03-P120 Fat4 and Dachsous1 regulate the apical membrane organization in the mouse cerebral cortex

S102

M E C H A N I S M S O F D E V E L O P M E N T 1 2 6 ( 2 0 0 9 ) S 6 7 –S 1 0 6

the actin cytoskeleton. Second, b-catenin is the intracellular

Pals1 complex in organizing the apical membrane architecture

signal transducer of canonical Wnt signaling and activates

of neural progenitor cells.

canonical Wnt target genes. b-catenin null mice die at E7.5. Since the conditional loss of b-catenin function in vivo does

doi:10.1016/j.mod.2009.06.172

not distinguish between adhesion and signaling, it is unclear whether the knock-out phenotype is due to defects in signaling, adhesion or both. Our aim is to generate conditional alleles for functionally mutant b-catenin isoforms. With the help of such signaling or adhesion impaired isoforms, we want to decipher the functional dualism of b-catenin in vivo. We will conditionally express the b-catenin from the ubiquitously active ROSA26 locus, and simultaneously delete endogenous b-catenin alleles.

03-P121 Expression pattern of proximodistal markers during avian lung development Takashi Miura Kyoto University Graduate School of Medicine, Kyoto, Japan

However, before analyzing mutant b-catenin isoforms, we have to test the suitability of our experimental approach. In a proof

The developing avian lung is formed mainly by branching

of principle experiment, we are studying whether the b-catenin

morphogenesis, but there is also a unique cystic structure, the

knock out phenotype can be rescued by expressing wild-type b-

air sac, in the ventral region. Using predictions from theoretical

catenin from the ROSA26 locus. In vitro, we can show that tar-

models, we have previously shown that the cystic structure

geted b-catenin null cells, derived from ES cells, express b-cate-

comes from fast FGF diffusion in the ventral mesenchyme tissue.

nin

cell

However, it is not still clear how the air sac tissue responds to the

morphology. Furthermore, we successfully generated mice car-

signal and whether the air sac structure comes from proximal or

rying the transgene. Currently, we are investigating the usabil-

distal structure.

on

the

membrane

and

display

wild-type

ES

ity of different Cre-mouse lines in order to generate b-catenin

In the present study, we examined several proximodistal mar-

null mice, which express wild-type b-catenin from the ROSA26

ker genes to elucidate the origin of air sac structure in avian lung.

locus. Ultimately, we want to substitute the wild-type gene with

We examined alpha smooth muscle actin and PCNA for general

our mutant isoforms and decipher the functions of b-catenin

proximo-distal markers, Shh, FGF, BMP4 and beta catenin for dis-

in vivo.

tal markers. We found that some proximal factors (alpha smooth actin) and distal factors (beta catenin, PCNA, Shh) are simulta-

doi:10.1016/j.mod.2009.06.171

neously expressed uniformly in air sac structure. This ambiguous result may reflect the fact that the air sac is evolutionally novel structure and not homologous to existing similar structure.

03-P120 Fat4 and Dachsous1 regulate the apical membrane organization

doi:10.1016/j.mod.2009.06.173

in the mouse cerebral cortex Takashi

Ishiuchi1,2, Kazuyo Misaki1, Shigenobu Yonemura1,

Masatoshi Takeichi1, Takuji Tanoue1,3

03-P122

1

RIKEN Center for Developmental Biology, Kobe, Japan

Molecular interactions and cellular events involved in palatal

2

Graduate School of Biostudies, Kyoto University, Kyoto, Japan

3

Graduate School of Medicine, Kobe University, Kobe, Japan Polarization of the plasma membrane in a cell is fundamen-

rugae development Wern-Joo Sohn1, Hye-In Jung2, Min-A. Choi3, Hitoshi Yamamoto4, Hong-In Shin3, Sang Gyu Lee1, Han-Sung Jung5, Jae-Young Kim2 1

School of Life Science and Biotechnology, Kyungpook National Univer-

tal for its proper functions. Fat and Dachsous cadherins are

sity, Daegu, Republic of Korea

known to regulate cell polarity in Drosophila, but their functions

2

in the vertebrates are poorly understood. Here we present evi-

National University, Daegu, Republic of Korea

dence that mammalian Fat4 and Dachsous1 regulate the apical

3

plasma membrane organization in the mouse embryonic cere-

Dentistry, IHBR, Kyungpook National University, Daegu, Republic of

bral cortex. In neural progenitor cells of the cortex, Fat4 and

Korea

Dachsous1 were concentrated together in a cell–cell contact area

4

positioned more apically than the adherens junction (AJ). These

University School of Dentistry, Chiba, Japan

molecules interacted in a heterophilic fashion, affecting their

5

respective protein levels. We further found that Fat4 associated

Biology, Research Center for Orofacial Hard Tissue Regeneration, Brain

and colocalized with the Pals1 complex whose ortholog in Dro-

Korea 21 Project, Oral Science Research Center, College of Dentistry, Yo,

sophila is well known to regulate the apical-basal polarity or api-

Seoul, Republic of Korea

Department of Biochemistry, School of Dentistry, IHBR, Kyungpook Department of Oral Pathology and Regenerative Medicine, School of

Department of Histology, Cytology and Developmental Anatomy, Nihon Division in Anatomy and Developmental Biology, Department of Oral

cal membrane size. Ultrastructurally, the apical junctions of the progenitor cells comprised the AJ and a stretch of plasma

Palatal rugae, epithelial ridges on secondary palatal shelves,

membrane apposition extending apically from the AJ, which

development showed the specific pattern formation with epithe-

positionally corresponded to the Fat4/Dachsous1-positive zone.

lial differentiation in mice embryonic development. Histological

Depletion of Fat4 or Pals1 abolished this membrane apposition.

and scanning electronic microscopic studies revealed the precise

These findings suggest the importance of the Fat-Dachsous1-

morphological changes of palatal rugae from E12 to E16. Cellular