| Pathological Cardiac Hypertrophy(PCH)is a common process of various cardiac diseases in late clinical stage.It was reported that the prevalence of pathological cardiac hypertrophy worldwide was 0.2%,and 0.18% in China.There were about 1 million patients in China and the occurrence of the disease is increasing year by year.The development of cardiac hypertrophy is a multi-gene involved and multi-channel process.Reports of genetic studies showed that hypertrophic cardiomyopathy is caused by dominant mutations in at least 20 genes so far.Nevertheless,we are still lack of comprehensive and in-depth understanding of the pathogensis of cardiac hypertrophy,and more substantial genetic susceptibility genes remain to be identified.Both Pygo1 and hHole are cardiac specific high expression genes.Our previous study indicated that there was abnormal expression of Pygo1 and hHole in human failing hearts.However,to the best of our knowledge,the potential role of Pygo1 and hHole in heart,especially in cardiac hypertrophy,has not been studied yet.In the present study,we would first analyze the physical and chemical properties of both hHole and Pygo1 by bioinformatics method,and then generate cardiac-specific overexpression mouse models by means of genetic modification in vivo.In this study,we aimed to explore whether hHole and Pygo1 regulate cardiac remodeling,and if any,what the underlying mechanism that may be involved in this process.1.Cardiac-specific over-expression of hHole attenuates isoproterenol-induced hypertrophic remodelingAs a highly expressed genes in heart at both adult and embryo stages,the hHole gene has been discovered for more than ten years.however,the biological function of HOLE has been ignored by peers worldwide.And to the best of our knowledge,the potential role of hHole in heart,especially in cardiac hypertrophy,remains unknown yet.Structural analysis in our previous study indicated that the N-terminal region of HOLE protein contained a ERK D-domain motif(a binding site of ERK)and proline-rich sequences(PXXP)in C-terminal region.Both ERKs D-domain motifs and proline-rich sequence motifs of HOLE protein functioned as inhibitors of ERKs signaling pathways.Besides,there were also reports that hHole with insertion-deletion(GCC/-)of SNP rs10569304 in the Southern Chinese population was correlated with higher risk of suffering from congenital heart disease(CHD).It seems that the role of hHole in heart can be predicted.Our previous study also showed that the hHole(TMEM121)mRNA expression levels were significantly increased in DCM hearts,and further experiments indicated that both mRNA and protein expressionlevels of h Hole were substaintal upregulated in murine failing hearts and hypertrophical neomatal rat cardiomyocytes.It was hypothesized that hHole might play an important role in cardiac hypertrophy.To study the role of hHole in the development of pathological cardiac hypertrophy,we first analyzed the physical and chemical properties of h Hole by bioinformatics method.Secondly,to further study and verify the functional role of hHole,we generated cardiac-specific overexpression of hHole mouse model using genetic modification in vivo for the first time,and found that hHole transgenic(TG)mice were healthy and showed no apparent morphological/pathological cardiac abnormalities under basal conditions.While the hHole TG mice exhibited resistance to ISO-induced cardiac hypertrophy compared with wild-type(WT)mice,as shown by slight changes in cell size,minor myocardial fibrosis,and smaller alteration in markers of cardiac hypertrophy.These results fully demonstrated that hHole may be a key molecule in the developmemt of HCM after ISO-induction.This is,to the best of our knowledge,an important in vivo Biological function of hHole revealed for the first time.To further investigate the molecular mechanism by which hHole exerts its anti-hypertrophic effect,we first evaluated the mRNA expression level of members of MAPK signaling in WT or TG mouse heart in response to pathological stimuli.Both mRNA levels of ERK1 and ERK2 were significantly blunted in TG mice heart in response to ISO compared to WTmice in response to ISO,while no statistically significant difference was found in JNK or P38 in TG mice heart in response to ISO induction.Furthermore,western blotting results revealed that phosphorylated ERK1/2 significantly increased in WT mice in response to ISO,and so did total ERK1/2 levels.Whereas both phosphorylated ERK1/2 and total ERK1/2 protein were blunted in TG mouse heart in response to ISO as compared to that in the WT mice.These results suggested that hHole might regulate cardiac remodeling in vivo in response to pathological stimulus by antagonizing ERK signaling through both transcriptional and post-translational mechanisms.2.Cardiac-specific overexpression of Pygo1 regulate pathological cardiac hypertrophy autonomouslyGenetic studies in Drosophila have identified the Pygopus(Pygo)gene as critical component of canonical Wnt signaling.In vertebrate,Pygopus is mainly involving in the regulation of tissue development,chromatin remodeling and transcriptional activation,with two orthologs of Drosophila Pygopus,Pygopus1(Pygo1)and Pygopus2(Pygo2).In adult mice,Pygo2 is widely expressed in various tissues,while Pygo1 is mainly expressed in heart.While the role of Pygo1,especially in adult heart has not yet been studied and remains completely unknown.Cardiac-specific high expression of Pygo1 raising the possibility that Pygo1 might regulate cardiac hypertrophy.Significant up-regulation of Pygo1 expression was observed in human failing hearts in our present study.And in animal model of cardiac hypertrophy,there was a consistent up-regulation of both mRNA and protein expression level of Pygo1 and fetal genes including ANF,?-MHC and SK-?-actin.Further research in cultured cardiomyocytes in vitro also indicated that overexpression of Pygo1 promted enlargement of cardiac myocyte area and up-regulation of hypertrophic marker genes;while cardiac hypertrophy induced by ISO or fetal bovine serum could be markedly blunted in cells transfected with Pygo1-RNAi.These data suggested that Pygo1 may play a key role in the development of HCM.To study the functional role of Pygo1,we first analyzed the physical and chemical properties of Pygo1 by bioinformatics method.Secondly,to verify the functional role of Pygo1 in vivo,we generated cardiac-specfic overexpression of Pygo1 mouse model under the promoter of ?-MHC.Preliminary study indicated that the mRNA expression level of hypertrophic maker genes including ANP,?-MHC and sk-?-actin increased significantly in TG mice without any Pathological hypertrophic stimulation,accompanied with size enlargement of cardiac myocyte area and age-related myocardial fibrosis.Our research demonstrated for the first time that overexpression ofPygo1 was sufficient to induce cardiac hypertrophy,but the underlying mechanisms that mediate cardiac hypertrophy remain elusive.The molecular mechanism of pathological cardiac hypertrophy is a difficult endeavor,we analyzed the physical and chemical properties of hHole and Pgyo1 by bioinformatics method for the first time,and further investigate the potential role in cardiac hypertrophy in vivo.Our data suggested that hHole may regulate cardiac remodeling in vivo in response to pathological stimulus by antagonizing ERK signaling through both transcriptional and post-translational mechanisms.And overexpression of Pygo1 could regulate cardiac hypertrophy autonomously.New findings from further research will provide new insights into intervention in HCM.Future study on the mechanism underlying HCM would have profound implication not only for the management of HCM but also for the prevention of heart failing. |
PDF Full Text Request