非编码RNA对哺乳动物精子发生过程的调控

doi:10.3864/j.issn.0578-1752.2017.02.016

摘要/Abstract

摘要： 精子发生始于精原干细胞（spermatogonial stem cells, SSCs），SSCs一部分自我更新，另一部分首先分裂形成Asingle（As）型精原细胞，进而形成Aparied（Apr）型精原细胞和Aaligned（Aal）型精原细胞；随后，Aal型精原细胞再发育为A1-A4型精原细胞、中间型精原细胞以及B型精原细胞；B型精原细胞有丝分裂可形成初级精母细胞，经历前细线期、细线期、偶线期、粗线期，再经减数分裂形成次级精母细胞；当圆形精子细胞形成之后，则经细胞核浓缩等过程形成晚期的细长型成熟精子，随之最终变形成为精子。这一复杂的生理过程需要相关基因的适时表达，并受到转录和转录后水平的调控。研究表明，多种类型的非编码RNA (ncRNAs)在精子发生过程中发挥着重要作用。ncRNAs包括微小RNAs (miRNAs)、与Piwi蛋白相互作用的RNAs (piRNAs)、长链非编码RNAs (lncRNAs)、环状RNAs（circRNAs）以及内源性小干扰RNAs (endo-siRNAs)等。这些ncRNAs的表达具有细胞组织特异性和发育阶段特异性，可从时间和空间上精确调控精子发生的整个过程。miRNAs是一类长约21—25 nt的内源性非编码单链RNA分子，广泛存在于各种生物中，其形成至少需要Drosha和Dicer等两种RNA酶的参与，可降解靶mRNA或抑制靶mRNA翻译，对SSCs干性的维持、自我更新和分化的调控以及生殖细胞减数分裂和精子发生过程具有重要的调控作用。此外，精子发生过程中，在生殖细胞不同阶段所表达的基因也可调控miRNAs的生成加工过程。piRNAs是2006年发现的一种新的小RNA，长度约24—32nt，其作用与Dicer酶无关，能够与生殖细胞特异性蛋白Piwi蛋白家族成员结合，进而行使生物学功能，其主要表现为：在表观遗传水平和转录后水平沉默转座子、反转座子等基因组移动遗传元件，维持生殖细胞自身基因组稳定性和完整性，调控生殖细胞增殖、减数分裂及精子发生过程。LncRNAs是一类长度大于200 nt的ncRNAs，其生成加工过程与mRNA类似，并且与mRNA有着相似的结构。不同来源的lncRNAs可通过转录前与转录后多种机制进而调控SSCs的干性及分化，并且调控生殖细胞凋亡。有些lncRNAs还可调控miRNAs的表达，进而调控精子发生过程。circRNAs是区别于传统线性RNA的一类新型RNA，在不同物种中具有保守性，在组织及不同发育阶段呈特异性表达。其生成加工方式与其序列相关，同一基因位点可通过选择性环化产生多种circRNAs进而发挥功能。研究表明，circRNAs可结合miRNAs从而调控生精过程。相对于其他ncRNAs，endo-siRNAs的生成加工方式更为简单，并有着与miRNAs相同的作用方式，在精子发生和雄性生殖中扮演着重要角色。文章结合最新的研究进展，综述了几种ncRNAs的生成及其在精子发生过程中的调控作用，旨在为精子发生过程中ncRNAs的进一步研究提供参考。

关键词: 精子发生, 非编码RNA (ncRNAs), 调控作用

Abstract: Spermatogenesis starts with spermatogonial stem cells (SSCs), which possess the ability of self-renewal and differentiation. SSCs are capable of differentiation to form Asingle (As) spermatogonia, Apaired (Apr) spermatogonia, Aaligned (Aal) spermatogonia, A1-A4 spermatogonia, intermediate spermatogonia, and B spermatogonia. Type B spermatogonia divide forming the primary spermatocytes, which undergo a long meiosis time to form secondary spermatocytes. Then secondary spermatocytes go through meiosis II to produce round spermatids, which will undergo a series of processes called spermiogenesis containing morphological changes, replacement histone by protamine, nuclear condensation and formation of flagellum. Finally, the mature spermatozoa are released into the lumen. This process requires precise and highly ordered regulation of gene expression at both the transcriptional and posttranscriptional levels. Recent advances in research have revealed that several types of noncoding RNAs (ncRNAs), including microRNAs (miRNAs), Piwi-interacting RNAs (piRNAs), long noncoding RNAs (lncRNAs), circular RNAs (circRNAs) and endogenous small-interfering RNAs (endo-siRNAs), are essential for spermatogenesis. These ncRNAs are expressed in a cell-specific and step-specific manner to participate in the control of spermatogenesis. MiRNAs are a class of endogenous non coding single stranded RNA molecules of about 21-25 nt that widely exist in various kinds of organisms, its formation needs at least two RNA enzymes such as Drosha and Dicer, which can also degrade target mRNA or inhibit target mRNA translation, have an important regulatory role in maintaining the stemness, self-renewal of SSCs, regulating differentiation, and involved germ cell meiosis and spermatogenesis. piRNAs are a large class of small RNAs that are 24-32 nt in length found in 2006, which could execute the biological function through interactions with Piwi proteins without Dicer enzyme, also silence transposons and retroposons at the epigenetic and posttranscriptional levels, maintain the genomic stability and integrity of germ cell, regulate cell proliferation, meiosis and spermatogenesis. LncRNAs are one of ncRNAs longer than 200 nt, their production process and structure are similar to the mRNA. Different sources of lncRNAs could regulate the stemness, differentiation of SSCs, and modulate germ cell apoptosis in a transcriptional and posttranscriptional manner. Some lncRNAs could also regulate the expression of miRNAs thus regulate the process of spermatogenesis. CircRNAs, differs from the traditional linear RNA, is a new type of RNA, which is conserved in different species, and specifically expressed in different tissues and developmental stages. Its formation processing mode is related to its sequence, the same gene locus could produce a variety of circRNAs through selective cyclization. Studies indicated that circRNAs can be combined with miRNAs to regulate spermatogenesis. Compared with other ncRNAs, the biogenesis of endo-siRNAs is simple, and has the same effect as miRNAs, which plays an important role in spermatogenesis and male reproduction. Therefore, this review summarized the regulatory role of ncRNAs during spermatogenesis, which provided insight into the further research on ncRNAs during spermatogenesis.

Key words: spermatogenesis, noncoding RNAs, regulatory role

陈瑞，于帅，陈晓旭，杜健，朱振东，潘传英，曾文先. 非编码RNA对哺乳动物精子发生过程的调控[J]. 中国农业科学, 2017, 50(2): 380-390.

CHEN Rui, YU Shuai, CHEN XiaoXu, DU Jian, ZHU ZhenDong, PAN ChuanYing, ZENG WenXian. Regulatory Role of Noncoding RNAs During Spermatogenesis[J]. Scientia Agricultura Sinica, 2017, 50(2): 380-390.

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参考文献

[1] SCHULZ R W, MIURA T. Spermatogenesis and its endocrine regulation. Fish Physiology and Biochemistry, 2003, 26: 43-56.

[2] KIMMINS S, SASSONE-CORSI P. Chromatin remodelling and epigenetic features of germ cells. Nature, 2005, 434(7033): 583-589.

[3] HERMO L, PELLETIER R M, CYR D G, SMITH C E. Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 1: background to spermatogenesis, spermatogonia, and spermatocytes. Microscopy Research Technique, 2010, 73(4): 241-278.

[4] HERMO L, PELLETIER R M, CYR D G, SMITH C E. Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 2: changes in spermatid organelles associated with development of spermatozoa. Microscopy Research Technique, 2010, 73(4): 279-319.

[5] HERMO L, PELLETIER R M, CYR D G, SMITH C E. Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 3: developmental changes in spermatid flagellum and cytoplasmic droplet and interaction of sperm with the zona pellucida and egg plasma membrane. Microscopy Research Technique, 2010, 73(4): 320-363.

[6] HERMO L, PELLETIER R M, CYR D G, SMITH C E. Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 4: intercellular bridges, mitochondria, nuclear envelope, apoptosis, ubiquitination, membrane/voltage-gated channels, methylation/acetylation, and transcription factors. Microscopy Research Technique, 2010, 73(4): 364-408.

[7] HERMO L, PELLETIER R M, CYR D G, SMITH C E. Surfing the wave, cycle, life History, and genes/proteins expressed by testicular germ cells. Part 5: intercellular junctions and contacts between germs cells and Sertoli cells and their regulatory interactions, testicular cholesterol, and genes/proteins associated with more than one germ cell generation. Microscopy Research Technique, 2010, 73(4): 409-494.

[8] FRANCA L R, AVELAR G F, ALMEIDA F F L. Spermatogenesis and sperm transit through the epididymis in mammals with emphasis on pigs. Theriogenology, 2005, 63(2): 300-318.

[9] MILLER D, BRINKWORTH M, ILES D. Paternal DNA packaging in spermatozoa: more than the sum of its parts? DNA, histones, protamines and epigenetics. Reproduction, 2010, 139(2): 287-301.

[10] YAN W, MA L, BURNS K H. HILS1 is a spermatidspecific linker histone H1 like protein implicated in chromatin remodeling during mammalian spermiogenesis. Proceeding of the National Academy Sciences of the United States of American, 2003, 100(7): 10546-10551.

[11] MARTIANOV I, BRANCORSINI S, CATENA R. Polar nuclear localization of H1T2, a histone H1 variant, required for spermatid elongation and DNA condensation during spermiogenesis. Proceeding of the National Academy Sciences of the United States of American, 2005, 102(8): 2808-2813.

[12] CARRELL D T. Epigenetics of the male gamete. Fertility and Sterility, 2012, 97(2): 267-274.

[13] DENLI A M, TOPS B B, PLAATERK R H, KETTING R F, Hannon G J. Processing of primary microRNAs by the microprocessor complex. Nature, 2004, 432(7014): 231-235.

[14] GREGORY R I, YAN K P, AMUTHAN G, CHENDRIMADA T, DORATOTAJ B, COOCH N, SHIEKHATTAR R. The microprocessor complex mediates the genesis of microRNAs. Nature, 2004, 432(7014): 235-240.

[15] LEE Y, AHN C, HAN J J, CHOI H, KIM J, YIM J, LEE J, PROVOST P, RADMARK O, KIM S. The nuclear RNase III Drosha initiates microRNA processing. Nature, 2003, 425(6956): 415-419.

[16] LUND E, GUTTINGER S, CALADO A, DAHLBERG J E, KUTAY U. Nuclear export of microRNA precursors. Science, 2004, 303(5654): 95-98.

[17] YI R, QIN Y, MACARA I G, CULLEN B R. Exportin-5 mediates the nuclear export of pre-microRNAs and short hairpin RNAs. Genes and Development, 2003, 17(24): 3011-3016.

[18] MEISTER G, TUSCHL T. Mechanisms of gene silencing by double-stranded RNA. Nature, 2004, 431(7006): 343-349.

[19] ZENG Y, YI R, CULLEN B R. MicroRNAs and small interfering RNAs can inhibit mRNA expression by similar mechanisms. Proceeding of the National Academy Sciences of the United States of American, 2003, 100(17):9779-9784.

[20] 朱文奇, 陈宽维, 李慧芳, 宋卫涛, 张静. 动物miRNA的最新研究进展. 中国畜牧兽医, 2009, 36(11): 66-69.

ZHU W q, CHEN K w, LI H f, SONG W t, ZHANG J. The latest research progress of animal miRNA. China Animal Husbandry and Veterinary Medicine, 2009, 36(11): 66-69. (in Chinese)

[21] LEE R C, FEINBAUM R L, AMBROS V. The C. elegansheterochronic gene lin-4 encodes small RNAs with antisense complementarity to lin-14. Cell, 1993, 75(5): 843-854.

[22] REINHART B J, SLACK F J, BASSON M, PASQUINELLI A E, BETTINGER J C, ROUGVIE A E, HORVITZ H R, RUVKUN G. The 21-nucleotide let-7 RNA regulates developmental timing in Caenorhabditis elegans. Nature, 2000, 403(6772): 901-906.

[23] WENG R, CHIN J S, YEW J Y. miR-124 controls male reproductive success in Drosophila. Elife, 2013, 2: e00640.

[24] FAGEGALTIER D, KöNIG A, GORDON A, LAI E C, GINGERAS T R, HANNON G J, SHCHERBATA H R. A genome-wide survey of sexually dimorphic expression of Drosophila miRNAs identifies the steroid hormone-induced miRNA let-7 as a regulator of sexual identity. Genetics, 2014, 198(2): 647-668.

[25] HE Z P, JIANG J J, KOKKINAKI M, TANG L, ZENG W X, GALLICANO I, DOBRINSKI I, DYM M. MiRNA-20 and miRNA-106a regulate spermatogonial stem cell renewal at the post-transcriptional level via targeting STAT3 and Ccnd1. Stem Cells, 2013, 31(10): 2205-2217.

[26] NIU B, WU J, MU H, LI B, WU C, HE X, BAI C, LI G, HUA J. miR-204 regulated the proliferation of dairy goat spermatogonial stem cells via targeting to Sirt1. Rejuvenation Research, 2016, 19(2): 120-130.

[27] LI M, YU M, LIU C, ZHU H, HE X, PENG S, HUA J. miR-34c works downstream of p53 leading to dairy goat male germline stem-cell (mGSCs) apoptosis. Cell Proliferation, 2013, 46(2): 223-231.

[28] MORITOKI Y, HAYASHI Y, MIZUNO K, KAMISAWA H, NISHIO H, KUROKAWA S, UGAWA S, KOJIMA Y, KOHRI K. Expression profiling of microRNA in cryptorchid testes: miR-135a contributes to the maintenance of spermatogonial stem cells by regulating FoxO1. Journal of Urology, 2014, 191(4): 1174-1180.

[29] NIU Z Y, GOODYEAR S M, RAO S, WU X, TOBIAS J W, AVARBOCK M R, BRINSTER R L. MicroRNA-21 regulates the self-renewal of mouse spermatogonial stem cells. Proceeding of the National Academy Sciences of the United States of American, 2011, 108(31): 12740-12745.

[30] SONG W C, MU H L, WU J, LIAO M Z, ZHU H J, ZHENG L M, HE X, NIU B W, ZHAI Y X, BAI C L. miR-544 regulates dairy goat male germline stem cell self-renewal via targeting PLZF. Journal of Cellular Biochemistry, 2015, 116(10): 2155-2165.

[31] HUSZAR J M, PAYNE C J. MicroRNA 146 (Mir146) modulates spermatogonial differentiation by retinoic acid in mice. Biology of Reproduction, 2013, 88(1): 15.

[32] TONG M H, MITCHELL D, EVANOFF R, GRISWOLD M D. Expression of Mirlet7 family microRNAs in response to retinoic acid-induced spermatogonial differentiation in mice. Biology of Reproduction, 2011, 85(1): 189-197.

[33] TONG M H, MITCHELL D A, MCGOWAN S D, EVANOFF R, GRISWOLD M D. Two miRNA clusters, Mir-17-92 (Mirc1) and Mir-106b-25 (Mirc3), are involved in the regulation of spermatogonial differentiation in mice. Biology of Reproduction, 2012, 86(3): 72.

[34] YAN N H, LU Y L, SUN H Q, TAO D C, ZHANG S Z, LIU W Y, MA Y X. A microarray for microRNA profiling in mouse testis tissues. Reproduction, 2007, 134(1): 73-79.

[35] YU Z R, RAABE T, HECHT N B. MicroRNA Mirn122a reduces expression of the posttranscriptionally regulated germ cell transition protein 2 (Tnp2) messenger RNA (mRNA) by mRNA cleavage. Biology of Reproduction, 2005, 73(3): 427-433.

[36] YU M, MU H, NIU Z, CHU Z, ZHU H, HUA J. miR-34c enhances mouse spermatogonial stem cells differentiation by targeting Nanos2. Journal of Cellular Biochemistry, 2014, 115(2): 232-242.

[37] NOVOTNY G W, SONNE S B, NIELSEN J E, JONSRUP S P, HANSEN M A, SKAKKEBAEK N E, RAJPERT-DE M E, KJEMS J, LEFFERS H. Translational repression of E2F1 mRNA in carcinoma in situ and normal testis correlates with expression of the miR-17-92 cluster. Cell Death and Differentiation, 2007, 14(4): 879-882.

[38] BJORK J K, SANDQVIST A, ELSING A N, KOTAJA N, SISTONEN L. miR-18, a member of Oncomir-1, targets heat shock transcription factor 2 in spermatogenesis. Development, 2010, 137(19): 3177-3184.

[39] WU J W, BAO J Q, KIM M, YUAN S Q, TANG C, ZHENG H L, MASTICK G S, XU C, YAN W. Two miRNA clusters, miR-34b/c and miR-449, are essential for normal brain development, motile ciliogenesis, and spermatogenesis. Proceeding of the National Academy Sciences of the United States of American, 2014, 111(28): 2851-2857.

[40] LIANG M, LI W Q, TIAN H, HU T, WANG L, LIN Y, LI Y L, HUANG H F, SUN F. Sequential expression of long noncoding RNA as mRNA gene expression in specific stages of mouse spermatogenesis. Scientific Reports, 2014, 4: 5966.

[41] DAI L S, TSAI-MORRIS C H, SATO H, VILLAR J, KANG J H, ZHANG J B, DUFAU M L. Testis-specific miRNA-469 up-regulated in gonadotropin-regulated testicular RNA helicase (GRTH/DDX25)- null mice silences transition protein 2 and protamine 2 messages at sites within coding region: implications of its role in germ cell development. Journal of Biological Chemistry, 2011, 286(52): 44306-44318.

[42] LIN H. piRNAs in the germ line. Science, 2007, 316(5823): 397.

[43] ARAVIN A A, LAGOS-QUINTANA M, YALCIN A, ZAVOLAN M, MARKS D, SNYDER B, GAASTERLAND T, MEYER J, TUSCHL T. The small RNA profile during Drosophila melanogaster development. Developmental Cell, 2003, 5(2): 337-350.

[44] Cox D N, Chao A, Baker J. A novel class of evolutionarily conserved genes defined by piwi are essential for stem cell self-renewal. Genes and Development, 1998, 12(23): 3715-3727.

[45] Carmell M A, Xuan Z, Zhang M Q. The Argonaute family: tentacles that reach in to RNAi, developmental control, stem cell maintenance, and tumorigenesis. Genes and Development, 2002, 16(21): 2733-2742.

[46] Saito K, Nishida K M, Mori T. Specific association of Piwi with rasiRNAs derived from retrotransposon and heterochromatic regions in the Drosophila genome. Genes and Development, 2006, 20(16): 2214-2222.

[47] Aravin A A, Lagos Q M, Yalcin A. The small RNA profile during Drosophila melanogaster development. Developmental Cell, 2003, 5(2): 337-350.

[48] Chen P Y, Manninga H, Slanchev K. The developmental miRNA profiles of zebrafish as determined by small RNA cloning. Genes and Development, 2005, 19(11): 1288-1293.

[49] Gunawardane L S, Saito K, Nishida K M. A slicer mediated mechanism for repeat associated siRNA5’end formation in Drosophila. Science, 2007, 315(5818): 1587-1590.

[50] Cox D N, Chao A, Lin H. Piwi encodes a nucleoplasmic factor whose activity modulates the number and division rate of germline stem cells. Development, 2000, 127(3): 503-514.

[51] Klattenhoff C, Theurkauf W. Biogenesis and germline functions of piRNAs. Development, 2008, 135: 3-9.

[52] Kiuchi T, Koga H, Kawamoto M. A single female-specific piRNA is the primary determiner of sex in the silkworm. Nature, 2014, 509(7502): 633-636.

[53] Tomari Y, Du T, Haley B, et a l. RISC assembly defects in the Drosophila RNAi mutant armitage. Cell, 2004, 116(6): 831-841.

[54] Kuramochi M S, Kimura T, Yomogida K. Two mouse piwi related genes: miwi and mili. Mechanisms and Development, 2001, 108(12): 121-133.

[55] Carmell M A, Girard A, vandeKant H J. MIWI2 is essential for spermatogenesis and repression of transposons in the mouse male germline. Developmental Cell, 2007, 12(4): 503-514.

[56] Kuramochi-Miyagawa S, Kimura T, Ijiri T W, Isobe T, Asada N, Fujita Y, Ikawa M, Iwai N, Okabe M, Deng W, Lin H F, Matsuda Y, Nakano T. Mili, a mammalian member of piwi family gene, is essential for spermatogenesis. Development, 2004, 131(4): 839-849.

[57] Reuter M, Berninger P, Chuma S, Shah H, Hosokawa M, Funaya C, Antony C, Sachidanandam R, Pillai R S. Miwi catalysis is required for piRNA amplification-independent LINE1 transposon silencing. Nature, 2011, 480(7376): 264-267.

[58] Gou L T, Dai P, Yang J H, Xue Y, Hu Y P, Zhou Y, Kang J Y, Wang X, Li H, Hua M M. Pachytene piRNAs instruct massive mRNA elimination during late spermiogenesis. Cell Research, 2014, 24(6): 680-700.

[59] Girard A, Sachidanandam R, Hannon G J, Carmell M A. A germline-specific class of small RNAs binds mammalian Piwi proteins. Nature, 2006, 442(7099): 199-202.

[60] Zhao S, Gou L T, Zhang M, Zu L D, Hua M M, Hua Y, Shi H J, Li Y, Li J, Li D. piRNA-triggered MIWI ubiquitination and removal by APC/C in late spermatogenesis. Developmental Cell, 2013, 24(1): 13-25.

[61] Rinn J L, Chang H Y. Genome regulation by long noncoding RNAs. Annual Review of Biochemistry, 2012, 81: 145-166.

[62] Wilusz J E, Sunwoo H, Spector D L. Long noncoding RNAs: functional surprises from the RNA world. Genes and Development, 2009, 23(13): 1494-1504.

[63] Sun J, Wu J. Expression profiling of long noncoding RNAs in neonatal and adult mouse testis. Data in Brief, 2015, 4: 322-327.

[64] Laiho A, Kotaja N, Gyenesei A, Sironen A. Transcriptome profiling of the murine testis during the first wave of spermatogenesis. PLoS One, 2013, 8(4): e61558.

[65] BAO J, WU J, SCHUSTER A S, HENNIG G W, YAN W. Expression profiling reveals developmentally regulated lncRNA repertoire in the mouse male germline. Biology of Reproduction, 2013, 89(5): 107.

[66] Liang M, Li W Q, Tian H, Hu T, Wang L, Lin Y, Li Y L, Huang H F, Sun F. Sequential expression of long noncoding RNA as mRNA gene expression in specific stages of mouse spermatogenesis, Scientific Reports, 2014, 4: 5966.

[67] Chalmel F, Lardenois A, Evrard B, Rolland A D, Sallou O, Dumargne M C, Coiffec I, Collin O, Primig M, Jegou B. High-resolution profiling of novel transcribed regions during rat spermatogenesis, Biology of Reproduction, 2014, 91(1): 5.

[68] Arun G, Akhade V S, Donakonda S, Rao M R S. mrhl RNA, a long noncoding RNA, negatively regulates Wnt signaling through its protein partner Ddx5/p68 in mouse spermatogonial cells. Molecular and Cellular Biology, 2012, 32(15): 3140-3152.

[69] Ni M J, Hu Z H, Liu Q, Liu M F, Lu M H, Zhang J S, Zhang L, Zhang Y L. Identification and characterization of a novel non-coding RNA involved in sperm maturation. PLoS One, 2011, 6(10): e26053.

[70] Lu M, Tian H, Cao Y X, He X, Chen L, Song X, Ping P, Huang H, sun F. Downregulation of miR-320a/383-sponge-like long non-coding RNA NLC1-C (narcolepsy candidate-region 1 genes) is associated with male infertility and promotes testicular embryonal carcinoma cell proliferation. Cell Death and Disease, 2015, 6: e1960.

[71] Lee T L, Xiao A, Rennert O M. Identification of novel long noncoding RNA transcripts in male germ cells. Methods in Molecular Biology, 2012, 825: 105-114.

[72] Anguera M C, Ma W Y, Clift D, Namekawa S, Kelleher R J, Lee J T. Tsx produces a long noncoding RNA and has general functions in the germline, stem cells, and brain. PLoS Genetics, 2011, 7(9): e1002248.

[73] Agbor V A, Tao S X, Lei N, Heckert L L. A Wt1-Dmrt1 transgene restores DMRT1 to sertoli cells of Dmrt1(-/-) testes: a novel model of DMRT1-Deficient germ cells. Biology Reproduction, 2013, 88(2): 51.

[74] Ottolenghi C, Veitia R, Barbieri M, Fellous M, McElreavey K. The human doublesex-related gene, DMRT2 is homologous to a gene involved in somitogenesis and encodes a potential bicistronic transcript. Genomics, 2000, 64(2): 179-186.

[75] EBBESEN K K, KJEMS J, HANSEN T B. Circular RNAs: identification, biogenesis and function. Biochimica et Biophysica Acta, 2016, 1859(1): 163-168.

[76] JECK W R, SORRENTINO J A, WANG K, SLEVIN M K, BURD C E, LIU J, MARZLUFF W F, SHARPLESS N E. Circular RNAs are abundant, conserved, and associated with ALU repeats. RNA, 2013, 19(2): 141-157.

[77] ZHANG Y, ZHANG X O, CHEN T, XIANG J F, YIN Q F, XING Y H, ZHU S, YANG L, CHENL L. Circular intronic long noncoding RNAs. Molecular Cell, 2013, 51(6): 792-806.

[78] 李培飞, 陈声灿, 邵永富, 蒋孝明, 肖丙秀, 郭俊明. 环状RNA的生物学功能及其在疾病发生中的作用. 生物物理学报, 2014, 30(1): 15-23.

LI P F, CHEN S C, SHAO Y F, JIANG X M, XIAO B X, GUO J M. Biology function of circular RNA and its effect on disease. Biophysics Reports, 201, 30(1): 15-23. (in Chinese)

[79] Hansen T B, Jensen T I, Clausen B H, Bramsen J B, Finsen B, Damgaard C K, Kjems J. Natural RNA circles function as efficient microRNA sponges. Nature, 2013, 495(7441): 384-388.

[80] Czech B, Malone C D, Zhou R, Stark A, Schlingeheyde C, Dus M, Perrimon N, Kellis M, Wohlschlegel J A, Sachidanandam R, Hannon G J, Brennecke J. An endogenous small interfering RNA pathway in Drosophila. Nature, 2008, 453(7196): 798-802.

[81] Garcia-Lopez J, HourcadeJde D, Alonso L, Cardenas D B, del Mazo J. Global characterization and target identification of piRNAs and endo-siRNAs in mouse gametes and zygotes. Biochimica et Biophysica Acta, 2014, 1839(6): 463-475.

[82] Suh N, Blelloch R. Small RNAs in early mammalian development: from gametes to gastrulation. Development, 2011, 138(9): 1653-1661.

[83] Han T, Manoharan A P, Harkins T T, Bouffard P, Fitzpatrick C, Chu D S, Thierry-Mieg D, Thierry-Mieg J, Kim J K. 26G endo-siRNAs regulate spermatogenic and zygotic gene expression in Caenorhabditis elegans. Proceeding of the National Academy Sciences of the United States of American, 2009, 106: 18674-18679.

[84] Wu Q, Song R, Ortogero N, Zheng H, Evanoff R, Small C L, Griswold M D, Namekawa S H, Royo H, Turner J M. The RNase III enzyme DROSHA is essential for microRNA production and spermatogenesis. Journal of Biology Chemistry, 2012, 287(30): 25173-25290.

[85] Wen J, Duan H, Bejarano F, Okamura K, Fabian L, Brill J A, Bortolamiol-Becet D, Martin R, Ruby J G, Lai E C. Adaptive regulation of testis gene expression and control of male fertility by the Drosophila hairpin RNA pathway. Molecular Cell, 2015, 57(1): 165-178.

[86] Tan T, Zhang Y, Ji W, Zheng P. miRNA signature in mouse spermatogonial stem cells revealed by high-throughput sequencing. Biomed Research International, 2014, 2014: 154251.

[87] Garcia-Lopez J, Alonso L, Cardenas D B, Artaza- Alvarez H, HourcadeJde D, Martinez S, Brieno- Enriquez M A, Del Mazo J. Diversity and functional convergence of small noncoding RNAs in male germ cell differentiation and fertilization. RNA, 2015, 21(5): 946-962.

[88] Zimmermann C, Romero Y, Warnefors M, Bilican A, Borel C, Smith L B, Kotaja N, Kaessmann H, Nef S. Germ cell-specific targeting of DICER or DGCR8 reveals a novel role for endo-siRNAs in the progression of mammalian spermatogenesis and male fertility. PLoS One, 2014, 9(9): e107023.