Plakoglobin Represses SATB1 Expression and Decreases In Vitro Proliferation,Migration and Invasion

Plakoglobin (γ-catenin) is a homolog of β-catenin with dual adhesive and signaling functions. Plakoglobin participates in cell-cell adhesion as a component of the adherens junction and desmosomes whereas its signaling function is mediated by its interactions with various intracellular protein partners. To determine the role of plakoglobin during tumorigenesis and metastasis, we expressed plakoglobin in the human tongue squamous cell carcinoma (SCC9) cells and compared the mRNA profiles of parental SCC9 cells and their plakoglobin-expressing transfectants (SCC9-PG). We observed that the mRNA levels of SATB1, the oncogenic chromatin remodeling factor, were decreased approximately 3-fold in SCC9-PG cells compared to parental SCC9 cells. Here, we showed that plakoglobin decreased levels of SATB1 mRNA and protein in SCC9-PG cells and that plakoglobin and p53 associated with the SATB1 promoter. Plakoglobin expression also resulted in decreased SATB1 promoter activity. These results were confirmed following plakoglobin expression in the very low plakoglobin expressing and invasive mammary carcinoma cell line MDA-MB-231 cells (MDA-231-PG). In addition, knockdown of endogenous plakoglobin in the non-invasive mammary carcinoma MCF-7 cells (MCF-7-shPG) resulted in increased SATB1 mRNA and protein. Plakoglobin expression also resulted in increased mRNA and protein levels of the metastasis suppressor Nm23-H1, a SATB1 target gene. Furthermore, the levels of various SATB1 target genes involved in tumorigenesis and metastasis were altered in MCF-7-shPG cells relative to parental MCF-7 cells. Finally, plakoglobin expression resulted in decreased in vitro proliferation, migration and invasion in different carcinoma cell lines. Together with the results of our previous studies, the data suggests that plakoglobin suppresses tumorigenesis and metastasis through the regulation of genes involved in these processes.     

Sequencing two Tyr::CreERT2 transgenic mouse lines

The Cre/loxP system is a powerful tool that has allowed the study of the effects of specific genes of interest in various biological settings. The Tyr::CreER^T2 system allows for the targeted expression and activity of the Cre enzyme in the melanocyte lineage following treatment with tamoxifen, thus providing spatial and temporal control of the expression of specific target genes. Two independent transgenic mouse models, each containing a Tyr::CreER^T2 transgene, have been generated and are widely used to study melanocyte transformation. In this study, we performed whole genome sequencing (WGS) on genomic DNA from the two Tyr::CreER^T2 mouse models and identified their sites of integration in the C57BL/6 genome. Based on these results, we designed PCR primers to accurately, and efficiently, genotype transgenic mice. Finally, we discussed some of the advantages of each transgenic mouse model.     

A histopathological classification system of Tyr::NRASQ61K murine melanocytic lesions: A reproducible simplified classification

Genetically engineered mouse models offer essential opportunities to investigate the mechanisms of initiation and progression in melanoma. Here, we report a new simplified histopathology classification of mouse melanocytic lesions in Tyr::NRAS^Q61K derived models, using an interactive decision tree that produces homogeneous categories. Reproducibility for this classification system was evaluated on a panel of representative cases of murine melanocytic lesions by pathologists and basic scientists. Reproducibility, measured as inter‐rater agreement between evaluators using a modified Fleiss’ kappa statistic, revealed a very good agreement between observers. Should this new simplified classification be adopted, it would create a robust system of communication between researchers in the field of mouse melanoma models.