dictyNews Volume 40 Number 19

eZine lover (@eZine)

Published in 

Dicty News

 · 11 months ago

dictyNews 
Electronic Edition 
Volume 40, number 19 
August 8, 2014 

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. 

Follow dictyBase on twitter: 
http://twitter.com/dictybase 

 
========= 
Abstracts 
========= 

 
TITLE: Comparison of Dictyostelium LvsB and endosomal fission defect  
mutants support a fusion regulatory role for LvsB 

AUTHORS: Kristin Falkenstein and Arturo De Lozanne 
Section of Molecular Cell & Developmental Biology 
and Institute for Cellular and Molecular Biology, 
University of Texas at Austin, Austin, TX 78712. 

 
JOURNAL: Journal of Cell Science 

ABSTRACT: Defects in human Lyst are associated with the lysosomal  
disorder Chediak Higashi Syndrome.  The absence of Lyst results in  
the formation of enlarged lysosome related compartments but the  
mechanism for how these compartments arise is not well established.   
Two opposing models have been proposed to explain Lyst function.   
The fission model describes Lyst as a positive regulator of fission  
from lysosomal compartments, while the fusion model identifies Lyst  
as a negative regulator of fusion between lysosomal vesicles. Here  
we used assays that can distinguish between defects in vesicle fusion  
versus fission. We compared the phenotype of Dictyostelium cells  
defective in LvsB, the ortholog of Lyst, with that of two known fission  
defect mutants (µ3 and WASH null mutants).  We found that the temporal  
localization characteristics of the post-lysosomal marker vacuolin, as  
well as vesicular acidity and fusion dynamics of LvsB null cells are  
distinct from those of both µ3 and WASH null fission defect mutants.   
These distinctions are predicted by the fusion defect model and  
implicate LvsB as a negative regulator of vesicle fusion. 

Submitted by Arturo De Lozanne [a.delozanne@utexas.edu] 
ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ 

 
A simple optical configuration for cell tracking by dark-field  
microscopy 

Vlatka Antolovic, Maja Marinovic, Vedrana Filic, Igor Weber 

 
Journal of Microbiological Methods  (2014), pp. 9-11 
DOI information: 10.1016/j.mimet.2014.06.006 
http://authors.elsevier.com/a/1PT8Kc8NxIVdE  
(free download until September 21, 2014) 

We describe a simple optical configuration for dark-field microscopy  
at low magnification, realized with the use of standard microscope  
components. An inherent high contrast makes this method attractive  
for computer-assisted tracking and counting of microorganisms. We  
applied this setup for dark-field microscopy to measure the speed  
of migrating Dictyostelium amoebae. 

Submitted by Vedrana Filic [vedrana.filic@irb.hr] 
ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ 

 
Actin and PIP3 waves in giant cells reveal the inherent length  
scale of an excited state 

Matthias Gerhardt, Mary Ecke, Michael Walz, Andreas Stengl, Carsten Beta,  
and GŸnther Gerisch 

 
Journal of Cell Science, accepted 

The membrane and actin cortex of a motile cell can autonomously  
differentiate into two states, one typical of the front, the other of  
the tail. On the substrate-attached surface of Dictyostelium cells,  
dynamic patterns of front-like and tail-like states are generated that  
are best suited to monitor transitions between these states. To image  
large-scale pattern dynamics independent of boundary effects, we produced  
giant cells by electric-pulse induced cell fusion. In these cells actin  
waves are coupled to the front and back of PIP3-rich bands that have a  
finite width. These composite waves propagate across the plasma membrane  
of the giant cells with undiminished velocity. After any disturbance, the  
bands of PIP3 return to their intrinsic width. Upon collision, the waves  
locally annihilate each other and change direction; at the cell border  
they are either extinguished or reflected. Accordingly, expanding areas of  
progressing PIP3 synthesis become unstable beyond a critical radius, their  
center switching from a front-like to a tail-like state. Our data suggest  
that PIP3 patterns in normal-sized cells are segments of the self-organizing  
patterns that evolve in giant cells. 

Submitted by GŸnther Gerisch [gerisch@biochem.mpg.de] 
============================================================== 
[End dictyNews, volume 40, number 19]