Distribution by Scientific Domains
Distribution within Life Sciences

Kinds of Lineages

  • adipogenic lineage
  • african lineage
  • american lineage
  • ancestral lineage
  • ancient lineage
  • asexual lineage
  • b lineage
  • bacterial lineage
  • basal lineage
  • blood lineage
  • branching lineage
  • cell lineage
  • cellular lineage
  • clonal lineage
  • different cell lineage
  • different genetic lineage
  • different lineage
  • differentiated lineage
  • distinct evolutionary lineage
  • distinct lineage
  • divergent lineage
  • diverging lineage
  • dna lineage
  • early diverging lineage
  • eastern lineage
  • endemic lineage
  • epithelial lineage
  • erythroid lineage
  • eukaryotic lineage
  • european lineage
  • evolutionary lineage
  • genetic lineage
  • glial lineage
  • granulocytic lineage
  • hematopoietic lineage
  • hybrid lineage
  • independent lineage
  • insect lineage
  • lymphocyte lineage
  • macrophage lineage
  • main lineage
  • major lineage
  • maternal lineage
  • mesenchymal lineage
  • mitochondrial dna lineage
  • mitochondrial lineage
  • monocytic lineage
  • monophyletic lineage
  • mtdna lineage
  • multiple lineage
  • myeloid lineage
  • neuronal lineage
  • new lineage
  • northern lineage
  • novel lineage
  • oligodendrocyte lineage
  • one lineage
  • osteoblastic lineage
  • osteogenic lineage
  • other lineage
  • parental lineage
  • parthenogenetic lineage
  • paternal lineage
  • phylogenetic lineage
  • phylogeographic lineage
  • protist lineage
  • relate lineage
  • separate lineage
  • several lineage
  • single lineage
  • sister lineage
  • southern lineage
  • specific lineage
  • stem lineage
  • various lineage
  • vertebrate lineage
  • well-supported lineage

  • Terms modified by Lineages

  • lineage analysis
  • lineage b
  • lineage cell
  • lineage commitment
  • lineage decision
  • lineage differentiation
  • lineage divergence
  • lineage diversification
  • lineage marker
  • lineage relationships
  • lineage sorting
  • lineage specificity
  • lineage tracing

  • Selected Abstracts


    PALAEONTOLOGY, Issue 4 2008
    Abstract:, We report on a new Early Cretaceous bird from China that sheds significant light on the evolutionary transition between primitive birds with a long bony tail and those with a short tail ending in a pygostyle. A cladistic analysis of basal birds supports the placement of the new fossil as the sister-taxon of all pygostylians. Possessing a unique hand morphology with a phalangeal formula of 2-3-3-x-x and a reduced number of caudal vertebrae lacking a pygostyle, the new specimen reveals anatomical information previously unknown and increases the taxonomic diversity of primitive, non-pygostylian birds. We infer from the specimen that during the evolution of the avian tail, a decrease in relative caudal length and number of vertebrae preceded the distal fusion of caudals into a pygostyle. [source]


    EVOLUTION, Issue 4 2007
    Lee Hsiang Liow
    Lineage persistence is as central to biology as evolutionary change. Important questions regarding persistence include: why do some lineages outlive their relatives, neither becoming extinct nor evolving into separate lineages? Do these long-duration lineages have distinctive ecological or morphological traits that correlate with their geologic durations and potentially aid their survival? In this paper, I test the hypothesis that lineages (species and higher taxa) with longer geologic durations have morphologies that are more average than expected by chance alone. I evaluate this hypothesis for both individual lineages with longer durations and groups of lineages with longer durations, using more than 60 published datasets of animals with adequate fossil records. Analyses presented here show that groups of lineages with longer durations fall empirically into one of three theoretically possible scenarios, namely: (1) the morphology of groups of longer duration lineages is closer to the grand average of their inclusive group, that is, their relative morphological distance is smaller than expected by chance alone, when compared with rarified samples of their shorter duration relatives (a negative group morpho-duration distribution); (2) the relative morphological distance of groups of longer duration lineages is no different from rarified samples of their shorter duration relatives (a null group morpho-duration distribution); and (3) the relative morphological distance of groups of longer duration lineages is greater than expected when compared with rarified samples of their shorter duration relatives (a positive group morpho-duration distribution). Datasets exhibiting negative group morpho-duration distributions predominate. However, lineages with higher ranks in the Linnean hierarchy demonstrate positive morpho-duration distributions more frequently. The relative morphological distance of individual longer duration lineages is no different from that of rarified samples of their shorter duration relatives (a null individual morpho-duration distribution) for the majority of datasets studied. Contrary to the common idea that very persistent lineages are special or unique in some significant way, both the results from analyses of long-duration lineages as groups and individuals show that they are morphologically average. Persistent lineages often arise early in a group's history, even though there is no prior expectation for this tendency in datasets of extinct groups. The implications of these results for diversification histories and niche preemption are discussed. [source]


    EVOLUTION, Issue 7 2004
    Ben L. Phillips
    Abstract Phylogeographic analyses of the fauna of the Australian wet tropics rainforest have provided strong evidence for long-term isolation of populations among allopatric refugia, yet typically there is no corresponding divergence in morphology. This system provides an opportunity to examine the consequences of geographic isolation, independent of morphological divergence, and thus to assess the broader significance of historical subdivisions revealed through mitochondrial DNA phylogeography. We have located and characterized a zone of secondary contact between two long isolated (mtDNA divergence > 15%) lineages of the skink Carlia rubrigularis using one mitochondrial and eight nuclear (two intron, six microsatellite) markers. This revealed a remarkably narrow (width<3 km) hybrid zone with substantial linkage disequilibrium and strong deficits of heterozygotes at two of three nuclear loci with diagnostic alleles. Cline centers were coincident across loci. Using a novel form of likelihood analysis, we were unable to distinguish between sigmoidal and stepped cline shapes except at one nuclear locus for which the latter was inferred. Given estimated dispersal rates of 90,133 m X gen,1/2 and assuming equilibrium, the observed cline widths suggest effective selection against heterozygotes of at least 22,49% and possibly as high as 70%. These observations reveal substantial postmating isolation, although the absence of consistent deviations from Hardy-Weinberg equilibrium at diagnostic loci suggests that there is little accompanying premating isolation. The tight geographic correspondence between transitions in mtDNA and those for nuclear genes and corresponding evidence for selection against hybrids indicates that these morphologically cryptic phylogroups could be considered as incipient species. Nonetheless, we caution against the use of mtDNA phylogeography as a sole criterion for defining species boundaries. [source]


    EVOLUTION, Issue 3 2000
    Loren H. Rieseberg
    Abstract., Reproductive barrier formation between newly derived hybrid taxa and their parental species represents a major evolutionary hurdle. Here, I examine the development of a sterility barrier during hybrid speciation by examining the fertility of progeny from all combinations of crosses involving three experimentally synthesized sunflower hybrid lineages, their natural hybrid counterpart, Helianthus anomalus, and their parents, H. annuus and H. petiolaris. Crosses between the parental species and H. anomalus generated almost completely sterile offspring (pollen viability < 5%; seed set < 1%). A fairly strong sterility barrier also has developed between three hybrid lineages and both parental species (pollen viability 11.1,41.6%; seed set 0.84,20.1%). In contrast, the three hybrid lineages are almost fully interfertile (pollen viabilities 83.1,88.6%; seed set 72.1,75.3%), as predicted by molecular mapping studies that indicate they have converged on a similar set of gene combinations and chromosomal rearrangements. A modest decline in compability is observed in crosses between the three hybrid lineages and H. anomalus (pollen viabilities 64.1,70.7%; seed set 37,43%), a result that agrees well with prior data demonstrating significant congruence between the genomes of the natural and experimental hybrid lineages. These observations not only indicate that reproductive isolation can arise as a by-product of fertility selection in hybrid populations, but also testify to the repeatability of this mode of speciation. [source]


    JOURNAL OF PHYCOLOGY, Issue 2 2006
    Hwan Su Yoon
    Previous phylogenetic studies of the Rhodophyta have provided a framework for understanding red algal phylogeny, but there still exists the need for a comprehensive analysis using a broad sampling of taxa and sufficient phylogenetic information to clearly define the major lineages. In this study, we determined 48 sequences of the PSI P700 chl a apoprotein A1 (psaA) and rbcL coding regions and established a robust red algal phylogeny to identify the major clades. The tree included most of the lineages of the Bangiophyceae (25 genera, 48 taxa). Seven well-supported lineages were identified with this analysis with the Cyanidiales having the earliest divergence and being distinct from the remaining taxa; i.e. the Porphyridiales 1,3, Bangiales, Florideophyceae, and Compsopogonales. We also analyzed data sets with fewer taxa but using seven proteins or the DNA sequence from nine genes to resolve inter-clade relationships. Based on all of these analyses, we propose that the Rhodophyta contains two new subphyla, the Cyanidiophytina with a single class, the Cyanidiophyceae, and the Rhodophytina with six classes, the Bangiophyceae, Compsopogonophyceae, Florideophyceae, Porphyridiophyceae classis nov. (which contains Porphyridium, Flintiella, and Erythrolobus), Rhodellophyceae, and Stylonematophyceae classis nov. (which contains Stylonema, Bangiopsis, Chroodactylon, Chroothece, Purpureofilum, Rhodosorus, Rhodospora, and Rufusia). We also describe a new order, Rhodellales, and a new family, Rhodellaceae (with Rhodella, Dixoniella, and Glaucosphaera). [source]

    Delinquent Pedigrees: Revision, Lineage, and Spatial Rhetoric in The Duchess of Malfi

    Michelle M. Dowd
    Locating John Webster's The Duchess of Malfi within a cluster of early seventeenth-century concerns about legitimacy and hereditary succession, this essay traces the ways in which Webster strategically alters his primary narrative source, William Painter's The Palace of Pleasure, so as to expose rather than to suppress the indeterminacy of patrilineality. Webster's tragedy focuses specifically on a remarrying widow and her children, a particular social problem that makes visible the contradictions inherent to the early modern system of patrilineal inheritance. The action of the play thus stages the tensions between the dominant legal form of patrilineality and the material practices shaping and changing it. Drawing in part on the theories of Michel de Certeau, this essay takes a fresh critical approach to the play by placing particular emphasis on the distinctively spatialized aspects of Webster's dramaturgical rendering of his source material and noting the ways in which he uses the ideological and physical spaces of the stage to highlight the inscrutability of the succession. In addition, in its focus on Webster's revisions of Painter, the essay considers how drama as a genre can spatially reimagine the social relationships and possibilities for agency that are produced through patterns of hereditary succession. As such, The Duchess of Malfi serves as a useful case study for theorizing the narrative and dramaturgical methods by which patriarchy is constructed, contested, and reformulated in early modern English culture (M.M.D.). [source]

    Role of the Osteoblast Lineage in the Bone Marrow Hematopoietic Niches,

    Joy Y Wu
    First page of article [source]

    Mechanically Strained Cells of the Osteoblast Lineage Organize Their Extracellular Matrix Through Unique Sites of ,V,3 -Integrin Expression

    Magdalena Wozniak
    Abstract Bone cells transduce mechanical signals into anabolic biochemical responses. However, the mechanisms of mechanotransduction are unknown. To address this issue, we performed studies in primary cells of the human osteoblast lineage grown on collagen/vitronectin-coated supports. We discovered that mechanical strain stimulated a redistribution of the ,v,3 -integrin to irregular plaque-like areas at the cell-extracellular matrix surface. Proteins involved in integrin-matrix interactions in focal adhesions, vinculin and talin, did not localize to the plaque-like areas of ,v,3 -expression, but signaling molecules such as focal adhesion kinase (FAK) did. Mechanical strain increased the number and size of the plaques defined by surface expression of ,v,3 -integrin. Osteopontin was secreted as a cross-linked macromolecular complex, likely through the action of tissue transglutaminase that also was found in the plaques of ,v,3 -integrin cell-matrix interaction. Mechanical strain increased mineralization of the extracellular matrix that developed in these plaques in ,v,3 -integrin-dependent manner. Because the plaque-like areas of cell-matrix interaction exhibit macromolecular assembly and mineralization, we conclude that they may represent subcellular domains of bone formation and that ,v,3 -integrin activation represents one mechanism by which mechanical strain stimulates bone formation. [source]

    NarE: a novel ADP-ribosyltransferase from Neisseria meningitidis

    Vega Masignani
    Summary Mono ADP-ribosyltransferases (ADPRTs) are a class of functionally conserved enzymes present in prokaryotic and eukaryotic organisms. In bacteria, these enzymes often act as potent toxins and play an important role in pathogenesis. Here we report a profile-based computational approach that, assisted by secondary structure predictions, has allowed the identification of a previously undiscovered ADP-ribosyltransferase in Neisseria meningitidis (NarE). NarE shows structural homologies with E. coli heat-labile enterotoxin (LT) and cholera toxin (CT) and possesses ADP-ribosylating and NAD-glycohydrolase activities. As in the case of LT and CT, NarE catalyses the transfer of the ADP-ribose moiety to arginine residues. Despite the absence of a signal peptide, the protein is efficiently exported into the periplasm of Neisseria. The narE gene is present in 25 out of 43 strains analysed, is always present in ET-5 and Lineage 3 but absent in ET-37 and Cluster A4 hypervirulent lineages. When present, the gene is 100% conserved in sequence and is inserted upstream of and co-transcribed with the lipoamide dehydrogenase E3 gene. Possible roles in the pathogenesis of N. meningitidis are discussed. [source]

    Rethinking Ancient Maya Social Organization: Replacing "Lineage" with "House"

    Susan D. Gillespie
    Long-standing disagreements concerning prehispanic Maya kinship and social organization have focused on the nature of their corporate groups, generally presumed to have been lineages. Specific debates center on whether the lineages were patrilineal or incorporated some kind of double-descent reckoning, how descent was combined with locality to define a group, and the status of lineage-outsiders within a group. It is argued here that Maya social organization is better approached within the contemporary critique of kinship, replacing "lineage" with Lévi-Strauss's model of the "house",a corporate group maintaining an estate perpetuated by the recruitment of members whose relationships are expressed "in the language" of kinship and affinity and affirmed by purposeful actions. In this perspective, the operation of corporate groups is the primary concern, and relationships construed in terms of consanguinity and affinity are seen as strategies pursued to enhance and perpetuate the group, [ancestor veneration, house society, kinship, Maya, social organization] [source]

    The Ordovician Trilobite Carolinites, A Test Case for Microevolution in A Macrofossil Lineage

    PALAEONTOLOGY, Issue 2 2002
    Tim McCormick
    We use geometric morphometrics to test a claim that the Ordovician trilobite Carolinites exhibits gradualistic evolution. We follow a previously proposed definition of gradualism, and define the criteria an ideal microevolutionary case study should satisfy. We consider the Lower,Middle Ordovician succession at Ibex, western Utah to meet these criteria. We discovered examples of: (1) morphometric characters which fluctuate with little or no net change; (2) characters which show abrupt ,step' change; (3) characters which show transitional change through intermediate states. Examples belonging to (2) and (3) exhibit reversals. The transitional characters were tested against a null hypothesis of symmetrical random walk. The tests indicated that they were not changing under sustained directional selection. Two alternative interpretations are possible. (1) The characters are responding to random causes (genetic drift or rapidly fluctuating selection pressures) or to causes that interact in so complex a way that they appear random. This observation may be applicable to most claimed cases of gradualistic evolution in the literature. (2) Sampling was at too poor a resolution to allow meaningful testing against the random walk. If so, then this situation is likely to apply in most evolutionary case studies involving Palaeozoic macrofossils. [source]

    Plasticity of Cadherin,Catenin Expression in the Melanocyte Lineage

    Cadherins are calcium-dependent cell adhesion receptors with strong morphoregulatory functions. To mediate functional adhesion, cadherins must interact with actin cytoskeleton. Catenins are cytoplasmic proteins that mediate the interactions between cadherins and the cytoskeleton. In addition to their role in cell,cell adhesion, catenins also participate in signaling pathways that regulate cell growth and differentiation. Cadherins and catenins appear to be involved in melanocyte development and transformation. Here, we investigated the function of cadherin,catenin complexes in the normal development and transformation of melanocytes by studying the patterns of expression of the cell,cell adhesion molecules, E-, N- and P-cadherin, and the expression of their cytoplasmic partners, ,-, ,- and ,-catenin, during murine development. Similar analyses were performed in vitro using murine melanoblast, melanocyte, and melanoma cell lines in the presence and absence of keratinocytes, the cells with which melanocytes interact in vivo. Overall, the results suggest that the expression of cadherins and catenins is very plastic and depends on their environment as well as the transformation status of the cells. This plasticity is important in fundamental cellular mechanisms associated with normal and pathological ontogenesis, as well as with tumorigenesis. [source]


    EVOLUTION, Issue 3 2003
    R. Stoks
    Abstract In a large behavioral experiment we reconstructed the evolution of behavioral responses to predators to explore how interactions with predators have shaped the evolution of their prey,behavior. All Enallagma damselfly species reduced both movement and feeding in the presence of coexisting predators. Some Enallagma species inhabit water bodies with both fish and dragonflies, and these species responded to the presence of both predators, whereas other Enallagma species inhabit water bodies that have only large dragonflies as predators, and these species only responded to the presence of dragonflies. Lineages that shifted to live with large dragonflies showed no evolution in behaviors expressed in the presence of dragonflies, but they evolved greater movement in the absence of predators and greater movement and feeding in the presence of fish. These results suggest that Enallagma species have evolutionarily lost the ability to recognize fish as a predator. Because species coexisting with only dragonfly predators have also evolved the ability to escape attacking dragonfly predators by swimming, the decreased predation risk associated with foraging appears to have shifted the balance of the foraging/predation risk trade-off to allow increased activity in the absence of mortality threats to evolve in these lineages. Our results suggest that evolution in response to changes in predation regime may have greater consequences for characters expressed in the absence of mortality threats because of how the balance between the conflicting demands of growth and predation risk are altered. [source]

    A biomechanical constraint on body mass in terrestrial mammalian predators

    LETHAIA, Issue 4 2008
    Observations on extant mammals suggest that large body mass is selectively advantageous for a terrestrial predator on large herbivores. Yet, throughout the Cenozoic, some lineages of terrestrial mammalian predators attained greater maximal body masses than others. In order to explain this evolutionary pattern, the following biomechanical constraint on body mass is hypothesized. The stress, set up in the humerus by the bending moment of the peak ground reaction force at maximal running speed, increased with increasing body mass within a given lineage of terrestrial mammalian predators, resulting in a decreasing safety factor for the bone, until a predator could no longer attain the maximal running speed of its smaller relatives. The selective disadvantage of reduced maximal running speed prevented further increase of body mass within the lineage. This hypothesis is tested by examining the scaling of humeral dimensions and estimating maximal body masses in several lineages of terrestrial mammalian predators. Among lineages with otherwise similar postcranial skeletons, those with the more robust humeri at a given body mass attained the greater maximal body masses. Lineages with the longer deltoid ridges/deltopectoral crests of the humeri and/or the more distally located deltoid scars (suggesting the more distal insertions of the humeral flexors) at a given body mass also attained the greater maximal body masses. These results support the existence of the proposed biomechanical constraint, although paleoecological data suggest that some lineages of terrestrial mammalian predators failed to reach the limits, imposed by this constraint, because of the small size of available prey. [source]

    A New Divergent Type of Eukaryotic Methionine Adenosyltransferase is Present in Multiple Distantly Related Secondary Algal Lineages

    ABSTRACT. S -adenosylmethionine is one of the most important metabolites in living cells and is synthesized in a single reaction catalyzed by methionine adenosyltransferase (MAT). At the sequence and structural level, this enzyme is one of the most conserved proteins known. Here we show that some representatives of three distantly related eukaryotic lineages,dinoflagellates, haptophytes, and euglenids,possess a highly divergent type of MAT, which we call MATX. Even though MATX contains all the sites known to be involved in catalysis and the association of monomers, it also has four insertions throughout the protein that are not observed in other MAT homologs. The phylogenetic distribution and affinities of MATX suggest that it originated in a single eukaryotic lineage and was spread via multiple events of eukaryote-to-eukaryote lateral gene transfer. We suggest a tentative model in which the origin of MATX is connected with the progression of secondary endosymbiosis. [source]

    Identification of Three Distinct Polytomella Lineages Based on Mitochondrial DNA Features

    ABSTRACT. Polytomella is composed of colorless green algae closely related to Chlamydomonas reinhardtii. Species in the genus have been used in diverse fields of biological research, most recently to study mitochondrial function and mitochondrial genome evolution in the Chlorophyceae, but the phylogenetic relationship between the various available taxa has not yet been clarified and it is not known whether they also possess fragmented mitochondrial genomes, as reported for Polytomella parva. We therefore examined cox1 sequence from seven Polytomella taxa with the goal of establishing their phylogenetic relationships and relating this information to their mitochondrial DNA (mtDNA) fragmentation pattern. We found that the Polytomella isolates examined fall into three distinct lineages, two of which possess fragmented mitochondrial genomes. The third and earliest branching lineage, represented by Polytomella capuana, appears to possess an intact mtDNA. In addition, there is evidence for variation in both size and number of mtDNA fragments between various Polytomella isolates, even within the same lineage. The considerable amount of sequence divergence between lineages seems to correlate with the geographic origin of the strains, leading us to believe that greater amounts of sequence divergence could be uncovered by a broader sampling of Polytomella. [source]

    Pyruvate Formate Lyase (PFL) and PFL Activating Enzyme in the Chytrid Fungus Neocallimastix frontalis: A Free-Radical Enzyme System Conserved Across Divergent Eukaryotic Lineages,

    ABSTRACT Fermentative formate production involves the activity of pyruvate formate lyase, an oxygen-sensitive enzyme that employs a glycyl radical in its reaction mechanism. While common among anaerobic prokaryotes, this enzyme has so far been found in only two distantly related eukaryotic lineages, anaerobic chytridiomycetes and chlorophytes. Sequence comparisons of homologues from the chytridiomycetes Piromyces and Neocallimastix, the chlorophyte Chlamydomonas, and numerous prokaryotes suggest a single, eubacterial origin of eukaryotic pyruvate formate lyases. Pyruvate formate lyase activating enzyme introduces the glycyl radical into the pyruvate formate lyase protein chain. We discovered this enzyme, which had not previously been reported from eukaryotes, in the same two eukaryotic lineages and show that it shares a similar evolutionary history to pyruvate formate lyase. Sequences with high homology to pyruvate formate lyase activating enzyme were identified in the genomes of the anaerobic protozoan parasites Trichomonas vaginalis, Entamoeba histolytica, and Giardia intestinalis. While the occurrence of pyruvate formate lyase activating enzyme together with pyruvate formate lyase in fungi and chlorophytes was to be expected, the target protein of a glycyl radical enzyme-activating enzyme in these protozoa remains to be identified. [source]

    Diversity of Mitochondrial DNA Lineages in South Siberia

    M. V. Derenko
    Summary To investigate the origin and evolution of aboriginal populations of South Siberia, a comprehensive mitochondrial DNA (mtDNA) analysis (HVR1 sequencing combined with RFLP typing) of 480 individuals, representing seven Altaic-speaking populations (Altaians, Khakassians, Buryats, Sojots, Tuvinians, Todjins and Tofalars), was performed. Additionally, HVR2 sequence information was obtained for 110 Altaians, providing, in particular, some novel details of the East Asian mtDNA phylogeny. The total sample revealed 81% East Asian (M*, M7, M8, M9, M10, C, D, G, Z, A, B, F, N9a, Y) and 17% West Eurasian (H, U, J, T, I, N1a, X) matrilineal genetic contribution, but with regional differences within South Siberia. The highest influx of West Eurasian mtDNAs was observed in populations from the East Sayan and Altai regions (from 12.5% to 34.5%), whereas in populations from the Baikal region this contribution was markedly lower (less than 10%). The considerable substructure within South Siberian haplogroups B, F, and G, together with the high degree of haplogroup C and D diversity revealed there, allows us to conclude that South Siberians carry the genetic imprint of early-colonization phase of Eurasia. Statistical analyses revealed that South Siberian populations contain high levels of mtDNA diversity and high heterogeneity of mtDNA sequences among populations (Fst = 5.05%) that might be due to geography but not due to language and anthropological features. [source]

    Transposable elements: powerful facilitators of evolution

    BIOESSAYS, Issue 7 2009
    Keith R. Oliver
    Abstract Transposable elements (TEs) are powerful facilitators of genome evolution, and hence of phenotypic diversity as they can cause genetic changes of great magnitude and variety. TEs are ubiquitous and extremely ancient, and although harmful to some individuals, they can be very beneficial to lineages. TEs can build, sculpt, and reformat genomes by both active and passive means. Lineages with active TEs or with abundant homogeneous inactive populations of TEs that can act passively by causing ectopic recombination are potentially fecund, adaptable, and taxonate readily. Conversely, taxa deficient in TEs or possessing heterogeneous populations of inactive TEs may be well adapted in their niche, but tend to prolonged stasis and may risk extinction by lacking the capacity to adapt to change, or diversify. Because of recurring intermittent waves of TE infestation, available data indicate a compatibility with punctuated equilibrium, in keeping with widely accepted interpretations of evidence from the fossil record. We propose a general and holistic synthesis on how the presence of TEs within genomes makes them flexible and dynamic, so that genomes themselves are powerful facilitators of their own evolution [source]

    Second lineage of heart forming region provides new understanding of conotruncal heart defects

    Yuji Nakajima
    ABSTRACT Abnormal heart development causes various congenital heart defects. Recent cardiovascular biology studies have elucidated the morphological mechanisms involved in normal and abnormal heart development. The primitive heart tube originates from the lateral-most part of the heart forming mesoderm and mainly gives rise to the left ventricle. Then, during the cardiac looping, the outflow tract is elongated by the addition of cardiogenic cells from the both pharyngeal and splanchnic mesoderm (corresponding to anterior and secondary heart field, respectively), which originate from the mediocaudal region of the heart forming mesoderm and are later located anteriorly (rostrally) to the dorsal region of the heart tube. Therefore, the heart progenitors that contribute to the outflow tract region are distinct from those that form the left ventricle. The knowledge that there are two different lineages of heart progenitors in the four-chambered heart provides new understanding of the morphological and molecular etiology of conotruncal heart defects. [source]

    Understanding heart development and congenital heart defects through developmental biology: A segmental approach

    Masahide Sakabe
    ABSTRACT The heart is the first organ to form and function during development. In the pregastrula chick embryo, cells contributing to the heart are found in the postero-lateral epiblast. During the pregastrula stages, interaction between the posterior epiblast and hypoblast is required for the anterior lateral plate mesoderm (ALM) to form, from which the heart will later develop. This tissue interaction is replaced by an Activin-like signal in culture. During gastrulation, the ALM is committed to the heart lineage by endoderm-secreted BMP and subsequently differentiates into cardiomyocyte. The right and left precardiac mesoderms migrate toward the ventral midline to form the beating primitive heart tube. Then, the heart tube generates a right-side bend, and the d-loop and presumptive heart segments begin to appear segmentally: outflow tract (OT), right ventricle, left ventricle, atrioventricular (AV) canal, atrium and sinus venosus. T-box transcription factors are involved in the formation of the heart segments: Tbx5 identifies the left ventricle and Tbx20 the right ventricle. After the formation of the heart segments, endothelial cells in the OT and AV regions transform into mesenchyme and generate valvuloseptal endocardial cushion tissue. This phenomenon is called endocardial EMT (epithelial-mesenchymal transformation) and is regulated mainly by BMP and TGF,. Finally, heart septa that have developed in the OT, ventricle, AV canal and atrium come into alignment and fuse, resulting in the completion of the four-chambered heart. Altered development seen in the cardiogenetic process is involved in the pathogenesis of congenital heart defects. Therefore, understanding the molecular nature regulating the ,nodal point' during heart development is important in order to understand the etiology of congenital heart defects, as well as normal heart development. [source]

    Routine immunophenotyping in acute leukemia: Role in lineage assignment and reassignment

    CYTOMETRY, Issue 5 2006
    Misbah Qadir
    Abstract Diagnostic evaluation of acute leukemia at Roswell Park Cancer Institute has routinely included immunophenotyping by multiparameter flow cytometry. In a retrospective analysis of 646 cases, morphology and cytochemistry established lineage in 612, but not in 34 (5%), of which 26, 5, and 3 were myeloid, undifferentiated, and lymphoid, respectively, based on immunophenotyping. In addition, immunophenotyping changed the lineage assigned based on morphology and cytochemistry in 11 cases (2%); 8 changed from lymphoid to myeloid, and 3 from myeloid to lymphoid. The data support routine inclusion of at least limited immunophenotyping in the diagnostic evaluation of acute leukemia. © 2006 International Society for Analytical Cytology [source]

    Flow cytometric measurement of circulating endothelial cells: The effect of age and peripheral arterial disease on baseline levels of mature and progenitor populations

    CYTOMETRY, Issue 2 2006
    Rebecca Gusic Shaffer
    Abstract Background: Age and cardiovascular disease status appear to alter numbers and function of circulating endothelial progenitor cells (EPCs). Despite no universal phenotypic definition, numerous studies have implicated progenitors with apparent endothelial potential in local responses to vascular injury and with cardiovascular disease in general. To further define the role of this lineage in peripheral artery disease (PAD), we developed a multiparameter flow cytometry assay to analyze multiple phenotypic definitions of progenitor cells (PCs), EPCs, and mature endothelial cells (ECs) and evaluate effects of age and PAD on baseline levels of each subset. Methods: Blood was collected from young healthy subjects (N = 9, mean age 33 ± 8 years), older healthy subjects (N = 13, mean age 66 ± 8 years), and older subjects with PAD (N = 15, mean age 69 ± 8 years). After ammonium chloride lysis, cells were stained and analyzed on a Becton-Dickinson LSR II with a 5-color antibody panel: FITC-anti-CD31, PE-anti-CD146, PE-anti-CD133, PerCP-Cy5.5-anti-CD3,-CD19,-CD33 (lineage panel), PE-Cy7-anti-CD34, and APC-anti-VEGF-R2. Viability was assessed by propidium iodide exclusion, and only viable, low to medium side scatter lineage-negative singlets were analyzed. In some studies, cells were sorted for morphological studies. Subsets were defined as indicated later. Results: Our results, using a comprehensive flow cytometric panel, indicate that CD133+, CD34+, and CD133+/CD34+ PCs are elevated in younger healthy individuals compared to older individuals, both healthy and with PAD. However, the number of EPCs and mature ECs did not significantly differ among the three groups. Assessment of endothelial colony forming units and dual acLDL-lectin staining supported the flow cytometric findings. Conclusions: We describe a comprehensive flow cytometric method to detect circulating mature and progenitor endothelial populations confirmed by conventional morphological and functional assays. Our findings suggest that aging may influence circulating levels of PCs, but not EPCs or ECs; PAD had no effect on baseline levels of any populations investigated. This study provides the basis for evaluating the potential effects of acute stress and therapeutic intervention on circulating progenitor and endothelial populations as a biomarker for cardiovascular status. © 2005 International Society for Analytical Cytology [source]

    Dermal fibroblasts contribute to multiple tissues in the accessory limb model

    Ayako Hirata
    The accessory limb model has become an alternative model for performing investigations of limb regeneration in an amputated limb. In the accessory limb model, a complete patterned limb can be induced as a result of an interaction between the wound epithelium, a nerve and dermal fibroblasts in the skin. Studies should therefore focus on examining these tissues. To date, however, a study of cellular contributions in the accessory limb model has not been reported. By using green fluorescent protein (GFP) transgenic axolotl tissues, we can trace cell fate at the tissue level. Therefore, in the present study, we transgrafted GFP skin onto the limb of a non-GFP host and induced an accessory limb to investigate cellular contributions. Previous studies of cell contribution to amputation-induced blastemas have demonstrated that dermal cells are the progenitors of many of the early blastema cells, and that these cells contribute to regeneration of the connective tissues, including cartilage. In the present study, we have determined that this same population of progenitor cells responds to signaling from the nerve and wound epithelium in the absence of limb amputation to form an ectopic blastema and regenerate the connective tissues of an ectopic limb. Blastema cells from dermal fibroblasts, however, did not differentiate into either muscle or neural cells, and we conclude that dermal fibroblasts are dedifferentiated along its developmental lineage. [source]

    Extrinsic factors derived from mouse embryonal carcinoma cell lines maintain pluripotency of mouse embryonic stem cells through a novel signal pathway

    Shinjirou Kawazoe
    Embryonic carcinoma (EC) cells, which are malignant stem cells of teratocarcinoma, have numerous morphological and biochemical properties in common with pluripotent stem cells such as embryonic stem (ES) cells. However, three EC cell lines (F9, P19 and PCC3) show different developmental potential and self-renewal capacity from those of ES cells. All three EC cell lines maintain self-renewal capacity in serum containing medium without Leukemia Inhibitory factor (LIF) or feeder layer, and show limited differentiation capacity into restricted lineage and cell types. To reveal the underlying mechanism of these characteristics, we took the approach of characterizing extrinsic factors derived from EC cells on the self-renewal capacity and pluripotency of mouse ES cells. Here we demonstrate that EC cell lines F9 and P19 produce factor(s) maintaining the undifferentiated state of mouse ES cells via an unidentified signal pathway, while P19 and PCC3 cells produce self-renewal factors of ES cells other than LIF that were able to activate the STAT3 signal; however, inhibition of STAT3 activation with Janus kinase inhibitor shows only partial impairment on the maintenance of the undifferentiated state of ES cells. Thus, these factors present in EC cells-derived conditioned medium may be responsible for the self-renewal capacity of EC and ES cells independently of LIF signaling. [source]

    Development of three-dimensional architecture of the neuroepithelium: Role of pseudostratification and cellular ,community'

    Takaki Miyata
    This review discusses the development of the neuroepithelium (NE) and its derivative ventricular zone (VZ), from which the central nervous system (CNS) is formed. First, the histological features of the NE and VZ are summarized, highlighting the phenomenon of pseudostratification, which is achieved by polarization and interkinetic nuclear migration (INM) of neural progenitor cells. Next, our current understanding of the cellular and molecular mechanisms and biological significance of INM and pseudostratification are outlined. The recent three-dimensional time-lapse observations revealing heterogeneity in cell lineages within the NE and VZ are also described, focusing on the neuronal lineage. Finally, the necessity of comprehensive studies on cell-cell interactions in the NE/VZ is discussed, as well as the importance of electrophysiological and biomechanical approaches. In particular, we suggest that a systems biology approach to the NE/VZ as a cellular ,community' may be fruitful. [source]

    Sequential activation of transcription factors in lens induction

    Hajime Ogino
    Since the pioneering work of the early 1900s, the lens has been used as a model system for the study of tissue development in vertebrates. A number of embryological transplantation experiments designed to elucidate the role of tissue interactions in the formation of the lens have led to the proposal of a stepwise determination model. This model has recently been refined through the identification of certain transcription factor genes, which exhibit distinct expression patterns and functional properties in the lens cell lineage. Otx2, Pax6, and Lens1 are induced by the adjacent anterior neural plate and expressed in predifferentiated lens ectoderm. Contact between the optic vesicle and lens ectoderm promotes expression of mafs, Soxs, and Prox1, which are responsible for the initiation of lens differentiation programs including crystallin expression, cell elongation, and cell cycle arrest. Further analysis of the expression and functional characteristics of these transcription factors will allow greater detail when describing the orchestration of genetic programs, which control tissue development from induction to maturation. [source]

    Lineage-independent mosaic expression and regulation of the Ciona multidom gene in the ancestral notochord

    Izumi Oda-Ishii
    Abstract The transcription factor Ciona Brachyury (Ci-Bra) plays an essential role in notochord development in the ascidian Ciona intestinalis. We characterized a putative Ci-Bra target gene, which we named Ci - multidom, and analyzed in detail its expression pattern in normal embryos and in embryos where Ci - Bra was misexpressed. Ci - multidom encodes a novel protein, which contains eight CCP domains and a partial VWFA domain. We show that an EGFP-multidom fusion protein localizes preferentially to the endoplasmic reticulum (ER), and is excluded from the nucleus. In situ hybridization experiments demonstrate that Ci - multidom is expressed in the notochord and in the anterior neural boundary (ANB). We found that the expression in the ANB is fully recapitulated by an enhancer element located upstream of Ci - multidom. By means of misexpression experiments, we provide evidence that Ci-Bra controls transcription of Ci - multidom in the notochord; however, while Ci-Bra is homogeneously expressed throughout this structure, Ci - multidom is transcribed at detectable levels only in a random subset of notochord cells. The number of notochord cells expressing Ci - multidom varies among different embryos and is independent of developmental stage, lineage, and position along the anterior,posterior axis. These results suggest that despite its morphological simplicity and invariant cell-lineage, the ancestral notochord is a mosaic of cells in which the gene cascade downstream of Brachyury is differentially modulated. Developmental Dynamics 236:1806,1819, 2007. © 2007 Wiley-Liss, Inc. [source]

    An in vivo comparison of photoactivatable fluorescent proteins in an avian embryo model

    Danny A. Stark
    Abstract Tracing the lineage or neighbor relationships of cells in a migratory population or deep within an embryo is difficult with current methods. The recent explosion of photoactivatable fluorescent proteins (PAFPs) offers a unique cell labeling tool kit, yet their in vivo performance in intact embryos and applicability have not been thoroughly explored. We report a comparison study of PAGFP, PSCFP2, KikGR, and Kaede analyzed in the avian embryo using confocal and 2-photon microscopy. PAFPs were introduced into the chick neural tube by electroporation and each photoconverted in the neural crest or cells in the neural tube with exposure to 405 nm light, but showed dramatic differences in photoefficiency and photostability when compared at the same 2% laser power. KikGR and Kaede photoconverted with ratios only slightly lower than in vitro results, but cells rapidly photobleached after reaching maximal photoefficiency. PSCFP2 had the lowest photoefficiency and photoconverted nearly 70 times slower than the other dual-color PAFPs tested, but was effective at single-cell marking, especially with 2-photon excitation at 760 nm. The dual-color PAFPs were more effective to monitor cell migratory behaviors, since non-photoconverted neighboring cells were fluorescently marked with a separate color. However, photoconverted cells were limited in all cases to be visually distinguishable for long periods, with PSCFP2 visible from background the longest (48 hr). Thus, photoactivation in embryos has the potential to selectively mark less accessible cells with laser accuracy and may provide an effective means to study cell,cell interactions and short-term cell lineage in developmental and stem cell biology. Developmental Dynamics 236:1583,1594, 2007. © 2007 Wiley-Liss, Inc. [source]

    The basic helix-loop-helix factor Hand2 regulates autonomic nervous system development

    Yuka Morikawa
    Abstract Mammalian autonomic nervous system (ANS) development requires the combinatorial action of a number of transcription factors, which include Mash1, Phox2b, and GATA3. Here we show that the bHLH transcription factor, Hand2 (dHAND), is expressed concurrently with Mash1 during sympathetic nervous system (SNS) development and that the expression of Hand2 is not dependent on Mash1. This suggests that these two bHLH factors work in parallel during SNS development. We also show that ectopic expression of Hand2 activates the neuronal program and promotes the acquisition of a phenotype corresponding to peripheral neurons including neurons of the SNS lineage in P19 embryonic carcinoma cells. We propose that Hand2 works in parallel with other members of the transcriptional network to regulate ANS developmental but can ectopically activate the program by a cross-regulatory mechanism that includes the activation of Mash1. We show that this function is dependent on its interaction with the histone acetyltransferase p300/CBP, indicating that Hand2 functions to promote ANS development as part of a larger transcriptional complex. Developmental Dynamics 234:613,621, 2005. © 2005 Wiley-Liss, Inc. [source]