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At least 19 recordsLinked to original sources
PubMed2000

Comparative study of Mitsuda reaction to nude mouse and armadillo lepromin preparations using nine-banded armadillos.

In 14 nine-banded armadillos the Mitsuda response to nude mouse-derived lepromin (lepromin-nu/nu) was compared to that of armadillo-derived lepromin (lepromin-A) by injecting the reagents intradermally into either side of the abdomen of the animal and examining the biopsies from the sites after 12 days. The histopathologic responses to both antigens were found to be similar, whether the animal was Mitsuda-negative (lepromatous) or Mitsuda-positive (tuberculoid). It is pointed out that armadillos are good experimental models for leprosy, and their use can replace humans in experimental studies.

Animals↗
PubMed2004

A complex of Armadillo, Legless, and Pygopus coactivates dTCF to activate wingless target genes.

BACKGROUND: Upon receiving a Wnt signal, cells accumulate beta-catenin (Armadillo in Drosophila), which binds directly to TCF transcription factors, leading to the transcription of Wnt target genes. It is generally thought that beta-catenin/Armadillo is a transcriptional coactivator when bound to TCF in the nucleus and that this function is mediated by its C terminus. However, recent findings in Drosophila indicated that Armadillo may activate dTCF in the cytoplasm. RESULTS: Here, I reexamine the mechanism of Armadillo's signaling function in light of Legless and Pygopus, two nuclear factors recently discovered to be essential for this function. I show that Armadillo, in order to activate dTCF, must enter the nucleus and form a complex with Legless and Pygopus. The ability of this complex to stimulate TCF-mediated transcription can be altered by linkage of a strong transcriptional activator or repressor to Armadillo. Furthermore, Armadillo is a strong transcriptional activator when fused to the yeast GAL4 DNA binding domain-an activity that depends on regions of the Armadillo repeat domain that mediate binding to Legless and to chromatin modifying and remodeling factors. Finally, linkage of the N-terminal region of Pygopus, but not the C terminus of Armadillo, to dominant-negative dTCF can restore its signaling activity in transgenic flies. CONCLUSIONS: My evidence argues in favor of a revised coactivator factor model in which Armadillo's coactivator function depends on regions within its Armadillo repeat domain to which Legless/Pygopus and other transcriptional coactivators can bind. In contrast, the C terminus of Armadillo plays a less direct role in this function.

Animals↗
PubMed1997

Negative regulation of Armadillo, a Wingless effector in Drosophila.

Drosophila Armadillo and its vertebrate homolog beta-catenin play essential roles both in the transduction of Wingless/Wnt cell-cell signals and in the function of cell-cell adherens junctions. Wingless and Wnts direct numerous cell fate choices during development. We generated a mutant protein, Armadillo(S10), with a 54 amino acid deletion in its N-terminal domain. This mutant is constitutively active in Wingless signaling; its activity is independent of both Wingless signal and endogenous wild-type Armadillo. Armadillo's role in signal transduction is normally negatively regulated by Zeste-white 3 kinase, which modulates Armadillo protein stability. Armadillo(S10) is more stable than wild-type Armadillo, suggesting that it is less rapidly targeted for degradation. We show that Armadillo(S10) has escaped from negative regulation by Zeste white-3 kinase, and thus accumulates outside junctions even in the absence of Wingless signal. Finally, we present data implicating kinases in addition to Zeste white-3 in Armadillo phosphorylation. We discuss two models for the negative regulation of Armadillo in normal development and discuss how escape from this regulation contributes to tumorigenesis.

Amino Acid Sequence↗
PubMed1998

Roles of Armadillo, a Drosophila catenin, during central nervous system development.

BACKGROUND: Neural development requires that neurons communicate and co-operate with one another and with other cell types in their environment. Drosophila Armadillo and its vertebrate homolog beta-catenin have dual roles in epithelial cells: transducing signals from the Wingless/Wnt family of proteins and working with cadherins to mediate cell adhesion. Wingless/Wnt signaling also directs certain cell fates in the central nervous system (CNS), and cadherins and catenins are thought to function together during neural development. RESULTS: We identified and analyzed the biochemical properties of a second armadillo isoform, with a truncated carboxyl terminus generated by alternative splicing. This isoform was found to accumulate in differentiating neurons. Using armadillo alleles that selectively inactivate the cell adhesion or the Wingless signaling functions of Armadillo, we found that Armadillo had two sequential roles in neural development. Armadillo function in Wingless signal transduction was required early in development for determination of neuroblast fate. Later in development, disruption of the cell-cell adhesion function of Armadillo resulted in subtle defects in the construction of the axonal scaffold. Mutations in the gene encoding the Drosophila tyrosine kinase Abelson substantially enhanced the severity of the CNS phenotype of armadillo mutations, consistent with these proteins functioning co-operatively at adherens junctions in both the CNS and the epidermis. CONCLUSIONS: This is one of the first demonstrations of a role for the cadherin-catenin system in the normal development of the CNS. The genetic interactions between armadillo and abelson point to a possible role for the tyrosine kinase Abelson in cell-cell adhesive junctions in both the CNS and the epidermis.

Alternative Splicing↗
PubMed2000

Armadillo exposure and Hansen's disease: an epidemiologic survey in southern Texas.

BACKGROUND: Naturally occurring leprosy has been demonstrated in wild nine-banded armadillos (Dasypus novemcinctus ). This suggests a possible mode of transmission of human leprosy in regions where armadillo contact is prevalent. OBJECTIVE: Our purpose was to study the possible relationship between armadillo exposure and Hansen's disease. METHOD: One hundred one patients (67 men, 34 women) with established Hansen's disease seen in the Hansen's Disease Clinic in Houston, Texas, were questioned about their exposure to armadillos. These patients were divided into two groups: Asian (n = 32) and non-Asian (n = 69). RESULTS: Seventy-one percent of the non-Asian patients surveyed reported either direct or indirect armadillo exposure. None of the Asian patients reported armadillo exposure (P <.001). Of the non-Asian patients, 75.4% had lepromatous disease versus 50.0% of the Asian patients (P <.001). The average age at diagnosis for the non-Asian group with Hansen's disease in this study was 51 versus 38 years for the Asian group (P <.001). CONCLUSION: Although it is yet to be determined whether direct transmission from the armadillo to human occurs, it is likely based on the high incidence of armadillo exposure in non-Asian patients with Hansen's disease in our study population that this animal acts as a reservoir for human disease. However, the Asian patients reporting no known armadillo exposure likely obtained the disease from person-to-person contact in their respective countries of origin where Hansen's disease has a much higher prevalence.

Adolescent↗
PubMed1996

An in vivo structure-function study of armadillo, the beta-catenin homologue, reveals both separate and overlapping regions of the protein required for cell adhesion and for wingless signaling.

Armadillo, the Drosophila homologue of vertebrate beta-catenin, plays a pivotal role both in Wingless signaling and in assembly of adherens junctions. We performed the first in vivo structure-function study of an adherens junction protein, by generating and examining a series of Armadillo mutants in the context of the entire animal. We tested each mutant by assaying its biological function, its ability to bind proteins that normally associate with Armadillo in adherens junctions, its cellular localization, and its pattern of phosphorylation. We mapped the binding sites for DE-cadherin and alpha-catenin. Although these bind to Armadillo independently of each other, binding of each is required for the function of adherens junctions. We identified two separate regions of Armadillo critical for Wingless signaling. We demonstrated that endogenous Armadillo accumulates in the nucleus and provide evidence that it may act there in transducing Wingless signal. We found that the Arm repeats, which make up the central two-thirds of Armadillo, differ among themselves in their functional importance in different processes. Finally, we demonstrated that Armadillo's roles in adherens junctions and Wingless signaling are independent. We discuss the potential biochemical role of Armadillo in each process.

Alleles↗
PubMed1994

wingless signal and Zeste-white 3 kinase trigger opposing changes in the intracellular distribution of Armadillo.

wingless/wnt-1 signaling directs cell fate during development. Genetic analysis in Drosophila identified genes that may encode components of the wingless signal transduction system. Drosophila Armadillo, homolog of vertebrate beta-catenin, is required for wingless signaling. Unlike armadillo RNA, Armadillo protein accumulates non-uniformly in different cells of each embryonic segment. We found that cells alter their intracellular distribution of Armadillo in response to Wingless signal, accumulating increased levels of cytoplasmic Armadillo relative to those of membrane-associated protein. Levels of cytoplasmic Armadillo are also regulated by Zeste-White 3 kinase. Analysis of double mutants demonstrates that Armadillo's role in wingless signaling is direct, and that Armadillo functions downstream of both wingless and zeste-white 3. We present a model for the role of Armadillo stripes in transduction of wingless signal.

Animals↗
PubMed1993

The product of the Drosophila melanogaster segment polarity gene armadillo is highly conserved in sequence and expression in the housefly Musca domestica.

Segmental pattern in Drosophila melanogaster is set up via a set of cell-cell interactions mediated by the products of the segment polarity genes. Among these is the armadillo gene, whose product seems to be required for the reception of an intercellular signal encoded by the wingless gene. As part of our effort to relate the structure of the armadillo protein to its function within the cell, we have examined the evolutionary conservation of the armadillo gene during insect evolution. We have cloned the armadillo gene from the housefly, Musca domestica, which diverged from Drosophila 100 million years ago. The Musca protein is 97.5% identical to that in Drosophila, while the noncoding sequences have diverged extensively. This remarkable degree of conservation at the protein level is mirrored in the expression pattern of the armadillo protein. Antibodies against the Drosophila protein cross-react with a Musca protein of the appropriate size. We have also used these antibodies to show that the Musca armadillo protein has a pattern of expression in larval and adult tissues similar to that of Drosophila armadillo. We discuss the implications of conservation of structure and expression for the cellular role of the armadillo protein and its mammalian homologs.

Amino Acid Sequence↗
PubMed1999

Roles of the C terminus of Armadillo in Wingless signaling in Drosophila.

Drosophila melanogaster Armadillo and its vertebrate homolog beta-catenin play multiple roles during development. Both are components of cell-cell adherens junctions and both transduce Wingless (Wg)/Wnt intercellular signals. The current model for Wingless signaling proposes that Armadillo binds the DNA-binding protein dTCF, forming a bipartite transcription factor that activates Wingless-responsive genes. In this model, Armadillo's C-terminal domain is proposed to serve an essential role as a transcriptional activation domain. In Xenopus, however, overexpression of C-terminally truncated beta-catenin activates Wnt signaling, suggesting that the C-terminal domain might not be essential. We reexamined the function of Armadillo's C terminus in Wingless signaling. We found that C-terminally truncated mutant Armadillo has a deficit in Wg-signaling activity, even when corrected for reduced protein levels. However, we also found that Armadillo proteins lacking all or part of the C terminus retain some signaling ability if overexpressed, and that mutants lacking different portions of the C-terminal domain differ in their level of signaling ability. Finally, we found that the C terminus plays a role in Armadillo protein stability in response to Wingless signal and that the C-terminal domain can physically interact with the Arm repeat region. These data suggest that the C-terminal domain plays a complex role in Wingless signaling and that Armadillo recruits the transcriptional machinery via multiple contact sites, which act in an additive fashion.

Amino Acid Sequence↗
PubMed1993

A role for the Drosophila segment polarity gene armadillo in cell adhesion and cytoskeletal integrity during oogenesis.

The epithelial sheet is a structural unit common to many tissues. Its organization appears to depend on the function of the multi-protein complexes that form adherens junctions. Elegant cell biological experiments have provided support for hypotheses explaining the function of adherens junctions and of their components. These systems, however, lack the ability to test function within an entire organism during development. The realization that the product of the Drosophila segment polarity gene armadillo is related to the vertebrate adhesive junction components plakoglobin and beta-catenin led to the suggestion that armadillo might provide a genetic handle to study adhesive junction structure and function. An examination of the potential function of Armadillo in cell-cell adhesive junctions was initiated using the Drosophila ovary as the model system. We examined the distribution of Armadillo in the Drosophila ovary and demonstrated that this localization often parallels the location of cell-cell adhesive junctions. The consequences of removing armadillo function from the germ-line cells of the ovary were also examined. Germ-line armadillo mutations appear to disrupt processes requiring cell adhesion and integrity of the actin cytoskeleton, consistent with a role for Armadillo in cell-cell adhesive junctions. We have also used armadillo mutations to examine the effects on ovarian development of altering the stereotyped cell arrangements of the ovary. The implications of these results for the role of adhesive junctions during development are discussed.

Animals↗
PubMed1999

Membrane-tethered Drosophila Armadillo cannot transduce Wingless signal on its own.

Drosophila Armadillo and its vertebrate homolog beta-catenin are key effectors of Wingless/Wnt signaling. In the current model, Wingless/Wnt signal stabilizes Armadillo/beta-catenin, which then accumulates in nuclei and binds TCF/LEF family proteins, forming bipartite transcription factors which activate transcription of Wingless/Wnt responsive genes. This model was recently challenged. Overexpression in Xenopus of membrane-tethered beta-catenin or its paralog plakoglobin activates Wnt signaling, suggesting that nuclear localization of Armadillo/beta-catenin is not essential for signaling. Tethered plakoglobin or beta-catenin might signal on their own or might act indirectly by elevating levels of endogenous beta-catenin. We tested these hypotheses in Drosophila by removing endogenous Armadillo. We generated a series of mutant Armadillo proteins with altered intracellular localizations, and expressed these in wild-type and armadillo mutant backgrounds. We found that membrane-tethered Armadillo cannot signal on its own; however it can function in adherens junctions. We also created mutant forms of Armadillo carrying heterologous nuclear localization or nuclear export signals. Although these signals alter the subcellular localization of Arm when overexpressed in Xenopus, in Drosophila they have little effect on localization and only subtle effects on signaling. This supports a model in which Armadillo's nuclear localization is key for signaling, but in which Armadillo intracellular localization is controlled by the availability and affinity of its binding partners.

Animals↗
PubMed2005

Leprosy in wild armadillos.

Wild nine-banded armadillos (Dasypus novemcinctus) in the south central United States are highly endemic natural hosts of Mycobacterium leprae. Surveys conducted over the last 30 years on more than 5000 animals confirm that the infection is present among armadillos in Arkansas, Louisiana, Mississippi and Texas. Highest prevalence rates are found among the animals in low-lying alluvial and coastal areas, primarily in Louisiana and Texas. Both animal density and local factors may contribute to the detectability of armadillo leprosy in those regions. Little evidence for M. leprae infection is found among armadillos elsewhere in the US range, and only a few reports relate finding the infection among animals in Central or South America. However, the issue has received only scant attention in other countries. Armadillos only recently expanded their range into the US, and leprosy was present in Texas and Louisiana prior to the arrival of armadillos. The ecological relationship between humans and armadillos with M. leprae in this region remains unclear. However, infected armadillos constitute a large reservoir of M. leprae and they may be a source of infection for some humans in this country, and perhaps in other locations across the animal's range.

Animals↗
PubMed1994

Phosphorylation of the Drosophila adherens junction protein Armadillo: roles for wingless signal and zeste-white 3 kinase.

The Drosophila segment polarity gene product Armadillo provides a link between two seemingly separate processes, regulation of segmental pattern by the Wingless intercellular signal and the function of cell-cell adherens junctions. armadillo was originally identified because of its segment polarity phenotype but subsequently was found to be the homolog of the vertebrate adherens junction protein beta-catenin. We examined the nature of the post-translational modification of Armadillo and its possible role in regulating Armadillo function. Armadillo is a phosphoprotein. Its level of phosphorylation varies both during embryonic development and from tissue to tissue. Phosphorylation occurs on both serine or threonine and tyrosine residues. Finally, Wingless signal negatively regulates Armadillo phosphorylation, while the segment polarity gene product Zeste-white 3, a serine/threonine protein kinase, promotes Armadillo phosphorylation. We discuss the implications of these results for regulation of Wingless/Wnt-1 signaling and adherens junction function.

Amino Acid Sequence↗