Project description:β-Catenin is a regulator of cutaneous wound repair. The expression of genes that are modulated in response to changes in β-Catenin levels initiated prior to injury was investigated during the proliferative phase of repair. We are particularly interested in genes that are modulated (in opposite directions) in response to both the induction ('stabilization') versus downregulation of β-Catenin. To investigate this, conditional β-Catenin stabilized mice (Harada, N., et al. EMBO J. 1999 Nov 1;18(21):5931-42) were injected with either a Cre-expressing adenovirus, or a GFP-expressing control virus, four days prior to injury, and wounds were harvested eight days following injury. For conditional knockdown of β-Catenin, mice generated from a cross between conditional β-Catenin knockdown mice (Brault, V. et al., Development. 2001 Apr;128(8):1253-64), and mice that express a tamoxifen-inducible form of Cre (Hayashi, S., and McMahon, A.P., Dev Biol. 2002 Apr 15;244(2):305-18), were treated with Tamoxifen for five days prior to injury. Wounds were harvested eight days after wounding. This provides insight into gene expression changes that occur during the proliferative stage of cutaneous wound repair in response to changes in β-Catenin levels initiated before/at the time of injury.
Project description:β-Catenin is a regulator of cutaneous wound repair. The expression of genes that are modulated in response to changes in β-Catenin levels (stabilization and downregulation) in cutaneous mouse wounds, post injury, during the proliferative phase of repair, was investigated. We are particularly interested in genes that are modulated (in opposite directions) in response to both the induction (stabilization) versus downregulation of β-Catenin. To investigate this, conditional β-Catenin stabilized (Harada, N., et al. EMBO J. 1999 Nov 1;18(21):5931-42) mice were injected with either a Cre-expressing adenovirus, or a GFP-expressing control virus, three days following injury, and wounds were harvested eight days post injury. For conditional knockdown of β-Catenin, mice generated from a cross between conditional β-Catenin knockdown mice (Brault, V. et al., Development. 2001 Apr;128(8):1253-64), and mice that express a tamoxifen-inducible form of Cre (Hayashi, S., and McMahon, A.P., Dev Biol. 2002 Apr 15;244(2):305-18), were treated with Tamoxifen for five days, beginning at the third day after injury. Wounds were harvested eight days after wounding. This provides insight into the identities of genes modulated in response to changes in β-Catenin levels during the proliferative stage of cutaneous wound repair.
Project description:Embryonic genome activation (EGA) is orchestrated by an intrinsic developmental program initiated during oocyte maturation with translation of stored maternal mRNAs. Here we show that tankyrase, a poly(ADP-ribosyl) polymerase that regulates β-catenin levels, undergoes programmed translation during oocyte maturation and serves an essential role in mouse EGA. Newly translated TNKS triggers proteasomal degradation of axin, reducing targeted destruction of β-catenin and promoting β-catenin-mediated transcription of target genes, including Myc. MYC mediates ribosomal RNA transcription in 2-cell embryos, supporting global protein synthesis. Suppression of tankyrase activity using knockdown or chemical inhibition causes loss of nuclear β-catenin and global reductions in transcription and histone H3 acetylation. Chromatin and transcriptional profiling indicate that development arrests prior to the mid-2-cell stage, mediated in part by reductions in β-catenin and MYC. These findings indicate that post-transcriptional regulation of tankyrase serves as a ligand-independent developmental mechanism for post-translational β-catenin activation and is required to complete EGA.
Project description:Renal repair after injury is dependent on clonal expansion of proliferation competent cells. In the human kidney, the expression of CD133+ characterizes a population of resident scattered cells with resistance to damage and ability to proliferate. However, the biological function of the CD133 molecule is unknown. We found by RNA sequencing that cells undergoing cisplatin damage lost the CD133 signature and acquired metanephric mesenchymal and regenerative genes such as SNAIL1, KLF4, SOX9 and WNT3. CD133 was reacquired in the recovery phase. Lack of CD133 was specifically correlated with deregulation of the Wnt signalling and E-cadherin pathway and, functionally, limited cell proliferation after injury. By immunoprecipitation, CD133 appeared to form a complex with E-cadherin and β-catenin. In parallel, CD133-Kd cells showed lower β-catenin levels in basal condition and after Wnt pathway activation and reduced TCF/LEF promoter activation in respect to CD133+ cells. Finally, the lack of CD133 impaired generation of nephrospheres while favored senescence. These data indicate that CD133 may act as a permissive factor for beta-catenin signalling, preventing its degradation in the cytoplasm. Therefore, CD133 itself appears to play a functional role in renal tubular repair trough maintenance of proliferative response and control of senescence.
Project description:Activation of Wnt/β-catenin signaling is frequent in human and rodent hepatocarcinogenesis. Although in mice, the tumor promoting activity of agonists of constitutive androstane receptor (CAR) occurs via selection of carcinogen-initiated cells harbouring β-catenin mutations, the molecular alterations leading to hepatocellular carcinoma (HCC) development by The CAR agonist 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP), in the absence of genotoxic injury are unknown. Here we show that CAR activation per se induced HCC in mice and that 91% of them carried β-catenin point mutations or large in-frame deletions/exon skipping targeting Ctnnb1 exon 3. Point mutations in HCCs induced by TCPOBOP alone displayed different nucleotide substitutions compared to those found in HCCs from mice pre-treated with diethylnitrosamine (DENA). Moreover, unlike those occurring in HCCs from DENA+TCPOBOP mice, they did not result in increased expression of β-catenin target genes, such as Glul, Lgr5, Rgn, Lect2 and Ccnd1, or nuclear translocation of β-catenin when compared to the control liver. Remarkably, in the non-tumoral liver tissue, chronic CAR activation led to down-regulation of these genes and to a partial loss of glutamine synthetase (GS)-positive hepatocytes. These results thus show that while chronic CAR activation per se induces HCCs carrying β-catenin mutations, it concurrently down-regulates the Wnt/β-catenin pathway in non-tumoral liver. They also indicate that the relationship between CAR and β-catenin may be profoundly different between normal and neoplastic hepatocytes.
Project description:In colorectal cancer, p53 is commonly inactivated, associated with chemo-resistance, and marks the transition from non-invasive to invasive disease. Cancers, including colorectal cancer, are thought to be diseases of aberrant stem cell populations, as stem cells are able to self-renew, making them long-lived enough to acquire mutations necessary to manifest the disease. We have shown that extracts from sweet sorghum stalk components eliminate colon cancer stem cells (CCSC) in a partial p53-dependent fashion. However, the underlying mechanisms are unknown. In the present study, CCSC were transfected with short hairpin-RNA against p53 (CCSC p53 shRNA) and treated with sweet sorghum phenolics extracted from different plant components (dermal layer, leaf, seed head and whole plant). While all components demonstrated anti-proliferative and pro-apoptotic effects in CCSC, phenolics extracted from the dermal layer and seed head were more potent in eliminating CCSC by elevating caspases 3/7 activity, PARP cleavage, and DNA fragmentation in a p53-dependent and p53-independent fashion, respectively. Further investigations revealed that the anti-proliferative and pro-apoptotic effects were associated with decreases in beta-catenin protein levels, and beta-catenin targets cyclin D1, cMyc, and survivin. These results suggest that the anti-proliferative and pro-apoptotic effects of sweet sorghum extracts against human colon cancer stem cells are via suppression of Wnt/beta-catenin pro-survival signaling in a p53-dependent (dermal layer) and partial p53-independent (seed head) fashion. LCMS used to identify phenolic compounds associated with extract activity
Project description:Transcription factors harbour defined intrinsically disordered regulatory regions, which raises the question of how they mediate binding to structured co-regulators and how this regulates activity. Here, we present a detailed molecular regulatory mechanism of Forkhead box O4 (FOXO4) by the structured transcriptional co-regulator β-catenin. We find that the largely disordered FOXO4 C-terminal region, which contains its transactivation domain binds β-catenin through two defined interaction sites, and this is regulated by combined PKB/AKT- and CK1-mediated phosphorylation. Binding of β-catenin competes with the auto-inhibitory interaction of the FOXO4 disordered region with its DNA-binding forkhead domain, and thereby enhances FOXO4 transcriptional activity. Furthermore, we show that binding of the β-catenin inhibitor protein ICAT is compatible with FOXO4 binding to β-catenin, suggesting that ICAT acts as a molecular switch between anti-proliferative FOXO and pro-proliferative Wnt/TCF/LEF signalling. Together these data illustrate how the interplay of intrinsically disordered regions, post-translational modifications and co-factor binding contribute to transcription factor function. Highlights • The interaction network between FOXO4 and β-catenin was deciphered • FOXO4 auto-inhibition interferes with DNA binding and is counter-acted by β-catenin • FOXO4 exists in multiple conformations regulated by phosphorylation and co-factors • ICAT switches between FOXO4 and TCF/LEF transcription factors
Project description:The inability of the adult mammalian heart to regenerate represents a fundamental barrier in heart failure management. In contrast, the neonatal heart retains a transient regenerative capacity, but the underlying mechanisms are not fully understood. Wnt/β-catenin signaling has been suggested as a key cardio-regenerative pathway. Here, we show that Wnt/β-catenin signaling potentiates neonatal mouse cardiomyocyte proliferation in vivo and immature human pluripotent stem cell-derived cardiomyocyte (hPSC-CM) proliferation in vitro. In contrast, Wnt/β-catenin signaling in adult mice is cardioprotective but fails to induce cardiomyocyte proliferation. Transcriptional profiling of neonatal mouse and hPSC-CM revealed a core Wnt/β-catenin-dependent transcriptional network governing cardiomyocyte proliferation. In contrast, β-catenin failed to re-engage this proliferative gene network in the adult heart, which instead reverted to a neonatal-like glycolytic program. These findings suggest that Wnt/β-catenin drives distinct transcriptional networks in regenerative and non-regenerative cardiomyocytes, which may contribute towards the inability of the adult heart to regenerate following injury.