Hélène Dumond

Müllerian Inhibiting Substance in the Caudate Amphibian Pleurodeles waltl

Müllerian inhibiting substance (MIS, also known as anti-Müllerian hormone), is a key factor of male sex differentiation in vertebrates. In amniotes, it is responsible for Müllerian duct regression in male embryos. In fish, despite the absence of Müllerian ducts, MIS is produced and controls germ cell proliferation during gonad differentiation. Here we show for the first time the presence of MIS in an amphibian species, Pleurodeles waltl. This is very astonishing because in caudate amphibians, Müllerian ducts do not regress in males. Phylogenetic analysis of MIS P. waltl ortholog revealed that the deduced protein segregates with MIS from other vertebrates and is clearly separated from other TGF-β family members. In larvae, MIS mRNA was expressed at higher levels in the developing testes than in the ovaries. In the testis, MIS mRNA expression was located within the lobules that contain Sertoli cells. Besides, expression of MIS was modified in the case of sex reversal: it increased after masculinizing heat treatment and decreased after estradiol feminizing exposure. In addition to the data obtained recently in the fish medaka, our results suggest that the role of MIS on Müllerian ducts occurred secondarily during the course of evolution.

Mammary epithelial cell phenotype disruption in vitro and in vivo through ERalpha36 overexpression

Estrogen receptor alpha 36 (ERα36) is a variant of the canonical estrogen receptor alpha (ERα66), widely expressed in hormone sensitive cancer cells and whose high expression level correlates with a poor survival prognosis for breast cancer patients. While ERα36 activity have been related to breast cancer progression or acquired resistance to treatment, expression level and location of ERα36 are poorly documented in the normal mammary gland. Therefore, we explored the consequences of a ERα36 overexpression in vitro in MCF-10A normal mammary epithelial cells and in vivo in a unique model of MMTV-ERα36 transgenic mouse strain wherein ERα36 mRNA was specifically expressed in the mammary gland. By a combination of bioinformatics and computational analyses of microarray data, we identified hierarchical gene networks, downstream of ERα36 and modulated by the JAK2/STAT3 signaling pathway. Concomitantly, ERα36 overexpression lowered proliferation rate but enhanced migration potential and resistance to staurosporin-induced apoptosis of the MCF-10A cell line. In vivo, ERα36 expression led to duct epithelium thinning and disruption in adult but not in prepubescent mouse mammary gland. These phenotypes correlated with a loss of E-cadherin expression. Here, we show that an enhanced expression of ERα36 is sufficient, by itself, to disrupt normal breast epithelial phenotype in vivo and in vitro through a dominant-positive effect on nongenomic estrogen signaling pathways. These results also suggest that, in the presence of adult endogenous steroid levels, ERα36 overexpression in vivo contributes to alter mammary gland architecture which may support pre-neoplastic lesion and augment breast cancer risk.

286 Estrogens and Alkylphenols Promote Proliferation of the Seminoma-like TCam-2 Cell Line Through ERa36-dependent Pathways

Background: Seminoma, originated from carcinoma in situ cells (CIS), is one of the main causes of cancer in young men. Postpubertal developmentof these testicular germ cell tumors suggests a hormone-sensitive way of CIS cell proliferation induction probably stimulated by lifelong exposure to endocrine disruptors. In a first step to understand the mechanisms underlying the deleterious effects of endocrine disrupting compounds on germ cells, we aimed to decipher the estrogen-dependent transduction pathways in TCam2 cells. Then, we began to assess the effects of a [4tert-octyl + 4-nonylphenol] mix on testicular germ cell tumors in vitro and in vivo. Material and Methods: In this study, we used the unique seminoma TCam-2 cell line which do not express the canonical ERa66 estrogen receptor but Era36, a truncated isoform retaining the DNA-binding, partial dimerisation and ligand-binding domains and a specific C-term 27 aa sequence. Cells were exposed to either estradiol at concentrations in the range of those detected in an adult human testis or to a [4tert-octyl + 4-nonylphenol] mix used at low doses − i.e. those found in food and drinking water. In vitro, we performed cell proliferation assays, siRNA- or shRNA-directed knockdown, microarray- directed gene targeting and signaling pathways identification after short term (1h) or mid-term (24h or 48h) treatment. We also addressed the question of TCam-2 derived tumor growth in xenografted Nude mice treated with the [4tert-octyl + 4-nonylphenol] mix. Results: We demonstrate in vitro that estradiol and the alkylphenol mix trigger TCam-2 cell proliferation through ERa36-dependent pathways. We establish that estradiol can activate GPER-cAMP/PKA signaling pathway. Stable ERa36 knockdown indicates that ERa36 is (i) necessary for cell proliferation (ii) a downstream target of estradiol-activated GPER/PKA/CREB pathway, (iii) required for estradiol-dependent EGFR expression. The [4tert-octyl + 4-nonylphenol] mix signaling pathway is clearly ERa36 dependent but seems to be partially non-estrogenic. Finally, we show that the [4tert-octyl+ 4-nonylphenol] mix stimulates tumor growth in TCam-2 xenografted Nude mice. Conclusions: Our results highlight the functional role of ERa36 in context of seminoma cell proliferation and the importance of testing ERa36 in vivo as apossible marker for endocrine disruptor susceptibility

Is leptin the link between obesity and osteoarthritis

In addition to aging, obesity is one of the most common underlying causes of osteoarthritis (OA). Mechanical loading, together with biochemical and systemic factors linked to altered lipid metabolism, are thought to contribute to the onset of OA. It has been suggested that OA is a systemic metabolic disease associated with lipid disorders affecting joint homeostasis. These gradual changes may be due to the local effect of adipokines, and especially leptin. Indeed, their relative levels in joints differ from that found in plasma. In particular, leptin levels are increased and adiponectin and resistin levels are reduced This hypothesis is supported by--leptin overexpression in OA cartilage and its correlation with the degree of cartilage destruction,--abundant leptin synthesis by osteophytes, and--the high leptin levels found in OA joints from female patients. This link between OA and adipokines provides new leads regarding the prevention of OA and the identification of new drug targets.