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Jenny Graves at SMBE2014: Sex, Genes and Sequence
The document discusses the origins and evolution of sex chromosomes, focusing on the differences between X and Y chromosomes, their gene structures, and their degradation over time. It highlights the unique roles of sex-determining genes, including the environmental influences on sex determination and various mechanisms across different vertebrates. Additionally, it explores how new sex genes can evolve from existing autosomal genes and the implications for sex chromosomal specialization and dysfunction.
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Jenny Graves at SMBE2014: Sex, Genes and Sequence
- 1. Sex, Genes andSequence Sex chromosomes – most interesting part of genome Origins, evolution, future of X and Y Epigenetics and environmental sex Origins, evolution of sex genes Jenny Graves LA Trobe University, ANU, U Canberra
- 2. Sex chromosomes areweird X 1669 genes Many different functions Many sex, intelligence genes Brains-and-balls genes Y Only 27 genes specific to Y Many copies, pseudogenes Male-specific functions Sex and spermatogenesis PAR Shared by X and Y Contains 24 genes Smart, Sexy X Wimpy Y
- 3. • Problems atmeiosis • Dosage problems • Sex-linked diseases • Sex-reversal syndromes Why so weird? • so they work optimally? • evolutionary accident? XXXXXXXXXXXXXXXXX X Y Dumb Sex chromosomes –> trouble • the Y self-destructs!
- 4. X Y proto-XY XY evolution Oncethe X and Y were an ordinary pair One partner acquires a male-determining gene Other male-advantage genes accumulate - recombination suppressed Y degraded by deletion, mutation And degraded and degraded And can even disappear The Y is a degraded X Evidence: XY homology; independent Y dropouts
- 5. Self-destruction of theY High variation • frequent mutation, deletion, insertion in testis Inefficient selection and drift • no recombination, no repair Rate of loss is ~10 genes/MY Y will self-destruct in 4.6 mY
- 6. How the Ychromosome determines sex female male X X X Y TDF testis hormones =SRY
- 7. Y genes aredegraded X genes TSPY Spermatogenesis? RBMY Spermatogenesis Y SRY Sex determination RBMX Mental retardation? X SOX3 Mental retardation spermatogenesis TSPX Cell cycle? Most Y genes have copies on X Brains-and-balls genes –> sex and fertility genes X-Y shared dosage-sensitive genes in added region
- 8.
- 9. Mammals Amniotes Tetrapods Fish Amphibians Reptiles and birdsMonotremes Marsupials Placentals 450 410 310 166 148 XY Origin of human sex chromosomes Human Mouse 105 X ? Elephant ??? Mammals
- 10. Y X Origin of humanXY Elephant XX A Kangaroo Human Map orthologues of human X genes
- 11. Y Chicken Platypus KangarooElephant Human X64 1q A X A X Origin of human XY
- 12. Male Female Z ZZ W Bird sex W is a degraded Z Chicken Emu
- 13. XY and ZWchromosomes follow the same evolutionary rules X Y W Z humans mice kangaroos ratite birds carinate birds
- 14. male female Z ZZ W What is the bird sex-determining gene? No SRY Dose-dependent sex determination DMRT1 on Z but not W Need two doses to make enough male-determining product Knockdown –> ZZ female
- 15. Platypus sex chromosomes X1Y1 X2 Y2 X3 Y3 X4 Y4 X5 Y5 Female: 26 pairsMale: 21 pairs + 10 Homology to chick ZW No homology to human XY No SRY AMH Sex determining?
- 16. Mammals Amniotes Tetrapods Fish Amphibians Reptiles and birdsMonotremes Marsupials Placentals 450 410 310 166 148 XYXYTSD,XY,ZW XY ZW XYXYXYXYXY Origin of human sex chromosomes ZW? SRY
- 17. XY and ZWchromosomes follow the same evolutionary rules X Y W Z humans mice kangaroos ratite birds carinate birds boid snakes colubrid snakes vipers
- 18. Snake sex chromosomes Vicosoet al, PLoS Biol 2013 Coverage for male ZZ (blue) and female ZW (red) Assembled against Anolis macrochromosomes 1-6 Conserved Z Boids show no ZW differentiation Colubrids and viperids show extreme ZW differentiation Snakes are ZZ male / ZW female Snake Z = chicken 2
- 19. SOX3 4 2 5 TSD turtle BirdsPlatypus Kangaroo HumanSnakes 1 DMRT1 SOX3 4 ZW 2 1 DMRT1 SOX3 SRY X Y 4 3,7,10 SOX3 SRY X Y 5 1 3 SOX3 6 15, 18 DMRT1 X Y X Y X Y X Y X Y ? DMRT1 SOX3 4 2 ZW 1 Different genome regions became sex chromosomes in different vertebrates
- 20. Sex in frogs Yoshimoto& Ito, FEBS J 2011 Conclude DMW inhibits DMRT1 2 DMRT1 –> male 2 DMRT1 + DMW –> female DMW defines new W Xenopus laevis has ZZ / ZW Found DMRT1 homologue on W DMW knockdown –> ZW males ZW=XY=human Xq SOX3 is sex determining Rana rugosa has ZZ / ZW and XY / XX Miura et al 2010
- 21. Sex in Fish Linkageanalysis –> chr 1=XY Y Positional cloning –>DMRT1 copy XX female XX+DMY male XY male Transgenic DMY –> XX male Matsuda et al, Nature 2002; PNAS 2007 soma testis Conclude: 2 DMRT1 female 2 DMRT1 + DMY male DMY defines a new Y Medaka Oryzias latipes
- 22. MALE FEMALE Z Z XY Z Z Z W X X Z W A A A A A A A A Neo-Y Neo-W Origin of new sex genes? from copy from inactive copy
- 23. Sex in othermedaka species O. latipes LG1 DMY O. curvinotos LG1 DMY => Change in expression level or timing O. dancera LG10 ? Oda (XY=LG10) Sox3 on X, Y –> same protein Overexpression of Sox3 –>male Olu ( XY=LG12) Gsdf on X, Y–>same protein Overexpression of GsdfY –>male O. luzonensis LG12 ? Ope (XY=LG12) Gsdf on X, Y–>same protein Early expression of GsdfbY –>male O. pectoralis LG12 ?
- 24. A A A A XY X Y A A A A Z W Z W Overexpression of one allele MALE FEMALE testis ovary New sex genes from expression change testis ovary Change in timing or tissue of expression
- 25. Ectopic expression intestis –>XX males SOX3 active in brain, germ-cells Evolution of SRY Fusion expression in gonad SRY testis determination New function Sato et al Mol Cell Biol 2010; Sutton et al J Clin Invest 2011
- 26. Mammals Amniotes Tetrapods Fish Amphibians Reptiles and birdsMonotremes Marsupials Placentals 450 410 310 166 148 XYXYTSD,XY,ZW XY ZW XYXYXYXYXY Independent recruitment of sex genes M Y DMY O. latipes DMW X. laevis DMRT1 birds SRY SOX3 SOX3 R. rugosa SOX3 O. dancera AMH sea bass AMH? DMRT1 tongue sole Mammals
- 27. Temperature Sex Determination- TSD e.g. Crocodiles and marine turtles No sex chromosomes Chick Z 6 6
- 28. Dragon lizard Pogonavitticeps %males Temperature –> 50 0 GSD TSD Identification of ZW by CGH W Quinn et al Science ‘07 A dragon with ZW and TSD GSD–> TSD ZW –> XY
- 29. male female Z ZZ W Normal temperature female female Z Z Z W High temperature Sex in dragons Finding dragon sex determining gene…. dose-dependent and temperature -dependent Microdissected W, screened for W BACs Sequenced W BAC –> RCC1, OPRD1, syntenic with RSPO1… Sequenced ZZ male, ZW female, ZZ female at BGI
- 30. ZZ ZW ZW malefemale pseudomale dmrt1 dmrt1 dmrt1 Epigenetic sex determination Half smooth tongue sole Chen et al Nature, Shao et al Genome Res AUTOSOMES SEX CHROMOSOMES methylation
- 31. Conclusions Vertebrate genome isvery conserved Different genome regions became sex chromosomes New sex genes evolve, often from same autosomal gene Sex chromosomes specialize, then self-destruct Sex can be determined or modified by environment