Tài liệu Báo cáo khoa học: Diego and friends play again Old planar cell polarity players in new

REVIEW ARTICLE

Diego and friends play again

Old planar cell polarity players in new positions

Jo´ zsef Miha´ly, Tama´ s Matusek and Csilla Pataki

Institute of Genetics, Biological Research Center, Hungarian Academy of Sciences, Szeged, Hungary

Functional tissues are comprised of polarized cell

types. Cellular polarization can be manifested in

many different ways, depending on the orientation

and axis of polarity. Well known examples include

the Drosophila ovary and embryo, where all major

body axes are determined in a single cell; neuronal

cells that typically exhibit axonal-dendritic polarity

and epithelial cells that are characterized by apical￾basal polarity. In many instances, however, tissue dif￾ferentiation also requires the coordination of cell

polarity within the plane of a tissue – a feature

referred to as planar cell polarization (PCP) or tissue

polarity for short. Although PCP can be observed

throughout the animal kingdom (vertebrate examples

include fish scales, bird feathers and hairs in mam￾mals, or the neurosensory epithelium in the inner

ear), the regulation of such coordinated cell polariza￾tion events has been best studied in the fruitfly, Dro￾sophila melanogaster.

PCP in flies is most evident in the wing, which is

covered by uniformly polarized, distally pointing hairs,

in the epidermis, where sensory bristles and trichomes

point to the posterior, and in the eye, where PCP

results in a mirror symmetry arrangement of the

ommatidia or unit eyes. Polarization in these tissues is

controlled by the gene products of the PCP genes,

mutants of which impair planar organization. Some of

the PCP genes, which have been placed into the core

group, appear to affect polarity in all of the tissues,

whereas others function in a tissue-specific way. The

core group includes the seven-pass transmembrane

receptor frizzled (fz), the cytoplasmic signal transducer

dishevelled (dsh), the cytoplasmic LIM domain protein

prickle (pk), the atypical cadherin flamingo (fmi), the

four-pass transmembrane protein strabismus (stbm)

and the ankyrin repeat protein diego (dgo) [1–9]. Gen￾etic analysis of the PCP genes indicates that polarity

establishment can be subdivided into three major steps.

Keywords

Diego; Drosophila; Four-jointed; inturned;

tissue polarity

Correspondence

J. Miha´ly, Institute of Genetics, Biological

Research Center, Hungarian Academy of

Sciences, H-6726 Szeged, Temesvari krt.

62, Hungary

Fax: +36 62 433503

Tel: +36 62 599687

E-mail: [email protected]

(Received 21 February 2005, accepted

27 April 2005)

doi:10.1111/j.1742-4658.2005.04758.x

The formation of properly differentiated organs often requires the planar

coordination of cell polarization within the tissues. Such planar cell polar￾ization (PCP) events are best studied in Drosophila, where many of the key

players, known as PCP genes, have already been identified. Genetic analy￾sis of the PCP genes suggests that the establishment of polarity consists of

three major steps. The first step involves the generation of a global polarity

cue; this in turn promotes the second step, the redistribution of the core

PCP proteins, leading to the formation of asymmetrically localized signa￾ling centers. During the third step, these complexes control tissue-specific

cellular responses through the activation of cell type specific effector genes.

Here we discuss some of the most recent advances that have provided

valuable new insight into each of the three major steps of planar cell

polarization.

Abbreviations

MF, morphogenetic furrow; PCP, planar cell polarization.

FEBS Journal 272 (2005) 3241–3252 ª 2005 FEBS 3241