Search tips
Search criteria

Results 1-4 (4)

Clipboard (0)

Select a Filter Below

Year of Publication
Document Types
1.  Drosophila Myc integrates multiple signaling pathways to regulate intestinal stem cell proliferation during midgut regeneration 
Cell Research  2013;23(9):1133-1146.
Intestinal stem cells (ISCs) in the Drosophila adult midgut are essential for maintaining tissue homeostasis, and their proliferation and differentiation speed up in order to meet the demand for replenishing the lost cells in response to injury. Several signaling pathways including JAK-STAT, EGFR and Hippo (Hpo) pathways have been implicated in damage-induced ISC proliferation, but the mechanisms that integrate these pathways have remained elusive. Here, we demonstrate that the Drosophila homolog of the oncoprotein Myc (dMyc) functions downstream of these signaling pathways to mediate their effects on ISC proliferation. dMyc expression in precursor cells is stimulated in response to tissue damage, and dMyc is essential for accelerated ISC proliferation and midgut regeneration. We show that tissue damage caused by dextran sulfate sodium feeding stimulates dMyc expression via the Hpo pathway, whereas bleomycin feeding activates dMyc through the JAK-STAT and EGFR pathways. We provide evidence that dMyc expression is transcriptionally upregulated by multiple signaling pathways, which is required for optimal ISC proliferation in response to tissue damage. We have also obtained evidence that tissue damage can upregulate dMyc expression post-transcriptionally. Finally, we show that a basal level of dMyc expression is required for ISC maintenance, proliferation and lineage differentiation during normal tissue homeostasis.
PMCID: PMC3760623  PMID: 23896988
Myc; ISC; Hpo; JAK-STAT; EGFR; regeneration
2.  An Orally Bioavailable Chemical Probe of the Lysine Methyltransferases EZH2 and EZH1 
ACS chemical biology  2013;8(6):1324-1334.
EZH2 or EZH1 is the catalytic subunit of the polycomb repressive complex 2 that catalyzes methylation of histone H3 lysine 27 (H3K27). The trimethylation of H3K27 (H3K27me3) is a transcriptionally repressive post-translational modification. Overexpression of EZH2 and hypertrimethylation of H3K27 have been implicated in a number of cancers. Several selective inhibitors of EZH2 have been reported recently. Herein we disclose UNC1999, the first orally bioavailable inhibitor that has high in vitro potency for wild-type and mutant EZH2 as well as EZH1, a closely related H3K27 methyltransferase that shares 96% sequence identity with EZH2 in their respective catalytic domains. UNC1999 was highly selective for EZH2 and EZH1 over a broad range of epigenetic and non-epigenetic targets, competitive with the cofactor SAM, and non-competitive with the peptide substrate. This inhibitor potently reduced H3K27me3 levels in cells and selectively killed diffused large B cell lymphoma cell lines harboring the EZH2Y641N mutant. Importantly, UNC1999 was orally bioavailable in mice, making this inhibitor a valuable tool for investigating the role of EZH2 and EZH1 in chronic animal studies. We also designed and synthesized UNC2400, a close analog of UNC1999 with >1,000-fold lower potency than UNC1999 as a negative control for cell-based studies. Finally, we created a biotin-tagged UNC1999 (UNC2399) which enriched EZH2 in pull-down studies, and a UNC1999 – dye conjugate (UNC2239) for co-localization studies with EZH2 in live cells. Taken together, these compounds represent a set of useful tools for the biomedical community to investigate the role of EZH2 and EZH1 in health and disease.
PMCID: PMC3773059  PMID: 23614352
3.  Left Atrial Reverse Remodeling in Dogs with Moderate and Advanced Heart Failure Treated with A Passive Mechanical Containment Device: An Echocardiographic Study 
Journal of cardiac failure  2007;13(4):312-317.
Assessment of global LV remodeling is important in evaluating the efficacy of pharmacologic and device therapies for the treatment of chronic heart failure (HF). The effects of pharmacologic or device therapies on global left atrial (LA) remodeling in HF, while also important, are not often examined. We showed that long-term therapy with the Acorn Cardiac Support Device (CSD), a passive mechanical ventricular containment device, prevents and/or reverses LV remodeling in dogs with HF. This study examined the effects of the CSD on global LA remodeling in dogs with moderate and advanced HF.
Methods and Results
Studies were performed in 24 dogs with coronary microembolization-induced HF. Of these, 12 had moderate HF (ejection fraction, EF 30% to 40%) and 12 advanced HF (EF ≤25%). In each group, the CSD was implanted in 6 dogs and the other 6 served as controls. Dogs were followed for 3 months in the moderate group and 6 months in the advanced HF group. LA maximal volume (LAVmax), LA volume at the onset of the p-wave (LAVp), LA minimal volume (LAVmin), LA active emptying volume (LAAEV) and LA active emptying fraction (LAAEF) were measured from 2-dimensional echocardiograms obtained prior to CSD implantation and at the end of the treatment period. Treatment effect (Δ) comparisons between CSD-treated dogs and controls showed that CSD therapy significantly decreased LA volumes (ΔLAVmax: 3.33 ± 0.70 vs. −2.87±1.31 ml, p=0.002; 7.77 ± 1.76 vs. −0.37 ± 0.87 ml, p=0.002) and improved LA function (ΔLAAEF: −6.00 ± 1.53 vs. 1.85 ± 1.32 %, p=0.003; −2.39 ± 1.10 vs. 3.13 ± 1.66 %, p=0.02) in the moderate HF and advanced HF groups respectively.
Progressive LA enlargement and LA functional deterioration occurs in untreated dogs with HF. Monotherapy with the CSD prevents LA enlargement and improves LA mechanical function in dogs with moderate and advanced HF indicating prevention and/or reversal of adverse LA remodeling.
PMCID: PMC1939806  PMID: 17517352
Atrium; Echocardiography; Heart failure; Heart-assist device
4.  Differential Involvement of Toll-Like Receptors 2 and 4 in the Host Response to Acute Respiratory Infections with Wild-Type and Mutant Haemophilus influenzae Strains  
Infection and Immunity  2005;73(4):2075-2082.
We used a mouse model of acute respiratory infections to investigate the role of Toll-like receptor 2 (TLR2) and TLR4 in the host response to Haemophilus influenzae. Acute aerosol exposures to wild-type strains of H. influenzae showed that TLR4 function was essential for TNF-α induction, neutrophil influx, and bacterial clearance. To determine how lipooligosaccharide (LOS) modifications would affect the role of TLR4 in inducing the host response, we used acute infections with an H. influenzae strain expressing a mutation in the htrB gene. This mutant strain expresses an LOS subunit with decreased acylation. In response to H. influenzae htrB infection, tumor necrosis factor alpha (TNF-α) secretion remained TLR4 dependent. But the decrease in LOS acylation made the neutrophil influx and the bacterial clearance also dependent on TLR2, as shown by the decreased host response elicited in TLR2 knockout mice compared to C57BL/6 mice. A subsequent analysis of TLR2 and TLR4 gene expression by quantitative PCR indicated that TLR4 function induces TLR2 expression and vice versa. These results indicate that some changes in the LOS subunit of H. influenzae can favor signaling through non-TLR4 receptors, such as TLR2. The results also indicate a close interaction between TLR4 and TLR2 that tightly regulates the expression of both receptors.
PMCID: PMC1087404  PMID: 15784548

Results 1-4 (4)