Current Genomics - Volume 6, Issue 5, 2005

Caveolae are microdomains of the plasma membrane enriched in cholesterol and glycosphingolipids. Caveolin- 3 is the structural protein component of caveolar membranes in muscle cells. The functional role of caveolin-3 in muscle cells has become more apparent over the last few years as several mutations of the caveolin-3 gene have been linked to muscle diseases, and animal models lacking or over-expressing caveolin-3 have been generated and characterized. In this review we give a summary of the current literature on the genetic mutations of the caveolin-3 gene and their effect on muscle and heart tissue functions, predominantly how it pertains to muscular dystrophy. We will look at how the caveolin- 3 protein regulates signaling pathways in muscle cells and the physiological ramifications of these interactions in normal and pathological conditions. We will also give an overview of the data from genetically engineered mouse models.

Ocular neovascularization in the form of retinopathy, choroidal neovascularization, and age-related macular degeneration can be sight-threatening. Therapies have been directed at tissue ablation consisting of laser surgery and cryotherapy as well as medical therapies to reduce intraocular pressure. These therapies occur later in the course of many kinds of ocular neovascularization. Advances in the field of angiogenesis biology have been critical to understanding the biology of various forms of ocular neovascularization. Vascular endothelial growth factor (VEGF) is the prime candidate for target of new therapies. Basic cellular experiments, animal studies and studies in genetically altered mice have been extremely helpful in elucidating ocular vascular pathology. Identification of factors involved in neovascularization, such as VEGF, and modification of their expression are vital to moving the field of ocular angiogenesis forward for ultimate clinical benefit. Applications of genomics to neovascularization are being developed both for detection of populations at high risk and for potential therapeutic intervention. Molecular biologic tools such as angiostatic gene transfer may prove to be sight-saving in the near future.

Neuroblastoma, one of the common malignant childhood tumors, arises from neuroblast cells derived from the neural crest and destined for the adrenal medulla and the sympathetic nervous system and shows remarkable biological heterogeneity, resulting in favorable or unfavorable outcomes. Some neuroblastomas tend to regress spontaneously in infants or to differentiate into a benign ganglioneuroma in older patients. In other instances, the tumors make rapid progress with a fatal outcome. This heterogeneity within neuroblastoma depends on the molecular characteristics of tumor cells. Several distinct genomic alterations have been found in neuroblastoma, including MYCN amplification, ploidy changes, deletion of the short arm of chromosome 1, gain of chromosome 17q, and deletion of 11q. The difference of expression was also found in genes related to cellular growth, differentiation, and apoptosis of neural network including Trk receptor tyrosine kinase and telomerase activity. This review discusses the extensive heterogeneity of neuroblastoma at molecular level, providing evidences that neuroblastoma is not a single disease. This should lead to more risk-adapted therapies according to the genetic markers by which individual neuroblastomas are biologically characterized.

The aberrant expression of cell adhesion molecules (CAMs) is correlated with the malignant progression of many tumors. MUC18/CD146/A32/MelCAM/S-endo, an integral membrane glycoprotein, is a CAM in the immunoglobulin gene superfamily. MUC18 has often been mistaken as a mucin because of the misleading nomenclature. Based on its biological functions and other known biochemical properties, we propose to re-name it as METCAM (metastasis CAM). METCAM/MUC18 expression has a very interesting effect on tumor formation and metastasis. The overexpression of METCAM/MUC18 has been correlated with the malignant progression of human melanoma and human prostate cancer. In melanoma, the ectopic over-expression of METCAM/MUC18 has no effect on tumorigenesis, but augments the metastasis of cancer cells. In prostate cancer, the ectopic over-expression of human METCAM/MUC18 has an even greater effect, increasing tumorigenesis and initiating the metastasis of cancer cells. However, an opposite effect of METCAM/MUC18 on tumorigenesis and metastasis of breast cancer, some mouse melanoma cell lines, and perhaps haemangioma and nasopharygeal carcinoma has also been suggested. Taken together, we suggest that the different effect of METCAM/MUC18 on tumor formation and metastasis is dependent on the intrinsic properties of each tumor cell line. This paper will review previous experiments and results and present some possible mechanisms of METCAM/MUC18- mediated tumorigenesis and metastasis for future studies.

Jun dimerization protein 2 (JDP2) forms a dimeric complex that can include members of the Jun, Fos, ATF-2, Maf and other families of AP-1 proteins. JDP2 acts as a repressor that binds to the AP-1 site in promoters and is a possible tumor-suppressor. We describe here how the transactivation of the c-Jun gene by p300 and ATF-2 involves recruitment of the histone deacetylase complex (HDAC3), with repression of retinoic acid-induced (RA-induced) transcription of the c- Jun gene and subsequent inhibition of the RA-mediated differentiation of F9 cells. We summarize that JDP2 has activities associated with histone binding and inhibition of histone acetyltransferases (INHAT), as well as with the regulation of chromatin assembly. These observations indicate that JDP2 not only acts as a sequence-specific DNA-binding protein but also controls the transcription of AP-1-responsive genes by direct regulation of histone modification. We discuss here a new perspective on the role of JDP2 in the chromatin-related mechanism that regulates the transcription of genes that are the targets of AP-1 proteins.