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Search Results: 1 - 10 of 224837 matches for " Misti C. White equal contributor "
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Inactivation of hnRNP K by Expanded Intronic AUUCU Repeat Induces Apoptosis Via Translocation of PKCδ to Mitochondria in Spinocerebellar Ataxia 10
Misti C. White equal contributor,Rui Gao equal contributor,Weidong Xu,Santi M. Mandal,Jung G. Lim,Tapas K. Hazra,Maki Wakamiya,Sharon F. Edwards,Salmo Raskin,Hélio A. G. Teive,Huda Y. Zoghbi,Partha S. Sarkar,Tetsuo Ashizawa
PLOS Genetics , 2010, DOI: 10.1371/journal.pgen.1000984
Abstract: We have identified a large expansion of an ATTCT repeat within intron 9 of ATXN10 on chromosome 22q13.31 as the genetic mutation of spinocerebellar ataxia type 10 (SCA10). Our subsequent studies indicated that neither a gain nor a loss of function of ataxin 10 is likely the major pathogenic mechanism of SCA10. Here, using SCA10 cells, and transfected cells and transgenic mouse brain expressing expanded intronic AUUCU repeats as disease models, we show evidence for a key pathogenic molecular mechanism of SCA10. First, we studied the fate of the mutant repeat RNA by in situ hybridization. A Cy3-(AGAAU)10 riboprobe detected expanded AUUCU repeats aggregated in foci in SCA10 cells. Pull-down and co-immunoprecipitation data suggested that expanded AUUCU repeats within the spliced intronic sequence strongly bind to hnRNP K. Co-localization of hnRNP K and the AUUCU repeat aggregates in the transgenic mouse brain and transfected cells confirmed this interaction. To examine the impact of this interaction on hnRNP K function, we performed RT–PCR analysis of a splicing-regulatory target of hnRNP K, and found diminished hnRNP K activity in SCA10 cells. Cells expressing expanded AUUCU repeats underwent apoptosis, which accompanied massive translocation of PKCδ to mitochondria and activation of caspase 3. Importantly, siRNA–mediated hnRNP K deficiency also caused the same apoptotic event in otherwise normal cells, and over-expression of hnRNP K rescued cells expressing expanded AUUCU repeats from apoptosis, suggesting that the loss of function of hnRNP K plays a key role in cell death of SCA10. These results suggest that the expanded AUUCU–repeat in the intronic RNA undergoes normal transcription and splicing, but causes apoptosis via an activation cascade involving a loss of hnRNP K activities, massive translocation of PKCδ to mitochondria, and caspase 3 activation.
The Protein Kinase Double-Stranded RNA-Dependent (PKR) Enhances Protection against Disease Cause by a Non-Viral Pathogen
Pauline Sebby Ogolla equal contributor,Jose-Andres C. Portillo equal contributor,Christine L. White,Krupen Patel,Bruce Lamb,Ganes C. Sen,Carlos S. Subauste
PLOS Pathogens , 2013, DOI: 10.1371/journal.ppat.1003557
Abstract: PKR is well characterized for its function in antiviral immunity. Using Toxoplasma gondii, we examined if PKR promotes resistance to disease caused by a non-viral pathogen. PKR?/? mice infected with T. gondii exhibited higher parasite load and worsened histopathology in the eye and brain compared to wild-type controls. Susceptibility to toxoplasmosis was not due to defective expression of IFN-γ, TNF-α, NOS2 or IL-6 in the retina and brain, differences in IL-10 expression in these organs or to impaired induction of T. gondii-reactive T cells. While macrophages/microglia with defective PKR signaling exhibited unimpaired anti-T. gondii activity in response to IFN-γ/TNF-α, these cells were unable to kill the parasite in response to CD40 stimulation. The TRAF6 binding site of CD40, but not the TRAF2,3 binding sites, was required for PKR phosphorylation in response to CD40 ligation in macrophages. TRAF6 co-immunoprecipitated with PKR upon CD40 ligation. TRAF6-PKR interaction appeared to be indirect, since TRAF6 co-immunoprecipitated with TRAF2 and TRAF2 co-immunoprecipitated with PKR, and deficiency of TRAF2 inhibited TRAF6-PKR co-immunoprecipitation as well as PKR phosphorylation induced by CD40 ligation. PKR was required for stimulation of autophagy, accumulation the autophagy molecule LC3 around the parasite, vacuole-lysosomal fusion and killing of T. gondii in CD40-activated macrophages and microglia. Thus, our findings identified PKR as a mediator of anti-microbial activity and promoter of protection against disease caused by a non-viral pathogen, revealed that PKR is activated by CD40 via TRAF6 and TRAF2, and positioned PKR as a link between CD40-TRAF signaling and stimulation of the autophagy pathway.
Melioidosis Vaccines: A Systematic Review and Appraisal of the Potential to Exploit Biodefense Vaccines for Public Health Purposes
Sharon J. Peacock equal contributor,Direk Limmathurotsakul equal contributor ,Yoel Lubell,Gavin C. K. W. Koh,Lisa J. White,Nicholas P. J. Day,Richard W. Titball
PLOS Neglected Tropical Diseases , 2012, DOI: 10.1371/journal.pntd.0001488
Abstract: Background Burkholderia pseudomallei is a Category B select agent and the cause of melioidosis. Research funding for vaccine development has largely considered protection within the biothreat context, but the resulting vaccines could be applicable to populations who are at risk of naturally acquired melioidosis. Here, we discuss target populations for vaccination, consider the cost-benefit of different vaccination strategies and review potential vaccine candidates. Methods and Findings Melioidosis is highly endemic in Thailand and northern Australia, where a biodefense vaccine might be adopted for public health purposes. A cost-effectiveness analysis model was developed, which showed that a vaccine could be a cost-effective intervention in Thailand, particularly if used in high-risk populations such as diabetics. Cost-effectiveness was observed in a model in which only partial immunity was assumed. The review systematically summarized all melioidosis vaccine candidates and studies in animal models that had evaluated their protectiveness. Possible candidates included live attenuated, whole cell killed, sub-unit, plasmid DNA and dendritic cell vaccines. Live attenuated vaccines were not considered favorably because of possible reversion to virulence and hypothetical risk of latent infection, while the other candidates need further development and evaluation. Melioidosis is acquired by skin inoculation, inhalation and ingestion, but routes of animal inoculation in most published studies to date do not reflect all of this. We found a lack of studies using diabetic models, which will be central to any evaluation of a melioidosis vaccine for natural infection since diabetes is the most important risk factor. Conclusion Vaccines could represent one strand of a public health initiative to reduce the global incidence of melioidosis.
Palladin Mutation Causes Familial Pancreatic Cancer and Suggests a New Cancer Mechanism
Kay L Pogue-Geile equal contributor,Ru Chen equal contributor,Mary P Bronner,Tatjana Crnogorac-Jurcevic,Kara White Moyes,Sally Dowen,Carol A Otey,David A Crispin,Ryan D George,David C Whitcomb,Teresa A Brentnall
PLOS Medicine , 2006, DOI: 10.1371/journal.pmed.0030516
Abstract: Background Pancreatic cancer is a deadly disease. Discovery of the mutated genes that cause the inherited form(s) of the disease may shed light on the mechanism(s) of oncogenesis. Previously we isolated a susceptibility locus for familial pancreatic cancer to chromosome location 4q32–34. In this study, our goal was to discover the identity of the familial pancreatic cancer gene on 4q32 and determine the function of that gene. Methods and Findings A customized microarray of the candidate chromosomal region affecting pancreatic cancer susceptibility revealed the greatest expression change in palladin (PALLD), a gene that encodes a component of the cytoskeleton that controls cell shape and motility. A mutation causing a proline (hydrophobic) to serine (hydrophilic) amino acid change (P239S) in a highly conserved region tracked with all affected family members and was absent in the non-affected members. The mutational change is not a known single nucleotide polymorphism. Palladin RNA, measured by quantitative RT-PCR, was overexpressed in the tissues from precancerous dysplasia and pancreatic adenocarcinoma in both familial and sporadic disease. Transfection of wild-type and P239S mutant palladin gene constructs into HeLa cells revealed a clear phenotypic effect: cells expressing P239S palladin exhibited cytoskeletal changes, abnormal actin bundle assembly, and an increased ability to migrate. Conclusions These observations suggest that the presence of an abnormal palladin gene in familial pancreatic cancer and the overexpression of palladin protein in sporadic pancreatic cancer cause cytoskeletal changes in pancreatic cancer and may be responsible for or contribute to the tumor's strong invasive and migratory abilities.
OSM-11 Facilitates LIN-12 Notch Signaling during Caenorhabditis elegans Vulval Development
Hidetoshi Komatsu equal contributor,Michael Y Chao equal contributor,Jonah Larkins-Ford,Mark E Corkins,Gerard A Somers,Tim Tucey,Heather M Dionne,Jamie Q White,Khursheed Wani,Mike Boxem,Anne C Hart
PLOS Biology , 2008, DOI: 10.1371/journal.pbio.0060196
Abstract: Notch signaling is critical for cell fate decisions during development. Caenorhabditis elegans and vertebrate Notch ligands are more diverse than classical Drosophila Notch ligands, suggesting possible functional complexities. Here, we describe a developmental role in Notch signaling for OSM-11, which has been previously implicated in defecation and osmotic resistance in C. elegans. We find that complete loss of OSM-11 causes defects in vulval precursor cell (VPC) fate specification during vulval development consistent with decreased Notch signaling. OSM-11 is a secreted, diffusible protein that, like previously described C. elegans Delta, Serrate, and LAG-2 (DSL) ligands, can interact with the lineage defective-12 (LIN-12) Notch receptor extracellular domain. Additionally, OSM-11 and similar C. elegans proteins share a common motif with Notch ligands from other species in a sequence defined here as the Delta and OSM-11 (DOS) motif. osm-11 loss-of-function defects in vulval development are exacerbated by loss of other DOS-motif genes or by loss of the Notch ligand DSL-1, suggesting that DOS-motif and DSL proteins act together to activate Notch signaling in vivo. The mammalian DOS-motif protein Deltalike1 (DLK1) can substitute for OSM-11 in C. elegans development, suggesting that DOS-motif function is conserved across species. We hypothesize that C. elegans OSM-11 and homologous proteins act as coactivators for Notch receptors, allowing precise regulation of Notch receptor signaling in developmental programs in both vertebrates and invertebrates.
High-Resolution Genome-Wide Dissection of the Two Rules of Speciation in Drosophila
John P Masly equal contributor ,Daven C Presgraves equal contributor
PLOS Biology , 2007, DOI: 10.1371/journal.pbio.0050243
Abstract: Postzygotic reproductive isolation is characterized by two striking empirical patterns. The first is Haldane's rule—the preferential inviability or sterility of species hybrids of the heterogametic (XY) sex. The second is the so-called large X effect—substitution of one species's X chromosome for another's has a disproportionately large effect on hybrid fitness compared to similar substitution of an autosome. Although the first rule has been well-established, the second rule remains controversial. Here, we dissect the genetic causes of these two rules using a genome-wide introgression analysis of Drosophila mauritiana chromosome segments in an otherwise D. sechellia genetic background. We find that recessive hybrid incompatibilities outnumber dominant ones and that hybrid male steriles outnumber all other types of incompatibility, consistent with the dominance and faster-male theories of Haldane's rule, respectively. We also find that, although X-linked and autosomal introgressions are of similar size, most X-linked introgressions cause hybrid male sterility (60%) whereas few autosomal introgressions do (18%). Our results thus confirm the large X effect and identify its proximate cause: incompatibilities causing hybrid male sterility have a higher density on the X chromosome than on the autosomes. We evaluate several hypotheses for the evolutionary cause of this excess of X-linked hybrid male sterility.
Shifting Baselines, Local Impacts, and Global Change on Coral Reefs
Nancy Knowlton equal contributor ,Jeremy B. C Jackson equal contributor
PLOS Biology , 2008, DOI: 10.1371/journal.pbio.0060054
Consequences of Eukaryotic Enhancer Architecture for Gene Expression Dynamics, Development, and Fitness
Michael Z. Ludwig equal contributor ,Manu equal contributor,Ralf Kittler,Kevin P. White,Martin Kreitman
PLOS Genetics , 2011, DOI: 10.1371/journal.pgen.1002364
Abstract: The regulatory logic of time- and tissue-specific gene expression has mostly been dissected in the context of the smallest DNA fragments that, when isolated, recapitulate native expression in reporter assays. It is not known if the genomic sequences surrounding such fragments, often evolutionarily conserved, have any biological function or not. Using an enhancer of the even-skipped gene of Drosophila as a model, we investigate the functional significance of the genomic sequences surrounding empirically identified enhancers. A 480 bp long “minimal stripe element” is able to drive even-skipped expression in the second of seven stripes but is embedded in a larger region of 800 bp containing evolutionarily conserved binding sites for required transcription factors. To assess the overall fitness contribution made by these binding sites in the native genomic context, we employed a gene-replacement strategy in which whole-locus transgenes, capable of rescuing even-skipped- lethality to adulthood, were substituted for the native gene. The molecular phenotypes were characterized by tagging Even-skipped with a fluorescent protein and monitoring gene expression dynamics in living embryos. We used recombineering to excise the sequences surrounding the minimal enhancer and site-specific transgenesis to create co-isogenic strains differing only in their stripe 2 sequences. Remarkably, the flanking sequences were dispensable for viability, proving the sufficiency of the minimal element for biological function under normal conditions. These sequences are required for robustness to genetic and environmental perturbation instead. The mutant enhancers had measurable sex- and dose-dependent effects on viability. At the molecular level, the mutants showed a destabilization of stripe placement and improper activation of downstream genes. Finally, we demonstrate through live measurements that the peripheral sequences are required for temperature compensation. These results imply that seemingly redundant regulatory sequences beyond the minimal enhancer are necessary for robust gene expression and that “robustness” itself must be an evolved characteristic of the wild-type enhancer.
Epigenetic Repression of p16INK4A by Latent Epstein-Barr Virus Requires the Interaction of EBNA3A and EBNA3C with CtBP
Lenka Skalska equal contributor,Robert E. White equal contributor,Melanie Franz,Michaela Ruhmann,Martin J. Allday
PLOS Pathogens , 2010, DOI: 10.1371/journal.ppat.1000951
Abstract: As an inhibitor of cyclin-dependent kinases, p16INK4A is an important tumour suppressor and inducer of cellular senescence that is often inactivated during the development of cancer by promoter DNA methylation. Using newly established lymphoblastoid cell lines (LCLs) expressing a conditional EBNA3C from recombinant EBV, we demonstrate that EBNA3C inactivation initiates chromatin remodelling that resets the epigenetic status of p16INK4A to permit transcriptional activation: the polycomb-associated repressive H3K27me3 histone modification is substantially reduced, while the activation-related mark H3K4me3 is modestly increased. Activation of EBNA3C reverses the distribution of these epigenetic marks, represses p16INK4A transcription and allows proliferation. LCLs lacking EBNA3A express relatively high levels of p16INK4A and have a similar pattern of histone modifications on p16INK4A as produced by the inactivation of EBNA3C. Since binding to the co-repressor of transcription CtBP has been linked to the oncogenic activity of EBNA3A and EBNA3C, we established LCLs with recombinant viruses encoding EBNA3A- and/or EBNA3C-mutants that no longer bind CtBP. These novel LCLs have revealed that the chromatin remodelling and epigenetic repression of p16INK4A requires the interaction of both EBNA3A and EBNA3C with CtBP. The repression of p16INK4A by latent EBV will not only overcome senescence in infected B cells, but may also pave the way for p16INK4A DNA methylation during B cell lymphomagenesis.
The RNA Export Factor, Nxt1, Is Required for Tissue Specific Transcriptional Regulation
Simona Caporilli equal contributor,Yachuan Yu equal contributor,Jianqiao Jiang,Helen White-Cooper
PLOS Genetics , 2013, DOI: 10.1371/journal.pgen.1003526
Abstract: The highly conserved, Nxf/Nxt (TAP/p15) RNA nuclear export pathway is important for export of most mRNAs from the nucleus, by interacting with mRNAs and promoting their passage through nuclear pores. Nxt1 is essential for viability; using a partial loss of function allele, we reveal a role for this gene in tissue specific transcription. We show that many Drosophila melanogaster testis-specific mRNAs require Nxt1 for their accumulation. The transcripts that require Nxt1 also depend on a testis-specific transcription complex, tMAC. We show that loss of Nxt1 leads to reduced transcription of tMAC targets. A reporter transcript from a tMAC-dependent promoter is under-expressed in Nxt1 mutants, however the same transcript accumulates in mutants if driven by a tMAC-independent promoter. Thus, in Drosophila primary spermatocytes, the transcription factor used to activate expression of a transcript, rather than the RNA sequence itself or the core transcription machinery, determines whether this expression requires Nxt1. We additionally find that transcripts from intron-less genes are more sensitive to loss of Nxt1 function than those from intron-containing genes and propose a mechanism in which transcript processing feeds back to increase activity of a tissue specific transcription complex.
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