© 2015. Published by The Company of Biologists Ltd | Development (2015) 142, 2261-2267 doi:10.1242/dev.121798
RESEARCH REPORT
STEM CELLS AND REGENERATION
Bag of Marbles controls the size and organization of the
Drosophila hematopoietic niche through interactions with the
Insulin-like growth factor pathway and Retinoblastoma-family
protein
Tsuyoshi Tokusumi, Yumiko Tokusumi, Dawn W. Hopkins and Robert A. Schulz*
Bag of Marbles (Bam) is known to function as a positive regulator
of hematopoietic progenitor maintenance in the lymph gland blood
cell-forming organ during Drosophila hematopoiesis. Here, we
demonstrate a key function for Bam in cells of the lymph gland
posterior signaling center (PSC), a cellular domain proven to function
as a hematopoietic niche. Bam is expressed in PSC cells, and gene
loss-of-function results in PSC overgrowth and disorganization,
indicating that Bam plays a crucial role in controlling the proper
development of the niche. It was previously shown that Insulin receptor
(InR) pathway signaling is essential for proper PSC cell proliferation.
We analyzed PSC cell number in lymph glands double-mutant for bam
and InR pathway genes, and observed that bam genetically interacts
with pathway members in the formation of a normal PSC. The elF4A
protein is a translation factor downstream of InR pathway signaling, and
functional knockdown of this crucial regulator rescued the bam PSC
overgrowth phenotype, further supporting the cooperative function
of Bam with InR pathway members. Additionally, we documented that
the Retinoblastoma-family protein (Rbf), a proven regulator of cell
proliferation, was present in cells of the PSC, with a bam functiondependent expression. By contrast, perturbation of Decapentaplegic or
Wingless signaling failed to affect Rbf niche cell expression. Together,
these findings indicate that InR pathway-Bam-Rbf functional
interactions represent a newly identified means to regulate the
correct size and organization of the PSC hematopoietic niche.
KEY WORDS: Bam, Drosophila, Hematopoietic niche, InR pathway, Rbf
INTRODUCTION
Drosophila melanogaster has emerged as a valuable model for the
study of hematopoiesis. Blood cell production occurs in separate waves
during two developmental stages (Evans et al., 2003; Fossett, 2013).
The first wave occurs during embryogenesis, with hematopoietic
progenitors initially derived from the cephalic mesoderm. The second
wave takes place in a defined hematopoietic organ, termed the lymph
gland, which is formed late in embryogenesis and grows substantially
in size and progenitor cell number during the larval periods of
development. This tissue is eventually composed of multiple pairs of
lobes, with the primary lobes of the third-instar larval lymph gland
containing three regionalized cell populations of distinct hematopoietic
function. These populations include cells of the medullary zone,
Department of Biological Sciences, University of Notre Dame, 147 Galvin Life
Science Building, Notre Dame, IN 46556, USA.
*Author for correspondence ([email protected])
Received 12 January 2015; Accepted 20 May 2015
cortical zone and the posterior signaling center (PSC) (Jung et al.,
2005; Krzemień et al., 2007; Mandal et al., 2007). The medullary
zone harbors progenitors called prohemocytes, whereas the outer
cortical zone is occupied by differentiated hemocytes, such as
plasmatocytes and crystal cells.
The PSC is a specialized cellular domain, as it functions as a
hematopoietic progenitor niche. The PSC functions in the
maintenance of blood cell progenitors, expressing several
signaling molecules, such as Hedgehog, Serrate, Unpaired 3 and
PDGF- and VEGF-related factor 1, and also plays a role in the
induction of lamellocytes in response to wasp infestation (Krzemień
et al., 2007; Mandal et al., 2007; Sinenko et al., 2012; Mondal et al.,
2011). The niche is composed of 30-40 cells of the ∼2000 cells
present in the lymph gland, and, given its important functions, PSC
cell proliferation is tightly controlled by several signaling networks,
including the Decapentaplegic (Dpp), Wingless (Wg) and Insulinlike growth factor pathways (Sinenko et al., 2009; Benmimoun
et al., 2012; Pennetier et al., 2012; Tokusumi et al., 2012).
The Bag of Marbles (Bam) protein is expressed in prohemocytes
of the lymph gland, where it functions as a key regulator of
hematopoietic progenitor maintenance (Tokusumi et al., 2011).
Here, we demonstrate that Bam is also expressed in cells of the PSC,
where it serves a seminal role in the control of niche cell number.
Bam interacts genetically with members of the Insulin-like receptor
(InR) pathway and positively regulates the expression of the
Retinoblastoma-family protein Rbf, another crucial regulator of
PSC cell proliferation. These results provide additional insights into
the complexity of the genetic and molecular control of PSC niche
size and organization.
RESULTS AND DISCUSSION
Bam expression and function in lymph gland PSC cells
Previous studies demonstrated that Bam is expressed in prohemocytes
of the lymph gland medullary zone, where it functions as a key
regulatory protein that promotes blood cell precursor maintenance and
prevents hemocyte differentiation (Tokusumi et al., 2011). To
investigate the possibility of Bam expression in the PSC domain of
the lymph gland, we immunostained lymph glands for Bam protein
and hhF4f-GFP expression, the latter being a definitive marker of
PSC cells (Tokusumi et al., 2010). Co-localization of Bam with
the GFP marker demonstrated that Bam is expressed in cells of the
hematopoietic progenitor niche (Fig. 1A). Bam expression was
completely abolished in PSC cells of bam null lymph glands or
decreased in col>bam RNAi PSC cells (supplementary material
Fig. S1A,C). To investigate bam function in these cells, we assessed
PSC cell number in lymph glands from bam Δ86 homozygous and
col>bam RNAi mutant larvae, the latter being a genetic condition in
2261
DEVELOPMENT
ABSTRACT
Development (2015) 142, 2261-2267 doi:10.1242/dev.121798
Fig. 1. Bam PSC expression and loss-of-function phenotypes. (A) Bam protein (red) co-localization with the PSC-specific marker hhF4f-GFP (green).
(A′-A‴) Higher magnification views of box in A. Dashed area indicates PSC. (B) PSC cell numbers in lymph glands from wild-type and bam mutant larvae. hhF4fGFP is used as control strain. (C-E) Antp protein (red) and col>gapGFP (green) expression serve as markers for PSC cells in lymph glands from (C) wild-type,
(D) bam Δ86 homozygous mutant and (E) col>bam RNAi mutant larvae. (F-H) Monitoring of PSC cell cycle by FlyFUCCI in (F) wild-type and (G) bam Δ86 mutant
lymph glands. (H) Quantification of these results. (I) col>gapGFP (green) and dome-MESO (red) serve as marker for PSC cells and for hematopoietic progenitors
in wild-type lymph glands, respectively. (J) PSC cells and hematopoietic progenitors in lymph glands from col>bam RNAi mutant larvae. (K) Densitometric means
of anti-β-Gal (dome-MESO) staining in col>wt and col>bam RNAi lymph glands. (L,M) hhF4f-GFP (green) serves as marker for PSC cells, and Eater protein (red)
serves as marker for differentiated plasmatocytes in lymph glands from (L) wild-type and (M) col>bam RNAi mutant larvae. P-values (Student’s t-test) indicate
significant differences. Scale bar: 20 μm in all images except higher magnification views.
2262
DEVELOPMENT
RESEARCH REPORT
which bam function is selectively knocked down in PSC cells. In both
cases, we observed the production of supernumerary PSC cells located
throughout the lymph gland (Fig. 1B,D,E). To monitor the status of the
cell cycle in PSC cells with a bam mutant background, we introduced
the FUCCI system into this analysis (Sakaue-Sawano et al., 2008;
Zielke et al., 2014). The system revealed that bam loss-of-function
enhanced the proliferation status of PSC cells compared with wildtype PSC cells (Fig. 1F-H). These studies demonstrated a crucial role
for Bam in the control of niche cell proliferation and PSC organization.
To investigate whether the expanded PSC in lymph glands of the
genotype col>bam RNAi maintained its ability to positively regulate
progenitor cell maintenance while preventing premature hemocyte
differentiation, we assayed these lymph glands for the expression of
the prohemocyte marker dome-MESO and plasmatocyte marker Eater
(Hombría et al., 2005; Kocks et al., 2005; Gao et al., 2009; Chung and
Kocks, 2011). In contrast to lymph glands from control animals
(Fig. 1I,K), col>bam RNAi lymph glands contained a substantially
increased population of hematopoietic progenitors (Fig. 1J,K) and
a greatly diminished population of differentiated plasmatocytes
(Fig. 1L,M). Both findings support the notion of the expanded
PSC niche in bam mutant lymph glands being functional in its
communication with neighboring progenitor cells.
Genetic interactions of bam with InR pathway and elF4A
genes
Previous studies documented a central role for InR pathway signaling
in the control of PSC cell proliferation in response to altered animal
nutrition status (Benmimoun et al., 2012; Tokusumi et al., 2012).
Noteworthy is the observation that lymph glands mutant for the Pten
or dFOXO genes, two negative regulators of InR pathway signaling,
presented with the same phenotype of PSC overgrowth and dispersion
as bam mutant lymph glands (Tokusumi et al., 2012). These
comparable phenotypes led us to hypothesize that bam functions
with InR pathway genes in the control of niche size. To address this
possibility, we generated animals that were double-heterozygous
mutant for bam and Pten (Fig. 2A) or for bam and dFOXO (Fig. 2B).
In both genetic backgrounds, we observed an expanded PSC domain
with increased cell number (Fig. 2G). In further support of bam and
dFOXO functional interactions, forced expression of dFOXO in niche
cells suppressed the increased PSC cell phenotype in lymph glands
from bam Δ86/bam Δ86;col>dFOXO mutant larvae (Fig. 2E,G).
Additionally, RNAi-mediated knockdown of dAkt1 function, a
proven positive regulator of InR pathway signaling, likewise
suppressed the increased PSC cell phenotype due to bam loss-offunction (Fig. 2D,G). Together, these findings indicate that Bam has
an important functional interaction with the InR pathway in the
control of hematopoietic niche cell number.
Thor/4EBP is a component of the eIF4F translational control
complex and is a known target of FOXO transcriptional regulation.
Thor mutants show a comparable expanded PSC phenotype, as
observed in dFOXO mutant lymph glands, suggesting that the elF4F
complex functions downstream of dFOXO and InR pathway signaling
(Tokusumi et al., 2012). It has been shown that, in germline cells, Bam
negatively interacts with the elF4A protein, a functional component of
the elF4F complex, to prevent the translation of the DE-cadherin
protein (Shen et al., 2009). As we had previously demonstrated that
selective RNAi-mediated knockdown of elF4A function in PSC cells
resulted in a decreased population of niche cells (Tokusumi et al.,
2012), we tested the effect of elF4A loss-of-function in a bam mutant
background. Intriguingly, knockdown of elF4A function suppressed
the increased PSC cell phenotype normally seen in bam mutant lymph
glands (Fig. 2F,G), suggesting that the Bam and elF4A proteins
Development (2015) 142, 2261-2267 doi:10.1242/dev.121798
function antagonistically to each other in the tight control of PSC cell
number during lymph gland development.
Rbf expression and function in the hematopoietic progenitor
niche
Rbf is a proven controller of cell proliferation and tissue growth
(Gordon and Du, 2011). Owing to these vital functions, we assayed
lymph glands for the potential expression of this regulatory protein. We
observed that Rbf is expressed in cells populating the medullary zone
and also in PSC cells (Fig. 3E). Rbf proteins have been characterized as
tumor suppressor proteins, as their mutation results in cell
overproliferation and tumor formation in various tissue types
(Gordon and Du, 2011). Owing to its expression in cells of the PSC,
we sought to identify Rbf PSC phenotypes due to gene mutation or
overexpression. To assess whether Rbf loss-of-function culminated in a
hyperproliferation of PSC cells, we assayed lymph glands of the
genotype Rbf120-3-3/Rbf15aΔ for Antp protein expression and observed a
doubling of PSC cell number (Fig. 3B,D). To test for a cellautonomous function for Rbf in the control of niche cell proliferation,
we knocked down Rbf function selectively in the PSC and again
quantified the number of Antp+ cells. col>Rbf RNAi lymph glands
likewise contained a PSC of increased cell number, demonstrating the
cell-autonomous requirement of Rbf in niche cells for their correctly
controlled proliferation (Fig. 3D,F). This study also demonstrated
the absence of Rbf protein from hhF4f-GFP+ PSC cells due to the
targeted functional knockdown (Fig. 3F). Finally, we forced the
expression of Rbf in PSC cells, which resulted in a significant reduction
of this cell population in the gain-of-function condition (Fig. 3C,D).
It is known that Rbf negatively regulates the G1/S transition of
the mitotic cell cycle (Du and Dyson, 1999). To monitor the status
of the PSC cell cycle in the various Rbf genetic backgrounds, we
employed the Fly-FUCCI assay system. We observed that, owing to
Rbf gain-of-function, PSC cells were arrested at the G1 phase
(Fig. 3G,I), whereas Rbf loss-of-function increased the number of
S phase cells (Fig. 3G,J). Together, these findings identified Rbf as
an essential regulator of niche cell number through regulation of cell
G1/S phase transition.
bam function is required for Rbf protein expression in PSC
niche cells
As lymph glands mutant for the bam or Rbf genes displayed the
same phenotypes of PSC cell overproliferation, we hypothesized
that a regulatory relationship between the two genes might exist. To
investigate this possibility, we forced the expression of Rbf in PSC
cells in bam loss-of-function lymph glands and observed that Rbf
expression in niche cells suppressed the increased PSC phenotype
normally found due to bam mutation (Fig. 4A,B). Additionally, we
observed a lack of Rbf protein in PSC cells in lymph glands from
bam Δ86/bam Δ86 larvae (Fig. 4C). These findings allowed the
conclusion that Bam function is required for Rbf expression in
PSC cells, and overproliferation of niche cells due to bam loss-offunction is probably due to the absence of downstream Rbf protein
function. Similarly, Rbf protein failed to be expressed in dFOXO
mutant lymph glands (Fig. 4D), and PSC cell overproliferation
induced by InR expression was suppressed due to Rbf expression
(supplementary material Fig. S2). Together, these results support
the hypothesis of a functional interaction of Bam, Rbf and InR
pathway components.
It has been reported that Dpp and Wg signaling controls PSC cell
number through regulation of the dMyc cell proliferation factor
(Sinenko et al., 2009; Pennetier et al., 2012). To investigate a
potential relationship between the Dpp/Wg/dMyc effectors and Rbf
2263
DEVELOPMENT
RESEARCH REPORT
RESEARCH REPORT
Development (2015) 142, 2261-2267 doi:10.1242/dev.121798
function, we assayed for Rbf protein expression in genetic
backgrounds that perturbed Dpp and Wg signaling or enhanced
dMyc function. Preventing Dpp signaling in PSC cells had no effect
on Rbf expression, as expressing a dominant-negative version of
Tkv resulted in an increased niche size but normal Rbf expression
(Fig. 4E). Additionally, forced expression of Wg in the niche
domain resulted in supernumerary PSC cells, but did not affect Rbf
expression (supplementary material Fig. S3). Comparably, forced
expression of dMyc selectively in the PSC resulted in an increased
number of niche cells, but again, PSC cells showed normal Rbf
expression (Fig. 4F). These findings suggested that the Bam/Rbf
regulators might regulate PSC cell number and organization via a
mechanism that functioned in parallel to Dpp/Wg signaling and
dMyc-negative regulation. However, co-expression of both dMyc
and Rbf suppressed the PSC cell overproliferation phenotype
normally observed in col>dMyc lymph glands (Fig. 4B,G), and,
strikingly, there was an absence of dMyc protein in PSC cells due to
2264
forced Rbf expression in niche cells (Fig. 4I). Finally, there was also
an absence of dMyc protein in PSC cells due to E2F gene function
knockdown (Fig. 4J). These results indicate that Rbf can directly or
indirectly repress dMyc expression, and the co-expression of the
two cell-proliferation regulators leads to a near-normal PSC cell
number, due to Rbf suppression of dMyc and resulting rescue of the
PSC overproliferation phenotype. Thus, it appears that the dMyc
cell proliferation controller is a common target for Dpp pathway
signaling and InR/Bam/Rbf functional interactions. Such an
integration of the Dpp, Wg and InR/Bam/Rbf genetic regulators
in the control of PSC cell number is shown in Fig. 4K.
Taken together, this work has demonstrated a vital function for
Bam in the regulation of cell number and organization of the
hematopoietic progenitor niche. bam works in conjunction with
members of the InR signaling pathway and has an essential role in
promoting the expression of the Rbf protein, which in turn is a direct or
indirect regulator of dMyc expression. The question remains as to how
DEVELOPMENT
Fig. 2. bam genetic interactions with
InR pathway genes and resultant PSC
phenotypes. PSC cells in lymph glands
from (A) Pten2L100/+;bam Δ86/+ doubleheterozygous mutant, (B) bam Δ86/
dFOXO25 double-heterozygous mutant,
(C) bam Δ86 homozygous mutant,
(D) bam Δ86/bam Δ86;col>Akt1 RNAi
mutant, (E) bam Δ86/bam Δ86;col>dFOXO
mutant and (F) bam Δ86/bam Δ86;
col>elF4A RNAi mutant larvae. Antp
protein (red) and hhF4f-GFP (green)
expression serve as PSC-specific
markers. (G) PSC cell numbers in lymph
glands from wild-type, bam mutant, InR
pathway gene mutant and double-mutant
larvae. P-values (Student’s t-test)
indicate significant differences. Scale
bar: 20 μm for all images.
RESEARCH REPORT
Development (2015) 142, 2261-2267 doi:10.1242/dev.121798
Bam positively regulates Rbf expression. As Bam has been shown to
function in germline cells as a translational regulator through binding
to target mRNA 3′-UTR sequences (Shen et al., 2009; Li et al., 2009;
Insco et al., 2012), Bam might function to prevent the expression or
activity of a repressor that would normally inhibit Rbf expression
(Fig. 4K). Also possible is a mechanism in which Bam directly
or indirectly facilitates Rbf gene expression and/or subsequent
mRNA translation and protein synthesis. In either case, Bam has
been proven to be an indispensable regulator of the final phase of
Drosophila hematopoiesis through its documented functions in both
hematopoietic progenitors and their instructive niche cells.
Tissue immunostaining
MATERIALS AND METHODS
PSC cell counting
Drosophila strains
Quantification of PSC cell numbers was performed as previously described
(Tokusumi et al., 2012). Antp+ PSC cells in lymph glands from mid-thirdinstar larvae were counted. Error bars in each graph show s.d. Natural
Drosophila strains used in this study are described in the supplementary
material.
Dissected lymph glands were fixed with 4% paraformaldehyde for at least
30 min. After fixation, samples were incubated with blocking solution
containing 5% goat serum in 0.05% Triton X-100 in PBS (PBST) for 1 h at
room temperature and then incubated with primary antibody diluted with
blocking solution at room temperature for 1 h (anti-Antp) or at 4°C overnight
(other antibodies). See supplementary material Table 1 for antibodies used.
After washing with PBST four times, Alexa 555-conjugated anti-mouse or
anti-rabbit antibody (1:500; Invitrogen, A-21422, A-21428, respectively)
was added to the samples for at least 1 h. After washing again, samples were
mounted with 50% glycerol in PBS. Images of immunostained samples
were captured using a Nikon A1R laser-scanning confocal microscope.
2265
DEVELOPMENT
Fig. 3. Rbf PSC expression and loss- and
gain-of-function phenotypes. (A-D) Antp
protein (red) serves as marker for PSC cells
in lymph glands from (A) control, (B) Rbf
loss-of-function and (C) Rbf gain-offunction larvae. (D) Quantification of PSC
cell numbers in lymph glands of these three
genotypes. (E) Rbf protein (red)
co-localization with the PSC-specific
marker hhF4f-GFP (green). (E′,E″) Higher
magnification views of box in E.
(F) Knockdown of Rbf function selectively
in the PSC results in an increased number
of niche cells. (F′,F″) Higher magnification
views of box in F. Filled arrowhead
indicates increase in PSC cell number,
empty arrowhead indicates lack of Rbf
expression in PSC cells. (G) Quantification
of FUCCI in PSC cells in (H) col>w1118,
(I) col>Rbf and (J) col>Rbf RNAi larvae.
P-values (Student’s t-test) indicate
significant differences. Scale bar: 20 μm in
all images except higher magnification
views.
Development (2015) 142, 2261-2267 doi:10.1242/dev.121798
Fig. 4. Positioning bam within the genetic hierarchy controlling PSC cell number. (A) PSC cells in bamΔ86/bam Δ86; col>Rbf mutant larvae. Antp protein (red)
serves as niche cell marker. (B) PSC cell numbers in lymph glands from wild-type and mutant larvae. (C) Lack of Rbf protein in PSC cells in lymph glands from bam Δ86/
bam Δ86 mutant larvae. (C′,C″) Higher magnification views of box in C. (D) dFOXO mutant diminishes Rbf expression in PSC cells. (D′,D″) Higher magnification views
of box in D. (E) Expressing a dominant-negative version of Tkv in PSC cells results in an increased niche size but normal Rbf expression. (E′,E″) Higher magnification
views of box in E. (F) Forced expression of dMyc selectively in the PSC results in an increased number of niche cells. (F′,F″) Higher magnification views of box in F. (G)
Forced expression of Rbf suppresses the increased PSC cell phenotype in lymph glands from col>dMyc>Rbf larvae. Antp protein (red) and hhF4f-GFP expression
(green) serve as PSC cell markers. (H) Control lymph gland stained for the PSC cell marker hhF4f-GFP (green) and dMyc protein (red). (H′,H″) Higher magnification
views of box in H. (I) Reduced number of PSC cells in lymph glands from Rbf gain-of-function larvae. (I′,I″) Higher magnification views of box in I. (J) Knockdown of E2F
function results in a decreased PSC cell number in lymph glands from col>E2F RNAi larvae. (J′,J″) Higher magnification views of box in J. Filled arrowheads highlight
hhF4f-GFP+, Rbf+ or dMyc+ PSC cells, whereas open arrowheads highlight Rbf– or dMyc– PSC cells. (K) Placing Bam within a genetic hierarchy controlling PSC cell
number and niche size. P-values (Student’s t-test) indicate significant differences. Scale bar: 20 μm in all images except higher magnification views.
2266
DEVELOPMENT
RESEARCH REPORT
logarithms of cell numbers for each PSC were determined and analyzed by
Student’s t-test (Sorrentino et al., 2007). All calculations were obtained with
Microsoft Excel or Apple Numbers.
Quantification of progenitor cells in lymph glands
Densitometric means of dome-MESO+ cells, which are blood progenitor
cells in lymph glands, were quantified with a modified method, as
previously described (Gao et al., 2009). After anti-β-galactosidase staining,
lymph gland images were captured with a Zeiss Axioplan, and their size and
densitometric mean values were determined with ImageJ (NIH).
Cell cycle monitoring
To monitor cell cycle status of PSC cells in various genetic backgrounds, the
fluorescent ubiquitylation-based cell cycle indicator (FUCCI) for
Drosophila (FlyFUCCI) system was used (Sakaue-Sawano et al., 2008;
Zielke et al., 2014). See supplementary material for fly stocks used. We
assessed mid-third-instar col>FlyFUCCI lymph glands in various genetic
backgrounds with a Nikon A1-R or C2 confocal microscope and counted
each color of the PSC cells (GFP+mRFP, only GFP and only mRFP).
Acknowledgements
We thank Drs I. Ando, N. Dyson, W. Du, N. Fossett, E. Hafen, M. Crozatier, C. Kocks
and stock centers for antibodies and fly lines.
Competing interests
The authors declare no competing or financial interests.
Author contributions
T.T., Y.T., D.W.H. and R.A.S. conceived/designed experiments; T.T., Y.T. and
D.W.H. performed experiments; T.T., Y.T., D.W.H. and R.A.S. analyzed the data;
and T.T. and R.A.S. wrote the paper.
Funding
This research received no specific grant from any funding agency in the public,
commercial or not-for-profit sectors.
Supplementary material
Supplementary material available online at
http://dev.biologists.org/lookup/suppl/doi:10.1242/dev.121798/-/DC1
References
Benmimoun, B., Polesello, C., Waltzer, L. and Haenlin, M. (2012). Dual role for
Insulin/TOR signaling in the control of hematopoietic progenitor maintenance in
Drosophila. Development 139, 1713-1717.
Chung, Y.-S. A. and Kocks, C. (2011). Recognition of pathogenic microbes by the
Drosophila phagocytic pattern recognition receptor Eater. J. Biol. Chem. 286,
26524-26532.
Du, W. and Dyson, N. (1999). The role of RBF in the introduction of G1 regulation
during Drosophila embryogenesis. EMBO J. 18, 916-925.
Du, W., Vidal, M., Xie, J. E. Dyson, N. (1996). RBF, a novel RB-related gene that
regulates E2F activity and interacts with cyclin E in Drosophila. Genes Dev. 10,
1206-1218.
Evans, C. J., Hartenstein, V. and Banerjee, U. (2003). Thicker than blood:
conserved mechanisms in Drosophila and vertebrate hematopoiesis. Dev. Cell 5,
673-690.
Fossett, N. (2013). Signal transduction pathways, intrinsic regulators, and the
control of cell fate choice. Biochim. Biophys. Acta 1830, 2375-2384.
Gao, H., Wu, X. and Fossett, N. (2009). Upregulation of the Drosophila Friend of
GATA gene U-shaped by JAK/STAT signaling maintains lymph gland
prohemocyte potency. Mol. Cell. Biol. 29, 6086-6096.
Development (2015) 142, 2261-2267 doi:10.1242/dev.121798
Gordon, G. M. and Du, W. (2011). Conserved RB functions in development and
tumor suppression. Protein Cell 2, 864-878.
Hombrı́a, J. C.-G., Brown, S., Hä der, S. and Zeidler, M. P. (2005).
Characterisation of Upd2, a Drosophila JAK/STAT pathway ligand. Dev. Biol.
288, 420-433.
Insco, M. L., Bailey, A. S., Kim, J., Olivares, G. H., Wapinski, O. L., Tam, C. H.
and Fuller, M. T. (2012). A self-limiting switch based on translational control
regulates the transition from proliferation to differentiation in an adult stem cell
lineage. Cell Stem Cell 11, 689-700.
Jung, S.-H., Evans, C. J., Uemura, C. and Banerjee, U. (2005). The Drosophila
lymph gland as a developmental model of hematopoiesis. Development 132,
2521-2533.
Kocks, C., Cho, J. H., Nehme, N., Ulvila, J., Pearson, A. M., Meister, M., Strom, C.,
Conto, S. L., Hetru, C., Stuart, L. M. et al. (2005). Eater, a transmembrane
protein mediating phagocytosis of bacterial pathogens in Drosophila. Cell 123,
335-346.
Krzemień , J., Dubois, L., Makki, R., Meister, M., Vincent, A. and Crozatier, M.
(2007). Control of blood cell homeostasis in Drosophila larvae by the posterior
signalling centre. Nature 446, 325-328.
Li, Y., Minor, N. T., Park, J. K., McKearin, D. M. and Maines, J. Z. (2009). Bam and
Bgcn antagonize Nanos-dependent germ-line stem cell maintenance. Proc. Nat.
Acad. Sci. USA 106, 9304-9309.
Mandal, L., Martinez-Agosto, J. A., Evans, C. J., Hartenstein, V. and Banerjee, U.
(2007). A Hedgehog- and Antennapedia-dependent niche maintains Drosophila
haematopoietic precursors. Nature 446, 320-324.
Mondal, B. C., Mukherjee, T., Mandal, L., Evans, C. J., Sinenko, S. A., MartinezAgosto, J. A. and Banerjee, U. (2011). Interaction between differentiating celland niche-derived signals in hematopoietic progenitor maintenance. Cell 147,
1589-1600.
Pennetier, D., Oyallon, J., Morin-Poulard, I., Dejean, S., Vincent, A. and
Crozatier, M. (2012). Size control of the Drosophila hematopoietic niche by bone
morphogenetic protein signaling reveals parallels with mammals. Proc. Nat. Acad.
Sci. USA 109, 3389-3394.
Sakaue-Sawano, A., Kurokawa, H., Morimura, T., Hanyu, A., Hama, H., Osawa,
H., Kashiwagi, S., Fukami, K., Miyata, T., Miyoshi, H. et al. (2008). Visualizing
spatiotemporal dynamics of multicellular cell-cycle progression. Cell 132,
487-498.
Shen, R., Weng, C., Yu, J. and Xie, T. (2009). eIF4A controls germline stem cell
self-renewal by directly inhibiting BAM function in the Drosophila ovary. Proc. Nat.
Acad. Sci. USA 106, 11623-11628.
Sinenko, S. A., Mandal, L., Martinez-Agosto, J. A. and Banerjee, U. (2009). Dual
role of wingless signaling in stem-like hematopoietic precursor maintenance in
Drosophila. Dev. Cell 16, 756-763.
Sinenko, S. A., Shim, J. and Banerjee, U. (2012). Oxidative stress in the
haematopoietic niche regulates the cellular immune response in Drosophila.
EMBO Rep. 13, 83-89.
Sorrentino, R. P., Tokusumi, T. and Schulz, R. A. (2007). The Friend of GATA
protein U-shaped functions as a hematopoietic tumor suppressor in Drosophila.
Dev. Biol. 311, 311-323.
Tokusumi, Y., Tokusumi, T., Stoller-Conrad, J. and Schulz, R. A. (2010).
Serpent, suppressor of hairless and U-shaped are crucial regulators of hedgehog
niche expression and prohemocyte maintenance during Drosophila larval
hematopoiesis. Development 137, 3561-3568.
Tokusumi, T., Tokusumi, Y., Hopkins, D. W., Shoue, D. A., Corona, L. and
Schulz, R. A. (2011). Germ line differentiation factor Bag of Marbles is a regulator
of hematopoietic progenitor maintenance during Drosophila hematopoiesis.
Development 138, 3879-3884.
Tokusumi, Y., Tokusumi, T., Shoue, D. A. and Schulz, R. A. (2012). Gene
regulatory networks controlling hematopoietic progenitor niche cell production
and differentiation in the Drosophila lymph gland. PLoS ONE 7, e41604.
Zielke, N., Korzelius, J., van Straaten, M., Bender, K., Schuhknecht, G. F. P.,
Dutta, D., Xiang, J. and Edgar, B. A. (2014). Fly-FUCCI: A versatile tool for
studying cell proliferation in complex tissues. Cell Rep. 7, 588-598.
DEVELOPMENT
RESEARCH REPORT
2267