-
[show abstract]
[hide abstract]
ABSTRACT: Understanding how cells move, change shape, and alter cellular behaviors to form organs, a process termed morphogenesis, is one of the great challenges of developmental biology. Formation of the C. elegans vulva is a powerful, simple, and experimentally accessible model for elucidating how morphogenetic processes produce an organ. In the first step of vulval development, three epithelial precursor cells divide and differentiate to generate 22 cells of seven different vulval subtypes. The 22 vulval cells then rearrange from a linear array into a tube, with each of the seven cell types undergoing characteristic morphogenetic behaviours that construct the vulva. Vulval morphogenesis entails many of the same cellular activities that underlie organogenesis and tissue formation across species, including invagination, lumen formation, oriented cell divisions, cell-cell adhesion, cell migration, cell fusion, extracellular matrix remodelling and cell invasion. Studies of vulval development have led to pioneering discoveries in a number of these processes and are beginning to bridge the gap between the pathways that specify cells and their connections to morphogenetic behaviors. The simplicity of the vulva and the experimental tools available in C. elegans will continue to make vulval morphogenesis a powerful paradigm to further our understanding of the largely mysterious mechanisms that build tissues and organs.
Wiley interdisciplinary reviews. Developmental biology. 01/2013; 2(1):75-95.
-
[show abstract]
[hide abstract]
ABSTRACT: Cell invasion through basement membrane is a specialized cellular behavior critical for many developmental processes and leukocyte trafficking. Invasive cellular behavior is also inappropriately co-opted during cancer progression. Acquisition of an invasive phenotype is accompanied by changes in gene expression that are thought to coordinate the steps of invasion. The transcription factors responsible for these changes in gene expression, however, are largely unknown. C. elegans anchor cell (AC) invasion is a genetically tractable in vivo model of invasion through basement membrane. AC invasion requires the conserved transcription factor FOS-1A, but other transcription factors are thought to act in parallel to FOS-1A to control invasion. Here we identify the transcription factor HLH-2, the C. elegans ortholog of Drosophila Daughterless and vertebrate E proteins, as a regulator of AC invasion. Reduction of HLH-2 function by RNAi or with a hypomorphic allele causes defects in AC invasion. Genetic analysis indicates that HLH-2 has functions outside of the FOS-1A pathway. Using expression analysis, we identify three genes that are transcriptionally regulated by HLH-2: the protocadherin cdh-3, and two genes encoding secreted extracellular matrix proteins, mig-6/papilin and him-4/hemicentin. Further, we show that reduction of HLH-2 function causes defects in polarization of F-actin to the invasive cell membrane, a process required for the AC to generate protrusions that breach the basement membrane. This work identifies HLH-2 as a regulator of the invasive phenotype in the AC, adding to our understanding of the transcriptional networks that control cell invasion.
Developmental Biology 07/2011; 357(2):380-91. · 4.07 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Large gaps in basement membrane occur at sites of cell invasion and tissue remodelling in development and cancer. Though never followed directly in vivo, basement membrane dissolution or reduced synthesis have been postulated to create these gaps. Using landmark photobleaching and optical highlighting of laminin and type IV collagen, we find that a new mechanism, basement membrane sliding, underlies basement membrane gap enlargement during uterine-vulval attachment in Caenorhabditis elegans. Laser ablation and mutant analysis reveal that the invaginating vulval cells promote basement membrane movement. Further, an RNA interference and expression screen identifies the integrin INA-1/PAT-3 and VAB-19, homologue of the tumour suppressor Kank, as regulators of basement membrane opening. Both concentrate within vulval cells at the basement membrane gap boundary and halt expansion of the shifting basement membrane. Basement membrane sliding followed by targeted adhesion represents a new mechanism for creating precise basement membrane breaches that can be used by cells to break down compartment boundaries.
Nature Cell Biology 06/2011; 13(6):641-51. · 19.49 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Cell invasion through basement membrane (BM) is a specialized cellular behavior critical to many normal developmental events, immune surveillance, and cancer metastasis. A highly dynamic process, cell invasion involves a complex interplay between cell-intrinsic elements that promote the invasive phenotype, and cell-cell and cell-BM interactions that regulate the timing and targeting of BM transmigration. The intricate nature of these interactions has made it challenging to study cell invasion in vivo and model in vitro. Anchor cell invasion in Caenorhabditis elegans is emerging as an important experimental paradigm for comprehensive analysis of BM invasion, revealing the gene networks that specify invasive behavior and the interactions that occur at the cell-BM interface.
Current opinion in cell biology 05/2011; 23(5):589-96. · 14.15 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: With unique genetic and cell biological strengths, C. elegans has emerged as a powerful model system for studying many biological processes. These processes are typically regulated by complex genetic networks consisting of genes. Identifying those genes and organizing them into genetic pathways are two major steps toward understanding the mechanisms that regulate biological events. Forward genetic screens with various designs are a traditional approach for identifying candidate genes. The completion of the genome sequencing in C. elegans and the advent of high-throughput experimental techniques have led to the development of two additional powerful approaches: functional genomics and systems biology. Genes that are discovered by these approaches can be ordered into interacting pathways through a variety of strategies, involving genetics, cell biology, biochemistry, and functional genomics, to gain a more complete understanding of how gene regulatory networks control a particular biological process. The aim of this review is to provide an overview of the approaches available to identify and construct the genetic pathways using C. elegans.
Methods in cell biology 01/2011; 106:113-57. · 2.05 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The Netrin family of extracellular ligands and their receptors were the first identified signaling pathway regulating axon guidance. Subsequent work across model systems has begun to reveal the interactions that take place downstream of Netrin reception to facilitate growth cone migration. Though intensely studied, many aspects of this signaling system remain unclear. Even less understood are the growing number of contexts in which Netrin signaling influences cells beyond axon guidance and even outside the nervous system. Genetic and cell-biological studies in C. elegans have played an instrumental role in identifying critical functions for Netrin ligands in setting up specialized and potentially adhesive membrane-associated domains within a broad range of cell types. Here we review recent literature implicating Netrin or its receptors in morphogenetic processes outside of growth cone regulation with a special focus on studies in C. elegans that suggest cell biological mechanisms for Netrin signaling.
Developmental Dynamics 05/2010; 239(5):1296-305. · 2.54 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Cell invasion through basement membranes during development, immune surveillance, and metastasis remains poorly understood. To gain further insight into this key cellular behavior, we performed an in vivo screen for regulators of cell invasion through basement membranes, using the simple model of Caenorhabditis elegans anchor cell invasion, and identified 99 genes that promote invasion, including the genes encoding the chaperonin complex cct. Notably, most of these genes have not been previously implicated in invasive cell behavior. We characterized members of the cct complex and 11 other gene products, determining the distinct aspects of the invasive cascade that they regulate, including formation of a specialized invasive cell membrane and its ability to breach the basement membrane. RNA interference-mediated knockdown of the human orthologs of cct-5 and lit-1, which had not previously been implicated in cell invasion, reduced the invasiveness of metastatic carcinoma cells, suggesting that a conserved genetic program underlies cell invasion. These results increase our understanding of the genetic underpinnings of cell invasion and also provide new potential therapeutic targets to limit this behavior.
Science Signaling 01/2010; 3(120):ra35. · 7.50 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Integrin expression and activity have been strongly correlated with developmental and pathological processes involving cell invasion through basement membranes. The role of integrins in mediating these invasions, however, remains unclear. Utilizing the genetically and visually accessible model of anchor cell (AC) invasion in C. elegans, we have recently shown that netrin signaling orients a specialized invasive cell membrane domain toward the basement membrane. Here, we demonstrate that the integrin heterodimer INA-1/PAT-3 plays a crucial role in AC invasion, in part by targeting the netrin receptor UNC-40 (DCC) to the AC's plasma membrane. Analyses of the invasive membrane components phosphatidylinositol 4,5-bisphosphate, the Rac GTPase MIG-2, and F-actin further indicate that INA-1/PAT-3 plays a broad role in promoting the plasma membrane association of these molecules. Taken together, these studies reveal a role for integrin in regulating the plasma membrane targeting and netrin-dependent orientation of a specialized invasive membrane domain.
Developmental cell 09/2009; 17(2):187-98. · 13.36 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Despite their profound importance in the development of cancer, the extracellular cues that target cell invasion through basement membrane barriers remain poorly understood. A central obstacle has been the difficulty of studying the interactions between invading cells and basement membranes in vivo. Using the genetically and visually tractable model of Caenorhabditis elegans anchor cell (AC) invasion, we show that UNC-6 (netrin) signalling, a pathway not previously implicated in controlling cell invasion in vivo, is a key regulator of this process. Site of action studies reveal that before invasion, localized UNC-6 secretion directs its receptor, UNC-40, to the plasma membrane of the AC, in contact with the basement membrane. There, UNC-40 polarizes a specialized invasive membrane domain through the enrichment of actin regulators, F-actin and phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P(2)). Cell ablation experiments indicate that UNC-6 promotes the formation of invasive protrusions from the AC that break down the basement membrane in response to a subsequent vulval cue. Together, these results characterize an invasive membrane domain in vivo, and reveal a role for UNC-6 (netrin) in polarizing this domain towards its basement membrane target.
Nature Cell Biology 01/2009; 11(2):183-9. · 19.49 Impact Factor
-
David R Sherwood
[show abstract]
[hide abstract]
ABSTRACT: To metastasize, cancer cells must acquire the ability to breach several basement membrane barriers. Cell invasions through basement membranes also occur during normal development and immune system function, enabling organ formation and cell dispersal. The mechanisms that cells use to cross basement membranes in vivo remain elusive. In cancer and development, these invasions occur in complex and inaccessible environments, which are difficult to study in vivo. Anchor-cell invasion in Caenorhabditis elegans is a simple, visually and experimentally accessible model of basement membrane invasion that is beginning to reveal a network of cellular and molecular control mechanisms that regulate the fundamental cellular process of invasion through basement membranes.
Trends in Cell Biology 06/2006; 16(5):250-6. · 12.35 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Cell invasion through basement membranes is crucial during morphogenesis and cancer metastasis. Here, we genetically dissect this process during anchor-cell invasion into the vulval epithelium in C. elegans. We have identified the fos transcription factor ortholog fos-1 as a critical regulator of basement-membrane removal. In fos-1 mutants, the gonadal anchor cell extends cellular processes normally toward vulval cells, but these processes fail to remove the basement membranes separating the gonad from the vulval epithelium. fos-1 is expressed in the anchor cell and controls invasion cell autonomously. We have identified ZMP-1, a membrane-type matrix metalloproteinase, CDH-3, a Fat-like protocadherin, and hemicentin, a fibulin family extracellular matrix protein, as transcriptional targets of FOS-1 that promote invasion. These results reveal a key genetic network that controls basement-membrane removal during cell invasion.
Cell 07/2005; 121(6):951-62. · 32.40 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: An understanding of cell-invasive behavior has been limited by the lack of in vivo models where this activity can be clearly visualized and manipulated. We show that a single cell in the Caenorhabditis elegans gonad, the anchor cell (AC), initiates uterine-vulval contact through a cell invasion event. Using genetic analysis, laser ablations, and cell-specific markers, we demonstrate that AC invasion is predominantly stimulated by the 1 degrees vulval lineage cells, which generate a diffusible signal that promotes AC invasive behavior toward these cells and further targets invasive processes between the two central 1 degrees vulval lineage cells. We also show that AC invasion is regulated by the AC response to this cue, as well as a vulval-independent mechanism that weakly drives invasion. These studies dissect the regulatory mechanisms that underlie a simple cell-invasive behavior in vivo, and introduce AC invasion as a model for understanding key checkpoints controlling cell invasion.
Developmental Cell 08/2003; 5(1):21-31. · 14.03 Impact Factor
-
Takao Inoue, David R Sherwood,
Gudrun Aspöck,
James A Butler,
Bhagwati P Gupta,
Martha Kirouac,
Minqin Wang,
Pei-Yun Lee,
James M Kramer,
Ian Hope,
Thomas R Bürglin,
Paul W Sternberg
[show abstract]
[hide abstract]
ABSTRACT: The analysis of cell fate patterning during the vulval development of Caenorhabditis elegans has relied mostly on the direct observation of cell divisions and cell movements (cell lineage analysis). However, reconstruction of the developing vulva from EM serial sections has suggested seven different cell types (vulA, vulB1, vulB2, vulC, vulD, vulE, and vulF), many of which cannot be distinguished based on such observations. Here we report the vulval expression of seven genes, egl-17, cdh-3, ceh-2, zmp-1, B0034.1, T04B2.6 and F47B8.6 based on gfp, cfp and yfp (green fluorescent protein and color variants) reporter fusions. Each gene expresses in a specific subset of vulval cells, and is therefore useful as a marker for vulval cell fates. Together, expressions of markers distinguish six cell types, and reveal a strict temporal control of gene expression in the developing vulva.
Mechanisms of Development 01/2003; 119 Suppl 1:S203-9. · 2.83 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The development of the reproductive system in Caenorhabditis elegans is a well-established model system for patterning and organogenesis. We report the characterization of the cog-1 gene, mutations in which cause novel phenotypes in late patterning in vulval lineages, establishment of the vulva-uterine connection, development and function of the spermathecal-uterine junction, and the development of vas deferens-proctodeal connection in the male. We positionally cloned cog-1 and found that it encodes a homeobox protein most similar to the mammalian GTX and Nkx6.1 proteins. Analysis of cog-1 transcripts revealed that cog-1 is likely a complex locus with two promoters. Two mutant alleles of cog-1 differentially affect alternative transcripts and cause different phenotypes, suggesting that the two forms of cog-1 have distinct functions in C. elegans.
Developmental Biology 01/2003; 252(2):202-13. · 4.07 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The gonad in Caenorhabditis elegans is an important model system for understanding complex morphogenetic processes including cellular movement, cell fusion, cell invasion and cell polarity during development. One class of signaling proteins known to be critical for the cellular events underlying morphogenesis is the Rho family GTPases, particularly RhoA, Rac and Cdc42. In C. elegans orthologues of these genes have been shown to be important for gonad development. In our current study we have extended those findings by examining the patterns of 5′ cis-regulatory element (5′CRE) activity associated with nineteen putative guanine nucleotide exchange factors (GEFs) encoded by the C. elegans genome predicted to activate Rho family GTPases. Here we identify 13 RhoGEF genes that are expressed during gonadogenesis and characterize the cells in which their 5′CREs are active. These data provide the basis for designing experiments to examine Rho GTPase activation during morphogenetic processes central to normal gonad development.
Gene Expression Patterns.
-
Takao Inoue, David R Sherwood,
Gudrun Aspöck,
James A Butler,
Bhagwati P Gupta,
Martha Kirouac,
Minqin Wang,
Pei-Yun Lee,
James M Kramer,
Ian Hope,
Thomas R Bürglin,
Paul W Sternberg
[show abstract]
[hide abstract]
ABSTRACT: The analysis of cell fate patterning during the vulval development of Caenorhabditiselegans has relied mostly on the direct observation of cell divisions and cell movements (cell lineage analysis). However, reconstruction of the developing vulva from EM serial sections has suggested seven different cell types (vulA, vulB1, vulB2, vulC, vulD, vulE, and vulF), many of which cannot be distinguished based on such observations. Here we report the vulval expression of seven genes, egl-17, cdh-3, ceh-2, zmp-1, B0034.1, T04B2.6 and F47B8.6 based on gfp, cfp and yfp (green fluorescent protein and color variants) reporter fusions. Each gene expresses in a specific subset of vulval cells, and is therefore useful as a marker for vulval cell fates. Together, expressions of markers distinguish six cell types, and reveal a strict temporal control of gene expression in the developing vulva.
Mechanisms of Development.
