Edouard Reyes-Gomez

Pax3 GFP , a new reporter for the melanocyte lineage, highlights novel aspects of PAX3 expression in the skin

The paired box gene 3 (Pax3) is expressed during pigment cell development. We tested whether the targeted allele Pax3GFP can be used as a reporter gene for pigment cells in the mouse. We found that enhanced green fluorescent protein (GFP) can be seen readily in every melanoblast and melanocyte in the epidermis and hair follicles of Pax3GFP/+ heterozygotes. The GFP was detected at all differentiation stages, including melanocyte stem cells. In the dermis, Schwann cells and nestin‐positive cells of the piloneural collars resembling the nestin‐positive hair follicle multipotent stem cells exhibited a weaker GFP signal. Pigment cells could be purified by fluorescent activated cell sorting and grown in vitro without feeder cells, giving pure cultures of melanocytes. The Schwann cells and nestin‐positive cells of the piloneural collars were FACS‐isolated based on their weak expression of GFP. Thus Pax3GFP can discriminate distinct populations of cells in the skin.

Histopathological atlas and proposed classification for melanocytic lesions in Tyr::NRas(Q61K) ; Cdkn2a(-/-) transgenic mice

Reference EPFL-ARTICLE-188431doi:10.1111/pcmr.12115View record in Web of Science Record created on 2013-09-09, modified on 2017-05-12

Vitamin D3 Prevents Calcium-Induced Progression of Early-Stage Prostate Tumors by Counteracting TRPC6 and Calcium Sensing Receptor Upregulation

Active surveillance has emerged as an alternative to immediate treatment for men with low-risk prostate cancer. Accordingly, identification of environmental factors that facilitate progression to more aggressive stages is critical for disease prevention. Although calcium-enriched diets have been speculated to increase prostate cancer risk, their impact on early-stage tumors remains unexplored. In this study, we addressed this issue with a large interventional animal study. Mouse models of fully penetrant and slowly evolving prostate tumorigenesis showed that a high calcium diet dramatically accelerated the progression of prostate intraepithelial neoplasia, by promoting cell proliferation, micro-invasion, tissue inflammation, and expression of acknowledged prostate cancer markers. Strikingly, dietary vitamin D prevented these calcium-triggered tumorigenic effects. Expression profiling and in vitro mechanistic studies showed that stimulation of PC-3 cells with extracellular Ca2+ resulted in an increase in cell proliferation rate, store-operated calcium entry (SOCE) amplitude, cationic channel TRPC6, and calcium sensing receptor (CaSR) expression. Notably, administration of the active vitamin D metabolite calcitriol reversed all these effects. Silencing CaSR or TRPC6 expression in calcium-stimulated PC3 cells decreased cell proliferation and SOCE. Overall, our results demonstrate the protective effects of vitamin D supplementation in blocking the progression of early-stage prostate lesions induced by a calcium-rich diet. Cancer Res; 77(2); 355-65. ©2016 AACR.

Haplosufficiency of PAX3 for melanoma development in Tyr: NRASQ61K; Cdkn2a-/- mice allows identification and sorting of melanoma cells using a Pax3GFP reporter allele

The role of the Pax3 gene in embryonic development of pigment cells is well characterized. By contrast, the function of Pax3 in melanoma development is controversial. Indeed, data obtained from cultured cells suggest that PAX3 may contribute to melanomagenesis. PAX3 is found to be overexpressed in melanomas and also in nevi compared with normal skin samples. Pax3 homozygous loss of function is embryonic lethal. To assess the role of Pax3 in melanoma development in vivo, we analyzed Pax3 haploinsufficiency in a mouse model of melanoma predisposition. The Pax3GFP/+ knock-in reporter system was combined with the Tyr::NRASQ61K; Cdkn2a−/− mouse melanoma model. Melanoma development was followed over 18 months. Histopathological, immunohistochemical, and molecular analyses of lesions at different stages of melanoma progression were carried out. Fluorescence-activated cell sorting on GFP of cells from primary or metastatic melanoma was followed by ex-vivo transformation tests and in-vivo passaging. We report here that Tyr::NRASQ61K; Cdkn2a−/−; Pax3GFP/+ mice developed metastasizing melanoma as their Tyr::NRASQ61K; Cdkn2a−/− littermates. Histopathology showed no differences between the two genotypes, although Pax3 mRNA and PAX3 protein levels in Pax3GFP/+ lesions were reduced by half. The Pax3GFP allele proved to be a convenient marker to identify and directly sort heterogeneous populations of melanoma cells within the tumor bulk at each stage of melanoma progression. This new mouse model represents an accurate and reproducible means for identifying melanoma cells in vivo to study the mechanisms of melanoma development.

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::NRASQ61K 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.

Aneurysmal bone cyst on the carpus of an African collared dove (Streptopelia roseogrisea).

Abstract An adult female African collared dove (Streptopelia roseogrisea) was presented for examination of a mass on the medial surface of the left wing. The mass had been present for 2 months but had grown rapidly over the previous 2 weeks. One week after presentation, the mass was surgically excised and the involved alular bone was removed. Results of histologic examination of the mass were consistent with an aneurysmal bone cyst. No underlying factor could be found in this case. The wound healing was uneventful, and no mass recurrence was observed during the following year. To our knowledge, this is the first report of an aneurysmal bone cyst in a columbiform bird.