title: DDX1 is required for testicular tumorigenesis, partially through the transcriptional activation of 12p stem cell genes.
abstract: Cytogenetic analysis has identified 12p gain as the most frequent abnormality in human testicular germ cell tumors (TGCTs). It has been suggested that amplification and overexpression of stem cell-associated genes, including cyclin-D2, on the human chromosome 12p region are involved in germ cell tumorigenesis. By subtractive cDNA analysis, we identified Ddx1, a member of the DEAD-box protein family, as a gene predominantly expressed in the primordial germ cells of mouse embryos. Knockdown of Ddx1 in a mouse spermatogonia-derived cell line, GC-1spg, by short interference RNA repressed the expression of cyclin-D2, CD9 and GDF3 genes. In the mouse cyclin-D2 gene, a genomic DNA region between -348 and -329 was responsible for transcriptional activation by DDX1 based on reporter and gel shift assays. Similarly, DDX1 knockdown in the human TGCT cell line NEC8 repressed the expression of stem cell-associated genes localized on chromosome 12p13.3, including cyclin-D2, CD9 and NANOG. DDX1-knocked-down TGCT cells could not form solid tumors in nude mice. Furthermore, in situ hybridization revealed that DDX1 mRNA was produced in both seminoma and nonseminoma types of human TGCT samples. We conclude that DDX1 is a critical factor for testicular tumorigenesis.
authors.affiliation: Stem Cell Project Group, The Tokyo Metropolitan Institute of Medical Science, Tokyo Metropolitan Organization for Medical Research, Tokyo, Japan. tanaka-ky@igakuken.or.jp
authors.forename: K
authors.initials: K
authors.lastname: Tanaka
authors.forename: S
authors.initials: S
authors.lastname: Okamoto
authors.forename: Y
authors.initials: Y
authors.lastname: Ishikawa
authors.forename: H
authors.initials: H
authors.lastname: Tamura
authors.forename: T
authors.initials: T
authors.lastname: Hara
mesh_terms: D000818:Animals; D001483:Base Sequence; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002881:Chromosomes, Human, Pair 12 / Q000235:genetics*; D056742:Cyclin D2; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D013094:Spermatozoa / Q000378:metabolism; D013234:Stem Cells / Q000378:metabolism*; D013736:Testicular Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D015533:Transcriptional Activation / Q000235:genetics*
chemical_list: C486196:Ccnd2 protein, mouse; D056742:Cyclin D2; D016213:Cyclins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C541494:DDX1 protein, mouse; C086252:DDX1 protein, human; D053487:DEAD-box RNA Helicases