Adult stem cells and niche cells segregate gradually from common precursors that build the adult Drosophila ovary during pupal development

Production of proliferative Follicle Cells (FCs) and quiescent Escort Cells (ECs) by Follicle Stem Cells (FSCs) in adult Drosophila ovaries is regulated by niche signals from anterior (Cap Cells, ECs) and posterior (polar FCs) sources. Here we show that ECs, FSCs and FCs develop from common pupal precursors, with different fates acquired by progressive separation of cells along the AP axis and a graded decline in anterior cell proliferation. ECs, FSCs and most FCs derive from Intermingled Cell (IC) precursors interspersed with germline cells. Precursors also accumulate posterior to ICs before engulfing a naked germline cyst projected out of the germarium to form the first egg chamber and posterior polar FC signaling center. Thus, stem and niche cells develop in appropriate numbers and spatial organization through regulated proliferative expansion together with progressive establishment of spatial signaling cues that guide adult cell behavior, rather than through rigid early specification events.

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Integrins control the positioning and proliferation of follicle stem cells in the Drosophila ovary

The Journal of Cell Biology ◽

10.1083/jcb.200710141 ◽

2008 ◽

Vol 182 (4) ◽

pp. 801-815 ◽

Cited By ~ 70

Author(s):

Alana M. O'Reilly ◽

Hsiu-Hsiang Lee ◽

Michael A. Simon

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Adult Stem Cells ◽

Cell Communication ◽

Self Renewal ◽

Ovarian Stem Cells ◽

Stem Cell Populations ◽

Integrin Ligand ◽

Follicle Stem Cells ◽

Drosophila Ovary

Adult stem cells are maintained in specialized microenvironments called niches, which promote self-renewal and prevent differentiation. In this study, we show that follicle stem cells (FSCs) in the Drosophila melanogaster ovary rely on cues that are distinct from those of other ovarian stem cells to establish and maintain their unique niche. We demonstrate that integrins anchor FSCs to the basal lamina, enabling FSCs to maintain their characteristic morphology and position. Integrin-mediated FSC anchoring is also essential for proper development of differentiating prefollicle cells that arise from asymmetrical FSC divisions. Our results support a model in which FSCs contribute to the formation and maintenance of their own niche by producing the integrin ligand, laminin A (LanA). Together, LanA and integrins control FSC proliferation rates, a role that is separable from their function in FSC anchoring. Importantly, LanA-integrin function is not required to maintain other ovarian stem cell populations, demonstrating that distinct pathways regulate niche–stem cell communication within the same organ.

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A Single-Cell Atlas and Lineage Analysis of the Adult Drosophila Ovary

10.1101/798223 ◽

2019 ◽

Cited By ~ 2

Author(s):

Katja Rust ◽

Lauren Byrnes ◽

Kevin Shengyang Yu ◽

Jason S. Park ◽

Julie B. Sneddon ◽

...

Keyword(s):

Stem Cells ◽

Single Cell ◽

Cell Types ◽

Somatic Tissue ◽

Lineage Tracing ◽

Major Cell Type ◽

Follicle Stem Cells ◽

Drosophila Ovary ◽

Adult Drosophila ◽

Lineage Analysis

AbstractThe Drosophila ovary is a widely used model for germ cell and somatic tissue biology. We have used single-cell RNA-sequencing to build a comprehensive cell atlas of the adult Drosophila ovary containing unique transcriptional profiles for every major cell type in the ovary, including the germline and follicle stem cells. Using this atlas we identify novel tools for identification and manipulation of known and novel cell types and perform lineage tracing to test cellular relationships of previously unknown cell types. By this we discovered a new form of cellular plasticity in which inner germarial sheath cells convert to follicle stem cells in response to starvation.Graphical Abstract

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The follicle epithelium in the Drosophila ovary is maintained by a small number of stem cells

eLife ◽

10.7554/elife.49050 ◽

2019 ◽

Vol 8 ◽

Cited By ~ 13

Author(s):

Jocelyne Fadiga ◽

Todd G Nystul

Keyword(s):

Stem Cells ◽

Cell Biology ◽

Clonal Analysis ◽

Follicle Cells ◽

Stem Cell Biology ◽

Research Support ◽

Clone Size ◽

New Methods ◽

Follicle Stem Cells ◽

Drosophila Ovary

The follicle stem cells (FSCs) in the Drosophila ovary are an important experimental model for the study of epithelial stem cell biology. Although decades of research support the conclusion that there are two FSCs per ovariole, a recent study used a novel clonal marking system to conclude that there are 15–16 FSCs per ovariole. We performed clonal analysis using both this novel clonal marking system and standard clonal marking systems, and identified several problems that may have contributed to the overestimate of FSC number. In addition, we developed new methods for accurately measuring clone size, and found that FSC clones produce, on average, half of the follicle cells in each ovariole. Our findings provide strong independent support for the conclusion that there are typically two active FSCs per ovariole, though they are consistent with up to four FSCs per germarium.

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Opposing Wnt and JAK-STAT signaling gradients define a stem cell domain by regulating spatially patterned cell division and differentiation at two borders

10.1101/2020.06.23.167536 ◽

2020 ◽

Author(s):

David Melamed ◽

Daniel Kalderon

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Cell Division ◽

Adult Stem Cells ◽

Wnt Pathway ◽

Opposite Polarity ◽

Follicle Cells ◽

Pathway Activity ◽

Stat Signaling ◽

Stat Pathway

AbstractMany adult stem cells are maintained as a community by population asymmetry, wherein stochastic actions of individual cells collectively result in a balance between stem cell division and differentiation. We have used Drosophila Follicle Stem Cells (FSCs) as a paradigm to explore the extracellular niche signals that define a stem cell domain and organize stem cell behavior. FSCs produce transit-amplifying Follicle Cells (FCs) from their posterior face and quiescent Escort Cells (ECs) to their anterior. Here we show that JAK-STAT pathway activity, which declines from posterior to anterior, dictates the pattern of divisions over the FSC and EC domains, promotes more posterior FSC locations and conversion to FCs, while opposing EC production. A Wnt pathway gradient of opposite polarity promotes more anterior FSC locations and EC production and opposes FC production. Promotion of both FSC division and conversion to FCs by JAK-STAT signaling buffers the effects of genetically altered pathway activity on FSC numbers and balances the four-fold higher rate of differentiation at the posterior face of the FSC domain with a higher rate of FSC division in the most posterior layer. However, genetic elimination of Wnt pathway activity exacerbated elevated FC production resulting from increased JAK-STAT pathway activity, leading to rapid FSC depletion despite high rates of division. The two pathways combine to define a stem cell domain through concerted effects on FSC differentiation to ECs (high Wnt, low JAK-STAT) and FCs (low Wnt, high JAK-STAT) at each end of opposing signaling gradients, further enforced by quiescence at the anterior border due to declining JAK-STAT pathway activity.

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EGFR signaling promotes self-renewal through the establishment of cell polarity in Drosophila follicle stem cells

eLife ◽

10.7554/elife.04437 ◽

2014 ◽

Vol 3 ◽

Cited By ~ 29

Author(s):

Angela Castanieto ◽

Michael J Johnston ◽

Todd G Nystul

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Cell Polarity ◽

Growth Factor Receptor ◽

Egfr Signaling ◽

Epithelial Stem Cells ◽

Cell Fates ◽

Liver Kinase B1 ◽

Follicle Stem Cells ◽

Drosophila Ovary

Epithelial stem cells divide asymmetrically, such that one daughter replenishes the stem cell pool and the other differentiates. We found that, in the epithelial follicle stem cell (FSC) lineage of the Drosophila ovary, epidermal growth factor receptor (EGFR) signaling functions specifically in the FSCs to promote the unique partially polarized state of the FSC, establish apical–basal polarity throughout the lineage, and promote FSC maintenance in the niche. In addition, we identified a novel connection between EGFR signaling and the cell-polarity regulator liver kinase B1 (LKB1), which indicates that EGFR signals through both the Ras–Raf–MEK–Erk pathway and through the LKB1–AMPK pathway to suppress apical identity. The development of apical–basal polarity is the earliest visible difference between FSCs and their daughters, and our findings demonstrate that the EGFR-mediated regulation of apical–basal polarity is essential for the segregation of stem cell and daughter cell fates.

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The number of Follicle Stem Cells in a Drosophila ovariole.

10.1101/2021.10.25.465475 ◽

2021 ◽

Author(s):

Daniel Kalderon ◽

David Melamed ◽

Amy Reilein

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Central Issue ◽

Cell Lineages ◽

General Relevance ◽

Follicle Stem Cells ◽

Drosophila Ovary ◽

Lineage Analysis

A paper by Reilein et al (2017) presented several fundamental new insights into the behavior of adult Follicle Stem Cells (FSCs) in the Drosophila ovary, including evidence that each ovariole hosts a large number of FSCs (14-16) maintained by population asymmetry (Reilein et al., 2017), rather than just two FSCs, dividing with largely individually asymmetric outcomes, as originally proposed (Margolis and Spradling, 1995; Nystul and Spradling, 2007). Fadiga and Nystul (2019) contest some of these conclusions on the basis of their repetition of a multicolor lineage strategy used by Reilein et al (2017) and repetition of earlier single-color lineage analysis. Here we outline a number of shortcomings in the execution and interpretation of those experiments that, in our opinion, undermine their conclusions. The central issue of general relevance concerns the importance of comprehensively analyzing all stem cell lineages, independent of any pre-conceptions, in order to identify all constituents and capture heterogeneous behaviors.

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Embryonic attenuated Wnt/β-catenin signaling defines niche location and long-term stem cell fate in hair follicle

eLife ◽

10.7554/elife.10567 ◽

2015 ◽

Vol 4 ◽

Cited By ~ 24

Author(s):

Zijian Xu ◽

Wenjie Wang ◽

Kaiju Jiang ◽

Zhou Yu ◽

Huanwei Huang ◽

...

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Hair Follicle ◽

Progenitor Cells ◽

Cell Fate ◽

Adult Stem Cells ◽

Stem Cell Markers ◽

Hair Follicle Stem Cells ◽

Follicle Stem Cells

Long-term adult stem cells sustain tissue regeneration throughout the lifetime of an organism. They were hypothesized to originate from embryonic progenitor cells that acquire long-term self-renewal ability and multipotency at the end of organogenesis. The process through which this is achieved often remains unclear. Here, we discovered that long-term hair follicle stem cells arise from embryonic progenitor cells occupying a niche location that is defined by attenuated Wnt/β-catenin signaling. Hair follicle initiation is marked by placode formation, which depends on the activation of Wnt/β-catenin signaling. Soon afterwards, a region with attenuated Wnt/β-catenin signaling emerges in the upper follicle. Embryonic progenitor cells residing in this region gain expression of adult stem cell markers and become definitive long-term hair follicle stem cells at the end of organogenesis. Attenuation of Wnt/β-catenin signaling is a prerequisite for hair follicle stem cell specification because it suppresses Sox9, which is required for stem cell formation.

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Division-independent differentiation mandates proliferative competition among stem cells

10.1101/208983 ◽

2017 ◽

Author(s):

Amy Reilein ◽

David Melamed ◽

Simon Tavaré ◽

Daniel Kalderon

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Cell Division ◽

Experimental Evidence ◽

Adult Stem Cells ◽

Proliferation Rate ◽

Quantitative Modeling ◽

Stem Cell Division ◽

Follicle Stem Cells ◽

The Impact

SUMMARYCancer-initiating gatekeeper mutations that arise in stem cells would be especially potent if they stabilize and expand an affected stem lineage (1, 2). It is therefore important to understand how different stem cell organization strategies promote or prevent variant stem cell amplification in response to different types of mutation, including those that activate stem cell proliferation. Stem cell numbers can be maintained constant while producing differentiated products through individually asymmetric division outcomes or by population asymmetry strategies, in which individual stem cell lineages necessarily compete for niche space. We considered alternative mechanisms underlying population asymmetry and used quantitative modeling to predict starkly different consequences of altering proliferation rate: a variant, faster-proliferating mutant stem cell should compete better only when stem cell division and differentiation are independent processes. For most types of stem cell it has not been possible to ascertain experimentally whether division and differentiation are coupled. However, Drosophila Follicle Stem Cells (FSCs) provided a favorable model system to investigate population asymmetry mechanisms and also for measuring the impact of altered proliferation on competition. We found from detailed cell lineage studies that FSC division and FSC differentiation are not coupled. We also found that FSC representation, reflecting maintenance and amplification, was highly responsive to genetic changes that altered only the rate of FSC proliferation. The FSC paradigm therefore provides definitive experimental evidence for the general principle that relative proliferation rate will always be a major determinant of competition among stem cells specifically when stem cell division and differentiation are independent.SIGNIFICANCEAdult stem cells support tissue maintenance throughout life but they also can be cells of origin for cancer, allowing clonal expansion and long-term maintenance of the first oncogenic mutations. We considered how a mutation that increases the proliferation rate of a stem cell would affect the probability of its competitive survival and amplification for different potential organizations of stem cells. Quantitative modeling showed that the key characteristic predicting the impact of relative proliferation rate on competition is whether differentiation of a stem cell is coupled to its division. We then used Drosophila Follicle Stem Cells to provide definitive experimental evidence for the general prediction that relative proliferation rates dictate stem cell competition specifically for stem cells that exhibit division-independent differentiation.

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Protocol for evaluating autophagy using LysoTracker staining in the epithelial follicle stem cells of the Drosophila ovary

STAR Protocols ◽

10.1016/j.xpro.2021.100592 ◽

2021 ◽

Vol 2 (2) ◽

pp. 100592

Author(s):

Iliana Correa ◽

Melissa Wang ◽

Eric H. Lee ◽

Dara M. Ruiz-Whalen ◽

Alana M. O’Reilly ◽

...

Keyword(s):

Stem Cells ◽

Follicle Stem Cells ◽

Drosophila Ovary

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Drosophila Boi limits Hedgehog levels to suppress follicle stem cell proliferation

The Journal of Cell Biology ◽

10.1083/jcb.201007142 ◽

2010 ◽

Vol 191 (5) ◽

pp. 943-952 ◽

Cited By ~ 44

Author(s):

Tiffiney R. Hartman ◽

Daniel Zinshteyn ◽

Heather K. Schofield ◽

Emmanuelle Nicolas ◽

Ami Okada ◽

...

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Cell Function ◽

Apical Cell ◽

Suppressive Effect ◽

Stem Cell Proliferation ◽

Apical Cells ◽

And Function ◽

Follicle Stem Cells ◽

Drosophila Ovary

Stem cells depend on signals from cells within their microenvironment, or niche, as well as factors secreted by distant cells to regulate their maintenance and function. Here we show that Boi, a Hedgehog (Hh)-binding protein, is a novel suppressor of proliferation of follicle stem cells (FSCs) in the Drosophila ovary. Hh is expressed in apical cells, distant from the FSC niche, and diffuses to reach FSCs, where it promotes FSC proliferation. We show that Boi is expressed in apical cells and exerts its suppressive effect on FSC proliferation by binding to and sequestering Hh on the apical cell surface, thereby inhibiting Hh diffusion. Our studies demonstrate that cells distant from the local niche can regulate stem cell function through ligand sequestration, a mechanism that likely is conserved in other epithelial tissues.

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