Abstracts - Society for Developmental Biology

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Moreover, our previous studies have shown that KLF13 acts as a cardiac transcriptional activator, and both functionally
and physically interacts with the cardiac master regulator GATA-4. In the current study, we examined KLF13’s mechanism
of action by investigating its transcriptional activity and its partnering profile with other transcription factors on target
genes; we found that KLF13 functionally and physically interacts with several critical cardiac regulators such as Tbx5 and
Nkx2.5. Structure-function studies identified distinct functional domains important for KLF13 DNA-binding and proteinprotein
interaction. Lastly, some mutant proteins associated with congenital heart defects were found to have impaired
interaction with KLF13. These experiments provide novel insight into cardiac transcription and KLF13 mechanisms of
action and suggest that KLF13 may be a genetic modifier of human congenital heart diseases.
Program/Abstract # 293
Essential role for KLF13 in heart development
Yamak, Abir, University of Ottawa, Ottawa, Canada; Hayek, Salim (Emory University, Atlanta, United States); Maharsy,
Wael; Darwich, Rami; Komati, Hiba (University of Ottawa, Ottawa, Canada); Andelfinger, Gregor (Sainte Justine
Hospital, Montreal, Canada); Nemer, Mona (University of Ottawa, Ottawa, Canada)
KLF13 is a member of the Krϋppel-like transcription factors that are important regulators of cell proliferation and
differentiation. Several KLF members are expressed in the heart in a spatial and temporal specific manner. KLF13 is
highly enriched in the developing heart where it is found in both myocardial and endocardial cells. In myocytes, it interacts
with GATA4 and regulates the A- and B-type natriuretic peptide genes, NPPA and NPPB. In xenopus, knock down of
KLF13 causes developmental heart defects which indicate an important role for KLF13 in heart morphogenesis. To test
whether this role is evolutionary conserved in the mammalian heart, we deleted the KLF13 gene in transgenic mice using
homologous recombination. Mice lacking both KLF13 alleles are born at reduced frequency; variable cardiac phenotypes
are observed in these knockouts mainly endocardial cushion defects including “Goose-neck” deformity and atrioventricular
(AV) valvular abnormalities. Epithelial-mesenchymal transformation (EMT) seems to be affected in these mice and they
have reduced proliferation in the AV cushion. Surviving KLF13 null mice have several structural cardiac anomalies. NPPB
mRNA levels are decreased by 50% and expression of several cardiac genes is altered. Our data uncover a role for a new
class of transcription factors in heart formation and point to KLF13 as a potential congenital heart disease causing gene.
Program/Abstract # 294
Akt mediates acute alcohol inotropic effects on the heart
Haddad, Georges, Howard University, Washington, United States; Walker, Robin; Cousins, Valerie; Umoh, Nsini; Burke,
Mark (Howard University, Washington, DC, United States)
Cardiovascular disease is among the major causes for increased morbidity and mortality rates. High alcohol consumption
may lead to cardiomyopathy, cardiac arrhythmias, and a suite of other disorders. Previous studies in our lab have linked the
AKT/PI3K pathway to cardiovascular disease. In this study we investigate the role of AKT gene expression (RT-PCR) that
contributes to changes in cardiac contraction (Ionoptix imaging) with acute alcohol retrograde coronary perfusion of the
heart. Our results demonstrate that AKT expression is diminished with Low alcohol (LA) exposure; however, high alcohol
(HA) treatment has increased expression over LA exposure. LA increased cellular and sarcomeric contraction associated
with increase in the velocity of contraction. Relaxation and calcium sequestration was also improved by LA. Inhibition of
PI3K negated the contractile effects of LA, but enhanced the relaxation ones. HA decreased the strength of contraction and
increased speed of relaxation and calcium sequestration. Our data suggest that LA improves cardiac function through a
reduction of the Akt pathway; furthermore, HA has detrimental inotropic effect through an elevation of the Akt gene
expression. Also, PI3K/Akt pathway seems to regulate the lusitropic effects of both LA and HA.
Program/Abstract # 295
A Xenopus-based system to study the biochemical and genetic etiology of Fetal Alcohol Spectrum Disorder
Fainsod, Abraham, Faculty of Medicine, Hebrew University Developmental Biology and Cancer Research, Jerusalem,
Israel; Shabtai, Yehuda (Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel)
Exposure of human embryos to ethanol results in a high incidence of Fetal Alcohol Spectrum Disorder (FASD). Children
with FASD can exhibit facial dysmorphology, microcephaly, short stature, central nervous system, neurodevelopmental
abnormalities, behavioral and psychological anomalies. We used Xenopus embryos to study the mechanism underlaying
the developmental malformations in alcohol (ethanol)-treated embryos. Ethanol and its detoxification compete with the
biosynthesis of retinoic acid resulting in abnormally low levels. The strongest effect of this competition takes place close to
the onset of gastrulation centering on the retinaldehyde dehydrogenase 2 (Raldh2; Aldh1a2) activity in Spemann’s
organizer. There is great difficulty in predicting the phenotype of children exposed to alcohol based solely on mother size,
amount and frequency of alcohol ingested, developmental stage of exposure and other environmental factors. Also