Page 66 - Mouse Molecular Genetics

Full Abstracts
Program number is above title. Author in bold is the presenter.
66
yellow fluorescent protein. We have used the
CBFRE::H2B-Venus
construct to generate transgenic ES cells and a strain of
transgenic mice designed to report a transcriptional readout of Notch activity.
Characterization of embryonic and adult stages of the resulting
CBFRE::H2B-Venus
strain reveal discrete and specific
expression of the transgene at previously characterized and uncharacterized sites of Notch signaling. Our current validation of
the
CBFRE::H2B-Venus
strain will be presented and should allow us to determine whether it faithfully reports Notch activity at
single cell resolution
in vivo
.
Models of Human Disease
93
Genetic deletion of p66
Shc
adaptor protein leads to increased myocardial infarction size. Alexander Akhmedov
1
,
Vincent
Braunersreuther
2
,
Fabrizio Montecucco
2
,
Philip Jakob
1
,
Giovanni G. Camici
1
,
Francois Mach
2
,
Thomas F. Luescher
1
. 1)
Institute
of Physiology, University of Zurich, Zurich, Switzerland; 2) Division of Cardiology, Faculty of Medicine, Foundation for
Medical Researches, Geneva University Hospitals.
Background
-
Formation of reactive oxygen species (ROS) contributes to many pathophysiological processes. Although ROS
production is also involved in some physiological processes, the imbalance between their generation and removal, i.e. oxidative
stress, plays a major role in particular in myocardial injury caused by ischemia-reperfusion (I/R). The mammalian Shc locus
encodes three Shc isoforms: p46
Shc
,
p52
Shc
and p66
Shc
.
The p66
Shc
is not involved in mitogenic signals as p46
Shc
/
p52
Shc
,
but it
functions as a critical mediator of intracellular oxidative signal transduction. Various studies relate p66
Shc
to cardiovascular
disease; however, few data are available on the role of p66
Shc
in myocardial I/R.
Methods and Results
- 8-12-
week-old male p66
Shc
deficient (
p66
Shc-/-
)
mice on C57Bl/6 pure background together with
corresponding C57Bl/6 wild-type (WT) control mice were subjected in vivo to different durations of ischemia (up to 60 min)
followed by 24h of reperfusion. Infarct size was assessed morphologically and by MRI. After 30 min of ischemia,
P66
Shc-/-
mice
developed markedly larger infarcts as compared to WT (infarct size [I]/area at risk [AAR]: 20.465.02 % vs. 7.721.31%, n=12-14,
p 0.05). This effect was confirmed by measurement of serum cardiac troponin I (cTnI).
P66
Shc-/-
mice showed elevated serum
levels of cTnI as compared to WT controls at 24 h of reperfusion (27.235.51 ng/ml vs. 10.051.3 ng/ml, n=13, p 0.05). However,
by increasing ischemia duration to either 45 or 60 min infarct size did no longer differ between
p66
Shc-/-
and WT mice. Moreover,
differently from WT, infarct size in
p66
Shc-/-
was not significantly larger with increasing duration of ischemia (from 30 to 60
min).
Conclusions
-
Our data suggest that genetic deletion of p66
Shc
leads to an increased sensitivity to myocardial infarction with
larger infarcts with shorter, but not prolonged ischemia. Therefore, activation of p66
Shc
may provide resistance to ischemia and
represent a novel therapeutic target in the early phase of myocardial infarction.
94
Endothelial overexpression of LOX-1 protects from
in vivo
arterial thrombosis and modulates TF expression. Alexander
Akhmedov
1
,
Giovani G. Camici
1
,
Simona Stivala
1
,
Erik W. Holy
1
,
Alexander Breitenstein
1
,
Christine Lohmann
1
,
Juerg-Hans
Beer
2
,
Felix C. Tanner
1
,
Christian M. Matter
1
,
Thomas F. Luescher
1
. 1)
Institute of Physiology, University of Zurich, Zurich,
Zurich, Switzerland; 2) Division of Internal Medicine, Kanton Hospital Baden, Switzerland.
Background
-
The hallmark of the initiation of atherosclerotic lesion is foam cell formation, and oxidized LDL (oxLDL) is
believed to play a key role in the initiation of the atherosclerotic process. OxLDL is internalized by several receptors, such as SR-
AI/II, SR-BI, CD36, and CD68. OxLDL is also internalized by endothelial cells, but this uptake depends on receptors other than
the classic scavenger receptors. In 1997, a lectin-like oxidized LDL receptor-1 (LOX-1, OLR1) was identified in bovine aortic
endothelial cells. LOX-1 is a type II membrane glycoprotein with an apparent molecular weight of 50 kDa. It has a C-terminal
extracellular C-type lectin-like domain. This lectin-like domain is essential for binding to oxLDL. Binding of oxLDL to LOX-1
induces several cellular events in endothelial cells, such as activation of transcription factor NF-B, upregulation of MCP-1, and
reduction in intracellular NO, which may trigger the onset of cardiovascular events or accelerate the development of
atherosclerosis.
Methods and Results
-
We generated endothelial-specific
LOX-1
transgenic mice using the
Tie2
promoter (
LOX-1TG
). 12-
week-old male
LOX-1TG
and wild-type (WT) mice were applied for carotid artery thrombosis model.
LOX-1TG
mice developed
carotid artery thrombosis within a mean occlusion time of 36.964.83 min, while WT control mice occluded within a mean time
period of 22.753.87 min (n=10, P 0.05). Initial blood flow in carotid artery did not differ between both groups of mice. Decreased
occlusion time in
LOX-1TG
mice was further associated with decreased tissue factor expression and surface activity as shown by
RT PCR and ELISA. Furthermore,
LOX-1TG
mice showed increased mRNA expression of histone deacetylase SIRT1 in carotid
artery, pointing out that SIRT1 may be involved in the observed downregulation of tissue factor through its known target
transcription factor NF-B.
Conclusions
-
Thus, our data suggest that LOX-1 plays a protective role in the arterial thrombosis and that SIRT1 may be
involved. Hence, modulation of LOX-1 may represent novel therapeutic options for targeting arterial thrombosis.