title: Identification of BARD1 splice-isoforms involved in human trophoblast invasion.
abstract: The tumor suppressor protein BARD1, originally discovered as BRCA1-binding protein, acts in conjunction with BRCA1 as ubiquitin ligase. BARD1 and BRCA1 form a stable heterodimer and dimerization, which is required for most tumor suppressor functions attributed to BRCA1. In addition, BARD1 has BRCA1-independent functions in apoptosis, and a role in control of tissue homeostasis was suggested. However, cancer-associated mutations of BARD1 are rare; on the contrary, overexpression of truncated BARD1 was found in breast and ovarian cancer and correlated with poor prognosis. Here we report that human cytotrophoblasts, which show a strong similarity with cancer cells in respect of their invasive behavior and capacity of matrix metalloprotease production, overexpress isoforms of BARD1 derived from differential splicing. We demonstrate that expression of BARD1 and its isoforms is temporally and spatially regulated by human chorionic gonadotropin and by hypoxia, both factors known to regulate the invasive phase and proliferation of cytotrophoblasts. Interestingly, we found a subset of BARD1 isoforms secreted by cytotrophoblasts. BARD1 repression by siRNAs, mitigates the interference of cytotrophoblasts with cell adhesion of collagen matrix-dependent epithelial cells, suggesting a role of BARD1 isoforms in extracellular matrix remodelling and in cytotrophoblasts invasion.
authors.affiliation: Laboratory of Molecular Gynecology and Obstetrics, Department of Gynecology and Obstetrics, Geneva University Hospitals, Maternité, 30, Bld de la Cluse, CH-1211 Geneva, Switzerland.
authors.forename: Lin
authors.initials: L
authors.lastname: Li
authors.forename: Marie
authors.initials: M
authors.lastname: Cohen
authors.forename: Jianyu
authors.initials: J
authors.lastname: Wu
authors.forename: Mamadou Hady
authors.initials: MH
authors.lastname: Sow
authors.forename: Branka
authors.initials: B
authors.lastname: Nikolic
authors.forename: Paul
authors.initials: P
authors.lastname: Bischof
authors.forename: Irmgard
authors.initials: I
authors.lastname: Irminger-Finger
mesh_terms: D017398:Alternative Splicing / Q000235:genetics*; D002448:Cell Adhesion; D045744:Cell Line, Tumor; D002465:Cell Movement; D002822:Choriocarcinoma / Q000473:pathology; D006063:Chorionic Gonadotropin / Q000235:genetics / Q000378:metabolism; D003094:Collagen / Q000378:metabolism; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014327:Trophoblasts / Q000166:cytology* / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: D006063:Chorionic Gonadotropin; D020033:Protein Isoforms; D025521:Tumor Suppressor Proteins; D003094:Collagen; C102449:BARD1 protein, human; D044767:Ubiquitin-Protein Ligases