Overexpression of hepatocyte growth factor/scatter factor promotes vascularization and granulation tissue formation in vivo

AbstractThe effect of hepatocyte growth factor/scatter factor (HGF/SF) during wound healing in the skin was investigated, using HGF/SF-overexpressing transgenic mouse model. Histological analysis of HGF/SF transgenic mouse excisional wound sites revealed increased granulation tissue with marked vascularization. Northern blot analysis demonstrated that, relative to control, vascular endothelial growth factor (VEGF) expression in transgenic skin was significantly higher at baseline and was robustly up-regulated during wound healing. Elevated levels of VEGF protein were detected immunohistochemically, predominantly in endothelial cells and fibroblasts within the granulation tissue of HGF/SF transgenic skin. Serum levels of VEGF were also elevated in HGF/SF transgenic mice. Thus, results from our study suggest that HGF/SF has a significant effect on vascularization and granulation tissue formation during wound healing in vivo, involving with induction of VEGF

Meeting Report: Fourth International Congress of the Society for Melanoma Research

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73384/1/j.1755-148X.2007.00437.x.pd

A melanin-independent interaction between Mc1r and Met signalling pathways is required for HGF-dependent melanoma

Melanocortin 1 receptor (MC1R) signaling stimulates black eumelanin production through a cAMP-dependent pathway. MC1R polymorphisms can impair this process, resulting in a predominance of red phaeomelanin. The red hair, fair skin and UV sensitive phenotype is a well-described melanoma risk factor. MC1R polymorphisms also confer melanoma risk independent of pigment. We investigated the effect of Mc1r deficiency in a mouse model of UV-induced melanoma. C57BL/6-Mc1r+/+-HGF transgenic mice have a characteristic hyperpigmented black phenotype with extra-follicular dermal melanocytes located at the dermal/epidermal junction. UVB induces melanoma, independent of melanin pigmentation, but UVA-induced and spontaneous melanomas are dependent on black eumelanin. We crossed these mice with yellow C57BL/6-Mc1re/e animals which have a non-functional Mc1r and produce predominantly yellow phaeomelanin. Yellow C57BL/6-Mc1re/e-HGF mice produced no melanoma in response to UVR or spontaneously even though the HGF transgene and its receptor Met were expressed. Total melanin was less than in C57BL/6-Mc1r+/+-HGF mice, hyperpigmentation was not observed and there were few extra-follicular melanocytes. Thus, functional Mc1r was required for expression of the transgenic HGF phenotype. Heterozygous C57BL/6-Mc1re/+-HGF mice were black and hyperpigmented and, although extra-follicular melanocytes and skin melanin content were similar to C57BL/6-Mc1r+/+-HGF animals, they developed UV-induced and spontaneous melanomas with significantly less efficiency by all criteria. Thus, heterozygosity for Mc1r was sufficient to restore the transgenic HGF phenotype but insufficient to fully restore melanoma. We conclude that a previously unsuspected melanin-independent interaction between Mc1r and Met signaling pathways is required for HGF-dependent melanoma and postulate that this pathway is involved in human melanoma

Change in expression of the actin gene family during early sea urchin development

Expression of the actin gene family was studied during early sea urchin development using in vitro translation and nucleic acid hybridization techniques. Poly(A)+ RNA from four-cell and gastrula-stage S. purpuratus embryos was translated in vitro and the translation products were monitored for the presence of actin. In addition, poly(A)+ and total RNA were prepared from various stages of development, electrophoresed on agarose gels, transferred to diazobenzyloxymethyl paper, and then hybridized with a cloned actin cDNA probe. Results of these experiments indicate that there is a sharp increase in the level of RNA coding for actin during early development, and that there are two forms of actin specific RNA exhibiting different patterns of control.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24301/1/0000567.pd

MiR-24 Tumor Suppressor Activity Is Regulated Independent of p53 and through a Target Site Polymorphism

MicroRNAs (miRNAs) are predicted to regulate approximately 30% of all human genes; however, only a few miRNAs have been assigned their targets and specific functions. Here we demonstrate that miR-24, a ubiquitously expressed miRNA, has an anti-proliferative effect independent of p53 function. Cell lines with differential p53 status were used as a model to study the effects of miR-24 on cell proliferation, cell cycle control, gene regulation and cellular transformation. Overexpression of miR-24 in six different cell lines, independent of p53 function, inhibited cell proliferation and resulted in G2/S cell cycle arrest. MiR-24 over expression in cells with wt-p53 upregulated TP53 and p21 protein; however, in p53-null cells miR-24 still induced cell cycle arrest without the involvement of p21. We show that miR-24 regulates p53-independent cellular proliferation by regulating an S-phase enzyme, dihydrofolate reductase (DHFR) a target of the chemotherapeutic drug methotrexate (MTX). Of interest, we found that a miR-24 target site polymorphism in DHFR 3′ UTR that results in loss of miR-24-function and high DHFR levels in the cell imparts a growth advantage to immortalized cells and induces neoplastic transformation. Of clinical significance, we found that miR-24 is deregulated in human colorectal cancer tumors and a subset of tumors has reduced levels of miR-24. A novel function for miR-24 as a p53-independent cell cycle inhibitory miRNA is proposed

Hippo-Independent Activation of YAP by the GNAQ Uveal Melanoma Oncogene through a Trio-Regulated Rho GTPase Signaling Circuitry

SummaryMutually exclusive activating mutations in the GNAQ and GNA11 oncogenes, encoding heterotrimeric Gαq family members, have been identified in ∼83% and ∼6% of uveal and skin melanomas, respectively. However, the molecular events underlying these GNAQ-driven malignancies are not yet defined, thus limiting the ability to develop cancer-targeted therapies. Here, we focused on the transcriptional coactivator YAP, a critical component of the Hippo signaling pathway that controls organ size. We found that Gαq stimulates YAP through a Trio-Rho/Rac signaling circuitry promoting actin polymerization, independently of phospholipase Cβ and the canonical Hippo pathway. Furthermore, we show that Gαq promotes the YAP-dependent growth of uveal melanoma cells, thereby identifying YAP as a suitable therapeutic target in uveal melanoma, a GNAQ/GNA11-initiated human malignancy

Characterization of five members of the actin gene family in the sea urchin

Hybridization of an actin cDNA clone (pSA38) to restriction enzyme digests of Strongylocentrotus purpuratus DNA indicates that the sea urchin genome contains at least five different actin genes. A sea urchin genomic clone library was screened for recombinants which hydridize to pSA38 and four genomic clones were isolated. Restriction maps were generated which indicate that three of these recombinants contain different actin genes, and that the fourth may be an allele to one of these. The restriction maps suggest that one clone contains two linked actin genes. This fact, which was confirmed by heteroduplex analysis, indicates that the actin gene family may be clustered. The linked genes are oriented in the same direction and spaced about 8.0 kilobases apart. In heteroduplexes between genomic clones two intervening sequences were seen. Significant homology is confined to the actin coding region and does not include any flanking sequence. Southern blot analysis reveals that repetitive DNA sequences are found in the region of the actin genes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24164/1/0000422.pd

Phylogenomic analysis of a global collection of Escherichia coli ST38: evidence of interspecies and environmental transmission?

We performed a comprehensive phylogenomic analysis of 925 extraintestinal pathogenic Escherichia coli (ExPEC) ST38 genomes from 38 countries and diverse hosts and sources. The phylogeny resolved two broad clades: A (593 strains; 91% human) and B (332 isolates; 42% human), each with distinct ST38 clusters linked to the carriage of specific bla CTX-M alleles, often in association with other antibiotic resistance genes, class 1 integrons and specific plasmid replicon types. Co-carriage of fyuA and irp2 virulence genes, a reliable proxy for carriage of the Yersinia high-pathogenicity island, featured in 580 (62.7%) genomes. ST38 lineages carrying combinations of ExPEC and intestinal pathogenic Escherichia coli virulence factors were also identified. The F plasmid replicon was identified in 536 (58%) genomes, and 112 of these (21%) carry cjrABC-senB, a virulence operon frequently identified in pandemic ExPEC sequence types. Most (108; 96.4%) cjrABC-senB+ ST38 isolates were from human and other sources, except food animals, and were associated with F5:A-:B10 (41 isolates), F1:A2:B20 (20 isolates), and F24:A-:B1 (15 isolates) F replicon types. ST38 genomes that were inferred to carry a ColV-F virulence plasmid (69; 7.4%) were mostly from human (12; 17.4%), avian (26; 37.7%), or poultry (10; 6.9%) sources. We identified multiple examples of putative inter-host and host-environment transmission events, where genomes differed by <35 SNPs. This work emphasizes the importance of adopting a One Health approach for phylogenomic studies that seek to improve understanding of antimicrobial resistance and pathogen evolution

Selenium and Selenoprotein Deficiencies Induce Widespread Pyogranuloma Formation in Mice, while High Levels of Dietary Selenium Decrease Liver Tumor Size Driven by TGFα

Changes in dietary selenium and selenoprotein status may influence both anti- and pro-cancer pathways, making the outcome of interventions different from one study to another. To characterize such outcomes in a defined setting, we undertook a controlled hepatocarcinogenesis study involving varying levels of dietary selenium and altered selenoprotein status using mice carrying a mutant (A37G) selenocysteine tRNA transgene ($Trsp^{tG37}$) and/or a cancer driver TGFα transgene. The use of $Trsp^{tG37}$ altered selenoprotein expression in a selenoprotein and tissue specific manner and, at sufficient dietary selenium levels, separate the effect of diet and selenoprotein status. Mice were maintained on diets deficient in selenium (0.02 ppm selenium) or supplemented with 0.1, 0.4 or 2.25 ppm selenium or 30 ppm triphenylselenonium chloride (TPSC), a non-metabolized selenium compound. $Trsp^{tG37}$ transgenic and TGFα/$Trsp^{tG37}$ bi-transgenic mice subjected to selenium-deficient or TPSC diets developed a neurological phenotype associated with early morbidity and mortality prior to hepatocarcinoma development. Pathology analyses revealed widespread disseminated pyogranulomatous inflammation. Pyogranulomas occurred in liver, lungs, heart, spleen, small and large intestine, and mesenteric lymph nodes in these transgenic and bi-transgenic mice. The incidence of liver tumors was significantly increased in mice carrying the TGFα transgene, while dietary selenium and selenoprotein status did not affect tumor number and multiplicity. However, adenoma and carcinoma size and area were smaller in TGFα transgenic mice that were fed 0.4 and 2.25 versus 0.1 ppm of selenium. Thus, selenium and selenoprotein deficiencies led to widespread pyogranuloma formation, while high selenium levels inhibited the size of TGFα–induced liver tumors