05-P013 Analysis of chromatin organization of Hox gene cluster by using 3C-based technique

S116

MECHANISMS OF DEVELOPMENT

1 2 6 (2 0 0 9) S1 1 3–S 11 9

commitment and cell cycle exit in multipotent neural progeni-

Prrxl1 isoforms. Transcriptional autoregulation of Prrxl1 is in line

tors, contribute to the specification of neuronal subtype identi-

with its highly restricted expression pattern.

ties, and promote neuronal migration and differentiation. Little is known, however, on the molecular mechanisms underlying

doi:10.1016/j.mod.2009.06.217

the gene regulatory functions of proneural factors. The identity of their target genes, and how do they co-ordinately regulate the neurogenic program is not known. These issues cannot be addressed in the mouse embryo,

05-P013

where the developing nervous system contains a mixture of cells

Analysis of chromatin organization of Hox gene cluster by using

at different developmental stages and with different fates. Neural

3C-based technique

stem cell lines derived from embryonic stem cells or primary neu-

Hyehyun Min, Ji-Yeon Lee, Myoung Hee Kim

ral progenitors represent an excellent model for studying neurogenesis in culture. We have engineered inducible versions of Mash1 and Ngn2, by fusing them to a modified version of the

Department of Anatomy, Embryology Laboratory, Brain Korea 21 project Project for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea

ligand binding domain of the estrogen receptor (ERT2). These quimeric proteins can only induce proneural target genes when acti-

Spatially and temporally programmed expression of the Hox

vated by the ERT2 ligand tamoxifen. When applied to the NS5 cell

genes along the antero-posterior (A-P) anterior–posterior (A–P)

line, this inducible system allows for the efficient generation of

axis is essential for correct pattern formation during embryonic

Mash1/Ngn2 induced neuronal progenitors that differentiate into

development. However, the precise mechanisms controlling the

mature neurons in a synchronized manner.

spatio-temporal expression of Hox genes during development

We are using a combination of locations analyses and expres-

are not fully understood. Accumulating evidence emphasize

sion profiling in order to characterize the transcription program

the importance of intra- and inter-chromosomal interaction

activated by Mash1/Ngn2 in differentiating NS5 cells and to gain

(’’DNA (‘‘DNA looping’’) between regulatory elements and their

novel insights into the molecular mechanisms underlying the

target genes as a beneath mechanism for gene regulation in

function of proneural factors.

the third dimension. Recently, chromosome conformation capture (3C) and its derivative techniques have been developed

doi:10.1016/j.mod.2009.06.216

and opened a new way to study chromosomal folding in the nucleus. To explore genome-wide chromosomal interactions with high resolution, we are now using circular 3C method,

05-P012 Evidence for autoregulation of the homeodomain transcription factor Prrxl1 Filipe Almeida Monteiro1, Carlos Reguenga1, Francois Guillemot2, Diogo Sampaio Castro2, Deolinda Lima1

termed 4C, which allows identification of regions throughout the genome that are physically close to a single locus of interest. In this study, we focused our analysis on mapping of chromatin interactions specific to upstream enhancer sequences of Hoxc8 and Hoxa7, well known regulatory elements specifying expression boundaries, during invitro induction of their expression in

1

Laboratory of Molecular Cell Biology, Faculty of Medicine of Porto and

F9 murine embryonic cells. Here we will present the dynamic

Morphophysiology of the somatosensory System, Instituto de Biologia

pattern of interactions linked with the active transcription sta-

Celular e Molecular, University of Porto, Porto, Portugal

tus of the Hox genes.

2

Division of Molecular Neurobiology, National Institute for Medical

Research, Mill Hill, London, United Kingdom

This work was supported by Korea Science and Engineering Foundation (KOSEF) grant funded by the Korean government (MEST). (grant (MEST) (Grant code: 7-2009-0034)7-2009-0034).

Prrxl1 is a paired-like homeodomain (HD) transcription factor involved in the development/maintenance of both peripheral and

doi:10.1016/j.mod.2009.06.218

spinal cord dorsal horn nociceptive neurons, dedicated to the processing of pain input. Contrary to the broad knowledge on the defects displayed at the cellular level by the absence of Prrxl1, very little is known about the transcriptional network downstream this

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factor. Dragon, a member of the repulsive guidance molecule-

Histone deacetylase-mediated control of forebrain neurogenesis:

related family that is co-expressed with Prrxl1 in embryonic DRG

Analyzing the role of specific HDACs through RNA interference

and spinal cord, is so far the only well established Prrxl1 target

Kathrin Weissmueller, Kerry Lee Tucker

gene. Here we show, by the use of in silico analysis, that the tran-

University of Heidelberg, Heidelberg, Germany

scription factor binding sites on Prrxl1 proximal promoter present a conserved HD putative binding site, suggesting the existence of

Histone deacetylases (HDACs) are a family of chromatin-mod-

an auto-regulatory mechanism controlling Prrxl1 expression. In

ifying enzymes that remove acetyl groups from the lysine tails of

vitro DNA pull-down assays using ND7/23 neuronal cell line over-

core histones, leading to modifications of gene transcription.

expressing Prrxl1 show that Prrxl1 interacts with its own promoter.

They have recently been associated with the control of both

This same interaction was confirmed invivo by chromatin immu-

neuro- and astrogliogenesis. Here, the role of specific HDACs in

noprecipitation (ChIP) performed on mouse dorsal spinal cord tis-

the development of the murine brain is adressed. addressed.

sue at embryonic age 14.5 (E14.5). Gain-of-function experiments in

Pharmacological inhibition of class I and II HDACs with trichosta-

ND7/23 cells reveal differential autoregulatory expression by two

tin A in invitro-differentiating neural precursors derived from