Lunatic Fringe Research Articles

Overexpression of lunatic fringe does not affect epithelial cell differentiation in the developing mouse lung

The Notch/Notch-ligand pathway regulates cell fate decisions and patterning in various tissues. Several of its components are expressed in the developing lung, suggesting that this pathway is important for airway cellular patterning. Fringe proteins, which modulate Notch signaling, are crucial for defining morphogenic borders in several organs. Their role in controlling cellular differentiation along anterior-posterior axis of the airways is unknown. Herein, we report the temporal-spatial expression patterns of Lunatic fringe (Lfng) and Notch-regulated basic helix-loop-helix factors, Hes1 and Mash-1, during murine lung development. Lfng was only expressed during early development in epithelial cells lining the larger airways. Those epithelial cells also expressed Hes1, but at later gestation Hes1 expression was confined to epithelium lining the terminal bronchioles. Mash-1 displayed a very characteristic expression pattern. It followed neural crest migration in the early lung, whereas at later stages Mash-1 was expressed in lung neuroendocrine cells. To clarify whether Lfng influences airway cell differentiation, Lfng was overexpressed in distal epithelial cells of the developing mouse lung. Overexpression of Lfng did not affect spatial or temporal expression of Hes1 and Mash-1. Neuroendocrine CGRP and protein gene product 9.5 expression was not altered by Lfng overexpression. Expression of proximal ciliated (beta-tubulin IV), nonciliated (CCSP), and distal epithelial cell (SP-C, T1alpha) markers also was not influenced by Lfng excess. Overexpression of Lfng had no effect on mesenchymal cell marker (alpha-sma, vWF, PECAM-1) expression. Collectively, the data suggest that Lunatic fringe does not play a significant role in determining cell fate in fetal airway epithelium.

Mouse Nkd1, a Wnt antagonist, exhibits oscillatory gene expression in the PSM under the control of Notch signaling

During vertebrate embryogenesis, the formation of reiterated structures along the body axis is dependent upon the generation of the somite by segmentation of the presomitic mesoderm (PSM). Notch signaling plays a crucial role in both the generation and regulation of the molecular clock that provides the spatial information for PSM cells to form somites. In a screen for novel genes involved in somitogenesis, we identified a gene encoding a Wnt antagonist, Nkd1, which is transcribed in an oscillatory manner, and may represent a new member of the molecular clock constituents. The transcription of nkd1 is extremely downregulated in the PSM of vestigial tail ( vt/vt), a hypomorphic mutant of Wnt3a, whereas nkd1 oscillations have a similar phase to lunatic fringe ( L-fng) transcription and they are arrested in Hes7 (a negative regulator of Notch signaling) deficient embryos. These results suggest that the transcription of nkd1 requires Wnt3a, and that its oscillation patterns depend upon the function of Hes7. Wnt signaling has been postulated to be upstream of Notch signaling but we demonstrate in this study that a Wnt-signal-related gene may also be regulated by Notch signaling. Collectively, our data suggest that the reciprocal interaction of Notch and Wnt signals, and of their respective negative feedback loops, function to organize the segmentation clock required for somitogenesis.

Her7 and hey1, but not lunatic fringe show dynamic expression during somitogenesis in medaka ( Oryzias latipes)

Epithelialized somites form repeatedly from the unsegmented presomitic mesoderm (PSM) in the tailbud of vertebrate embryos. Mutant analysis has shown that the Delta-Notch pathway is essential for the temporal and spatial control of somite formation. Several components of this pathway show cyclic transcription, which is driven by a molecular oscillator. This oscillator is thought to act similarly in different vertebrates. In this study, we used the Japanese Medaka ( Oryzias latipes) to examine the expression of three factors of the Delta-Notch cascade that are known to show cyclic expression in the PSM of higher vertebrates. We report that in contrast to the situation in mice, lunatic fringe ( lfng) in medaka is expressed in a non-dynamic fashion in the rostral halves of the formed somites and the anteriormost PSM. On the other hand, her7, a member of the hairy/Enhancer-of-split related ( Her) gene family, shows cyclic expression in the medaka PSM. Although this is similar in zebrafish, there are important differences in the distribution of transcripts in the PSM indicating different modes of regulation in both fish species. Finally, we show that hey1, another Delta-Notch regulated bHLH gene, is dynamically expressed in the PSM of medaka, similar to hey1 in zebrafish and the hey2 orthologs in mice and chicken. Interestingly, medaka hey1 is also expressed in the dorsal aorta and the heart, two tissues where hey2, but not hey1, is expressed in zebrafish. This shows that several components of the Delta-Notch pathway are differently regulated during somitogenesis in different species.

New perspectives on tooth development and the dental stem cell niche.

Adult stem cells have the capacity to self-renew and differentiate along multiple lineages in addition to contributing to ongoing tissue maintenance and regeneration after injury. They reside in specific locations called stem cell niches. In biology of the tooth, the discovery of dental epithelial stem cells in continuously growing teeth has been a recent breakthrough. The niche for the adult stem cells of these teeth is formed at the region of the apical end in tooth development. The region possesses a commonly specialized histological structure for the maintenance of adult stem cells and the production of various progenitor cells producing dental tissues. The molecular signals regulating the maintenance and cell fate decision of adult stem cells, such as Notch1, Lunatic fringe, fibroblast growth factor (FGF)-10, are expressed in the epithelial structure and the surrounding mesenchyme. Based on histological and molecular biological studies, we propose a new concept that the eternal tooth buds producing various dental progeny are formed at the apical end in the development of continuously growing teeth, and coin a new term of "apical bud" for indicating this specialized epithelial structure. Furthermore, the relationship between signaling centers and the expression of FGF-10 mRNA as the determinant of morphogenesis is discussed with an emphasis on tooth and limb development, taking note that the expression pattern of FGF-10 is an important key for understanding the mechanisms for the diversity of cusp patterns and between continuous and limited growth.

Lunatic fringe regulates Delta-Notch induction of hypochord in zebrafish.

Cells that occupy the midline of vertebrate embryos arise from a common population of precursors. Several lines of evidence indicate that Delta-Notch signaling regulates specification of midline precursors for different fates. We show that zebrafish midline precursors transiently express lunatic fringe, which encodes a glycosyltransferase that modifies Notch activity in response to its ligands, and that lunatic fringe function is required for Delta-Notch-mediated induction of hypochord cells at the lateral borders of the midline precursor domain.

Periodic repression by the bHLH factor Hes7 is an essential mechanism for the somite segmentation clock.

Hes7, a bHLH gene essential for somitogenesis, displays cyclic expression of mRNA in the presomitic mesoderm (PSM). Here, we show that Hes7 protein is also expressed in a dynamic manner, which depends on proteasome-mediated degradation. Spatial comparison revealed that Hes7 and Lunatic fringe (Lfng) transcription occurs in the Hes7 protein-negative domains. Furthermore, Hes7 and Lfng transcription is constitutively up-regulated in the absence of Hes7 protein and down-regulated by stabilization of Hes7 protein. Thus, periodic repression by Hes7 protein is critical for the cyclic transcription of Hes7 and Lfng, and this negative feedback represents a molecular basis for the segmentation clock.

Transcriptional oscillation of lunatic fringe is essential for somitogenesis.

A molecular oscillator that controls the expression of cyclic genes such as lunatic fringe (Lfng) in the presomitic mesoderm has been shown to be coupled with somite formation in vertebrate embryos. To address the functional significance of oscillating Lfng expression, we have generated transgenic mice expressing Lfng constitutively in the presomitic mesoderm in addition to the intrinsic cyclic Lfng activity. These transgenic lines displayed defects of somite patterning and vertebral organization that were very similar to those of Lfng null mutants. Furthermore, constitutive expression of exogenous Lfng did not compensate for the complete loss of cyclic endogenous Lfng activity. Noncyclic exogenous Lfng expression did not abolish cyclic expression of endogenous Lfng in the posterior presomitic mesoderm (psm) but affected its expression pattern in the anterior psm. Similarly, dynamic expression of Hes7 was not abolished but abnormal expression patterns were obtained. Our data are consistent with a model in which alternations of Lfng activity between ON and OFF states in the presomitic mesoderm prior to somite segmentation are critical for proper somite patterning, and suggest that Notch signaling might not be the only determinant of cyclic gene expression in the presomitic mesoderm of mouse embryos.

Fringe Modifies O-Fucose on Mouse Notch1 at Epidermal Growth Factor-like Repeats within the Ligand-binding Site and the Abruptex Region

Fringe plays a key role in the specification of boundaries during development by modulating the ability of Notch ligands to activate Notch receptors. Fringe is a fucose-specific beta1,3-N-acetylglucosaminyltransferase that modifies O-fucose moieties on the epidermal growth factor-like (EGF) repeats of Notch. To investigate how the change in sugar structure caused by Fringe modulates Notch activity, we have analyzed the sites of O-fucose and Fringe modification on mouse Notch1. The extracellular domain of Notch1 has 36 tandem EGF repeats, many of which are predicted to be modified with O-fucose. We recently proposed a broadened consensus sequence for O-fucose, C(2)X(3-5)(S/T)C(3) (where C(2) and C(3) represent the second and third conserved cysteines), significantly expanding the potential number of modification sites on Notch. Here we demonstrate that sites predicted using this broader consensus sequence are modified with O-fucose on mouse Notch1, and we present evidence suggesting that the consensus can be further refined to C(2)X(4-5)(S/T)C(3). In particular, we demonstrate that EGF 12, a portion of the ligand-binding site, is modified with O-fucose and that this site is evolutionarily conserved. We also show that endogenous Fringe proteins in Chinese hamster ovary cells (Lunatic fringe and Radical fringe) as well as exogenous Manic fringe modify O-fucose on many but not all EGF repeats of mouse Notch1. These findings suggest that the Fringes show a preference for O-fucose on some EGF repeats relative to others. This specificity appears to be encoded within the amino acid sequence of the individual EGF repeats. Interestingly, our results reveal that Manic fringe modifies O-fucose both at the ligand-binding site (EGF 12) and in the Abruptex region. These findings provide insight into potential mechanisms by which Fringe action on Notch receptors may influence both the affinity of Notch-ligand binding and cell-autonomous inhibition of Notch signaling by ligand.

The protocadherin papc is involved in the organization of the epithelium along the segmental border during mouse somitogenesis

The anterior and posterior halves of individual somites adopt distinct fates during somitogenesis, which is crucial for establishing the metameric pattern of axial tissues such as the vertebral column and peripheral nerves. Genetic analyses have demonstrated that the specification of cells to an anterior or posterior fate is intimately related to the process of segmentation. Inactivation of the transcription factor Mesp2, or components of the Notch signaling pathway, led to defects in segmentation and a loss of anterior/posterior polarity. Target genes in mice that could mediate the morphological events associated with segmentation or polarity have not been identified. Studies in Xenopus and zebrafish have demonstrated that the protocadherin, papc, is expressed in an anterior-specific manner in the presumptive somites of the presomitic mesoderm and is required for normal somitogenesis. Here, we examine the role of papc in directing segmentation in the mouse. We demonstrate that papc is expressed in a dynamic pattern within the first two presumptive somites (0 and −1) at the anterior end of the presomitic mesoderm. The domain of papc transcription in somite 0 starts broad and becomes progressively restricted to the anterior edge. Transcription in somite −1 over the same time remains broad. Analysis of targeted null mutations revealed that transcription of papc is dependent on Mesp2. The dynamic nature of papc transcription in somite 0 requires the expression of lunatic fringe, which modifies the activation of the Notch signaling pathway and is required for proper segmentation of somites. Treatment of embryonic mouse tails in a hanging drop culture with a putative dominant-negative mutation of papc disrupted the epithelial organization of cells at the segmental borders between somites. Together, these data indicate that papc is an important regulator of somite epithelialization associated with segmentation.

Формирование Фашистского “Неоевразийского” Интеллектуального Движения в России. Путь Александра Дугина от маргинального экстремиста до вдохновителя постсоветской академической и политической элиты (1989–2001 гг.)

SUMMARY: Since the early 1990’s, the mystic Alexander G. Dugin (b. 1962) has been a prominent figure in Russia’s neo-fascist scene and the chief propagator of an extremely anti-Western ideology labeled “Neo-Eurasianism” - a Russian adaptation of the ideas of the German inter-war “Conservative Revolution” and West Europe’s post-war “New Right” to post-Soviet realities. During the 1990s, Western observers largely ignored Dugin – one of the most productive and original publicists of the extreme right who enjoys an increasing influence on the political mainstream, and his think-tank “Arctogaia” (Northern Land) even though their continuous rise was an important expression of Russia’s growing post-Soviet “uncivil society” and was marked intensive contacts to leading West European proto-fascist intellectuals. Having, been the lead ideologist for Eduard Limonov’s National-Bolshevik Party between 1994 and 1998, Dugin became an advisor to State Duma Speaker Gennadii Seleznev in 1998. Dugin’s major work Foundations of Geopolitics was first published in 1997 and has since become an influential manifesto of radical anti-Americanism. The book is already in its fourth edition, is used in university courses on geopolitics, and has found a wide readership beyond the lunatic fringe, and even outside Russia. With the foundation of the “Eurasia” movement in spring 2001, Dugin and his followers completed their qualitative leap from the margins to the mainstream of Russian politics. They follow a Gramscian strategy, seeking to attain cultural hegemony in Russian society through an impregnation of Russia’s political and academic elite with “neo-Eurasian” ideas. The deep interest and undisguised support for the “Eurasia” movement shown by parts of the the presidential administration as well as such figures as eminent political philosopher Aleksandr Panarin (b. 1940) and well-known TV-journalist Mikhail Leont’ev (b. 1958) indicate that Dugin has become a major actor on Russia’s current ideas marketplace.

Periodic notch inhibition by lunatic fringe underlies the chick segmentation clock.

The segmented aspect of the vertebrate body plan first arises through the sequential formation of somites. The periodicity of somitogenesis is thought to be regulated by a molecular oscillator, the segmentation clock, which functions in presomitic mesoderm cells. This oscillator controls the periodic expression of 'cyclic genes', which are all related to the Notch pathway. The mechanism underlying this oscillator is not understood. Here we show that the protein product of the cyclic gene lunatic fringe (Lfng), which encodes a glycosyltransferase that can modify Notch activity, oscillates in the chick presomitic mesoderm. Overexpressing Lfng in the paraxial mesoderm abolishes the expression of cyclic genes including endogenous Lfng and leads to defects in segmentation. This effect on cyclic genes phenocopies inhibition of Notch signalling in the presomitic mesoderm. We therefore propose that Lfng establishes a negative feedback loop that implements periodic inhibition of Notch, which in turn controls the rhythmic expression of cyclic genes in the chick presomitic mesoderm. This feedback loop provides a molecular basis for the oscillator underlying the avian segmentation clock.

Defending the Color Line

Drawing on structured action theory, the author examines the ways in which racially and ethnically motivated hate crime emerges as a forceful means of constructing identity and difference within the institutional settings of culture, labor, sexuality, and power. The author summarizes the trends in racially and ethnically motivated violence nationwide and then explores hate crimes as a readily available means of doing difference. The author argues that racially motivated violence is not an aberration associated with a lunatic or extremist fringe. Instead, it is a normative means of asserting racial identity relative to the victimized other ; it is an enactment—of the racism that allocates privilege along racial lines.

Lunatic Fringe, FGF, and BMP Regulate the Notch Pathway during Epithelial Morphogenesis of Teeth

Teeth develop as epithelial appendages, and their morphogenesis is regulated by epithelial–mesenchymal interactions and conserved signaling pathways common to many developmental processes. A key event during tooth morphogenesis is the transition from bud to cap stage when the epithelial bud is divided into specific compartments distinguished by morphology as well as gene expression patterns. The enamel knot, a signaling center, forms and regulates the shape and size of the tooth. Mesenchymal signals are necessary for epithelial patterning and for the formation and maintenance of the epithelial compartments. We studied the expression of Notch pathway molecules during the bud-to-cap stage transition of the developing mouse tooth. Lunatic fringe expression was restricted to the epithelium, where it formed a boundary flanking the enamel knot. The Lunatic fringe expression domains overlapped only partly with the expression of Notch1 and Notch2, which were coexpressed with Hes1. We examined the regulation of Lunatic fringe and Hes1 in cultured explants of dental epithelium. The expression of Lunatic fringe and Hes1 depended on mesenchymal signals and both were positively regulated by FGF-10. BMP-4 antagonized the stimulatory effect of FGF-10 on Lunatic fringe expression but had a synergistic effect with FGF-10 on Hes1 expression. Recombinant Lunatic fringe protein induced Hes1 expression in the dental epithelium, suggesting that Lunatic fringe can act also extracellularly. Lunatic fringe mutant mice did not reveal tooth abnormalities, and no changes were observed in the expression patterns of other Fringe genes. We conclude that Lunatic fringe may play a role in boundary formation of the enamel knot and that Notch-signaling in the dental epithelium is regulated by mesenchymal FGFs and BMP.

Morphological boundary forms by a novel inductive event mediated by Lunatic fringe and Notch during somitic segmentation.

Boundary formation plays a central role in differentiating the flanking regions that give rise to discrete tissues and organs during early development. We have studied mechanisms by which a morphological boundary and tissue separation are regulated by examining chicken somite segmentation as a model system. By transplanting a small group of cells taken from a presumptive border into a non-segmentation site, we have found a novel inductive event where posteriorly juxtaposed cells to the next-forming border instruct the anterior cells to become separated and epithelialized. We have further studied the molecular mechanisms underlying these interactions by focusing on Lunatic fringe, a modulator of Notch signaling, which is expressed in the region of the presumptive boundary. By combining DNA in ovo electroporation and embryonic transplantation techniques we have ectopically made a sharp boundary of Lunatic fringe activity in the unsegmented paraxial mesoderm and observed a fissure formed at the interface. In addition, a constitutive active form of Notch mimics this instructive phenomenon. These suggest that the boundary-forming signals emanating from the posterior border cells are mediated by Notch, the action of which is confined to the border region by Lunatic fringe within the area where mRNAs of Notch and its ligand are broadly expressed in the presomitic mesoderm.

Periodic Lunatic fringe Expression Is Controlled during Segmentation by a Cyclic Transcriptional Enhancer Responsive to Notch Signaling

A molecular oscillator regulates the pace of vertebrate segmentation. Here, we show that the oscillator (clock) controls cyclic initiation of transcription in the unsegmented presomitic mesoderm (PSM). We identify an evolutionarily conserved 2.3 kb region in the murine Lunatic fringe (Lfng) promoter that drives periodic expression in the PSM. This region includes conserved blocks required for enhancing and repressing cyclic Lfng transcription, and to prevent continued expression in formed somites. We also show that dynamic expression in the cycling PSM is lost in the total absence of Notch signaling, and that Notch signaling acts directly via CBF1/RBP-Jκ binding sites to regulate Lfng. These results are consistent with a model in which oscillatory Notch signaling underlies the segmentation clock and directly activates and indirectly represses Lfng expression.

Clock Regulatory Elements Control Cyclic Expression of Lunatic fringe during Somitogenesis

Somitogenesis requires a segmentation clock and Notch signaling. Lunatic fringe (Lfng) expression in the presomitic mesoderm (PSM) cycles in the posterior PSM, is refined in the segmenting somite to the rostral compartment, and is required for segmentation. We identify distinct cis-acting regulatory elements for each aspect of Lfng expression. Fringe clock element 1 (FCE1) represents a conserved 110 bp region that is necessary to direct cyclic Lfng RNA expression in the posterior PSM. Mutational analysis of E boxes within FCE1 indicates a potential interplay of positive and negative transcriptional regulation by cyclically expressed bHLH proteins. A separable Lfng regulatory region directs expression to the prospective rostral aspect of the condensing somite. These independent Lfng regulatory cassettes advance a molecular framework for deciphering somite segmentation.

Enemies within: the culture of conspiracy in modern America

There is a hunger for conspiracy news in America. Hundreds of Internet websites, magazines, newsletters, even entire publishing houses, disseminate information on invisible enemies and their secret activities, subversions, and coverups. Those who suspect conspiracies behind events in the news, such as the crash of TWA Flight 800 or the death of Marilyn Monroe, join generations of Americans, from the colonial period to the present day, who have entertained visions of vast plots. In this enthralling book Robert Goldberg focuses on five major conspiracy theories of the past half-century, examining how they became widely popular in the United States and why they have remained so. In the post-World War II decades conspiracy theories have become more numerous, more commonly believed, and more deeply embedded in our culture, Goldberg contends. He investigates conspiracy theories regarding the Roswell UFO incident, the Communist threat, the rise of the Antichrist, the assassination of President John Kennedy, and the Jewish plot against black America, in each case taking historical, social, and political environments into account. Conspiracy theories are not merely the products of a lunatic fringe, the author shows. Rather, paranoid rhetoric and thinking are disturbingly central in America today. With media validation and dissemination of conspiracy ideas, and federal government behaviour that damages public confidence and faith, the ground is fertile for conspiracy thinking.

Hypomorphic Mesp allele distinguishes establishment of rostrocaudal polarity and segment border formation in somitogenesis.

A bHLH-type transcription factor, Mesp2, plays an essential role in somite segmentation in mice. Zebrafish mespb (mesp-b), a putative homologue of mouse Mesp2, is transiently expressed in the rostral presomitic mesoderm similarly to Mesp2. To determine whether zebrafish mespb is a functional homologue of mouse Mesp2, zebrafish mespb was introduced into the mouse Mesp2 locus by homologous recombination. Introduced mespb almost rescued the Mesp2 deficiency in the homozygous mespb knockin mouse, indicating that mespb is a functional homologue of mouse Mesp2. Segmented somites were clearly observed although the partial fusion of the vertebral columns still occurred. Interestingly, however, the nature and dosage of the mespb gene affected the rescue event. A mouse line, which has a hypomorphic Mesp2 allele generated by the introduction of neo-mespb, gave rise to an epithelial somite without normal rostrocaudal (RC) polarity. RC polarity was also lacking in the presomitic mesoderm. The defects in RC polarity were determined by the altered expressions of Uncx4.1 and Dll1 in the segmented somites and presomitic mesoderm, respectively. In contrast, the expression of EphA4 (Epha4), lunatic fringe or protocadherin, thought to be involved in segment border formation, was fairly normal in hypomorphic mutant embryos. These results suggest that the Mesp family of transcription factors is involved in both segment border formation and establishment of RC polarity through different genetic cascades.

Notch signalling is linked to epidermal cell differentiation level in basal cell carcinoma, psoriasis and wound healing.

Epidermal homeostasis involves the monitoring of continuous proliferative and differentiative processes as keratinocytes migrate from the basal layer to the skin surface. Recently, differentiation of epidermal stem cells was shown to be promoted by the Notch pathway. This pathway is characterised by cell-cell interactions between transmembrane proteins and was first implicated in lateral inhibition, patterning and cell binary choices during embryogenesis. By in situ hybridisation, we investigated the in vivo expression of related genes, namely; Notch 1-3, Delta 1, Jagged 1, Lunatic Fringe, Radical Fringe and Manic Fringe during keratinocyte proliferation and differentiation in humans in basal cell carcinoma, psoriasis and in wound healing experiments, compared with normal adult skin. We show that the highest level of transcription of these genes is in the basal cell layer of non-lesional skin. Conversely, when keratinocytes were hyperproliferating, as in basal cell carcinoma, psoriasis, and during the first step of re-epithelialisation, expression was weak or non-existent. Furthermore, normal levels of transcripts were rescued in psoriatic plaques when treated by phototherapy, as well as in newly regenerated stratified epidermis following wound healing. The Notch signalling involved in the differentiation programme of normal adult human epidermis is altered under experimental conditions and pathologies which modify this programme.

Segmentation defects of Notch pathway mutants and absence of a synergistic phenotype in lunatic fringe/radical fringe double mutant mice.

The Notch signaling pathway is important in regulating formation and anterior-posterior patterning of somites in vertebrate embryos. Here we show that distinct segmentation defects are displayed in embryos mutant for the Notch pathway genes Notch1, Lunatic fringe (Lfng), Delta-like 1 (Dll1), and Delta-like 3 (Dll3). Lfng-deficient mice and Dll3-deficient mice exhibit very similar defects, and marker analysis suggests that progression of the segmentation clock is disrupted in Dll3 mutants. We also show that Radical fringe (Rfng)-deficient mice exhibit no obvious phenotypic defects. To assess whether the absence of a phenotype in Rfng-deficient mice was the result of functional redundancy with the Lfng gene, we generated Lfng/Rfng double homozygous mutant mice. These mice exhibit the skeletal defects normally observed in Lfng-deficient mice, but we detected no obvious synergistic or additive effects in the double mutant animals.