Conditional knockout technology research Smad4 gene function in heart development and disease
|School||PLA Military Academy of Medical Sciences|
|Keywords||Smad4 Conditions knockout Myocardial cells Cardiac hypertrophy|
Transforming growth factor-β (TGF-β) superfamily of molecules has an important role in the regulation of cell proliferation, lineage differentiation, migration, adhesion and apoptosis. Smad4 molecule is the center of the TGF-β superfamily of molecular signaling pathways mediated. TGF-β superfamily of molecules in cardiac function in development and disease processes in order to further study, we used the Cre-loxP system developed cardiac myocyte-specific Smad4 gene knockout mice. We established in the cardiac tissue-specific expression of Cre recombinase transgenic mice (α-MHC-Cre). The tissue distribution of the Cre recombinase in the transgenic mice and their mediated gene recombination in vivo study, found that the transgenic mice specific Cre recombinase only in myocardial cells, and in vivo successfully mediated myocardial recombination between LoxP sites in the cell genome, as in the myocardial cells mouse knockout of tools. Myocardial cell-specific Cre transgenic mice with Smad4 conditional gene targeting mice were crossed to obtain a cardiac myocyte-specific Smad4 knockout mice. Smad4 knockout mice embryonic lethality, and the death of about 70% of the knockout mice 5-12 months of age. Smad4 knockout mice began to appear in the 1-month-old myocardial hypertrophy, heart and body weight (HW / BW), heart and tibia length (HW / TL) ratio compared with the control The mice significantly increased MHCβ, ANF, BNP myocardial hypertrophy of iconic molecules in the mutant mice myocardial expression levels were also significantly raised. Histological analysis as well as the separation of the adult mouse cardiomyocytes measurement results show that Smad4 knockout mice myocardial cell size increased significantly. Smad4 knockout mouse heart age significant fibrosis, myocardial mitochondrial damage and myocardial fiber Z with a disordered arrangement of electron microscopy results show pathological changes. M-mode ultrasound and carotid artery catheterization to detect cardiac function and hemodynamic changes found in mice Smad4 gene mutation leads to impaired contractile function of the mouse heart. In order to study the molecular mechanisms of myocardial hypertrophy formed, we also detected the expression of important molecules such as MAPK and PI3K signaling pathway in cardiac hypertrophy mutant mouse hearts and found that MEK1-ERK1 / 2 pathway is activated may lead Smad4 mutant mice myocardial Hypertrophy one of the reasons. Our results provide the first in vivo genetic evidence that Smad4 molecule an important role in the ventricular remodeling process. First proposed reactive changes of myocardial cells to TGF-β molecules may be caused by a mechanism of cardiac hypertrophy. The myocardial cell specific Smad4 knockout mice successfully developed provides an ideal animal model for in-depth study of the pathogenesis of heart disease as well as the new drug screening and pharmacodynamic evaluation.