Spermatogenetic Defects in Mouse Hybrids
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MASARYK UNIVERSITY FACULTY OF SCIENCE DEPARTMENT OF BOTANY AND ZOOLOGY Spermatogenetic defects in mouse hybrids PhD. Dissertation Iva Martincová Supervisor: Prom . biol. Jaroslav Piálek CSc. Institute of Vertebrate Biology, Czech Academy of Science Brno, 2019 Bibliographic Entry: Aut h or: Mgr. Iva Martincová Faculty of Science, Masaryk University Department of Botany and Zoology Title of Thesis: Sp ermatogenetic defects in mice hybrids Degree programe: Biology Field of Study: Zoology Supervisor: Prom. biol. Jaroslav Piálek CSc. Institute of Vertebrate Biology, Czech Academy of Sciences Academic year: 2018/2019 Number of pages: 146 Key words: Mus musculus musculus , Mus musculus domesticus , X chromosome, Y chromosome, hybrid sterility, wild - derived strains, phenotype variation, sperm heads, Y introgression Bibliografický záznam: Autor: Mgr. Iva Martincová Přírodovědecká fakulta, Masarykova univerzita Ústav botaniky a zoologie Název práce: Poruchy spermatogeneze u hybridních samců myší Studinjí program: Biologie Studijní obor: Zoologie Školitel: Prom. biol. Jaroslav Piálek CSc. Ústav biologie obratlovců, Akademie Věd České Republiky. Akademický rok: 2018/2019 Počet stránek: 146 Klíčová slova: Mus musculus musculus , Mus musculus domesticus , X chromosome, Y chromosome, hybrid sterility, wild - derived strains, phenotype variation, sperm heads, Y introgr ession Abstract The hybrid zone between two house mouse subspecies, Mus musculus musculus and M. m. domesticus , which diverged 0.5 MY ago, is thought to be a tension zone, maintained by a balance between migration of parental genomes into the area of the hybrid zone and by selection against hybrids. The selection is driven by the decreased fertility of hybrids. Thus these two subspecies represent an invaluable model for speciation studies. In this thesis I present the results from four papers conducted both in situ in the hybrid zone and under controlled laboratory condition s . The minor part of the results is focused on the effect of chromosome X on the fertility of hybrids, which seems to be well described elsewhere . However, in our study the position and role of a new X associated locus Hstx2 and three autosomal loci, polymorphic in M. m. musculus , which contribute to asymmetric hybrid sterility are described. The main focus of the thesis is concerned with the effec t of Y chromosome to male fitness, which has been rather neglected up to now. Firstly, the behaviour of M. m. musculus Y chromosome in the hybrid zone is examined. We discovered that the asymmetric introgression of M. m. musculus Y across the hybrid zone i nto M. m. domesticus territory is not restricted only to the Czech - Bavarian hybrid zone area , but is a common phenomenon in central Europe. The possible mechanisms of the Y chromosome spread across the hybrid zone are suggested by two studies utilising exp erimental crosses of strains derived from natural house mouse populations. In both studies we found a significant difference in the sperm quality in hybrid males possessing the Y chromosome from M. m. musculus and M. m. domesticus . In general, the hybrids carrying the M. m. domesticus Y chromosome display ed a higher incidence of sperm heads dissociated from the tail. We concluded that those differences are associated with the X chromosome and modulated by interaction with the Y chromosome. Given that these effects are strengthened in promiscuous species due to male - male competition, they can contribute to reproductive barriers and thus to speciation. Abstrakt Hybridní zóna mezi dvěma poddruhy myši domácí, Mus musculus musculus a M. m. domesticus , které se od společného předka oddělily před půl milionem let, je považována za tenzní hybridní zónu, udžovanou migrací rodičovských genomů do oblasti hybridní zóny a selekcí proti hybridům. Selekce je asociována se sníženou plodností hybridů. To dělá z tě chto dvou poddruhů neocenitelný model pro studium speciace. V této práci představuji výsledky ze čtyř studií , které byly provedeny jak in situ v hybridní zóně, tak v řízených laboratorních podmínkách. Menší část výsledků se týká vlivu chromozomu X na ferti litu hydridů, který se jeví být dobře zdokumentován. Přesto jsme v naší studii popsali pozici a roli nového lokusu Hstx2 na chromozomu X a tří autozomálních lokusů, polymorfních v populaci M. m. musculus , které přispívají k asymetrii hybridní sterility. Vě tší část práce je věnována dosud spíš opomíjenému vlivu chromozomu Y na plodnost samců. Nejprve jsme se zaměřili na chování chromozomu Y v hybridní zóně. Zjistili jsme že asymetrická introgrese chromozomu Y M. m. musculus na území M. m. domesticus není ome zena pouze na Česko - Bavorskou část hybridní zóny. Zdá se, že k tomuto jevu dochází ve střední Evropě běžně. Mechanismus, který může přispívat k šíření chromosomu Y přes hybridní zónu, byl naznačen dvěma studiemi, využívajícími experimentální křížení kmenů odvozených z divokých populací myši domácí. V obou studiích jsme zjistili podstatné rozdíly v kvalitě spermií mezi hybridy nesoucími chromozom Y původu M. m. musculus a M. m. domesticus . Obecně lze říci, že hybridi s chromozomem Y z poddruhu M. m. domestic us trpí zvýšeným výskytem spermií s disociovaným bičíkem. Z výsledků jsme vyvodili, že tyto rozdíly jsou asociovány s chromozomem X, ale jsou modulovány jeho interakcí s chromozomem Y. V situaci, kdy jsou tyto vlivy posilovány kompeticí mezi samci u promis kuitních druhů, mohou přispívat k posílení reprodukčích bariér a ke vzniku nových druhů. © Iva Martincová, Masaryk University, 2019 Acknowledgement Firstly , I would like to thank to my supervisor Jaroslav Piálek , who has taught me how to be a scientist. He has also enabled me to gain invaluable skills in managing, organizing and surviving. Many thanks also belong to Miloš Macholán who helped me to carry this burden. I want to thank the amazing collective in Stude nec, Institute of Vertebrate Biology CAS, the place which can hardly be compare d with anything else. Here I spent my best years. I would like to thank all people who helped me with the thesis. They know. Many thanks belong to my friends, who always accep ted all those crazy scientific things I’ve been doing. Special thanks to my family which supported me all the time. Last but not least, great thank to all those mice which sacrificed their lives on altar of science. The PhD thesis was supported by fundi ng of Czech Grant Agency. Project numbers: GA206/08/0640 , 17 - 25320S , and 19 - 12774S Declaration I declare that I elaborate the dissertation thesis on my own, with the usage of information sources, referenced in the thesis. Brno, 14 th June 2019 Iva Martincová Contents Preface ................................ ................................ ................................ ............................... 19 Introduction ................................ ................................ ................................ ....................... 21 Speciation ................................ ................................ ................................ ....................... 21 “Two rules of speciation” ................................ ................................ ............................... 21 Speciation genes ................................ ................................ ................................ ............ 23 Model organisms for speciation studies ................................ ................................ ........ 24 House mouse ( Mus musculus ) ................................ ................................ .......................... 25 House mouse hybrid zone ................................ ................................ .............................. 25 Aims of th e thesis ................................ ................................ ................................ .............. 27 What can the house mouse hybrid zone tell us about speciation? ................................ 28 The large X - effect in the hybrid zone ................................ ................................ ............. 28 Haldane’s rule in the hybrid zone ................................ ................................ .................. 29 What can laboratory experiments on mice tell us about speciation? ............................ 32 The laboratory evidence of large X - effect ................................ ................................ ..... 32 Laboratory evidence of Y chromosome effect to male fitness ................................ ...... 35 Summary ................................ ................................ ................................ ............................ 42 Reference s ................................ ................................ ................................ ......................... 44 Paper I ………………………………………………………………………………………………………………………………… …. 5 3 Paper II ………………………………………………………………………………………………………………………… 83 Paper III ……………………………………………………………………………………… ……………………………..10 1 Paper IV ……………………………………………… ……………………………………………………………………………….. 11 7 List of conferences …………………………………………………………………………………………………… ..1 45 Preface From the earliest time scientists start to ask a question how the animal species (including humans) came into being. During human history, many theories arose and vanished. Nowadays, the theory of evolution is generally accepted. It explains the origin of new species as a conse quence of natural selection. However simple and elegant the theory is , detailed knowledge about the mechanisms leading to new species origin still remain unclear. This thesis