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Genetic interactions of the Prdm9 gene
Šebestová, Lenka ; Trachtulec, Zdeněk (advisor) ; Král, Jiří (referee)
The Prdm9 gene (PR domain containing 9, Meisetz, Hybrid sterility 1) encodes enzyme that trimethylates histone 3 on lysines 4 and 36. These methylation marks determine the positions of DNA double-strand breaks that are repaired by meiotic homologous recombination. In this study, we assayed genetic interactions of Prdm9 with two genes important for spermatogenesis - Mili (Piwil2) involved in piRNA biogenesis and Mybl1 encoding transcription factor that regulates many genes important for prophase I, including piRNA precursors. We crossed laboratory mice carrying mutation in Prdm9 with heterozygotes for mutation in Mybl1 or Mili, and created compound heterozygotes and, in case of Mybl1, also double homozygotes. We assessed body weight and male fertility parameters (weight of testes, sperm count, malformed sperm, percentage of tubules containing spermatocytes and of abnormal nuclei of pachytene spermatocytes) of these mice and compared them to controls. We also investigated the effect of Mybl1 and Mili mutations on fecundity of F1 intersubspecific hybrids. Our results revealed possible interactions of Prdm9 and Mybl1 in the laboratory mouse. Decreased gene dosage of Mybl1 reduced fertility of intersubspecific F1 hybrids. Interaction between Prdm9 and Mili in both laboratory mouse and F1 hybrids remain...
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The role of methylation of histone 3 on lysine 4 (H3K4) during mouse spermatogenesis
Blumenstein, Jan ; Trachtulec, Zdeněk (advisor) ; Král, Jiří (referee)
Epige eti ké odifika e hro ati u hrají z ač ou roli v regula i přístup osti DNA. odifika í je etyla e histo ů. V H a lysi u ěhe sper atoge eze yši do á í a to zej é a ve Běhe eioti ké profáze I do hází k hro ozo ů, a k eioti ké reko i a i. Tyto pro esy jsou kriti ký ode tvor y pohlav í h u ěk a jeji h selhá í vede k eioti ké zástavě a tí páde k poruše tvor y haploid í h u ěk. Histo ová etyltra sferáza PRDM9 hraje klíčovou roli v eioti ké reko i a e, e oť je zodpověd á za urče í progra ova ý h dvouřetěz ový h zlo ů v íste h zva ý h hotspoty. Ni é ě ge je důležitý i ve spe ia i, a to řed i tví fe o é u hy rid í sterility. Další i protei y, které se podílí a etyla i histo u H a lysi u ěhe sper atoge eze, jsou MLL KMT D , MLL KMT E a yší h varlate h ovše az ačují, že regula i této odifika e hro ati u podílí ví e ge ů. Avšak ejsou z á é ko krét í fu k e, které ají tyto z ývají í ge y ěhe vývoje sa čí h pohlav í h u ěk. Další zkou á í tě hto ge ů ohou ýt užiteč á pro o jas ě í částeč é e o úpl é eplod os Klíčová slova: eioti ká reko i a e, dvouřetěz ové zlo y, hy rid í sterilita, sper atoge eze, etyla e histo ů
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Haldne's rule and mechanisms of hybrid female sterility in birds
Baránková, Lucie ; Reifová, Radka (advisor) ; Jansa, Petr (referee)
Hybrid sterility is one of the mechanisms of intrinsic postzygotic reproduction barriers between species and plays a key role in the process of speciation, which is emergence of new species. In accordance with Haldane's rule, hybrid sterility affects preferably the heterogametic sex, which means that in organisms with XY chromosomes, such as mammals or drosophila, male sterility will be affected by sterility of hybrid offspring, while organisms with ZW chromosomes such as birds or butterflies, will be a sterile hybrid female. Symptoms and mechanisms of hybrid sterility are well studied in organisms with heterogametic males, whereas far fewer studies have been performed on organisms with heterogamous females. In my bachelor thesis I will introduce the basic theories explaining the two general rules of speculation, the Haldane rule and the associated great influence of chromosome X or Z on the occurrence of hybrid sterility. Furthermore, in my work I will deal with the manifestations of hybrid sterility of females in birds and in the selected species will introduce the mechanisms that cause this sterility. Key words: Haldane's rule, hybrid sterility, speciation, birds, postzygotic izolation
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Evolution of intrinsic postzygotic reproductive isolation in birds
Opletalová, Kamila ; Reifová, Radka (advisor) ; Vošlajerová, Barbora (referee)
Hybrid sterility plays a key role in reproductive isolation during evolution of species. The mechanisms responsible for hybrid sterility are relatively well understood in organisms with heterogametic males, such as drosophila or mouse but are largely unknown in organisms with heterogametic females (e.g. birds). Studies on reproductive isolation in birds takes place in natural hybrid zones, instead of captivity. Hybrid sterility preferentially affects the heterogametic sex, males in mammals (XY) and females in birds (ZW), according to Haldane's rule. This leads to reduced introgression in sex chromosomes and mitochondrial DNA compared to autosomal DNA. The purpose of this thesis is to summarize known information on hybrid sterility and its expression in two models of interspecies hybridization: flycatchers and nightingales. Additionally, this thesis contains also a practical part, which compares morfology of sperms of two species of nightingales. Powered by TCPDF (www.tcpdf.org)
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Characterization of the Hstx1 and Hstx2 hybrid sterility candidate genes
Kašíková, Lenka ; Jansa, Petr (advisor) ; Rothová, Olga (referee)
Speciation, the formation of new species, is an essential evolutionary process that causes species diversity on the Earth. At the beginning of this process is the separation of two populations by a reproductive barrier that prevents gene flow between these populations. One of the mechanisms, which enable reproductive isolation, is hybrid sterility (HS). It is a mechanism of postzygotic isolation that is described in a number of eukaryotes. The first discovered gene of hybrid sterility in vertebrates is the mice gene Hst1, later identified as gene Prdm9. By genetic and molecular analysis the locus on the X chromosome was determined, whose interaction with Prdm9 causes sterility or reduced fitness in male hybrids. This locus contains two genetic factors: Hstx1, causing an abnormal morphology of spermatozoa, and Hstx2, causing an arrest in spermatogenesis in pachytene spermatocytes and sterility. In my thesis I focus on the effect of deletion of a candidate hybrid sterility gene Fmr1nb on the X chromosome. The analysis of males B6N.Fmr1nbmut with deletion variants of the Fmr1nb gene showed that Fmr1nb is one of the factors influencing spermatogenesis. An increase in morphologic abnormalities in spermatozoa occurred in males with Fmr1nb gene deletion. This phenotype is identical with Hstx1. The effect...
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Maping of genes modifying the subspecies-specific roles of the meiotic gene Prdm9
Škaloudová, Eliška ; Trachtulec, Zdeněk (advisor) ; Schierová, Michaela (referee)
The PRDM9 (PR domain containing 9) protein is an epigenetic factor that trimethylates lysine 4 of histone H3 and thereby determines the future meiotic double-strand breaks - sites important for proper segregation of homologous chromosomes. Males of the Mus musculus domesticus (Mmd) origin with homozygous deletion in Prdm9 (Prdm9-/- ) are sterile with a complete arrest in meiotic prophase I, in contrast to the same mutant males of the M. m. musculus (Mmm) subspecies. The aim of this diploma thesis was to identify the genomic loci responsible for the phenotypic difference of these Prdm9-/- males. The major research tool was a population of 182 Mmm x Mmd Prdm9-/- males. The mapping method of quantitative trait loci (QTLs) was based on relating the genotypes of single-nucleotide and microsatellite polymorphisms to the observed phenotypes. At least two QTLs on Chr X were identified. The Mmm alleles of these QTLs reduced fertility of Prdm9-/- males. Both QTLs were confirmed and narrowed down using two types of subconsomic strains. It was not possible to confirm other QTLs, particularly on autosomes. This QTL mapping is the first step towards the identification of genes that modify the resulting phenotype of Prdm9-/- animals. This identification should help designing studies of human infertility that...
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Genetics and Genomics of Hybrid Sterility
Bhattacharyya, Tanmoy ; Forejt, Jiří (advisor) ; Pravenec, Michal (referee) ; Macholán, Miloš (referee)
Charles University in Prague Faculty of Science Ph.D. study program: Molecular and Cellular Biology, Genetics and Virology Abstract Genetics and genomics of hybrid sterility Mgr. Tanmoy Bhattacharyya Supervisor: Prof. MUDr. Jiří Forejt, DrSc. Praha 2013 Abstract Male-limited hybrid sterility restricts gene flow between the related species, an important pre- requisite of speciation. The F1 hybrid males of PWD/Ph female (Mus m. musculus subspecies) and C57BL/6J or B6 male (Mus m. domesticus) are azoospermic and sterile (PB6F1), while the hybrids from the reciprocal (B6PF1) cross are semi fertile. A disproportionately large effect of the X chromosome (Chr) on hybrid male sterility is a widespread phenomenon accompanying the origin of new species. In the present study, we mapped two phenotypically distinct hybrid sterility loci Hstx1 and Hstx2 to a common 4.7 Mb region on Chr. X. Analysis of meiotic prophase I of PB6F1 sterile males revealed meiotic block at mid-late pachynema and the TUNEL assay showed apoptosis of arrested spermatocytes. In sterile males over 95% of pachytene spermatocytes showed one or more unsynapsed autosomes visualized by anti SYCP1, HORMAD2 and SYCP3 antibodies. The phosphorylated form of H2AFX histone, normally restricted only to XY chromosome containing sex body decorated unsynapsed...
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Genetic conflicts and speciation
Kropáčková, Lucie ; Munclinger, Pavel (referee) ; Reifová, Radka (advisor)
In this thesis I'll examine the role of genetic conflicts in the origin of new species. Genetic conflicts can lead to an origin of reproductive barrier between the emerging species, especially postzygotic reproductive isolation. An example of such conflict could be meiotic drive on sex chromosomes, which distort sex ratio and seems to act a role in a hybrid male sterility. Another example may be genomic imprinting causing an abnormal placenta and embryo development in interspecies hybrids. Coevolution between cytoplasmic and nuclear genes can cause sterility of pollen in hybrids from plants. Similarly, the intracellular bacterium Wolbachia induces cytoplasmic incompatibility in animals. Mobilization of transposons may also lead to hybrid dysgenesis.
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