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Horacio M. Frydman - One of the best experts on this subject based on the ideXlab platform.

  • Extreme Divergence of Wolbachia Tropism for the Stem-Cell-Niche in the Drosophila Testis
    PLOS Pathogens, 2014
    Co-Authors: Michelle E. Toomey, Horacio M. Frydman
    Abstract:

    Microbial tropism, the infection of specific Cells and tissues by a microorganism, is a fundamental aspect of host-microbe interactions. The intraCellular bacteria Wolbachia have a peculiar tropism for the Stem Cell Niches in the Drosophila ovary, the microenvironments that support the Cells producing the eggs. The molecular underpinnings of Wolbachia Stem Cell Niche tropism are unknown. We have previously shown that the patterns of tropism in the ovary show a high degree of conservation across the Wolbachia lineage, with closely related Wolbachia strains usually displaying the same pattern of Stem Cell Niche tropism. It has also been shown that tropism to these structures in the ovary facilitates both vertical and horizontal transmission, providing a strong selective pressure towards evolutionary conservation of tropism. Here we show great disparity in the evolutionary conservation and underlying mechanisms of Stem Cell Niche tropism between male and female gonads. In contrast to females, Niche tropism in the male testis is not pervasive, present in only 45% of Niches analyzed. The patterns of Niche tropism in the testis are not evolutionarily maintained across the Wolbachia lineage, unlike what was shown in the females. Furthermore, hub tropism does not correlate with cytoplasmic incompatibility, a Wolbachia-driven phenotype imprinted during spermatogenesis. Towards identifying the molecular mechanism of hub tropism, we performed hybrid analyses of Wolbachia strains in non-native hosts. These results indicate that both Wolbachia and host derived factors play a role in the targeting of the Stem Cell Niche in the testis. Surprisingly, even closely related Wolbachia strains in Drosophila melanogaster, derived from a single ancestor only 8,000 years ago, have significantly different tropisms to the hub, highlighting that Stem Cell Niche tropism is rapidly diverging in males. These findings provide a powerful syStem to investigate the mechanisms and evolution of microbial tissue tropism.

  • Somatic Stem Cell Niche tropism in Wolbachia
    Nature, 2006
    Co-Authors: Horacio M. Frydman, Jennifer M. B. Li, Drew N. Robson, Eric Francis Wieschaus
    Abstract:

    Wolbachia are remarkably successful intraCellular parasites. They are found in most Arthropods and are also in the news as possible tools for malaria control — transgenic variants could block maturation of malaria parasites in mosquitoes. Like mitochondria, these bacteria are transmitted by the mother. They also spread horizontally between species, but little is known about the Cellular mechanisms involved. Frydman et al. now report that Wolbachia can cross tissue barriers to reach the germline. They preferentially populate the somatic Stem Cell Niche of the Drosophila germarium (where the ova form) in newly initiated or inherited infections. The Stem Cell Niche appears to act as a reservoir of bacteria for germline infection. Wolbachia migrate through several tissues and reach the germ line of their arthropod hosts through the somatic Stem Cell Niche during horizontal transmission. In addition, a high abundance of bacteria in this Niche suggests that this location may also contribute to efficient vertical transmission. Wolbachia are intraCellular bacteria found in the reproductive tissue of all major groups of arthropods1,2. They are transmitted vertically from the female hosts to their offspring, in a pattern analogous to mitochondria inheritance. But Wolbachia phylogeny does not parallel that of the host, indicating that horizontal infectious transmission must also occur3,4,5. Insect parasitoids are considered the most likely vectors, but the mechanism for horizontal transfer is largely unknown4,6,7. Here we show that newly introduced Wolbachia cross several tissues and infect the germline of the adult Drosophila melanogaster female. Through investigation of bacterial migration patterns during the course of infection, we found that Wolbachia reach the germline through the somatic Stem Cell Niche in the D. melanogaster germarium. In addition, our data suggest that Wolbachia are highly abundant in the somatic Stem Cell Niche of long-term infected hosts, implying that this location may also contribute to efficient vertical transmission. This is, to our knowledge, the first report of an intraCellular parasite displaying tropism for a Stem Cell Niche.

  • Somatic Stem Cell Niche tropism in Wolbachia
    Nature, 2006
    Co-Authors: Horacio M. Frydman, Drew N. Robson, Eric Francis Wieschaus
    Abstract:

    Wolbachia are intraCellular bacteria found in the reproductive tissue of all major groups of arthropods. They are transmitted vertically from the female hosts to their offspring, in a pattern analogous to mitochondria inheritance. But Wolbachia phylogeny does not parallel that of the host, indicating that horizontal infectious transmission must also occur. Insect parasitoids are considered the most likely vectors, but the mechanism for horizontal transfer is largely unknown. Here we show that newly introduced Wolbachia cross several tissues and infect the germline of the adult Drosophila melanogaster female. Through investigation of bacterial migration patterns during the course of infection, we found that Wolbachia reach the germline through the somatic Stem Cell Niche in the D. melanogaster germarium. In addition, our data suggest that Wolbachia are highly abundant in the somatic Stem Cell Niche of long-term infected hosts, implying that this location may also contribute to efficient vertical transmission. This is, to our knowledge, the first report of an intraCellular parasite displaying tropism for a Stem Cell Niche.

Zhaojun Ding - One of the best experts on this subject based on the ideXlab platform.

  • Topoisomerase II-associated protein PAT1H1 is involved in the root Stem Cell Niche maintenance in Arabidopsis thaliana.
    Plant cell reports, 2016
    Co-Authors: Jiajia Liu, Huiyu Tian, Huihui Zheng, Yuebin Jia, Zhaojun Ding
    Abstract:

    PAT1H1, one of the homologues of Topoisomerase II-associated protein, is involved in the maintenance of root Stem Cell Niche through the interaction with NINJA. The root Stem Cell Niche, which possesses four mitotically inactive quiescent Cells (QC) and the surrounding mitotically active Stem Cells, is critical for root development in Arabidopsis thaliana. However, the molecular regulation of the maintenance of root Stem Cell Niche identity is still not fully understood. Here we show that one of the homologues of Topoisomerase II-associated protein, here named as PAT1H1, could regulate root Stem Cell Niche identity. The pat1h1 mutant showed higher frequency of QC Cell division and root distal Stem Cell (DSC) differentiation. With a high expression in roots, PAT1H1 was found to interact with the jasmonic acid (JA) signalling negative regulator Novel Interactor of JAZ (NINJA) and thus regulate root DSC Niche identity. Consistent with the active QC Cell division, which rarely occurs in wild-type controls, the pat1h1 mutant displayed higher expression of CYCB1 in the root Stem Cell Niche. Together our data reveals that PAT1H1 maintains root Stem Cell Niche stability through the interaction with NINJA and the regulation of Cell division.

  • WOX5 is Shining in the Root Stem Cell Niche.
    Trends in Plant Science, 2015
    Co-Authors: Xiangpei Kong, Songchong Lu, Huiyu Tian, Zhaojun Ding
    Abstract:

    The WUS-RELATED HOMEOBOX 5 (WOX5) gene is expressed in the quiescent center (QC) to regulate the columella Stem Cell (CSC) identity. Three recent reports not only show how WOX5 is controlled but also highlight the key role of WOX5 in root Stem Cell Niche maintenance.

Eric Francis Wieschaus - One of the best experts on this subject based on the ideXlab platform.

  • Somatic Stem Cell Niche tropism in Wolbachia
    Nature, 2006
    Co-Authors: Horacio M. Frydman, Jennifer M. B. Li, Drew N. Robson, Eric Francis Wieschaus
    Abstract:

    Wolbachia are remarkably successful intraCellular parasites. They are found in most Arthropods and are also in the news as possible tools for malaria control — transgenic variants could block maturation of malaria parasites in mosquitoes. Like mitochondria, these bacteria are transmitted by the mother. They also spread horizontally between species, but little is known about the Cellular mechanisms involved. Frydman et al. now report that Wolbachia can cross tissue barriers to reach the germline. They preferentially populate the somatic Stem Cell Niche of the Drosophila germarium (where the ova form) in newly initiated or inherited infections. The Stem Cell Niche appears to act as a reservoir of bacteria for germline infection. Wolbachia migrate through several tissues and reach the germ line of their arthropod hosts through the somatic Stem Cell Niche during horizontal transmission. In addition, a high abundance of bacteria in this Niche suggests that this location may also contribute to efficient vertical transmission. Wolbachia are intraCellular bacteria found in the reproductive tissue of all major groups of arthropods1,2. They are transmitted vertically from the female hosts to their offspring, in a pattern analogous to mitochondria inheritance. But Wolbachia phylogeny does not parallel that of the host, indicating that horizontal infectious transmission must also occur3,4,5. Insect parasitoids are considered the most likely vectors, but the mechanism for horizontal transfer is largely unknown4,6,7. Here we show that newly introduced Wolbachia cross several tissues and infect the germline of the adult Drosophila melanogaster female. Through investigation of bacterial migration patterns during the course of infection, we found that Wolbachia reach the germline through the somatic Stem Cell Niche in the D. melanogaster germarium. In addition, our data suggest that Wolbachia are highly abundant in the somatic Stem Cell Niche of long-term infected hosts, implying that this location may also contribute to efficient vertical transmission. This is, to our knowledge, the first report of an intraCellular parasite displaying tropism for a Stem Cell Niche.

  • Somatic Stem Cell Niche tropism in Wolbachia
    Nature, 2006
    Co-Authors: Horacio M. Frydman, Drew N. Robson, Eric Francis Wieschaus
    Abstract:

    Wolbachia are intraCellular bacteria found in the reproductive tissue of all major groups of arthropods. They are transmitted vertically from the female hosts to their offspring, in a pattern analogous to mitochondria inheritance. But Wolbachia phylogeny does not parallel that of the host, indicating that horizontal infectious transmission must also occur. Insect parasitoids are considered the most likely vectors, but the mechanism for horizontal transfer is largely unknown. Here we show that newly introduced Wolbachia cross several tissues and infect the germline of the adult Drosophila melanogaster female. Through investigation of bacterial migration patterns during the course of infection, we found that Wolbachia reach the germline through the somatic Stem Cell Niche in the D. melanogaster germarium. In addition, our data suggest that Wolbachia are highly abundant in the somatic Stem Cell Niche of long-term infected hosts, implying that this location may also contribute to efficient vertical transmission. This is, to our knowledge, the first report of an intraCellular parasite displaying tropism for a Stem Cell Niche.

Kenneth D. Birnbaum - One of the best experts on this subject based on the ideXlab platform.

  • Organ regeneration does not require a functional Stem Cell Niche in plants.
    Nature, 2009
    Co-Authors: Giovanni Sena, Hugo Hofhuis, Xiaoning Wang, Kenneth D. Birnbaum
    Abstract:

    Stem Cells are widely seen as the mechanism that permits organ regeneration in both plants and animals. In the plant root syStem, the Stem Cell Niche has been assumed to be a local pattern organizer, required for both continuous post-embryonic growth and regeneration. New work in a root-tip regeneration syStem now shows that the root Stem Cell Niche is in fact not necessary for pattern formation and re-establishment of Cell identity, thus separating the functions of growth and repatterning. When the Arabidopsis root tip is cut off, taking with it the Stem Cell Niche, the plant's remaining Cells are able to regenerate all the major tissues that make up the root tip. This finding suggests that there are as yet unknown mechanisms that coordinate organogenesis independently of a central organizer. In the plant root syStem it is thought that the Stem Cell Niche is a local pattern 'organizer' required for both continuous post-embryonic growth and regeneration. Here, the root Stem Cell Niche is shown to be not necessary for pattern formation and re-establishment of Cell identity, separating growth from re-patterning. Plants rely on the maintenance of Stem Cell Niches at their apices for the continuous growth of roots and shoots. However, although the developmental plasticity of plant Cells has been demonstrated1, it is not known whether the Stem Cell Niche is required for organogenesis. Here we explore the capacity of a broad range of differentiating Cells to regenerate an organ without the activity of a Stem Cell Niche. Using a root-tip regeneration syStem in Arabidopsis thaliana to track the molecular and functional recovery of Cell fates, we show that re-specification of lost Cell identities begins within hours of excision and that the function of specialized Cells is restored within one day. Critically, regeneration proceeds in plants with mutations that fail to maintain the Stem Cell Niche. These results show that Stem-Cell-like properties that mediate complete organ regeneration are dispersed in plant meriStems and are not restricted to Niches, which nonetheless seem to be necessary for indeterminate growth. This regenerative reprogramming of an entire organ without transition to a stereotypical Stem Cell environment has intriguing parallels to recent reports of induced transdifferentiation of specific Cell types in the adult organs of animals2,3.

  • Organ regeneration does not require a functional Stem Cell Niche in plants
    Nature, 2009
    Co-Authors: Giovanni Sena, Hugo Hofhuis, Xiaoning Wang, Hsiao Yun Liu, Kenneth D. Birnbaum
    Abstract:

    Plants rely on the maintenance of Stem Cell Niches at their apices for the continuous growth of roots and shoots. However, although the developmental plasticity of plant Cells has been demonstrated, it is not known whether the Stem Cell Niche is required for organogenesis. Here we explore the capacity of a broad range of differentiating Cells to regenerate an organ without the activity of a Stem Cell Niche. Using a root-tip regeneration syStem in Arabidopsis thaliana to track the molecular and functional recovery of Cell fates, we show that re-specification of lost Cell identities begins within hours of excision and that the function of specialized Cells is restored within one day. Critically, regeneration proceeds in plants with mutations that fail to maintain the Stem Cell Niche. These results show that Stem-Cell-like properties that mediate complete organ regeneration are dispersed in plant meriStems and are not restricted to Niches, which nonetheless seem to be necessary for indeterminate growth. This regenerative reprogramming of an entire organ without transition to a stereotypical Stem Cell environment has intriguing parallels to recent reports of induced transdifferentiation of specific Cell types in the adult organs of animals.

Linheng Li - One of the best experts on this subject based on the ideXlab platform.

  • Stem Cell Niche: microenvironment and beyond.
    Journal of Biological Chemistry, 2008
    Co-Authors: Jiwang Zhang, Linheng Li
    Abstract:

    The multipotentiality and self-renewal ability of Stem Cells are controlled by intrinsic genetic pathways that are subject to regulation by extrinsic signals emanating from the Stem Cell Niche. The Stem Cell Niche provides a microenvironment composed of Cellular structures or extraCellular matrix in which Stem Cells are maintained as undifferentiated (1-6). The concept of “the Stem Cell Niche” was first proposed in the studies of hematopoietic Stem Cell (HSC) (7), however in vivo evidence of its existence was first shown in the Drosophila germline Stem Cell (GSC) (8-10). Over the past several years there has been much progress made in identifing Stem Cell Niches in different mammal tissues, including nerve, hair follicle, intestine, teeth and bone marrow (11-16). In this review our focus is on comparing Drosophila GSC-Niches and mouse HSC-Niches (two of the best characterized Niches). By such comparison, we hope to provide some common principles of Stem Cell Niches that will be useful in other tissue Stem Cell Niche studies. In recent years remarkable progress has been made in identification and charaterization of the Stem Cell Niches in invertebrate syStems (10,17-22). In studies of GSCs in Drosophila, the ovary and testis provide relatively simple but elegant anatomic structures with few Cell types and unique Stem Cell markers. These advantages facilitated identification of the Cellular components of the Stem Cell Niche and definition of the molecular basis of physical interaction between Stem Cells and their Niches (23,24), and revealed key Niche signals involved in Stem Cell regulation (18,25-31). In the murine hematopoietic syStem, HSCs have been well defined (32,33) but identification of the HSC Niches is just beginning. This search has been hampered by the complexity of the bone marrow (BM) structure and Cellular components, and by the lack of unique HSC markers or distinctive characteristics of BM stromal Cells. Two HSC-Niches have been proposed in murine BM, an osteoblastic Niche and a vascular Niche, in which osteoblasts and vascular endothelial Cells have been respectively demonstrated as major components (34-41). A recent study suggested a population of reticular Cells, named CXCL12-abundant-reticular (CAR) Cells, expressing a high level of CXCL12 (also known as stromal Cell-derived factor [SDF]-1 or pre-B-Cell-growth-stimulating factor [PBSF]), are in contact with HSCs in both osteoblastic and vascular Niches (42). Intriguingly, megakaryocytic progenitors attach to vascular endothelial Cells for proliferation and maturation, suggesting they are different from HSCs that directly contact CAR Cells instead of endothelial Cells in the vascular Niche (43). Early B Cell progenitors also attach to CAR Cells for their growth and maintenance (44). Shared use of the vascular Niche by other hematopoietic progenitors, including myeloid progenitors, suggests it may play additional roles in regulation of lineage commitment and differentiation (43,45). Thus the Niche model established in studies of Drosophila GSCs may provide insight for further investigate of the different BM Niches and their roles in regulation HSCs.

  • Stem Cell Niche: Structure and Function
    Annual Review of Cell and Developmental Biology, 2005
    Co-Authors: Linheng Li
    Abstract:

    Adult tissue-specific Stem Cells have the capacity to self-renew and generate functional differentiated Cells that replenish lost Cells throughout an organism’s lifetime. Studies on Stem Cells from diverse syStems have shown that Stem Cell function is controlled by extraCellular cues from the Niche and by intrinsic genetic programs within the Stem Cell. Here, we review the remarkable progress recently made in research regarding the Stem Cell Niche. We compare the differences and commonalities of different Stem Cell Niches in Drosophila ovary/testis and Caenorhabditis elegans distal tip, as well as in mammalian bone marrow, skin/hair follicle, intestine, brain, and testis. On the basis of this comparison, we summarize the common features, structure, and functions of the Stem Cell Niche and highlight important Niche signals that are conserved from Drosophila to mammals. We hope this comparative summary defines the basic elements of the Stem Cell Niche, providing guiding principles for identification of the Niche in other syStems and pointing to areas for future studies.