dictyNews
Electronic Edition
Volume 29, number 2
July 13, 2007

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Abstracts
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Induction of cAMP signaling and spore differentiation in
Dictyostelium development by a novel protein, DIA2

Kaori Hirata, Aiko Amagai, Soo-Cheon Chae , Shigenori Hirose¤ and 
Yasuo Maeda*

Department of Developmental Biology and Neurosciences, Graduate School of 
Life Sciences, Tohoku University, Aoba, Sendai 980-8578, Japan

*Author for correspondence

 Present address: Department of Pathology, Wonkwang University, Iksan-shi, 
Chonbuk 570-749, South Korea 
¤Present address: Departments of Molecular and Human Genetics, Biochemistry 
and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA


Differentiation, in press

The novel gene dia2 (differentiation-associated gene 2) was originally 
isolated as a gene expressed specifically in response to initial 
differentiation of Dictyostelium discoideum Ax-2 cells. Using dia2AS cells 
in which the dia2 expression was inactivated by the antisense RNA method, 
DIA2 protein was found to be required for cAMP signaling during cell 
aggregation. During late development, the DIA2 protein changed its location 
from the endoplasmic reticulum (ER) to prespore-specific vacuoles (PSVs) 
that are specifically present in prespore cells at the slug. In 
differentiating prestalk cells, however, DIA2 was found to be nearly lost 
from the cells. Importantly, exocytosis of PSVs from prespore cells and the 
subsequent spore differentiation were almost completely impaired in dia2AS 
cells. In addition, spore induction by externally applied 8-bromo cAMP was 
significantly suppressed in dia2AS cells. Taken together these results 
strongly suggested that DIA2 might be closely involved in cAMP signaling 
and spore differentiation as well as in the initiation of differentiation 
during Dictyostelium development.


Submitted by: Yasuo Maeda [ymaeda@mail.tains.tohoku.ac.jp]
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Toward the structure of dynamic membrane-anchored actin networks: 
an approach using cryo-electron tomography.

Guenther Gerisch1 and Igor Weber2

1Max-Planck-Institut fuer Biochemie, Am Klopferspitz 18a, D-82152 Germany
2Rudjer Boskovic Institute, Bijenicka cesta 54, P.O.B.180, 10002 Zagreb, 
Croatia


Cell Adhesion & Migration, in press

In the cortex of a motile cell, membrane-anchored actin filaments assemble 
into structures of varying shape and function. Filopodia are distinguished 
by a core of bundled actin filaments within finger-like extensions of the 
membrane. In a recent paper by Medalia et al. [1]  cryo-electron tomography 
has been used to reconstruct, from filopodia of Dictyostelium cells, the 
3-dimensional organization of actin filaments in connection with the plasma 
membrane. A special arrangement of short filaments converging toward the 
filopodÕs tip has been called a Òterminal coneÓ. In this region force is 
applied for protrusion of the membrane. Here we discuss actin organization 
in the filopodia of Dictyostelium in the light of current views on forces 
that are generated by polymerizing actin filaments, and on the resistance 
of membranes against deformation that counteracts these forces.


Submitted by: Guenther Gerisch [Cgerisch@biochem.mpg.de]
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[End dictyNews, volume 29, number 2]