CpCs, ESCs and ECs (see also
Decotto and Spradling, 2005).
(D) Detection of upd, upd2 and upd3 mRNAs by RT-PCR
in ovaries from virgin females. The expression of the embryonic gene
ftz was used as a control for the specificity of the ovarian cDNA
library (lanes 1 and 2). The expression of hedgehog (hh,
lane 3) provided a positive control. Lanes 4, 5 and 6 show that upd,
upd2 and upd3 are expressed in the ovary. (E) Germarium
from a bab1-Gal4/UASt-DsRed female stained with anti-Hts
(red). bab1-Gal4 directs DsRed expression (green) in TFCs,
CpCs, ESCs and ECs. (F) Germarium from a
tub-Gal80ts/UASt-upd2; bab1-Gal4/+
female stained with anti-Hts to show the tumour of spectrosome-containing
cells produced after bab1-Gal4-driven overexpression of Upd2 in adult
germaria. Anterior is up in all figures unless otherwise stated. Open
arrowheads, TFCs; white arrowheads, CpCs; arrows, ESCs and ECs; asterisks,
GSCs. Scale bars: 10 µm.
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CYT/+;
bab1-Gal4/+ germarium grown at 25°C and dissected 25 days AE. The
staining with anti-Hts shows that the two GSCs present in the niche possess an
anchorless spectrosome. (C-E') FRT101
hop2/FRT101 ubi-GFP; bab1-Gal4
UASt-flp germaria stained with anti-Hts (red), anti-GFP (green) and
the DNA dye Hoechst (white) to label hop2 mutant CpCs.
(C,C') GSC in contact with both mutant and wild-type CpCs showing a
normal spectrosome. (D,D') GSCs in contact with mutant CpCs displaying
anchorless spectrosomes. (E,E') Mutant CpCs in direct contact with a
differentiating 8-cell cyst. Asterisks, GSCs; yellow and red dashed lines,
CpCs; white dashed line, germline cyst. Scale bars: 10 µm.
3.25-fold
in experimental ovaries, whereas the amount of gbb mRNA did not vary
substantially under the same experimental conditions. The black triangle
denotes that the mean difference was statistically significant in the case of
dpp mRNA but not in the case of gbb mRNA (Student's
t-test, P<0.01; the mean values are averages of three
different replicas from three independent experiments). (C-D''')
Wild-type (C) and tub-Gal80ts/UASt-upd2;
bab1-Gal4/+ (D) germaria stained with anti-Hts (red), anti-pMad (a
reporter of Dpp pathway activation, green) and the DNA dye TOPRO-3 (blue). The
white dashed lines demarcate the areas magnified in C',C'' and
D'-D'''. (C-C'') Wild-type germarium showing pMad protein
restricted to the GSCs. (D-D''') A
tub-Gal80ts/UASt-upd2; bab1-Gal4/+
germarium showing expanded pMad staining within the ectopic GSC tumour.
Asterisks, GSCs. Scale bars: 10 µm.