New proteins and modules have been invented throughout evolution. Gene "birth dates" in Caenorhabditis elegans range from the origins of cellular life through adaptation to a soil habitat. Possibly ...half are "metazoan" genes, having arisen sometime between the yeast-metazoan and nematode-chordate separations. These include basement membrane and cell adhesion molecules implicated in tissue organization. By contrast, epithelial surfaces facing the environment have specialized components invented within the nematode lineage. Moreover, interstitial matrices were likely elaborated within the vertebrate lineage. A strategy for concerted evolution of new gene families, as well as conservation of adaptive genes, may underlie the differences between heterochromatin and euchromatin.
Spirit of the Delta Shawhan, Dorothy Sample; Black, Patti Carr; Rankin, Tom ...
06/2011
eBook
Raised in West Virginia, self-taught artist Carolyn Norris (b. 1948) moved as a young woman of twenty-one to Cleveland, Mississippi, a quintessential Delta railroad town on the famous blues Highway ...61. To create one of her first paintings, she tore the wooden back off a dresser to use as a canvas. She painted with available house paint and completed the painting with face makeup. Thus began the realization of a passionate need to paint.
Eventually, Norris came to serve as the visual griot of Cleveland. She has used a variety of media, painting on canvas, wood, paper, cardboard, glass, plates, tiles, sheets, floor covering, and mirrors. She also uses her garage door as a giant mural chronicling community events. In her extraordinary images, Norris shows daily black life in the modern Delta.
Spirit of the Deltacontains 115 color images pulled from Norris's twenty-five years as a painter. Her existing artwork has been photographed by noted local photographer Kim Rushing and copies of the works that no longer exist have been found whenever possible. The book features a biographical essay on Carolyn Norris by Dorothy Sample Shawhan and an essay on her artwork by critic Patti Carr Black, who places Norris within self-taught traditions. In an interview with folklorist Tom Rankin, which took place in 1991, Norris explains the centrality of art in her life.
Endocytosis regulates many processes, including signaling pathways, nutrient uptake, and protein turnover. During clathrin‐mediated endocytosis (CME), adaptors bind to cytoplasmic regions of ...transmembrane cargo proteins, and many endocytic adaptors are also directly involved in the recruitment of clathrin. This clathrin‐associated sorting protein family includes the yeast epsins, Ent1/2, and AP180/PICALM homologs, Yap1801/2. Mutant strains lacking these four adaptors, but expressing an epsin N‐terminal homology (ENTH) domain necessary for viability (4Δ+ENTH), exhibit endocytic defects, such as cargo accumulation at the plasma membrane (PM). This CME‐deficient strain provides a sensitized background ideal for revealing cellular components that interact with clathrin adaptors. We performed a mutagenic screen to identify alleles that are lethal in 4Δ+ENTH cells using a colony‐sectoring reporter assay. After isolating candidate synthetic lethal genes by complementation, we confirmed that mutations in VPS4 led to inviability of a 4Δ+ENTH strain. Vps4 mediates the final step of endosomal sorting complex required for transport (ESCRT)‐dependent trafficking, and we found that multiple ESCRTs are also essential in 4Δ+ENTH cells, including Snf7, Snf8 and Vps36. Deletion of VPS4 from an end3Δ strain, another CME mutant, similarly resulted in inviability, and upregulation of a clathrin‐independent endocytosis pathway rescued 4Δ+ENTH vps4Δ cells. Loss of Vps4 from an otherwise wild‐type background caused multiple cargoes to accumulate at the PM because of an increase in Rcy1‐dependent recycling of internalized protein to the cell surface. Additionally, vps4Δ rcy1Δ mutants exhibited deleterious growth phenotypes. Together, our findings reveal previously unappreciated effects of disrupted ESCRT‐dependent trafficking on endocytic recycling and the PM.
In a WT cell (left), endocytosis delivers protein cargoes to late endosomes; given the recently changing views on the structure of the yeast endomembrane system, dotted lines are used here to represent the multiple potential trafficking pathways between multivesicular bodies and the plasma membrane (PM). Cargoes can then be trafficked into vesicles within late endosomes and delivered to the vacuole lumen for degradation. In many endocytosis mutants (center), cargoes accumulate at the PM as a result of decreased endocytic efficiency. In cells that lack Vps4, protein cargoes that are normally trafficked to the vacuole lumen instead accumulate in class E organelles, stacks of membranous tubules adjacent to vacuoles. In the absence of Vps4, internalized cargoes are aberrantly returned to the PM via endocytic recycling. We propose that, when these mutations are combined (right), the redirection of cargo to the PM in an endocytosis mutant, which already has an elevated concentration of cell‐surface proteins, leads to the synthetic lethality observed in this study.
Receptor tyrosine kinases and Notch are crucial for tube formation and branching morphogenesis in many systems, but the specific cellular processes that require signaling are poorly understood. Here ...we describe sequential roles for Notch and Epidermal growth factor (EGF)-Ras-ERK signaling in the development of epithelial tube cells in the C. elegans excretory (renal-like) organ. This simple organ consists of three tandemly connected unicellular tubes: the excretory canal cell, duct and G1 pore. lin-12 and glp-1/Notch are required to generate the canal cell, which is a source of LIN-3/EGF ligand and physically attaches to the duct during de novo epithelialization and tubulogenesis. Canal cell asymmetry and let-60/Ras signaling influence which of two equivalent precursors will attach to the canal cell. Ras then specifies duct identity, inducing auto-fusion and a permanent epithelial character; the remaining precursor becomes the G1 pore, which eventually loses epithelial character and withdraws from the organ to become a neuroblast. Ras continues to promote subsequent aspects of duct morphogenesis and differentiation, and acts primarily through Raf-ERK and the transcriptional effectors LIN-1/Ets and EOR-1. These results reveal multiple genetically separable roles for Ras signaling in tube development, as well as similarities to Ras-mediated control of branching morphogenesis in more complex organs, including the mammalian kidney. The relative simplicity of the excretory system makes it an attractive model for addressing basic questions about how cells gain or lose epithelial character and organize into tubular networks.
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We have constructed a website (
www.wormatlas.org
) which describes all cells and tissues of the hermaphrodite and male
Caenorhabditis elegans
for teaching purposes. New data will soon ...cover tissue development in the embryo. Imaging modalities used in the atlas include LM/DIC, confocal imaging, SEM, serial section electron microscopy (TEM), and illustrations depicting basic concepts and relationships for nematode development and physiology. Among various sections, the Handbook is designed as a text‐based resource with annotated images, which are color‐coded for individual tissues. The Slidable Worm uses Zoomify (open source) to view consecutive TEM sections of the worm at incremental magnifications, with or without color‐coded annotations. A Glossary defines all anatomical terms, with links to text and images. The site also offers an anatomical methods section, “neuron pages” describing individual cells of the nervous system, and HTML‐converted canonical anatomy texts. A printed version of the atlas is available as a portable resource (
C. elegans
Atlas, Hall and Altun, 2008, CSHL Press). Related websites that can be linked via the atlas offer catalogues of archival TEM images (
www.wormimage.org
) or GFP images (
www.gfpworm.org
), and a discussion forum for the worm community. Many
C. elegans
labs have supplied key data for this work, which is supported by NIH RR 12596.
To investigate the development of corpus callosal connectivity in the hamster sensorimotor cortex, we have used the sensitive axonal tracer 1,1 dioctadecyl-3,3,3',3', tetramethylindocarbocyanine ...perchlorate (DiI), which was injected either in vivo or in fixed brains of animals 3-6 days postnatal. First, to study changes in the overall distribution of developing callosal afferents we made large injections of DiI into the corpus callosal tract. We found that the anterogradely labeled callosal axons formed a patchy distribution in the contralateral sensorimotor cortex, which was similar to the pattern of adult connectivity described in earlier studies of the rodent corpus callosum. This result stands in contrast to previous retrograde studies of developing callosal connectivity which showed that the distribution of callosal neurons early in development is homogeneous and that the mature, patchy distribution arises later, primarily as a result of the retraction of exuberant axons. The initial patchy distribution of callosal axon growth into the sensorimotor cortex described in the present study suggests that exuberant axons destined to be eliminated do not enter the cortex. In addition, small injections of DiI into developing cortex resulted in homotopic patterns of callosal topography in which reciprocal regions of sensorimotor cortex are connected, as has been shown in the adult. Second, to study the radial growth of callosal afferents we followed the extension of individual callosal axons into the developing cortex. We found that callosal axons began to invade the contralateral cortex on about postnatal day 3, with little or no waiting period in the callosal tract. Callosal afferents then advanced steadily through the cortex, never actually invading the cortical plate but extending into layers on the first day that they could be distinguished from the cortical plate. The majority of callosal axons grew radially through the cortex and did not exhibit substantial branching until postnatal day 8, the age when the cortical plate disappears and callosal afferents reach the outer layer of cortex. This mode of radial growth through cortex prior to axon branching could serve to align callosal afferents with their radial or columnar targets before arborizing laterally.
After the 1989 fall of Communism in Romania, the world became aware of the plight of the country's thousands of institutionalized children, and an international adoption system saw the adoption of ...many of these children to other countries. Thousands of children, however, remained in institutions as the newly Democratic Romania struggled with the legacy of its Communist era. During the process of applying to join the European Union, Romania in 2000 initiated the eventual banning of international adoption. Using a qualitative approach that relies on interviews, document review, and observation, this study finds both positive and negative interpretations of the ban, with subjects pointing to Romania's desire to join the EU as a supposed major factor in its decision to ban international adoption. The implications of the ban include the emergence of a foster care system and domestic adoption, efforts to reunify families and to prevent the abandonment, relinquishment, and removal of children from their biological families, and the development of alternative forms of care in tandem with a new deinstitutionalization initiative.
Equinus, crouch and crouch/equinus are common gait patterns seen in children with cerebral palsy. Six normal subjects simulated each of the above gait abnormalities to determine the effect on gait ...parameters, electromyography, joint moments and physiological cost index. Assessment of normal and the pathological gait patterns was performed using gait analysis. The results indicate that as the complexity of the gait pattern increases, the gait parameters decrease and the physiological cost index increases. Although abnormalities were found in electromyographic activity and joint moments, the patterns were similar to those found in children with cerebral palsy when walking in equinus, crouch and crouch/equinus. Abnormal joint positions produce significant effects on the parameters of gait used to assess the child with cerebral palsy. During interpretation of the gait analysis data significant emphasis must be placed on clinical evaluation and the determination of primary and secondary responses.
Like a molecular bulletin board, the extracellular matrix allows indirect communication between cells during development. For posting messages, soluble molecules from various sources are incorporated ...into more-or-less stable, matrix polymers surrounding tissues and individual cells. Integrins and other cell surface receptors tether these components and coordinate their assembly. Later, for reading messages, cells can express receptors for particular matrix components. In particular, motile cells and axons use matrix cues originating from path or target cells to control their direction and extent of migration. Laminin and netrin Among the oldest and most conserved extracellular matrix proteins are the laminins, which form the basement membranes surrounding epithelia and other tissues, and provide a matrix substrate for various motile and stationary cells. Three homologous subunits, designated alpha , beta and gamma , twine together with their C-termini, and interact with other laminin molecules with their N-termini. A current model is that ternary interactions involving distinct subunits from three different laminin molecules create a quasi-regular, two-dimensional polymer with polarized faces. This scaffold of polymeric laminin supports other matrix molecules and interacts with several integrins and other receptors directly. Specific laminins can stimulate or inhibit cell movement on the basement membrane. Netrins, a family of laminin-related proteins, were discovered in screens of nematode locomotor (uncoordinated, unc) mutants for defective guidance of commissural and motor axons along the dorsoventral body axis, and independently, as soluble factors from floor plate cells responsible for attracting commissural axons towards the ventral midline of the developing spinal cord. From nematodes to vertebrates, these genes are expressed by neuroglia and neurons along the ventral midline of the central nervous system. These netrin cues help attract commissural axons to the ventral midline, and repulse motor and other axons from this same region; moreover, they help to determine the dorsoventral positions of various longitudinal axon tracts. Finally, specific midline neuroglia, neurons, or skeletal muscles might provide localized netrin cues for the major commissures and peripheral nerves, respectively while the C-terminus is unique to netrin. The LN (laminin N-terminal) domain might allow netrin incorporation into basement membranes by co-polymerization with laminin, while the growth-factor-like modules LE1 to LE3 could provide binding sites for netrin receptors on motile cells. Finally, the basic NC (netrin C-terminal) domain might tether netrin to other molecules for display on cell surfaces or unique matrix sites. These features suggest how a complex and dynamic pattern of netrin secretion, combined with tethering to specific cell surface or matrix sites, can produce stable extracellular cues for guiding cells and axons throughout development.
Thesis (Ph. D.)--University of Wisconsin--Madison, 1990.
Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
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