Genomic structure ofHstx2modifier ofPrdm9-dependent hybrid male sterility in mice

Abstract

F1 hybrids between mouse inbred strains PWD and C57BL/6 represent the 37 most thoroughly genetically defined model of hybrid sterility in vertebrates. Hybrid male 38 sterility can be fully reconstituted from three components of this model, namely the Prdm9 39 hybrid sterility gene, intersubspecific homeology of Mus musculus musculus and Mus 40 musculus domesticus autosomes, and the X-linked Hstx2 locus. Hstx2 modulates the extent of 41Prdm9-dependent meiotic arrest and harbors two additional genetic factors responsible for 42 intersubspecific introgression-induced oligospermia (Hstx1) and reduced global meiotic 43 recombination rate (Meir1). To facilitate positional cloning and to overcome the 44 recombination suppression within the 4.3 Mb genomicDob interval encompassing the Hstx2 45 locus we designed Hstx2-CRISPR and SPO11/Cas9 transgenes aimed to induce DNA double-46 strand breaks specifically within the Hstx2 locus. The resulting recombinant reduced the 47Hstx2 locus to 2.70 Mb (Chr X:66.51-69.21 Mb). The newly defined Hstx2 still operates as 48 the major X-linked factor of the F1 hybrid sterility, controls meiotic chromosome synapsis, 49 and modifies meiotic recombination rate. Despite extensive further crosses, the 2.70 Mb 50Hstx2 interval behaved as a recombination cold spot with reduced PRDM9-mediated H3K4 51 hotspots and absence of DMC1-defined DNA DSB hotspots. To search for structural 52 anomalies as a possible cause of recombination suppression we used optical mapping of the 53 Hstx2 interval and observed high incidence of subspecies-specific structural variants along the 54 X chromosome, with a striking copy number polymorphism of the microRNA Mir465 cluster. 55Finally, we analyzed the role of one of the Hstx2 candidate genes, the Fmr1 neighbor 56 (Fmr1nb) gene in male fertility. 57 58 Article summary 59 Early meiotic arrest of mouse intersubspecific hybrids depends on the interaction 60 between the Prdm9 gene and Hybrid sterility X2 (Hstx2) locus on chromosome X. 61 4 Lustyk et al. conducted high-resolution genetic and physical mapping of the Hstx2 62 locus, reduced it to 2.7 Mb interval within a constitutive recombination cold spot and 63 found that the newly defined Hstx2 still operates as the X-linked hybrid sterility factor, 64 controls meiotic chromosome synapsis, and modifies recombination rate. Optical 65 mapping of the Hstx2 genomic region excluded inversion as a cause of recombination 66 suppression and revealed a striking copy number polymorphism of the microRNA 67 Mir465 cluster. 68 69 70 REPRODUCTIVE isolation is a basic prerequisite of speciation implemented by a range of 71 prezygotic and postzygotic mechanisms under complex genetic control (DOBZHANSKY 1951; 72 DION-COTE AND BARBASH 2017). Hybrid sterility, one of the reproductive isolation 73 mechanisms between closely related taxa appears in the early stages of speciation. Hybrid 74 sterility is a universal phenomenon, since infertility of many animal and plant species hybrids 75 share common features, such as preferential involvemen...

Stage-specific disruption of X chromosome expression during spermatogenesis in sterile house mouse hybrids

“…The copyright holder for this preprint this version posted November 13, 2021. ; https://doi.org/10.1101/2021.11.12.468424 doi: bioRxiv preprint the musculus X chromosome (Hstx2, Storchová et al 2004;Bhattacharyya et al 2014;Lustyk et al 2019). A characteristic signal of Prdm9-associated sterility is the overexpression of the X chromosome during early meiosis I (Good et al 2010;Bhattacharyya et al 2013;Campbell et al 2013;Larson et al 2017), a developmental stage where the X chromosome would normally be transcriptionally inactive known as Meiotic Sex Chromosome Inactivation (MSCI, Turner 2015).…”

Age and Genetic Background Modify Hybrid Male Sterility in House Mice

“…Fertility in this HMS system can be rescued by decreasing the extent of asymmetric PRDM9 binding through transgenic rescue ( Mihola et al 2009 ), replacing the dom2 allele with dom3 or humanized Prdm9 alleles ( Flachs et al 2012 , 2014 ; Davies et al 2016 ), or by artificially creating random stretches of symmetric homology between certain chromosome pairs ( Gregorova et al 2018 ). The M. m. musculus allele of Hstx2 ( Dzur-Gejdosova et al 2012 ; Bhattacharyya et al 2014 ; Balcova et al 2016 ; Lustyk et al 2019 ) is necessary for HMS in all of the reported M. m. musculus x M. m. domesticus hybrids, though the nature of its interaction with Prdm9 remains uncharacterized.…”

Differential effects of two catalytic mutations on full-length PRDM9 and its isolated PR/SET domain reveal a case of pseudo-modularity

“…The ZnF DNA-binding domain is among the most rapidly evolving protein-coding regions known in vertebrates, in contrast to other ZnF proteins where these domains are mostly conserved (NAJAFABADI et al 2015;WOLF et al 2020). Second, it is the only mammalian hybrid sterility gene identified to date (MIHOLA et al 2009;BHATTACHARYYA et al 2013;LUSTYK et al 2019). Third, its loss was thought to lead to unconditional infertility, but the growing list of exceptions to this rule suggests modifiers and different degrees of dependence on PRDM9 for successful meiosis among mammalian species, subspecies, and populations (NARASIMHAN et al 2016;MIHOLA et al 2019;POWERS et al 2020).…”