title: A distinct expression pattern of cyclin K in mammalian testes suggests a functional role in spermatogenesis.
abstract: Germ cell and embryonic stem cells are inextricably linked in many aspects. Remarkably both can generate all somatic cell types in organisms. Yet the molecular regulation accounting for these similarities is not fully understood. Cyclin K was previously thought to associate with CDK9 to regulate gene expression. However, we and others have recently shown that its cognate interacting partners are CDK12 and CDK13 in mammalian cells. We further demonstrated that cyclin K is essential for embryonic stem cell maintenance. In this study, we examined the expression of cyclin K in various murine and human tissues. We found that cyclin K is highly expressed in mammalian testes in a developmentally regulated manner. During neonatal spermatogenesis, cyclin K is highly expressed in gonocytes and spermatogonial stem cells. In adult testes, cyclin K can be detected in spermatogonial stem cells but is absent in differentiating spermatogonia, spermatids and spermatozoa. Interestingly, the strongest expression of cyclin K is detected in primary spermatocytes. In addition, we found that cyclin K is highly expressed in human testicular cancers. Knockdown of cyclin K in a testicular cancer cell line markedly reduces cell proliferation. Collectively, we suggest that cyclin K may be a novel molecular link between germ cell development, cancer development and embryonic stem cell maintenance.
authors.affiliation: Center of Growth, Metabolism, and Aging, Key Laboratory of Bio-Resources and Eco-Environment, and State Key Laboratory of Biotherapy, College of Life Sciences, Sichuan University, Chengdu, Sichuan, China.
authors.forename: Xiaocong
authors.initials: X
authors.lastname: Xiang
authors.affiliation: Center of Growth, Metabolism, and Aging, Key Laboratory of Bio-Resources and Eco-Environment, and State Key Laboratory of Biotherapy, College of Life Sciences, Sichuan University, Chengdu, Sichuan, China.
authors.forename: Li
authors.initials: L
authors.lastname: Deng
authors.affiliation: 363 Hospital, Aviation Industry Corporation of China, Chengdu, Sichuan, China.
authors.forename: Jingli
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Center of Growth, Metabolism, and Aging, Key Laboratory of Bio-Resources and Eco-Environment, and State Key Laboratory of Biotherapy, College of Life Sciences, Sichuan University, Chengdu, Sichuan, China.
authors.forename: Xudong
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Center of Growth, Metabolism, and Aging, Key Laboratory of Bio-Resources and Eco-Environment, and State Key Laboratory of Biotherapy, College of Life Sciences, Sichuan University, Chengdu, Sichuan, China.
authors.forename: Tingjun
authors.initials: T
authors.lastname: Lei
authors.affiliation: Center of Growth, Metabolism, and Aging, Key Laboratory of Bio-Resources and Eco-Environment, and State Key Laboratory of Biotherapy, College of Life Sciences, Sichuan University, Chengdu, Sichuan, China.
authors.forename: Guangxin
authors.initials: G
authors.lastname: Luan
authors.affiliation: Center of Growth, Metabolism, and Aging, Key Laboratory of Bio-Resources and Eco-Environment, and State Key Laboratory of Biotherapy, College of Life Sciences, Sichuan University, Chengdu, Sichuan, China.
authors.forename: Chunlei
authors.initials: C
authors.lastname: Yang
authors.affiliation: Center of Growth, Metabolism, and Aging, Key Laboratory of Bio-Resources and Eco-Environment, and State Key Laboratory of Biotherapy, College of Life Sciences, Sichuan University, Chengdu, Sichuan, China.
authors.forename: Zhi-Xiong
authors.initials: ZX
authors.lastname: Xiao
authors.affiliation: 363 Hospital, Aviation Industry Corporation of China, Chengdu, Sichuan, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Li
authors.affiliation: Center of Growth, Metabolism, and Aging, Key Laboratory of Bio-Resources and Eco-Environment, and State Key Laboratory of Biotherapy, College of Life Sciences, Sichuan University, Chengdu, Sichuan, China.
authors.forename: Qintong
authors.initials: Q
authors.lastname: Li
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000235:genetics; D002460:Cell Line; D049109:Cell Proliferation; D016213:Cyclins / Q000235:genetics* / Q000378:metabolism; D053595:Embryonic Stem Cells / Q000378:metabolism; D015870:Gene Expression; D018507:Gene Expression Regulation, Developmental; D005854:Germ Cells / Q000378:metabolism; D006801:Humans; D008297:Male; D008322:Mammals / Q000235:genetics; D051379:Mice; D013091:Spermatogenesis / Q000235:genetics*; D013736:Testicular Neoplasms / Q000235:genetics / Q000378:metabolism; D013737:Testis / Q000378:metabolism*
chemical_list: C113028:CCNK protein, human; D016213:Cyclins