title: A novel regulator of human villous trophoblast fusion: the Krüppel-like factor 6.
abstract: Cell-cell fusion is an essential event during life. Throughout human pregnancy, the syncytiotrophoblast (STB) layer of the placenta is formed by continuous fusion of the underlying villous cytotrophoblasts, thus maintaining placental functionality. Defects in this process are associated with pathologies like pre-eclampsia and intrauterine growth restriction. Krüppel-like factor 6 (KLF6) is a transcription factor highly expressed in human and murine placenta. However, KLF6 functions in trophoblast cells remain largely unexplored. The aim of this work was to address the role of KLF6 during STB formation. KLF6 knockdown through small interfering RNA experiments hindered cell-cell fusion revealed by immunofluorescence microscopy in human primary villous cytotrophoblast as well as in the human placental-derived BeWo cell line. Furthermore, KLF6 silencing led to a decrease in the expression of the fusogenic protein Syncytin-1 and the cell cycle regulator p21 CIP1/WAF1: measured by quantitative RT-PCR and western blot assays. On the contrary, transcript levels of genes that encode for proteins involved in STB formation such as Syncytin-1, Syncytin-2, Connexin-43 and Zonula Occludens-1 increased when KLF6 was overexpressed in differentiating villous cytotrophoblasts and in non-fusing placental-derived JEG-3 cells. Interestingly, the expression of two trophoblast biochemical differentiation markers, βhCG and PSG3, were not reduced after KLF6 silencing in differentiating trophoblast cells. Present results support the notion that KLF6 is a relevant participant in cytotrophoblast fusion.
authors.affiliation: Centro de Investigaciones en Bioquímica Clínica e Inmunología (CIBICI-CONICET), Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA, Córdoba, Argentina.
authors.forename: Ana Cristina
authors.initials: AC
authors.lastname: Racca
authors.affiliation: Centro de Investigaciones en Bioquímica Clínica e Inmunología (CIBICI-CONICET), Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA, Córdoba, Argentina.
authors.forename: Magali Evelin
authors.initials: ME
authors.lastname: Ridano
authors.affiliation: Centro de Investigaciones en Bioquímica Clínica e Inmunología (CIBICI-CONICET), Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA, Córdoba, Argentina.
authors.forename: Soledad
authors.initials: S
authors.lastname: Camolotto
authors.affiliation: Centro de Investigaciones en Bioquímica Clínica e Inmunología (CIBICI-CONICET), Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA, Córdoba, Argentina.
authors.forename: Susana
authors.initials: S
authors.lastname: Genti-Raimondi
authors.affiliation: Centro de Investigaciones en Bioquímica Clínica e Inmunología (CIBICI-CONICET), Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA, Córdoba, Argentina gpan@fcq.unc.edu.ar.
authors.forename: Graciela María
authors.initials: GM
authors.lastname: Panzetta-Dutari
mesh_terms: D000328:Adult; D002459:Cell Fusion; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000235:genetics / Q000378:metabolism; D002824:Chorionic Villi / Q000254:growth & development / Q000378:metabolism*; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D015686:Gene Products, env / Q000235:genetics / Q000378:metabolism; D006801:Humans; D000075723:Kruppel-Like Factor 6; D051741:Kruppel-Like Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011247:Pregnancy; D011257:Pregnancy Proteins / Q000235:genetics / Q000378:metabolism; D061251:Primary Cell Culture; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D014327:Trophoblasts / Q000166:cytology / Q000378:metabolism*; D062826:Zonula Occludens-1 Protein / Q000235:genetics / Q000378:metabolism
chemical_list: C493956:CDKN1A protein, human; D018997:Chorionic Gonadotropin, beta Subunit, Human; D018031:Connexin 43; D050759:Cyclin-Dependent Kinase Inhibitor p21; C518353:ERVFRD-1 protein, human; D015686:Gene Products, env; C105465:KLF6 protein, human; D000075723:Kruppel-Like Factor 6; D051741:Kruppel-Like Transcription Factors; D011257:Pregnancy Proteins; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D062826:Zonula Occludens-1 Protein; C405335:syncytin
keywords: cell fusion; gene expression; human trophoblast; syncytin-1; transcription factors