Hybrid sterility contributes to speciation by preventing gene flow between related taxa. Prdm9, the first and only hybrid male sterility gene known in vertebrates, predetermines the sites of recombination between homologous chromosomes and their synapsis in early meiotic prophase. The asymmetric binding of PRDM9 to heterosubspecific homologs of Mus musculus musculus × Mus musculus domesticus F1 hybrids and increase of PRDM9-independent DNA double-strand break hotspots results indificult- to- repair double-strand breaks, incomplete synapsis of homologous chromosomes, and meiotic arrest at the first meiotic prophase. Here, we show that Prdm9 behaves as a major hybrid male sterility gene in mice outside the Mus musculus musculus × Mus musculus domesticus F1 hybrids, in the genomes composed of Mus musculus castaneus and Mus musculus musculus chromosomes segregating on the Mus musculus domesticus background. The Prdm9cst/dom2 (castaneus/domesticus) allelic combination secures meiotic synapsis, testes weight, and sperm count within physiological limits, while the Prdm9msc1/dom2 (musculus/domesticus) males show a range of fertility impairment. Out of 5 quantitative trait loci contributing to the Prdm9msc1/dom2-related infertility, 4 control either meiotic synapsis or fertility phenotypes and 1 controls both, synapsis, and fertility. Whole-genome genotyping of individual chromosomes showed preferential involvement of nonrecombinant musculus chromosomes in asynapsis in accordance with the chromosomal character of hybrid male sterility. Moreover, we show that the overall asynapsis rate can be estimated solely from the genotype of individual males by scoring the effect of nonrecombinant musculus chromosomes. Prdm9-controlled hybrid male sterility represents an example of genetic architecture of hybrid male sterility consisting of genic and chromosomal components.

• Klíčová slova
• HORMAD2, SYCP3, homologous synapsis, meiosis, spermatogenesis, synaptonemal complex,
• MeSH
• chromozomy MeSH
• histonlysin-N-methyltransferasa genetika   metabolismus   MeSH
• meióza * genetika   MeSH
• mužská infertilita * genetika   MeSH
• myši MeSH
• sperma metabolismus   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• histonlysin-N-methyltransferasa MeSH
• prdm9 protein, mouse MeSH Prohlížeč

The classical definition posits hybrid sterility as a phenomenon when two parental taxa each of which is fertile produce a hybrid that is sterile. The first hybrid sterility gene in vertebrates, Prdm9, coding for a histone methyltransferase, was identified in crosses between two laboratory mouse strains derived from Mus mus musculus and M. m. domesticus subspecies. The unique function of PRDM9 protein in the initiation of meiotic recombination led to the discovery of the basic molecular mechanism of hybrid sterility in laboratory crosses. However, the role of this protein as a component of reproductive barrier outside the laboratory model remained unclear. Here, we show that the Prdm9 allelic incompatibilities represent the primary cause of reduced fertility in intersubspecific hybrids between M. m. musculus and M. m. domesticus including 16 musculus and domesticus wild-derived strains. Disruption of fertility phenotypes correlated with the rate of failure of synapsis between homologous chromosomes in meiosis I and with early meiotic arrest. All phenotypes were restored to normal when the domesticus Prdm9dom2 allele was substituted with the Prdm9dom2H humanized variant. To conclude, our data show for the first time the male infertility of wild-derived musculus and domesticus subspecies F1 hybrids controlled by Prdm9 as the major hybrid sterility gene. The impairment of fertility surrogates, testes weight and sperm count, correlated with increasing difficulties of meiotic synapsis of homologous chromosomes and with meiotic arrest, which we suppose reflect the increasing asymmetry of PRDM9-dependent DNA double-strand breaks.

• Klíčová slova
• Prdm9 polymorphism, HORMAD2, meiotic chromosome synapsis, reproductive isolation, synaptonemal complex,
• MeSH
• fylogeografie MeSH
• genová introgrese * MeSH
• histonlysin-N-methyltransferasa genetika   MeSH
• infertilita genetika   MeSH
• meióza MeSH
• myši genetika   MeSH
• reprodukční izolace * MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši genetika   MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• histonlysin-N-methyltransferasa MeSH
• prdm9 protein, mouse MeSH Prohlížeč

F1 hybrids between mouse inbred strains PWD and C57BL/6 represent the most thoroughly genetically defined model of hybrid sterility in vertebrates. Hybrid male sterility can be fully reconstituted from three components of this model, the Prdm9 gene, intersubspecific homeology of Mus musculus musculus and Mus musculus domesticus autosomes, and the X-linked Hstx2 locus. Hstx2 modulates the extent of Prdm9-dependent meiotic arrest and harbors two additional factors responsible for intersubspecific introgression-induced oligospermia (Hstx1) and meiotic recombination rate (Meir1). To facilitate positional cloning and to overcome the recombination suppression within the 4.3 Mb encompassing the Hstx2 locus, we designed Hstx2-CRISPR and SPO11/Cas9 transgenes aimed to induce DNA double-strand breaks specifically within the Hstx2 locus. The resulting recombinant reduced the Hstx2 locus to 2.70 Mb (chromosome X: 66.51-69.21 Mb). The newly defined Hstx2 locus still operates as the major X-linked factor of the F1 hybrid sterility, and controls meiotic chromosome synapsis and meiotic recombination rate. Despite extensive further crosses, the 2.70 Mb Hstx2 interval behaved as a recombination cold spot with reduced PRDM9-mediated H3K4me3 hotspots and absence of DMC1-defined DNA double-strand-break hotspots. To search for structural anomalies as a possible cause of recombination suppression, we used optical mapping and observed high incidence of subspecies-specific structural variants along the X chromosome, with a striking copy number polymorphism of the microRNA Mir465 cluster. This observation together with the absence of a strong sterility phenotype in Fmr1 neighbor (Fmr1nb) null mutants support the role of microRNA as a likely candidate for Hstx2.

• Klíčová slova
• Bionano optical mapping, Fmr1nb, Hybrid sterility X2, Prdm9, SPO11Cas9 transgene, Speciation,
• MeSH
• chromozom X genetika   MeSH
• histonlysin-N-methyltransferasa genetika   MeSH
• homologní rekombinace MeSH
• meióza MeSH
• mikro RNA genetika   MeSH
• modifikátorové geny * MeSH
• mužská infertilita genetika   MeSH
• myši inbrední C57BL MeSH
• myši MeSH
• polymorfismus genetický * MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• histonlysin-N-methyltransferasa MeSH
• mikro RNA MeSH
• prdm9 protein, mouse MeSH Prohlížeč

Hybrid sterility is one of the reproductive isolation mechanisms leading to speciation. Prdm9, the only known vertebrate hybrid-sterility gene, causes failure of meiotic chromosome synapsis and infertility in male hybrids that are the offspring of two mouse subspecies. Within species, Prdm9 determines the sites of programmed DNA double-strand breaks (DSBs) and meiotic recombination hotspots. To investigate the relation between Prdm9-controlled meiotic arrest and asynapsis, we inserted random stretches of consubspecific homology on several autosomal pairs in sterile hybrids, and analyzed their ability to form synaptonemal complexes and to rescue male fertility. Twenty-seven or more megabases of consubspecific (belonging to the same subspecies) homology fully restored synapsis in a given autosomal pair, and we predicted that two or more DSBs within symmetric hotspots per chromosome are necessary for successful meiosis. We hypothesize that impaired recombination between evolutionarily diverged chromosomes could function as one of the mechanisms of hybrid sterility occurring in various sexually reproducing species.

• Klíčová slova
• Prdm9, chromosomes, evolutionary biology, gene expression, genomics, homology-dependent meiotic chromosome pairing, mouse, speciation, synaptonemal complex,
• MeSH
• biologická evoluce * MeSH
• chiméra genetika   MeSH
• chromozomy genetika   MeSH
• dvouřetězcové zlomy DNA MeSH
• histonlysin-N-methyltransferasa genetika   MeSH
• hybridizace genetická MeSH
• infertilita genetika   MeSH
• meióza genetika   MeSH
• mužská infertilita genetika   MeSH
• myši MeSH
• párování chromozomů genetika   MeSH
• rekombinace genetická MeSH
• reprodukční izolace MeSH
• synaptonemální komplex genetika   MeSH
• vznik druhů (genetika) MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• histonlysin-N-methyltransferasa MeSH
• prdm9 protein, mouse MeSH Prohlížeč

PR-domain 9 (Prdm9) is the first hybrid sterility gene identified in mammals. The incompatibility between Prdm9 from Mus musculus domesticus (Mmd; the B6 strain) and the Hstx2 region of chromosome (Chr) X from M. m. musculus (Mmm; the PWD strain) participates in the complete meiotic arrest of mouse intersubspecific (PWD×B6)F1 hybrid males. Other studies suggest that also semisterile intersubspecific hybrids are relevant for mouse speciation, but the genes responsible remain unknown. To investigate the causes of this semisterility, we analyzed the role of Prdm9 and Chr X in hybrids resulting from the crosses of PWK, another Mmm-derived inbred strain. We demonstrate that Prdm9 and Chr X control the partial meiotic arrest and reduced sperm count in (PWK×B6)F1 males. Asynapsis of heterosubspecific chromosomes and semisterility were partially suppressed by removal of the B6 allele of Prdm9. Polymorphisms between PWK and PWD on Chr X but not in the Prdm9 region were responsible for the modification of the outcome of Prdm9-Chr X F1 hybrid incompatibility. Furthermore, (PWK×B6)F1 hybrid males displayed delayed fertility dependent on the Prdm9 incompatibility. While the Drosophila hybrid sterility gene Overdrive causes both delayed fertility and increased transmission of its own chromosome to the offspring, the segregation of Chr X and the Prdm9 region from the mouse (PWK×B6)F1 males was normal. Our results indicate extended functional consequences of Prdm9-Chr X intersubspecific incompatibility on the fertility of hybrids and should influence the design of fertility analyses in hybrid zones and of laboratory crosses between Mmm and Mmd strains.

• MeSH
• alely MeSH
• fenotyp MeSH
• genotyp MeSH
• genová dávka MeSH
• histonlysin-N-methyltransferasa genetika   MeSH
• křížení genetické * MeSH
• lokus kvantitativního znaku MeSH
• meióza MeSH
• mužská infertilita genetika   MeSH
• myši MeSH
• oligospermie genetika   MeSH
• savčí chromozomy MeSH
• testis metabolismus   patologie   MeSH
• věkové faktory MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• histonlysin-N-methyltransferasa MeSH
• prdm9 protein, mouse MeSH Prohlížeč

The Dobzhansky-Muller model of incompatibilities explains reproductive isolation between species by incorrect epistatic interactions. Although the mechanisms of speciation are of great interest, no incompatibility has been characterized at the gene level in mammals. The Hybrid sterility 1 gene (Hst1) participates in the arrest of meiosis in F(1) males of certain strains from two Mus musculus subspecies, e.g., PWD from M. m. musculus and C57BL/6J (henceforth B6) from M. m. domesticus. Hst1 has been identified as a meiotic PR-domain gene (Prdm9) encoding histone 3 methyltransferase in the male offspring of PWD females and B6 males, (PWD×B6)F(1). To characterize the incompatibilities underlying hybrid sterility, we phenotyped reproductive and meiotic markers in males with altered copy numbers of Prdm9. A partial rescue of fertility was observed upon removal of the B6 allele of Prdm9 from the azoospermic (PWD×B6)F(1) hybrids, whereas removing one of the two Prdm9 copies in PWD or B6 background had no effect on male reproduction. Incompatibility(ies) not involving Prdm9(B6) also acts in the (PWD×B6)F(1) hybrids, since the correction of hybrid sterility by Prdm9(B6) deletion was not complete. Additions and subtractions of Prdm9 copies, as well as allelic replacements, improved meiotic progression and fecundity also in the progeny-producing reciprocal (B6×PWD)F(1) males. Moreover, an increased dosage of Prdm9 and reciprocal cross enhanced fertility of other sperm-carrying male hybrids, (PWD×B6-C3H.Prdm9)F(1), harboring another Prdm9 allele of M. m. domesticus origin. The levels of Prdm9 mRNA isoforms were similar in the prepubertal testes of all types of F(1) hybrids of PWD with B6 and B6-C3H.Prdm9 despite their different prospective fertility, but decreased to 53% after removal of Prdm9(B6). Therefore, the Prdm9(B6) allele probably takes part in posttranscriptional dominant-negative hybrid interaction(s) absent in the parental strains.

• MeSH
• alely MeSH
• chiméra * genetika   fyziologie   MeSH
• fertilita genetika   MeSH
• genetická epistáze * MeSH
• histonlysin-N-methyltransferasa genetika   MeSH
• hybridizace genetická MeSH
• mapování chromozomů MeSH
• meióza MeSH
• mužská infertilita genetika   MeSH
• myši MeSH
• reprodukční izolace MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• histonlysin-N-methyltransferasa MeSH
• prdm9 protein, mouse MeSH Prohlížeč

The hybrid sterility-1 (Hst1) locus at Chr 17 causes male sterility in crosses between the house mouse subspecies Mus musculus domesticus (Mmd) and M. m. musculus (Mmm). This locus has been defined by its polymorphic variants in two laboratory strains (Mmd genome) when mated to PWD/Ph mice (Mmm genome): C57BL/10 (carrying the sterile allele) and C3H (fertile allele). The occurrence of sterile and/or fertile (wild Mmm x C57BL)F1 males is evidence that polymorphism for this trait also exists in natural populations of Mmm; however, the nature of this polymorphism remains unclear. Therefore, we derived two wild-origin Mmm strains, STUS and STUF, that produce sterile and fertile males, respectively, in crosses with C57BL mice. To determine the genetic basis underlying male fertility, the (STUS x STUF)F1 females were mated to C57BL/10 J males. About one-third of resulting hybrid males (33.8%) had a significantly smaller epididymis and testes than parental animals and lacked spermatozoa due to meiotic arrest. A further one-fifth of males (20.3%) also had anomalous reproductive traits but produced some spermatozoa. The remaining fertile males (45.9%) displayed no deviation from values found in parental individuals. QTL analysis of the progeny revealed strong associations of male fitness components with the proximal end of Chr 17, and a significant effect of the central section of Chr X on testes mass. The data suggest that genetic incompatibilities associated with male sterility have evolved independently at the proximal end of Chr 17 and are polymorphic within both Mmd and Mmm genomes.

• MeSH
• epididymis abnormality   patologie   MeSH
• lokus kvantitativního znaku MeSH
• mužská infertilita genetika   MeSH
• myši inbrední C57BL MeSH
• myši MeSH
• polymorfismus genetický * MeSH
• savčí chromozomy genetika   MeSH
• spermie abnormality   MeSH
• testis abnormality   patologie   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Extensive linkage disequilibrium among classical laboratory strains represents an obstacle in the high-resolution haplotype mapping of mouse quantitative trait loci (QTL). To determine the potential of wild-derived mouse strains for fine QTL mapping, we constructed a haplotype map of a 250-kb region of the t-complex on chromosome 17 containing the Hybrid sterility 1 (Hst1) gene. We resequenced 33 loci from up to 80 chromosomes of five mouse (sub)species. Trans-species single-nucleotide polymorphisms (SNPs) were rare between Mus m. musculus (Mmmu) and Mus m. domesticus (Mmd). The haplotypes in Mmmu and Mmd differed and therefore strains from these subspecies should not be combined for haplotype-associated mapping. The haplotypes of t-chromosomes differed from all non-t Mmmu and Mmd haplotypes. Half of the SNPs and SN indels but only one of seven longer rearrangements found in classical laboratory strains were useful for haplotype mapping in the wild-derived M. m. domesticus. The largest Mmd haplotype block contained three genes of a highly conserved synteny. The lengths of the haplotype blocks deduced from 36 domesticus chromosomes were in tens of kilobases, suggesting that the wild-derived Mmd strains are suitable for fine interval-specific mapping.

• MeSH
• druhová specificita MeSH
• fylogeneze MeSH
• genová přestavba MeSH
• haplotypy * MeSH
• lidé MeSH
• lidské chromozomy, pár 6 genetika   MeSH
• myši genetika   MeSH
• pilotní projekty MeSH
• savčí chromozomy genetika   MeSH
• sekvenční analýza DNA MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši genetika   MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Consomic (chromosome substitution) strains (CSs) represent the most recent addition to the mouse genetic resources aimed to genetically analyze complex trait loci (QTLs). In this study, we report the development of a set of 28 mouse intersubspecific CSs. In each CS, we replaced a single chromosome of the C57BL/6J (B6) inbred strain (mostly Mus m. domesticus) with its homolog from the PWD/Ph inbred strain of the Mus m. musculus subspecies. These two progenitor subspecies diverged less than 1 million years ago and accumulated a large number of genetic differences that constitute a rich resource of genetic variation for QTL analyses. Altogether, the 18 consomic, nine subconsomic, and one conplastic strain covered all 19 autosomes, X and Y sex chromosomes, and mitochondrial DNA. Most CSs had significantly lower reproductive fitness compared with the progenitor strains. CSs homosomic for chromosomes 10 and 11, and the C57BL/6J-Chr X males, failed to reproduce and were substituted by less affected subconsomics carrying either a proximal, central, or distal part of the respective chromosome. A genome-wide scan of 965 DNA markers revealed 99.87% purity of the B6 genetic background. Thirty-three nonsynonymous substitutions were uncovered in the protein-coding regions of the mitochondrial DNA of the B6.PWD-mt conplastic strain. A pilot-phenotyping experiment project revealed a high number of variations among B6.PWD consomics.

• MeSH
• fenotyp MeSH
• genetická variace MeSH
• inbrední kmeny myší genetika   MeSH
• lokus kvantitativního znaku * MeSH
• mitochondriální DNA chemie   MeSH
• molekulární sekvence - údaje MeSH
• myši inbrední C57BL MeSH
• myši MeSH
• poměr pohlaví MeSH
• rozmnožování MeSH
• savčí chromozomy MeSH
• sekvence nukleotidů MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Názvy látek
• mitochondriální DNA MeSH

Hybrid sterility is a common postzygotic reproductive isolation mechanism that appears in the early stages of speciation of various organisms. Mus musculus musculus and Mus musculus domesticus represent two recently separated mouse subspecies particularly suitable for genetic studies of hybrid sterility. Here we show that the introgression of Chr X of M. m. musculus origin (PWD/Ph inbred strain, henceforth PWD) into the genetic background of the C57BL/6J (henceforth B6) inbred strain (predominantly of M. m. domesticus origin) causes male sterility. The X-linked hybrid sterility is associated with reduced testes weight, lower sperm count, and morphological abnormalities of sperm heads. The analysis of recombinant Chr Xs in sterile and fertile males as well as quantitative trait locus (QTL) analysis of several fertility parameters revealed an oligogenic nature of the X-linked hybrid sterility. The Hstx1 locus responsible for male sterility was mapped near DXMit119 in the central part of Chr X. To ensure full sterility, the PWD allele of Hstx1 has to be supported with the PWD allelic form of loci in at least one proximal and/or one distal region of Chr X. Mapping and cloning of Hstx1 and other genes responsible for sterility of B6-X PWD Y B6 males could help to elucidate the special role of Chr X in hybrid sterility and consequently in speciation.

• MeSH
• akrozomální reakce MeSH
• alely MeSH
• chromozom X * MeSH
• fenotyp MeSH
• genetická vazba * MeSH
• genetické markery MeSH
• genotyp MeSH
• křížení genetické MeSH
• lokus kvantitativního znaku MeSH
• monoklonální protilátky chemie   MeSH
• mužská infertilita genetika   MeSH
• myši inbrední BALB C MeSH
• myši inbrední C57BL MeSH
• myši MeSH
• rekombinantní proteiny chemie   MeSH
• sexuální faktory MeSH
• spermie patologie   MeSH
• testis patologie   MeSH
• ženská infertilita genetika   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• genetické markery MeSH
• monoklonální protilátky MeSH
• rekombinantní proteiny MeSH