The nucleotide sequence of a CpG island demonstrates the presence of the first exon of the gene encoding the human lysosomal membrane protein lamp2 and assigns the gene to Xq24

Activation of TRPV4 Induces Exocytosis and Ferroptosis in Human Melanoma Cells

TRPV4 (transient receptor potential vanilloid 4), a calcium permeable TRP ion channel, is known to play a key role in endocytosis. However, whether it contributes to exocytosis remains unclear. Here, we report that activation of TRPV4 induced massive exocytosis in both melanoma A375 cell and heterologous expression systems. We show here that, upon application of TRPV4-specific agonists, prominent vesicle priming from endoplasmic reticulum (ER) was observed, followed by morphological changes of mitochondrial crista may lead to cell ferroptosis. We further identified interactions between TRPV4 and folding/vesicle trafficking proteins, which were triggered by calcium entry through activated TRPV4. This interplay, in turn, enhanced TRPV4-mediated activation of folding and vesicle trafficking proteins to promote exocytosis. Our study revealed a signaling mechanism underlying stimulus-triggered exocytosis in melanoma and highlighted the role of cellular sensor TRPV4 ion channel in mediating ferroptosis.

Epigenetic regulation of HGF/Met receptor axis is critical for the outgrowth of bone metastasis from breast carcinoma

Our translational research deals with the influence of microenvironment on the phenotype and colonization of bone metastases from breast carcinoma, and on pre-metastatic niche formation. The aim of the present study was to clarify the origin of hepatocyte growth factor (HGF), ligand of Met receptor, the control of the axis HGF/Met by DNA methylation, and its importance for the nexus supportive cells-metastatic cells and for metastasis outgrowth. In bone metastasis of the 1833-xenograft model, DNA methyltransferase blockade using the chemotherapic drug 5-aza-2′-deoxycytidine (decitabine) strongly reduced the expression of HGF/Met receptor axis and of E-cadherin, with decrease of metastasis wideness and osteolysis, prolonging mice survival. Thus, DNA methylation events acted as commanders of breast carcinoma cells metastatizing to bone influencing the epithelial phenotype. HGF emerged as a bone-marrow stimulus, and the exosomes seemed to furnish HGF to metastatic cells. In fact, decitabine treatment similarly affected some markers of these microvesicles and HGF, indicating that its supply to recipient cells was prevented. Notably, in bone metastasis the hypomethylation of HGF, Met and E-cadherin promoters did not appear responsible for their elevated expression, but we suggest the involvement of hypermethylated regulators and of Wwox oncosuppressor, the latter being affected by decitabine. Wwox expression increased under decitabine strongly localizing in nuclei of bone metastases. We hypothesize a role of Wwox in Met activity since in vitro Wwox overexpression downregulated the level of nuclear-Met protein fragment and Met stability, also under long exposure of 1833 cells to decitabine. HGF enhanced phosphoMet and the activity in nuclei, an effect partially prevented by decitabine. Altogether, the data indicated the importance to target the tumor microenvironment by blocking epigenetic mechanisms, which control critical events for colonization such as HGF/Met axis and Wwox, as therapy of bone metastasis.

Identification of a new member (ZNF183) of the Ring finger gene family in Xq24-25

Four genes were mapped to the Xq24-25 region by searching the EST and the non-redundant database with short tracts of genomic sequences. These were random STSs present in the STS database or sequences derived from CpG islands (EagI-based STSs). One of the four matches corresponded to the full length transcript from the intronless glutamate dehydrogenase gene. The second was the human homolog of the bovine NADH ubiquinone oxidoreductase MWFE subunit gene (GDB symbol: NDUFA1). The other two, ZNF183 and ITBA4, were novel genes whose function cannot directly be inferred from their sequence analysis. However, a known motif, the C3HC4 Ring finger domain, shared by various tumor suppressors, DNA repair genes and cytokine receptor-associated molecules, is present at the C terminus of the ubiquitously expressed ZNF183 gene. ITBA4 is expressed at various levels in different tissues and is alternatively processed in brain. Similarity search did not detect any significant match in databases. These results, together with others previously reported by our laboratory, suggest that comparison of genomic and transcribed sequences which are continuously accumulating in databases, can provide 'virtual' mapping of a substantial number of ESTs to the specific genomic region which the STSs have been derived from.

Construction of a library of bovine genomic fragments enriched in CpG islands

A procedure is described to isolate DNA probes from the bovine genome that are enriched in sites for the so-called rare cutter restriction endonucleases. A collection of SacII (CvCGCGG)-Hin-dIII fragments from bovine sperm was established in the plasmid Bluescript. 180 clones were picked at random and analysed for the presence of inserts with sites for the following rare cutters: EagI, BsshII, NarI, MluI, NruI, NaeI: 70% of the clones contained at least 1 site and 5% contained four different such sites. 22.8% had multiple sites for one or more of the rare cutters tested. Sequence analysis for 16 clones confirmed the cloning of DNA with a G+C content and a proportion of CpG vs GpCs indicative of CpG islands.

Telomere-associated chromosome fragmentation: applications in genome manipulation and analysis

Telomere-associated chromosome fragmentation (TACF) is a new approach for chromosome mapping based on the non-targeted introduction of cloned telomeres into mammalian cells. TACF has been used to generate a panel of somatic cell hybrids with nested terminal deletions of the long arm of the human X chromosome, extending from Xq26 to the centromere. This panel has been characterized using a series of X chromosome loci. Recovery of the end clones by plasmid rescue produces a telomeric marker for each cell line and partial sequencing will allow the generation of sequence tagged sites (STSs). TACF provides a powerful and widely applicable method for genome analysis, a general way of manipulating mammalian chromosomes and a first step towards constructing artificial mammalian chromosomes.

Methylation and sequence analysis around EagI sites: identification of 28 new CpG islands in XQ24-XQ28

Thirty-two probes for CpG islands of the distal long arm of the human X chromosome have been identified. From a genomic library of DNA of the hamster-human cell hybrid X3000.1 digested with the rare cutter restriction enzyme EagI, 53 different human clones have been isolated and characterized by methylation and sequence analysis. The characteristic pattern of DNA methylation of CpG islands at the 5' end of genes of the X chromosome has been used to distinguish between EagI sites in CpG islands versus isolated EagI sites. The sequence analysis has confirmed and completed the characterization showing that sequences at the 5' end of known genes were among the clones defined CpG islands and that the non-CpG islands clones were mostly repetitive sequences with a non-methylated or variably methylated EagI site. Thus, since clones corresponding to repetitive sequences can be easily identified by sequencing, such libraries are a very good source of CpG islands. The methylation analysis of 28 different new probes allows to state that demethylation of CpG islands of the active X and methylation of those on the inactive X chromosome are the general rule. Moreover, the finding, in all instances, of methylation differences between male and female DNA is in very strong support of the notion that most genes of the distal long arm of the X chromosome are subject to X inactivation.