PDF(Pubmed)
Abstract：
BACKGROUND: Aging is associated with cardiac myocyte loss, sarcopenia, and cardiac dysfunction. Adult cardiac myocytes are postmitotic cells with an insufficient proliferative capacity to compensate for myocyte loss. The canonical WNT (cWNT) pathway is involved in the regulation of cell cycle reentry in various cell types. The effects of the cWNT pathway on the expression of genes involved in cell cycle reentry in the postmitotic cardiac myocytes are unknown.
OBJECTIVE: The aim of the study was to identify genes whose expression is regulated by the β-catenin, the indispensable component to the cWNT signaling, in the postmitotic myocytes.
RESULTS: Cardiac myocyte-specific tamoxifen-inducible MerCreMer (Myh6-Mcm) mice were used to delete the floxed exon 3 or exons 8 to 13 of the Ctnnb1 gene to induce gain-of-function (GoF) or loss-of-function (LoF) the β-catenin, respectively. Deletion of exon 3 leads to the expression of a stable β-catenin. In contrast, deletion of exons 8-13 leads to the expression of transcriptionally inactive truncated β-catenin, which is typically degraded. GoF or LoF of the β-catenin was verified by reverse transcription-polymerase chain reaction (RT-PCR), immunoblotting, and immunofluorescence. Myocyte transcripts were analyzed by RNA-Sequencing (RNA-Seq) at 4 weeks of age. The GoF of β-catenin was associated with differential expression of ~1700 genes, whereas its LoF altered expression of ~400 genes. The differentially expressed genes in the GoF myocytes were enriched in pathways regulating the cell cycle, including karyokinesis and cytokinesis, whereas the LoF was associated with increased expression of genes involved in mitochondrial oxidative phosphorylation. These findings were validated by RT-PCR in independent samples. Short-term GoF nor LoF of β-catenin did not affect the number of cardiac myocytes, cardiac function, myocardial fibrosis, myocardial apoptosis, or adipogenesis at 4 weeks of age.
CONCLUSIONS: Activation of the β-catenin of the cWNT pathway in postmitotic myocytes leads to cell cycle reentry and expression of genes involved in cytokinesis without leading to an increase in the number of myocytes. In contrast, suppression of the β-catenin modestly increases the expression of genes involved in oxidative phosphorylation. The findings provide insights into the role of β-catenin of the cWNT pathway in the regulation of cell cycle reentry and oxidative phosphorylation in the postmitotic cardiac myocytes.
OBJECTIVE: The aim of the study was to identify genes whose expression is regulated by the β-catenin, the indispensable component to the cWNT signaling, in the postmitotic myocytes.
RESULTS: Cardiac myocyte-specific tamoxifen-inducible MerCreMer (Myh6-Mcm) mice were used to delete the floxed exon 3 or exons 8 to 13 of the Ctnnb1 gene to induce gain-of-function (GoF) or loss-of-function (LoF) the β-catenin, respectively. Deletion of exon 3 leads to the expression of a stable β-catenin. In contrast, deletion of exons 8-13 leads to the expression of transcriptionally inactive truncated β-catenin, which is typically degraded. GoF or LoF of the β-catenin was verified by reverse transcription-polymerase chain reaction (RT-PCR), immunoblotting, and immunofluorescence. Myocyte transcripts were analyzed by RNA-Sequencing (RNA-Seq) at 4 weeks of age. The GoF of β-catenin was associated with differential expression of ~1700 genes, whereas its LoF altered expression of ~400 genes. The differentially expressed genes in the GoF myocytes were enriched in pathways regulating the cell cycle, including karyokinesis and cytokinesis, whereas the LoF was associated with increased expression of genes involved in mitochondrial oxidative phosphorylation. These findings were validated by RT-PCR in independent samples. Short-term GoF nor LoF of β-catenin did not affect the number of cardiac myocytes, cardiac function, myocardial fibrosis, myocardial apoptosis, or adipogenesis at 4 weeks of age.
CONCLUSIONS: Activation of the β-catenin of the cWNT pathway in postmitotic myocytes leads to cell cycle reentry and expression of genes involved in cytokinesis without leading to an increase in the number of myocytes. In contrast, suppression of the β-catenin modestly increases the expression of genes involved in oxidative phosphorylation. The findings provide insights into the role of β-catenin of the cWNT pathway in the regulation of cell cycle reentry and oxidative phosphorylation in the postmitotic cardiac myocytes.
摘要：
背景：衰老与心肌细胞丢失有关，少肌症,和心脏功能障碍。成年心肌细胞是有丝分裂后的细胞，其增殖能力不足以补偿心肌细胞的损失。典型的WNT（cWNT）途径参与各种细胞类型中细胞周期重新进入的调节。cWNT途径对有丝分裂后心肌细胞中细胞周期重新进入相关基因表达的影响尚不清楚。
目的：本研究的目的是鉴定表达受β-catenin调节的基因，CWNT信令不可或缺的组成部分，有丝分裂后的心肌细胞。
结果：使用心肌细胞特异性他莫昔芬诱导的MerCreMer（Myh6-Mcm）小鼠删除Ctnnb1基因的Floxed外显子3或外显子8至13，以诱导β-catenin的功能获得（GoF）或功能丧失（LoF），分别。外显子3的缺失导致稳定的β-连环蛋白的表达。相比之下,外显子8-13的缺失导致转录失活的截短β-catenin的表达，通常是退化的。通过逆转录聚合酶链反应（RT-PCR）验证了β-catenin的GoF或LoF，免疫印迹,和免疫荧光。在4周龄时通过RNA-测序(RNA-Seq)分析心肌细胞转录物。β-catenin的GoF与~1700基因的差异表达有关,而其LoF改变了约400个基因的表达。GoF肌细胞中差异表达的基因富集在调节细胞周期的途径中，包括核分裂和胞质分裂，而LoF与线粒体氧化磷酸化相关的基因表达增加。通过RT-PCR在独立样品中验证了这些发现。β-catenin的短期GoF或LoF不影响心肌细胞的数量，心功能,心肌纤维化，心肌细胞凋亡，或4周龄时的脂肪生成。
结论：有丝分裂后肌细胞中cWNT途径的β-catenin的激活导致细胞周期重新进入和参与胞质分裂的基因表达，而不导致肌细胞数量增加。相比之下,β-连环蛋白的抑制适度增加参与氧化磷酸化的基因的表达。这些发现为cWNT途径的β-catenin在有丝分裂后心肌细胞中细胞周期再进入和氧化磷酸化的调节中的作用提供了见解。
目的：本研究的目的是鉴定表达受β-catenin调节的基因，CWNT信令不可或缺的组成部分，有丝分裂后的心肌细胞。
结果：使用心肌细胞特异性他莫昔芬诱导的MerCreMer（Myh6-Mcm）小鼠删除Ctnnb1基因的Floxed外显子3或外显子8至13，以诱导β-catenin的功能获得（GoF）或功能丧失（LoF），分别。外显子3的缺失导致稳定的β-连环蛋白的表达。相比之下,外显子8-13的缺失导致转录失活的截短β-catenin的表达，通常是退化的。通过逆转录聚合酶链反应（RT-PCR）验证了β-catenin的GoF或LoF，免疫印迹,和免疫荧光。在4周龄时通过RNA-测序(RNA-Seq)分析心肌细胞转录物。β-catenin的GoF与~1700基因的差异表达有关,而其LoF改变了约400个基因的表达。GoF肌细胞中差异表达的基因富集在调节细胞周期的途径中，包括核分裂和胞质分裂，而LoF与线粒体氧化磷酸化相关的基因表达增加。通过RT-PCR在独立样品中验证了这些发现。β-catenin的短期GoF或LoF不影响心肌细胞的数量，心功能,心肌纤维化，心肌细胞凋亡，或4周龄时的脂肪生成。
结论：有丝分裂后肌细胞中cWNT途径的β-catenin的激活导致细胞周期重新进入和参与胞质分裂的基因表达，而不导致肌细胞数量增加。相比之下,β-连环蛋白的抑制适度增加参与氧化磷酸化的基因的表达。这些发现为cWNT途径的β-catenin在有丝分裂后心肌细胞中细胞周期再进入和氧化磷酸化的调节中的作用提供了见解。
