hypoxia for 10 postnatal days. After the last hypoxic exposure,

all animals were kept for additional 3 months under normoxic

conditions. All experiments were performed on 90-day-old

rats. Ventricular ischemic arrhythmias were assessed on

isolated perfused hearts during 30-min of LAD coronary artery

occlusion. Infarct size was measured on isolated hearts (40-min

regional ischemia; 120-min reperfusion) and on open chest

animals (20-min regional ischemia; 3-h reperfusion).

Perinatal exposure to hypoxia significantly increased

cardiac tolerance to ischemic injury in adult females, as

evidenced by lower incidence and severity of ischemic

ventricular arrhythmias, compared with normoxic group.

The effect of perinatal hypoxia on ischemic arrhythmias in

males was quite opposite. Myocardial infarct size measured in

open-chest animals only was significantly smaller in nor-

moxic females than in normoxic males. Perinatal exposure to

hypoxia had no effect on infarct size in both settings and

genders.

The results support the hypothesis that perinatal hypoxia is a

primary programming stimulus in the heart, which may lead to

gender-dependent changes in cardiac tolerance to acute

ischemia in later adult life. This fact would have important

implications for patients who have experienced prolonged

hypoxemia in early life.

doi:10.1016/j.yjmcc.2006.03.205

191. Characterization of cardiac defects in the l11Jus27

mutant mouse

Karen Mitchell, Kathryn Hentges. Faculty of Life Sciences,

University of Manchester, UK

Congenital heart defects are one of the most common birth

defects. Phenotype driven mutagenesis is a genetic approach

that can be undertaken to isolate mouse models for human

congenital heart defects. Mouse ENU mutagenesis screens

create point mutations throughout the genome and can be

employed to elucidate the function of genes that are conserved

between the mouse and human. Region-specific mutagenesis

screens, which employ balancer chromosomes, can determine

the functional content of a defined chromosomal region based

on the mutant phenotype isolated. We have performed a

balancer mutagenesis screen to isolate mutations on chromo-

some 11. Many of these mutants have cardiovascular defects.

One such mutant; l11Jus27 exhibits a cardiac phenotype

resulting in embryonic lethality at approximately E9.5–

E10.5. To date no mutation that displays a similar cardiac

phenotype has been assigned to chromosome 11, indicating

that a point mutation has been induced in a novel gene essential

for heart development. A combination of meiotic mapping and

deletion mapping has been performed to refine the candidate

region underlying the l11Jus27 mutation. The l11Jus27 mouse

mutant has been studied by whole mount in-situ hybridization

using cardiac-specific markers. Ultrasound analysis has also

been conducted to study the mutant heart in vivo. Mutants such

as l11Jus27 can be used to identify genes involved in heart

development that may contribute to congenital heart defects

in humans.

doi:10.1016/j.yjmcc.2006.03.206

192. Characterization of cardiac and neural

tube defects in the l11Jus8 mouse line

Michael Risley, Kathryn Hentges. Faculty of Life Sciences,

University of Manchester, UK

Congenital heart defects are the most prevalent category of

major birth defects in humans. Highly conserved genetic

pathways that control cardiac development allow the use of

mouse mutants to provide model systems for the character-

isation of abnormal cardiac development. ENU random

mutagenesis screens produce point mutations throughout the

genome and allow the generation of such mouse models.

Random mutagenesis and the use of a balancer chromosome

have identified recessive lethal mutations mapped to mouse

chromosome 11 between the Wnt3 and Trp53 loci, a region

highly conserved with human chromosome 17. This approach

produced a number of mutants with a variety of phenotypes.

One such mutant, the l11Jus8 mouse, has both cardiac and

neural tube defects that result in lethality by E12.0-12.5. In

order to identify the mutant gene associated with the

phenotype, a combination of meiotic mapping and PCR

sequencing of candidate genes have been performed. Histo-

logical staining has been used to study the heart structure of

l11Jus8 mutants. Analysis of cardiac and vascular development

using specific markers was carried out to further analyse

cardiac development in l11Jus8 embryos. Whole-mount in situ

hybridisation using specific neural crest markers was carried

out to analyse the neural tubes of mutant embryos. Mouse

mutant models such as l11Jus8 can be used to identify some of

the genes involved in cardiac development with the overall aim

of providing an insight into possible causes of CHD in humans.

doi:10.1016/j.yjmcc.2006.03.207

193. Genome-wide transcriptional profiling of human

embryonic stem cells differentiating to

cardiomyocytes

A. Beqqali a, J. Kloots a, D. Ward-van Oostwaard a,b, C.

Mummery a,b, R. Passier a,b. a Hubrecht Laboratory, Utrecht,

the Netherlands. b Interuniversity Cardiology Institute of the

Netherlands

Mammals are unable to regenerate their heart after

cardiomyocyte loss caused by myocardial infarction. Human

embryonic stem cells (hESCs) can give rise to functional

cardiomyocytes and therefore have exciting potential as a

source of cells for replacement therapy.

We have previously shown that human embryonic stem cells

can be induced to form beating cardiomyocytes, when co-

cultured with the endoderm-like cell line END-2. These hESC-

ABSTRACTS / Journal of Molecular and Cellular Cardiology 40 (2006) 920–1015990