Plenary abstracts

PL-02

Vernalization – Cold-mediated epigenetic regulation of a

developmental switch

Caroline Dean

John Innes Centre, Norwich, United Kingdom

At a certain stage in their life-cycle plants flower, that is they

undergo the transition from vegetative to reproductive develop-

ment. The correct timing of this transition is crucial for reproduc-

tive success, so the plant integrates multiple environmental and

endogenous signals to judge when to flower. The Dean laboratory

is studying the importance of prolonged cold for flowering, a pro-

cess known as vernalization.

Our current view of the vernalization pathway has been built

up though identification of Arabidopsis mutants and analysis of

the corresponding genes, complemented by chromatin biochem-

istry. The vernalization pathway in Arabidopsis mediates the

silencing of a target – FLC, by a conserved Polycomb mechanism.

The talk will describe our understanding of the triggering of FLC

repression by prolonged cold; the nucleation of chromatin silenc-

ing at a specific site in FLC; and the spreading of the silencing yet

spatial restriction to FLC. We are aiming to describe this epige-

netic silencing in a quantitative model and our efforts to date will

be presented.

Arabidopsis accessions have adapted to a wide range of lati-

tudes and climates. We are studying whether variation in vernal-

ization has contributed to this adaptation and have found that

molecular variation at FLC is an important component. Our cur-

rent understanding of this variation, its evolutionary origins

and ecological significance will be discussed.

doi:10.1016/j.mod.2009.06.1073

PL-01

Patterning transcription and cell shape change in the Drosophila

embryo

Eric Wieschaus

Princeton University, New Jersey, United States

With the first three hours of development, the Drosophila

embryo establishes an precise pattern of transcription factors

that divides the blastoderm into groups of cells destined to form

different organs and tissues in the adult. Along the dorsal ven-

tral axis, the first and perhaps most important of these cell fate

decisions is the establishment of mesoderm controlled by

expression of Twist and Snail. The immediate response of these

cell fates decisions is the formation of the ventral furrow and

involves re-organization of the cytoskeleton, adhesion and

motor activities to achieve distinct shape. These individual cell

behaviors rapidly transform the global morphology of the

embryo. In my talk I will discuss the quantitative relationship

between the initial transcription profiles, the visible re-organiza-

tion of the actin and myosin II cytoskeletons, the changes in

adhesive junctions and the distribution of mechanical forces

that control cell shape.

doi:10.1016/j.mod.2009.06.1074

PL-06

How to generate neurons in the adult mammalian brain – Fate

determinants of neurogenesis from glia

Magdalena Goetz

Helmholtz Zentrum Munchen, Munich, Germany

To understand the fate determinants that regulate adult neu-

rogenesis, we have isolated adult stem cells and their progeny

from the adult neurogenic niche and performed transcriptome

analysis in comparison to progenitors and glial cells outside this

niche. This comparative expression analysis yielded interesting

similarities with neurogenic radial glial cells, including a novel

nuclear protein whose function will be discussed. Also known

fate determinants such as the transcription factor Pax6 share a

potent neurogenic role in radial glial cells during development

and in adult neurogenesis of olfactory bulb interneurons. For

its potent neurogenic role in adult neurogenesis, interaction of

Pax6 with a SWI/SNF chromatin remodeling factor is essential

and inducible deletion of Brg1 like Pax6 in adult neural stem

cells causes a fate switch from neurogenesis to gliogenesis.

Interestingly, Pax6 has further subsequent roles in adult neuro-

genesis by distinct molecular mechanisms. It is involved in

specifying neuronal subtypes in adult neurogenesis by interac-

tion with the transcription factor Dlx2 and regulates the survival

of fully differentiated postmitotic dopaminergic interneurons in

the olfactory bulb via a distinct DNA-binding domain as the one

implicated in its former two functions. Finally, these molecular

mechanisms indeed allow reprogramming of glial cells towards

injury even from adult glial cells local to the injury site as will

be presented.

doi:10.1016/j.mod.2009.06.1075

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 1 – S 3

ava i lab le a t www.sc iencedi rec t . com

journal homepage: www.elsevier .com/ locate /modo