205,107 research outputs found
Evolutionary Conservation of the Heterochronic Pathway in C. elegans and C. briggsae
Heterochronic genes control the sequence and timing of developmental events during four larval stages of Caenorhabitis nematodes. Mutations in these genes may cause skipping or reiteration of developmental events.
C. briggsae is a close relative of C. elegans. These species have similar morphology and share the same ecological niche. C. briggsae undergoes the same developmental pathway consisting of four larval stages before reaching adulthood. It also has the same set of heterochronic genes.
Lin-28 is one of the heterochronic genes that also exists in other animals from flies to humans. It conservatively blocks the maturation of let-7 miRNA, the process is generally associated with the stem cell state. lin-28 is silenced as cells differentiate.
C. elegans mutants of lin-28 have a reduced number of seam cells and precocious alae. Despite the highly conserved protein sequence, C. briggsae develop a distinct phenotype when its lin 28 is disrupted. Worms did not have a characteristic vulval development defect, they also became lethargic and had a reduced fertility.
This observation led to a question of how conserved the heterochronic pathway is in close species
Conditions at infinity for the inhomogeneous filtration equation
We investigate existence and uniqueness of solutions to the filtration
equation with an inhomogeneous density in , approaching at
infinity a given continuous datum of Dirichlet type.Comment: To appear in Annales de l'Institut Henri Poincar\'e (C) Analyse Non
Lin\'eair
Centro-affine normal flows on curves: Harnack estimates and Ancient solutions
We prove that the only compact, origin-symmetric, strictly convex ancient
solutions of the planar centro-affine normal flows are contracting
origin-centered ellipses.Comment: I changed the title and fixed some typos. To appear in Annales de
l'Institut Henri Poincar\'e (C) Analyse Non Lin\'eair
Visualization of C. elegans transgenic arrays by GFP
BACKGROUND: Targeting the green fluorescent protein (GFP) via the E. coli lac repressor (LacI) to a specific DNA sequence, the lac operator (lacO), allows visualization of chromosomes in yeast and mammalian cells. In principle this method of visualization could be used for genetic mosaic analysis, which requires cell-autonomous markers that can be scored easily and at single cell resolution. The C. elegans lin-3 gene encodes an epidermal growth factor family (EGF) growth factor. lin-3 is expressed in the gonadal anchor cell and acts through LET-23 (transmembrane protein tyrosine kinase and ortholog of EGF receptor) to signal the vulval precursor cells to generate vulval tissue. lin-3 is expressed in the vulval cells later, and recent evidence raises the possibility that lin-3 acts in the vulval cells as a relay signal during vulval induction. It is thus of interest to test the site of action of lin-3 by mosaic analysis. RESULTS: We visualized transgenes in living C. elegans by targeting the green fluorescent protein (GFP) via the E. coli lac repressor (LacI) to a specific 256 sequence repeat of the lac operator (lacO) incorporated into transgenes. We engineered animals to express a nuclear-localized GFP-LacI fusion protein. C. elegans cells having a lacO transgene result in nuclear-localized bright spots (i.e., GFP-LacI bound to lacO). Cells with diffuse nuclear fluorescence correspond to unbound nuclear localized GFP-LacI. We detected chromosomes in living animals by chromosomally integrating the array of the lacO repeat sequence and visualizing the integrated transgene with GFP-LacI. This detection system can be applied to determine polyploidy as well as investigating chromosome segregation. To assess the GFP-LacI•lacO system as a marker for mosaic analysis, we conducted genetic mosaic analysis of the epidermal growth factor lin-3, expressed in the anchor cell. We establish that lin-3 acts in the anchor cell to induce vulva development, demonstrating this method's utility in detecting the presence of a transgene. CONCLUSION: The GFP-LacI•lacO transgene detection system works in C. elegans for visualization of chromosomes and extrachromosomal transgenes. It can be used as a marker for genetic mosaic analysis. The lacO repeat sequence as an extrachromosomal array becomes a valuable technique allowing rapid, accurate determination of spontaneous loss of the array, thereby allowing high-resolution mosaic analysis. The lin-3 gene is required in the anchor cell to induce the epidermal vulval precursors cells to undergo vulval development
Recognizing and Curating Photo Albums via Event-Specific Image Importance
Automatic organization of personal photos is a problem with many real world
ap- plications, and can be divided into two main tasks: recognizing the event
type of the photo collection, and selecting interesting images from the
collection. In this paper, we attempt to simultaneously solve both tasks:
album-wise event recognition and image- wise importance prediction. We
collected an album dataset with both event type labels and image importance
labels, refined from an existing CUFED dataset. We propose a hybrid system
consisting of three parts: A siamese network-based event-specific image
importance prediction, a Convolutional Neural Network (CNN) that recognizes the
event type, and a Long Short-Term Memory (LSTM)-based sequence level event
recognizer. We propose an iterative updating procedure for event type and image
importance score prediction. We experimentally verified that image importance
score prediction and event type recognition can each help the performance of
the other.Comment: Accepted as oral in BMVC 201
Genetics of intercellular signalling in C. elegans
Cell-cell interactions play a significant role in controlling cell fate during development of the nematode Caenorhabditis elegans. It has been found that two genes, glp-1 and lin-12, are required for many of these decisions. glp-1 is required for induction of mitotic proliferation in the germline by the somatic distal tip cell and for induction of the anterior pharynx early in embryogenesis. lin-12 is required for the interactions between cells of equivalent developmental potential, which allow them to take on different fates. Comparison of these two genes on a molecular level indicates that they are similar in sequence and organization, suggesting that the mechanisms of these two different sets of cell-cell interactions are similar
Controlling occupational cancers in Australia
Lin Fritschi, Renae C Fernandez, Deborah A Vallance, Terry J Slevin, Alison Reid, Timothy R Driscoll, Deborah C Glas
Exploring the EGF/Ras and Notch/DSL Signaling Pathways in Members of the Caenorhabditis Genus
Many pathways exist in animal systems for cells to communicate and facilitate proper cell division; two such pathways are the EGF/Ras pathway and the Notch/DSL pathway, both of which are crucial to proper vulval development in nematodes of the Caenorhabditis genus. These pathways are conserved in humans and many other species as well, making them viable topics for research. This project seeks to study these pathways, especially the diversity of each path, and how the they work together to allow successful vulvagenesis. To examine pathway diversity, evolutionary trees (generated by TreeFam.org) for genes vital to each pathway were collected and compared to each other. This analysis revealed more gene duplication in the Notch pathway among members of the Caenorhabditis genus, while relatively little gene duplication exists in the EGF/Ras pathway. This suggests that the Notch pathway is more flexible, and allows more evolutionary diversity. To test this prediction, I am comparing the function of these pathways between Caenorhabditis elegans and Caenorhabditis briggsae. For studying the EGF/Ras pathway, I am examining the gene lin-3/EGF. Over expression of lin-3/EGF in C. elegans leads to the inappropriate division of epithelial cells. My data show overexpression of C. briggsae lin-3 causes a similar phenotype in both C. elegans and C. briggsae worms. Additionally, during this project new splice variants of the lin-3 gene were discovered in C. elegans, C. briggsae, and C. remanei. Notably, several of these variants either include or exclude a possible processing site. The tools developed in this project will be valuable assets for further studying these critical signaling pathways in various animal systems.Undergraduate Research Scholarship - College of Arts and SciencesPelotonia FellowshipNo embargoAcademic Major: Zoolog
Deformable Part-based Fully Convolutional Network for Object Detection
Existing region-based object detectors are limited to regions with fixed box
geometry to represent objects, even if those are highly non-rectangular. In
this paper we introduce DP-FCN, a deep model for object detection which
explicitly adapts to shapes of objects with deformable parts. Without
additional annotations, it learns to focus on discriminative elements and to
align them, and simultaneously brings more invariance for classification and
geometric information to refine localization. DP-FCN is composed of three main
modules: a Fully Convolutional Network to efficiently maintain spatial
resolution, a deformable part-based RoI pooling layer to optimize positions of
parts and build invariance, and a deformation-aware localization module
explicitly exploiting displacements of parts to improve accuracy of bounding
box regression. We experimentally validate our model and show significant
gains. DP-FCN achieves state-of-the-art performances of 83.1% and 80.9% on
PASCAL VOC 2007 and 2012 with VOC data only.Comment: Accepted to BMVC 2017 (oral
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