the miRNA and its target mRNA involves a 7 nt seed region at the

miRNA 5 end being fully complementary to the target mRNA, with

binding of the 3 miRNA end varying. Many predictive algorithms

have been produced to identify potential miRNA-target pairs.

However many ignore full and near-full complementarity miR-

NA-mRNA pairs as they are considered unusual or potential false

positives. However miRNA-mRNA pairs of this nature have been

previously verified as functional in regulating a Hox gene (Yekta

etal., 2004). Here we conducted a bioinformatics exploration of

the possible full and near-full (to a maximum of 3 GU wobbles)

miRNA-mRNA interactions across a number of different species

(mouse, rat, human, chimp). We then assessed the candidate miR-

NA-mRNA pairs for their quality as probable targets with a specific

focus in their possible involvement in developmental pathways.

doi:10.1016/j.mod.2009.06.014

01-P014

Complement and genomic distribution of miRNAs in deutero-

stomes: Conservation and diversification of the miRNA regulatory

network

Florent Campo-Paysaa1, Marie Smon1, Kevin Peterson2,

Michael Schubert1

1IGFL - ENS Lyon, Lyon, France2Dartmouth College, Hanover, NH, United States

Extensive studies have emphasized the role of non-coding

RNAs (ncRNAs) in the control of a wide range of cellular processes,

through the regulation of expression of genes or genomic loci. In

particular, microRNA (miRNA) genes that encode 22 base-long

mature RNAs have been proposed as key factors in the evolution

and diversification of animal body plans, for example at the inver-

tebrate–vertebrate transition. Thus, lineage-specific radiations of

miRNA families might have triggered the apparition of develop-

mental and thus morphological novelties during evolution. To test

this hypothesis, we investigated and compared the miRNA com-

plements in several deuterostomes. We based our analysis on data

from three invertebrate deuterostomes: two ambulacrarians (the

sea urchin Strongylocentrotus purpuratus and the acorn worm Sac-

coglossus kowalewskii) and one chordate (the cephalochordate

Branchiostoma floridae). We established the complete set of miRNAs

in these species, analyzed their genomic organization and com-

pared it to human data, used as an outgroup. Our results show

that previous studies have significantly underestimated the total

number of miRNA families in non-vertebrate deuterostomes and

that lineage-specific expansions of miRNA families, at least some

of which massive, are detectable in different deuterostome lin-

eages. Furthermore, the identification of several well-conserved

syntenic regions containing miRNA genes suggests the presence

of a miRNA-dependent regulatory network common to at least

all deuterostomes. Finally, we propose a scenario for the evolution

of novel miRNAs, which is based on the observation that almost

half of the miRNA genes identified in our study are located in

intronic regions of protein coding genes.

doi:10.1016/j.mod.2009.06.015

01-P015

Dissected leaf development in Cardamine hirsuta

Huw Jenkins, Alexander Tattersall, Michalis Barkoulas, Evagelia

Kougioumoutzi, Angela Hay, Miltos Tsiantis

Department of Plant Sciences, University of Oxford, United Kingdom

How genetic pathways act to sculpt morphology, and how

such pathways can be modified during evolution to produce

new forms are key questions in developmental biology. Plant

leaves offer an attractive opportunity to study these problems

as they occur in a wide variety of different forms. For instance

leaves may be simple, where the leaf blade is undivided, or dis-

sected, where the blade is divided into distinct leaflets. Cardamine

hirsuta has dissected leaves and is a close relative of the simple

leaved model species Arabidopsis thaliana. Forward genetic

screens in Cardamine have identified a range of mutants with

altered leaf dissection, from those with simple leaves like Arabid-

opsis to those which have increased leaflet number. The identifi-

cation and characterisation of these mutants is leading to an

understanding of how regulatory genes interact to control leaflet

development. Furthermore, the comparative study of how these

genes act between Cardamine and Arabidopsis is leading to an

emerging understanding of how different leaf forms may have

arisen during evolution.

doi:10.1016/j.mod.2009.06.016

01-P016

The Drosophila LIM-only, dLMO transcription factor that controls

sensory organ and wing developments, is regulated by mir-9a

Inna Biryukova, Jolle Asmar, Claudine Ackermann, Nadine

Arbogast, Pascal Heitzler

IGBMC, Strasbourg, France

The Drosophila LIM only transcription factor, dLMO controls cell

proliferation and apoptosis, and its human counterpart acts as

protooncogene during hematopoiesis. dLMO gene encodes two

isoforms, dLMO-RA and dLMO-RB, besides their biological contri-

butions are poorly understood. We demonstrated that dLMO- and

dLMO-RA-deletions have similar phenotypes, lacking some tho-

racic and wing margin sensory organs, while a dLMO-RB-deletion

has normal sensory organs. At early stages of peripheral nervous

system development, dLMO-RA is expressed in clusters of cells

(proneural clusters). However, later dLMO expression is excluded

from the sensory organ precursors. We demonstrated that

dLMO-PA functions as a coactivator of Pannier, the GATA tran-

scription factor, to promote expression of proneural activators,

Achaete and Scute. Interestingly, dLMO-RA but not dLMO-RB is

regulated through common 3 untranslated region (3 UTR). We

found that a small non-coding endogenous RNA, microRNA,

mir-9a belonging to the mir-9 family, regulates steady level of

dLMO during development. Deletions of the 3 UTR, including the

mir-9a site, generate gain-of-function dLMO mutants (Beadex)

associated with high levels of dLMO-RA mRNA and protein. Bea-

dex mutants lack wing margins, a phenotype also observed in null

mir-9a mutants. We found that mir-9a and dLMO are co-expressed

S55M 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 5 1 – S 5 9