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dictyNews Volume 39 Number 16
dictyNews
Electronic Edition
Volume 39, number 16
May 31, 2013
Please submit abstracts of your papers as soon as they have been
accepted for publication by sending them to dicty@northwestern.edu
or by using the form at
http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit.
Back issues of dictyNews, the Dicty Reference database and other
useful information is available at dictyBase - http://dictybase.org.
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Abstracts
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Aberrant spindle dynamics and cytokinesis in Dictyostelium
discoideum cells that lack glycogen synthase kinase 3
Adrian J. Harwood, Josephine E. Forde-Thomas, Hazel Williams,
Matthias Samereier and Annette Mueller-Taubenberger
European Journal of Cell Biology, in press
Eukaryotic cell division requires the co-ordinated assembly and
disassembly of the mitotic spindle, accurate chromosome
segregation and temporal control of cytokinesis to generate two
daughter cells. While the absolute details of these processes
differ between organisms, there are evolutionarily conserved core
components common to all eukaryotic cells, whose identification
will reveal the key processes that control cell division. Glycogen
synthase kinase 3 (GSK-3) is a major protein kinase found
throughout the eukaryotes and regulates many processes,
including cell differentiation, growth, motility and apoptosis. In
animals, GSK-3 associates with mitotic spindles and its inhibition
causes mis-regulation of chromosome segregation. Two
suppressor screens in yeast point to a more general effect of
GSK-3 on cell division, however the direct role of GSK-3 in
control of mitosis has not been explored outside the animal
kingdom. Here we report that the Dictyostelium discoideum
GSK-3 orthologue, GskA, associates with the mitotic spindle
during cell division, as seen for its mammalian counterparts.
Dictyostelium possesses only a single GSK-3 gene that can be
deleted to eliminate all GSK-3 activity. We found that gskA-null
mutants failed to elongate their mitotic spindle and were unable
to divide in shaking culture, but have no chromosome segregation
defect. These results suggest further conservation for the role of
GSK-3 in the regulation of spindle dynamics during mitosis, but
also reveal differences in the mechanisms ensuring accurate
chromosome segregation.
Submitted by Adrian Harwood [harwoodaj@cf.ac.uk]
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The use of streptavidin conjugates as immunoblot loading controls
& mitochondrial markers for use with Dictyostelium discoideum
Andrew J. Davidson*, Jason S. King*1 and Robert H. Insall
Beatson Institute for Cancer Research, Garscube Estate, Bearsden,
Glasgow, UK. G61 1BD
*These authors contributed equally to this work
1Corresponding author
BioTechniques, in press
The loading controls used from quantitative immunoblotting in
mammalian cells are not appropriate for use with Dictyostelium
discoideum. Actin, for example changes greatly during development,
and other antibodies are not commercially available. Here we
demonstrate the use of labeled streptavidin to detect the biotinylated,
mitochondrial MCCC1, providing a robust and convenient tool for the
quantitative normalization of Dictyostelium western blots as well as
labeling mitochondria in fixed cells.
Submitted by Jason King [j.king@beatson.gla.ac.uk]
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Dictyostelids:
Evolution, genomics and cell biology
Editors: Maria Romeralo, Sandra Baldauf, Ricardo Escalante
Soon available at:
http://www.springer.com/life+sciences/evolutionary+%26+developmental+biology/book/978-3-642-38486-8
Chapter 1. Dictyostelium discoideum as a model in biomedical research
Sandra Munoz-Braceras, Ana Mesquita and Ricardo Escalante
The simple eukaryote Dictyostelium discoideum has been traditionally
used to understand basic principles of cell and developmental biology
and now has also become a useful system in biomedical research.
What are the similarities and differences between D. discoideum and
other simple microbial models such as Saccharomyces cerevisiae?
Which aspects are more advantageous to address in D. discoideum?
Are there any processes or specific proteins present in D. discoideum
that are difficult or impossible to study in other systems? Does it make
sense to use such a simple organism in biomedicine? These and other
questions will be addressed in this chapter, together with some specific
examples in which D. discoideum has proved its potential to model
human disease.
Chapter 2. Genome analysis of social amoebae
Gernot Gloeckner
Genomics is now an indispensible part of the biological sciences.
Today a species description without genome information is incomplete.
This chapter describes the current knowledge on the genome of the
model species D. discoideum. A comparison with other social amoebae
genomes covering the whole breadth of this branch of evolution carves
out driving forces of speciation and the common toolkit of all social
amoebae. The vast evolutionary distance within this branch makes
ortholog detection difficult. While the coding capacity of all social
amoebae is largely conserved, species specific gene family expansions
of proteins for environmental sensing, signaling, and secondary
metabolites provide for diversification. The sequences of the functional
chromosomal elements (telomeres and centromeres) are not conserved,
rather they seem to have underwent severe modifications. Nucleosome
patterns link the social amoebae to other, more sophisti-cated
multicellular systems. Comparative curated databases make this wealth
of genome information accessible and play an important role for the
dissemination of the knowledge on this evolutionary branch.
Chapter 3. Signalling during Dictyostelium development
Cornelis J Weijer
Dictyostelium has become an important model system to study the
molecular details of the signalling pathways controlling gradient
sensing and cell polarisation that control localised activation of the
actin myosin cytoskeleton responsible for evolutionary highly
conserved mechanisms of chemotactic cell movement up chemo-
attractant gradients. 3'-5' cyclic AMP is the chemo-attractant that
controls the chemotactic cell movements that result in aggregation
of up to several hundred thousand cells, slug formation, migration
and fruiting body formation. The coordination of these complex cell
movements require long range cAMP mediated cell-cell signalling
based on periodic initiation of cAMP signals in the aggregation
centre and slug tip and relay by surrounding cells, resulting in
highly dynamic patterns of cAMP wave propagation. Model
calculations have shown that the dynamic feedbacks between
autocatalytic cell-cell cAMP signalling and cAMP mediated
collective chemotactic cell movement result in emergent properties
that readily explain multi cellular morphogenesis. cAMP signalling
not only controls cell movement but also acts as a key morphogen
to control cell differentiation, which in turn affects celltype specific
cell-cell signalling and cell movement, adding an additional layer
of feedback. To fully understand the multicellular morphogenesis
of this organism at the level of cell behaviours it will be needed to
integrate the detailed celltype proportioning mechanisms in models
describing cell-cell signalling and movement. Dictyostelium is likely
to be the first eukaryotic organism where it will be possible to
quantitatively understand how multicellular development and
morphogenesis arise as emergent properties from a few relatively
simple collective cell behaviours.
Chapter 4. The chemotactic compass
Dawit Jowhar and Chris Janetopoulos
Cells have an amazing ability to sense very shallow gradients of
chemoattractants and move directionally. This fundamental
process is critical for development and numerous disease states.
Dictyostelium has emerged as one of the best understood model
systems for elucidating the complex signaling pathways that drive
chemotaxis. This review focuses on the signaling mechanisms
regulating directed migration and discusses the role of polarity
and development on our current understanding of this process.
We highlight new findings using a second chemoattractant, folic
acid and suggest that this chemical cue should be used when a
developmental defect is suspected. We also speculate on recent
studies, which suggest that researchers should use our new
understanding of the temporal and spatial relationships of signaling
and cytoskeletal proteins to guide future experiments.
Chapter 5. Transcriptional Regulators - Dynamic Drivers of
Multicellular Formation, Cell Differentiation and Development
Rafael Rosengarten, Balaji Santhanam, and Mariko Katoh-Kurasawa
In this chapter we examine what is known about the roles of individual
transcription regulators in mediating development in Dictyostelium
discoideum. We present a broad review of the field, covering genetic,
biochemical, molecular and bioinformatic experiments that illuminate
transcriptional regulation in the context of developmental events. We
highlight evidence for evolutionary conservation where it exists, and
have sought to underscore the power of RNA sequencing as a tool
for comparative studies and global analysis. We believe that as next
generation 'omics approaches are more widely applied, we may paint
a more complete picture of the gene regulatory networks governing
dictyostelid development, and gain insight into general evolutionary
processes that shape developmental biology.
Chapter 6. Non-coding RNAs in Dictyostelium discoideum and other
dictyostelid social amoebae
Lotta Avesson, Andrea Hinas, and Fredrik Soederbom
Non-coding (nc)RNAs have recently emerged as ubiquitous and
important regulators of a multitude of different processes, such as
stress response, cell differentiation, infection, and cell death. The
means by which ncRNAs affect these processes are numerous and
diverse, ranging from protein localization to regulation of gene
expression. ncRNA-mediated gene expression control has been the
subject of especially intense study in recent years and shown to occur
through several mechanisms. Different ncRNAs can regulate gene
expression transcriptionally by inducing modification of DNA or
chromatin, or post-transcriptionally by directing cleavage, degradation,
or translational inhibition of messenger (m)RNAs. ncRNAs come in a
broad spectrum of sizes, from ~20 nucleotides (nt) to several thousand
nt, and function in complexes with various proteins that usually exert a
catalytic function while the RNAs act as guides. In Dictyostelia, we
have only started to understand the extent of ncRNA regulation,
mostly from studies in Dictyostelium discoideum, which is the focus
of this chapter.
Chapter 7. Sex in Dictyostelia
Gareth Bloomfield
Dictyostelid social amoebae possess both sexual and parasexual
cycles. In the former, diploid zygotes attract surrounding haploids
and then cannibalise them, forming large immobile structures known
as macrocysts. In the parasexual cycle, amoebae of the same sex
fuse to form diploids that can continue to grow and multiply. Species
with more than two sexes (or mating types) are not unusual among
dictyostelia, and recently the genetic basis for sex determination was
described in the model species Dictyostelium discodeum. Macrocysts
have so far only been observed in a minority of the known species,
and their ecological context and significance is still not understood.
Important questions regarding altruism, genetics, and the basic cell
biology of both the sexual and parasexual cycles remain to be
addressed experimentally, so there remains tremendous scope for
future research.
Chapter 8. A global overview of Dictyostelid Ecology with special
emphasis in North American forest
James C. Cavender
Development in 1965 of a quantitative method for dictyostelid
isolation from soil samples, made possible ecological studies based
on frequency and density of occurrence. Information has subsequently
been obtained on a number of aspects of dictyostelid ecology. I
discuss some of them along this chapter, especially those aspects
studied after Raper's publication in 1984 of his famous book
'The Dictyostelids'. These include dispersal, relative abundance,
optimum conditions for maximum diversity, comparison of temperate
and tropical populations, ecological individuality of species (especially
Dictyostelium discoideum), possible decline in species numbers and
global distribution of Dictyostelia.
Chapter 9. Evolution of Dictyostelid Social Amoebas inferred from
the use of molecular tools
Maria Romeralo and Omar Fiz.
Dictyostelid social amoebas are eukaryotic microbes distributed
all around the globe. As with many other protist groups, one
fundamental and revolutionary event in the study of dictyostelid
(Amoebozoa) systematics has been the use of molecular tools.
This has radically changed our understanding of evolution across
the group and has greatly expanded the potential use of dictyostelids
as model organisms for a wide range of areas including biomedicine,
development, evolutionary biology and molecular ecology. This is
further supported by genome sequencing that has been carried out
for at least one species in each of the major groups. Phylogenomic
data is also essential to pinpointing the origin of diversification of
dictyostelids in terrestrial ecosystems, which is basic for
understanding the evolutionary history across eukaryotic amoeboid
lineages.
Chapter 10. The Evolution of the Cellular Slime Molds
John Tyler Bonner
The cellular slime molds have existed for a very long time; they
have an ancient history. It is surprising that the early morphological
species have not been supplanted and gone extinct, as is the case
for larger organisms; a sizable number of ancient cellular slime
molds still exist today - they are living fossils. This unusual
phenomenon can be explained if one assumes that their morphology
is only weakly affected by natural selection leading to a modest
variation of morphology among the different species. I argue that
the reason for their apparent relative immunity to the effects of natural
selection can be explained by their small size; this is a general rule
among all microorganisms.
Chapter 11. Social selection in the cellular slime moulds
Vidyanand Nanjundiah and Santosh Sathe
Starvation triggers a complex series of intercellular interactions in
the cellular slime mould amoebae. As a result the amoebae aggregate,
form a coherent multicellular structure with division of labour and,
eventually, differentiate into a fruiting body made up of a stalk and a
spore mass. Whether an amoeba dies and forms part of the stalk or
becomes a stress-resistant spore depends both on pre-existing biases
and on post-starvation signalling between amoebae. Mutual
communication permits one amoeba to influence the phenotype, and
therefore affect the fitness, of another. The implication is that social
selection has been a major factor in the evolution of cooperative
behaviour in these amoebae.
Chapter 12. The non-dictyostelid sorocarpic amoebae
Matthew W. Brown, Jeffrey D. Silberman
The social life cycle made famous through research on the
dictyostelids is not an evolutionary innovation that is solely unique
to the dictyostelids. Since 1873 other protistans with a similar life
styles have been recognized. Historically, they have been allied
under various taxonomic classifications over the last 140 years;
however, the recent influx of molecular data has proven that
analogous methods through a social means to form a spore
dispersal structure have independently arose in seven different
lineages of eukaryotic organisms. Here we provide a brief
introduction to each of the amoeboid organisms that display this
behavior focusing on their life histories and the history of the
research on each taxon. These organisms represent one of the
most striking examples of ultimate convergent evolution across
the greatest possible evolutionary distances in eukaryotic
evolution. Research into the molecular and developmental
biology that underlies the evolution of a social life cycle and
formation of a fruiting body is still in its infancy when compared
to the dictyostelids. However, the genomes from several non-
dictyostelid sorocarpic amoebae are soon becoming available,
and a new age of research into these fascinating organisms is
beginning to gain traction.
Submitted by Ricardo Escalante [rescalante@iib.uam.es]
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[End dictyNews, volume 39, number 16]
