piRNAs and transposon silencing
Piwi-interacting RNAs are a diverse class of small non-coding RNAs implicated in the silencing of transposable elements and the safeguarding of genome integrity. In mammals, male germ cells express two genetically and developmentally distinct populations of piRNAs at the pre-pachytene and pachytene stages of meiosis, respectively.
Pre-pachytene piRNAs are mostly derived from retrotransposons and required for their silencing. In contrast, pachytene piRNAs originate from ~3,000 genomic clusters and their biogenesis and function remain enigmatic. We previously reported that MOV10L1, a putative RNA helicase, is required for biogenesis of pre-pachytene piRNAs. Mov10l1 is one of the 36 germ cell-specific genes identified in our genomic screen.
Recently we have demonstrated that conditional inactivation of the putative RNA helicase MOV10L1 in mouse spermatocytes produces a specific loss of pachytene piRNAs, significant accumulation of pachytene piRNA precursor transcripts, and unusual polar conglomeration of Piwi proteins with mitochondria. Pachytene piRNA-deficient spermatocytes progress through meiosis without derepression of LINE1 retrotransposons, but become arrested at the post-meiotic round spermatid stage with massive DNA damage.
Our results demonstrate that MOV10L1 acts upstream of Piwi proteins in the primary processing of pachytene piRNAs and suggest that, distinct from pre-pachytene piRNAs, pachytene piRNAs fulfill a unique function in maintaining post-meiotic genome integrity. Our studies have demonstrated that MOV10L1 is a master regulator of the piRNA pathway in mammals.
The X chromosome and Male Infertility
We have identified TEX11 as the first X chromosome-encoded meiosis-specific factor in mammals. In principle, meiosis-specific genes could be located anywhere in the genome. However, no mouse sex chromosome-linked mutants with meiosis-specific defects had been reported, leading to the perception that meiosis-specific factors are rarely if ever encoded by the sex chromosomes. We were the first to clone Tex11, an X-linked germ cell-specific gene, in our genomic screen.
In a recent study, by ablating the function of Tex11 in mice, we have demonstrated that Tex11 is essential for meiosis and fertility in males. Our findings have important implications for male infertility in humans, which accounts for about half of the cases of infertility among couples. An estimated 15% of couples are affected by infertility worldwide. Given that disruption of Tex11 causes azoospermia in mice, we surmise that mutations in the human TEX11 gene could be found in infertile men.
Regulation of Homologous Recombination
During meiosis, homologous chromosomes undergo synapsis and recombination. Meiotic recombination enables the reciprocal exchange of genetic material between parental homologous chromosomes, and ensures faithful chromosome segregation during meiosis in sexually reproducing organisms.
This process relies on the complex interaction of DNA repair factors and many steps remain poorly understood in mammals. The arrangement of homologous chromosomes is tightly regulated by the synaptonemal complex (SC). SYCP2 is an integral component of SCs in mammals. Our genetic and cell biological studies demonstrate that SYCP2 is required for the formation of SCs and chromosomal synapsis.
We also find that TEX11 interacts with SYCP2 and is a novel constituent of meiotic nodules involved in recombination. TEX11 promotes both synapsis and recombination, and thus may provide a physical link between these two fundamental meiotic processes.
We recently identified MEIOB, a meiosis-specific protein, in a proteomics screen for novel meiotic chromatin-associated proteins in mice. MEIOB contains an OB domain with homology to one of the RPA1 OB folds and thus is a meiosis paralogue of RPA1, a ubiquitously expressed single-strand DNA-binding protein. MEIOB binds to single-stranded DNA and exhibits 3'-5' exonuclease activity. MEIOB forms a complex with RPA and with SPATA22, another meiosis-specific protein in vertebrates. These three proteins co-localize in foci that are associated with meiotic chromosomes. Strikingly, chromatin localization and stability of MEIOB depends on SPATA22 and vice versa. Meiob-null mouse mutants exhibit a failure in meiosis and sterility in both sexes. Our data suggest that MEIOB may be required for the second end capture during meiotic recombination in mammals.
2011 - present
Qi F and Wang PJ. Mammalian piRNAs: biogenesis, function, and mysteries. Spermatogenesis. In Press.
Zhou J, Leu NA, Goldberg EM, Coulter DA, Wang PJ. Respiratory failure, cleft palate, and epilepsy in the mouse model of human Xq22.1 deletion syndrome. Hum. Mol. Genetics. 2014;23(14):3823-3829. PMCID: PMC4065155 [Available on 2015/7/15]
Penn press release: Scientists from Penn and CHOP Confirm Link Between Missing DNA and Birth Defects.
Zhou J, Pan J, Eckardt S, Leu NA, McLaughlin KJ, Wang PJ. STK31/TDRD8, a germ cell-specific factor, is dispensable for reproduction in mice. PLoS One. 2014;9(2):e89471. PMCID: PMC3929691
Luo M, Yang F, Leu NA, Landaiche J, Handel MA, Benavente R, La Salle S, and Wang PJ. MEIOB exhibits single-stranded DNA-binding and exonuclease activities and is essential for meiotic recombination. Nature Communications. 2013;4:2788. PMCID: PMC3891831
Zhou H, Grubisic I, Zheng K, He Y, Wang PJ, Kaplan T, Tjian R. Taf7l cooperates with Trf2 to regulate spermiogenesis. Proc Natl Acad Sci U S A. 2013;110(42):16886-16891. PMCID: PMC3801064
Zhou J, McCarrey JR, Wang PJ. A 1.1 Mb segmental deletion on the X chromosome causes meiotic failure in male mice. Biol. Reprod. 2013;88(6):159. PMCID: PMC4070866
Reynolds A, Qiao H, Yang Y, Chen JK, Jackson N, Biswas K, Holloway JK, Baudat F, de Massy B, Wang PJ, Höög C, Cohen PE, Hunter N. RNF212 is a dosage-sensitive regulator of crossing-over during mammalian meiosis. Nature Genetics. 2013;45(3):269-278. PMID: 23396135
Zhou H, Kaplan T, Li Y, Grubisic I, Zhang Z, Wang PJ, Eisen MB, Tjian R. Dual Functions of TAF7L in Adipocyte Differentiation. eLife. 2013;2:e00170. PMCID: PMC3539393
Zheng K and Wang PJ. Blockade of pachytene piRNA biogenesis reveals a novel requirement for maintaining post-meiotic germline genome integrity in mice. PLoS Genetics. 2012;8(11): e1003038. PMCID: PMC3499362
Penn press release: A Class of RNA Molecules Protects Germ Cells From Damage, Penn Vet Researchers Show.
Berkowitz KM, Sowash AR, Koenig LR, Urcuyo D, Khan F, Yang F, Wang PJ, Jongens TA, and Kaestner KH. Disruption of Chtf18 causes defective meiotic recombination in male mice. PloS Genetics. 2012;8(11):e1002996. PMCID: PMC3486840
Yang F, Wei Q, Adelstein RS, Wang PJ. Non-muscle myosin IIB is essential for cytokinesis during male meiotic cell divisions. Dev Biol. 2012;369(2):356-61. PMCID: PMC3584343
Zhou J, Yang F, Leu NA, Wang PJ. MNS1 is essential for spermiogenesis and motile ciliary functions in mice. PLoS Genetics. 2012;8(3):e1002516. PMCID: PMC3291534
Penn press release: Penn Vet Team Identifies a Gene Responsible for Male Infertility and a Respiratory Disorder.
Zhou J, Pan J, Eckardt S, Leu NA, McLaughlin KJ, Wang PJ. Nxf3 is expressed in Sertoli cells, but is dispensable for spermatogenesis. Mol Reprod Dev. 2011;78(4):241-9. PMCID: PMC3081378
2006 - 2010
Yang F, Cheng Y, An JY, Kwon YT, Eckardt S, Leu NA, McLaughlin KJ, Wang PJ. The ubiquitin ligase Ubr2, a recognition E3 component of the N-end rule pathway, stabilizes Tex19.1 during spermatogenesis. PLoS One. 2010; 5(11):e14017. PMCID: PMC2982839
Shin YH, Choi Y, Erdin SU, Yatsenko SA, Kloc M, Yang F, Wang PJ, Meistrich ML, Rajkovic A. Hormad1 mutation disrupts synaptonemal complex formation, recombination, and chromosome segregation in mammalian meiosis. PLoS Genetics. 2010;6(11):e1001190. PMCID: PMC2973818
Zheng K, Xiol J, Reuter M, Eckardt S, Leu NA, McLaughlin KJ, Stark A, Sachidanandam R, Pillai RS, Wang PJ. Mouse MOV10L1 associates with Piwi proteins and is an essential component of the Piwi-interacting RNA (piRNA) pathway. Proc Natl Acad Sci U S A. 2010;107(26):11841-11846. PMCID: PMC2900664
Zheng K, Yang F, Wang PJ. Regulation of male fertility by X-linked genes. J Androl. 2010;31(1):79-85. PMCID: PMC2931805
Zheng K, Wu X, Kaestner KH, Wang PJ. The pluripotency factor LIN28 marks undifferentiated spermatogonia in mouse. BMC Dev Biol. 2009; 9(1):38. PMCID: PMC2719617
Pan J, Eckardt S, Leu NA, Buffone, M.G., Zhou J., Gerton G.L., McLaughlin KJ, Wang PJ. Inactivation of Nxf2 causes defects in male meiosis and age-dependent depletion of spermatogonia. Dev. Biol. 2009; 330:167-174. PMCID: PMC2702087
Yang F. and Wang P.J. The mammalian synaptonemal complex: a scaffold and beyond. Genome Dynamics. 2009(5):69-80. PMID: 18948708
Newell AE, Fiedler SE, Ruan JM, Pan J, Wang PJ, Deininger J, Corless CL, Carr DW. Protein kinase A RII-like (R2D2) proteins exhibit differential localization and AKAP interaction. Cell Motil. Cytoskeleton 2008; 65(7):539-52. PMID:18421703
Yang F, Eckardt S, Leu NA, McLaughlin KJ, Wang PJ. Mouse TEX15 is essential for DNA double-strand break repair and chromosomal synapsis during male meiosis. J. Cell Biol. 2008; 180(4):673-679. PMCID: PMC2265566
Yang F, Gell K, van der Heijden GW, Eckardt S, Leu NA, Page DC, Benavente R, Her C, Höög C, McLaughlin KJ, Wang PJ. Meiotic failure in male mice lacking an X-linked factor. Genes & Development. 2008; 22(5):682-691. PMCID: PMC2259036
This article was featured in Penn Press Release on March 14, 2008: Penn Researchers Identify First Sex Chromosome Gene Involved in Meiosis and Male Infertility.
Honaramooz A, Megee S, Zeng W, Destrempes MM, Overton SA, Luo J, Galantino-Homer H, Modelski M, Chen F, Blash S, Melican DT, Gavin WG, Ayres S, Yang F, Wang PJ, Echelard Y, Dobrinski I. Adeno-associated virus (AAV) -mediated transduction of male germ line stem cells results in transgene transmission after germ cell transplantation. FASEB J. 2008;22(2):374-82. PMID: 17873102
Wang P.J. and Pan J. The role of spermatogonially expressed germ cell-specific genes in mammalian meiosis. Chromosome Res. 2007;15(5):623-32. PMID: 17674150
Cheng Y., Buffone, M.G., Kouadio M., Goodheart M., Page D.C., Gerton G.L., Davidson I., and Wang P.J. Abnormal sperm in mice lacking the Taf7l gene. Mol. Cell. Biol. 2007; 27(7):2582-2589. PMCID: PMC1899882
Yang F., Skaletsky H., and Wang P.J. Ubl4b, an X-derived retrogene, is specifically expressed in post-meiotic germ cells in mammals. Gene Expr Patterns. 2007; 7(1-2):131-136. PMCID: PMC1647293
Yang F., De La Fuente R. Leu N.A., Baumann C, McLaughlin K.J., and Wang P.J. The mouse SYCP2 is required for synaptonemal complex assembly and chromosomal synapsis during male meiosis. J. Cell Biol. 2006;173(4):497-507. PMCID: PMC2063860
2001 - 2005
Pan J., Goodheart M., Chuma S., Nakatsuji N., Page D.C., and Wang P.J. RNF17, a component of the mammalian germ cell nuage, is essential for spermiogenesis. Development 2005;132:4029-4039. PMCID: PMC1994335
Wang P.J., Page D.C. and McCarrey J.R. Differential expression of sex-linked and autosomal germ-cell-specific genes during spermatogenesis in the mouse. Hum. Mol. Genet. 2005;14:2911-2918. PMCID: PMC1994333
Wang P. J. (2004) X chromosomes, retrogenes and their role in male reproduction. Trends Endocrinol. Metab. 15(2):79-83. PMID: 15036254
Wang P.J. and Page D.C. (2002) Functional substitution for TAFII250 by a retroposed homologue that is expressed in human spermatogenesis. Hum. Mol. Genet. 11(19):2341-2346. PMID: 12217962
Yang J., Bogerd H.P., Wang P.J., Page D.C. and Cullen B.R. (2001) Two closely related human nuclear export factors utilize entirely distinct export pathways. Mol. Cell 8:397-406. PMID: 11545741
Kosco K.A., Pearson C.G., Maddox P.S., Wang P.J., Adams I.R., Salmon E.D., Bloom K. and Huffaker T.C. (2001) Control of microtubule dynamics by Stu2p is essential for spindle orientation and metaphase chromosome alignment in yeast. Mol. Biol. Cell 12(9):2870-2880. PMCID: PMC59720
Wang P.J., McCarrey J.R., Yang F. and Page D.C. (2001) An abundance of X-linked genes expressed in spermatogonia. Nature Genetics. 27: 422-426. PMID:11279525
Wang P.J., Chabes A., Casagrande R., Tian X.C., Thelander L. and Huffaker T.C. (1997) Rnr4p, a novel ribonucleotide reductase small-subunit protein. Mol. Cell. Biol. 17:6114-6121. PMCID: PMC232461
Wang P.J. and Huffaker T.C. (1997) Stu2p: A microtubule-binding protein that is an essential component of the yeast spindle pole body. J. Cell Biol. 139:1271-1280. PMCID: PMC2140218