CARF promotes spermatogonial self-renewal and proliferation through Wnt signaling pathway

AbstractCollaborator of ARF (CARF) regulates cell proliferative fate through both p53-dependent and -independent mechanisms. Recently, we reported a new function of CARF as a positive regulator of Wnt signaling. Despite these findings, the physiological function of CARF has not been well studied. Here, we generated CARF knockout mice and found that male CARF−/− mice exhibited significantly impaired fertility and Sertoli-cell-only (SCO) syndrome phenotypes. Further studies revealed that loss of CARF in Sertoli cells led to decreased GDNF expression, which hindered spermatogonial stem cells (SSCs) self-renewal. Meanwhile, CARF loss in undifferentiated spermatogonia impaired their proliferation. These two mechanisms together led to SCO syndrome phenotypes, which could be functionally rescued by pharmacological or genetic reactivation of Wnt signaling. Finally, we identified CARFS351F as a potential pathogenic mutation in an SCO patient. Overall, our findings reveal important roles of CARF in spermatogonial self-renewal and proliferation through the Wnt signaling pathway.

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Silencing of long noncoding RNA HOXA11-AS inhibits the Wnt signaling pathway via the upregulation of HOXA11 and thereby inhibits the proliferation, invasion, and self-renewal of hepatocellular carcinoma stem cells

Experimental & Molecular Medicine ◽

10.1038/s12276-019-0328-x ◽

2019 ◽

Vol 51 (11) ◽

pp. 1-20 ◽

Cited By ~ 2

Author(s):

Jun-Cheng Guo ◽

Yi-Jun Yang ◽

Jin-Fang Zheng ◽

Jian-Quan Zhang ◽

Min Guo ◽

...

Keyword(s):

Hepatocellular Carcinoma ◽

Stem Cells ◽

Stem Cell ◽

Wnt Signaling ◽

Signaling Pathway ◽

Methylation Level ◽

Wnt Signaling Pathway ◽

The Self ◽

Self Renewal

AbstractHepatocellular carcinoma (HCC) is a major cause of cancer-related deaths, but its molecular mechanisms are not yet well characterized. Long noncoding RNAs (lncRNAs) play crucial roles in tumorigenesis, including that of HCC. However, the role of homeobox A11 antisense (HOXA11-AS) in determining HCC stem cell characteristics remains to be explained; hence, this study aimed to investigate the effects of HOXA11-AS on HCC stem cell characteristics. Initially, the expression patterns of HOXA11-AS and HOXA11 in HCC tissues, cells, and stem cells were determined. HCC stem cells, successfully sorted from Hep3B and Huh7 cells, were transfected with short hairpin or overexpression plasmids for HOXA11-AS or HOXA11 overexpression and depletion, with an aim to study the influences of these mediators on the self-renewal, proliferation, migration, and tumorigenicity of HCC stem cells in vivo. Additionally, the potential relationship and the regulatory mechanisms that link HOXA11-AS, HOXA11, and the Wnt signaling pathway were explored through treatment with Dickkopf-1 (a Wnt signaling pathway inhibitor). HCC stem cells showed high expression of HOXA11-AS and low expression of HOXA11. Both HOXA11-AS silencing and HOXA11 overexpression suppressed the self-renewal, proliferation, migration, and tumorigenicity of HCC stem cells in vivo, as evidenced by the decreased expression of cancer stem cell surface markers (CD133 and CD44) and stemness-related transcription factors (Nanog, Sox2, and Oct4). Moreover, silencing HOXA11-AS inactivated the Wnt signaling pathway by decreasing the methylation level of the HOXA11 promoter, thereby inhibiting HCC stem cell characteristics. Collectively, this study suggested that HOXA11-AS silencing exerts an antitumor effect, suppressing HCC development via Wnt signaling pathway inactivation by decreasing the methylation level of the HOXA11 promoter.

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Polycomb Repressive Complex 1 Enhances HSC Self-Renewal through Repressing the Canonical Wnt Signaling Pathway

Blood ◽

10.1182/blood.v126.23.2378.2378 ◽

2015 ◽

Vol 126 (23) ◽

pp. 2378-2378

Author(s):

Sisi Chen ◽

Xicheng Liu ◽

Rui Gao ◽

Michihiro Kobayashi ◽

Hao Yu ◽

...

Keyword(s):

Stem Cells ◽

Hematopoietic Stem Cells ◽

Wnt Signaling ◽

Signaling Pathway ◽

Wnt Signaling Pathway ◽

Canonical Wnt Signaling ◽

Self Renewal ◽

Hematopoietic Stem ◽

Canonical Wnt

Abstract Polycomb group (PcG) proteins are epigenetic gene silencers that have been implicated in stem cell maintenance and cancer development. Genetic and biochemical studies indicate that Polycomb group proteins exist in at least two protein complexes, Polycomb repressive complex 2 (PRC2) and Polycomb repressive complex 1 (PRC1), that act in concert to initiate and maintain stable gene repression. While studies on individual PRC1 component suggest that PRC1 plays an important role in hematopoiesis, how PRC1 regulates transcriptional repression in hematopoietic stem cells (HSCs) is largely unknown. Bmi1 and Mel18 are two major homologs of the PCGF subunit within the PRC1 complex. Bmi1 is a positive regulator of HSC self-renewal; however, the role of Mel18 in hematopoiesis has been controversial. To determine whether Bmi1 and Mel18 play redundant or distinct role in HSC self-renewal, we have generated Bmi1 and Mel18 conditional knockout mice. While acute deletion of Mel18 affects neither HSC frequency nor lineage commitment, we found that Mel18-deficent hematopoietic progenitor cells showed enhanced replating potential compared to wild type cells. To determine the role of Mel18 in HSC self-renewal, we performed serial HSC transplantation assays and found that the repopulating ability of Mel18-/- HSCs was significantly higher than WT HSCs in both primary and secondary transplantation assays, demonstrating that the loss of Mel18 enhances HSC self-renewal in vivo. We hypothesize that loss of Bmi1 and Mel18 in hematopoietic stem cells will disrupt PRC1 complex and impairs HSC self-renewal. To determine the role of PRC1 complex in HSCs, we analyzed the HSC behavior in Bmi1 and Mel18 double-deficient mice. While we found that Bmi1-deficient HSCs showed decreased repopulating potential compared to WT HSCs 16 weeks following transplantation, loss of both Bmi1 and Mel18 in HSCs resulted in even more severe self-renewal defects. In addition, loss of both Bmi1 and Mel18 resulted in decreased myeloid differentiation and increased B cell differentiation compared to WT, Mel18 KO, and Bmi1 KO mice. These data demonstrate that Bmi1 and Mel18 have non-overlapping role in HSC maintenance and lineage commitment. Given that Bmi1 plays a dominant role in the PRC1 complex, we decided to identify Bmi1 target genes in hematopoietic stem cells to understand how PRC1 complex regulates HSC self-renewal. We performed transcript profiling assays to compare gene expression in HSCs isolated from wild type and Bmi1-/- mice. The Ingenuity Pathways indicates that the canonical Wnt signaling is significantly elevated in Bmi1 null HSCs compared to WT HSCs. We confirmed the upregulation of several genes of the Wnt pathway in Bmi1 null HSCs by quantitative real-time PCR analysis. To determine whether Bmi1 can repress the activation of Wnt signaling in cells, we utilized the Top-Flash Wnt reporter system. Stimulation of 293T cells with Wnt3a activates the Wnt reporter and this activation can be efficiently repressed by Bmi1. Furthermore, we detected the association of Bmi1 with the Lef1, Tcf4, and Axin2 promoters in Baf3 cells by ChIP experiment. Thus, Bmi1 directly represses the expression of several Wnt genes in hematopoietic cells. To determine the functional significance of activation of Wnt signaling in Bmi1 null HSCs, we have generated R26StopFL Bmi1-Apcf/f-Mx1-Cre+ and Bmi1f/f-Ctnnb1f/f-Mx1-Cre+ mice. Loss of Apc in hematopoietic cells activates the Wnt signaling pathway and impairs HSC self-renewal. We found that expressing three-copies of Bmi1 from the Rosa26 locus enhanced the self-renewal capabilities of Apc deficient HSCs in transplantation assays. Ctnnb1 encodes b-catenin and loss of Ctnnb1 in HSCs diminishes Wnt signaling. Acute deletion of Bmi1 in hematopoietic compartments resulted in decreased bone marrow cellularity and enhanced apoptosis of hematopoietic stem and progenitor cells. Deletion of Ctnnb1 in Bmi1 null hematopoietic cells rescued these defects. Thus, impaired HSC self-renewal seen in Bmi1 null mice is, at least in part, due to activation of the canonical Wnt signaling pathway. Taken together, we demonstrate that PRC1 complex enhances HSC self-renewal through inhibiting the canonical Wnt signaling. Disclosures No relevant conflicts of interest to declare.

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