Pseudoautosomal Research Articles

The Location of the Pseudoautosomal Boundary in Silene latifolia.

Y-chromosomes contain a non-recombining region (NRY), and in many organisms it was shown that the NRY expanded over time. How and why the NRY expands remains unclear. Young sex chromosomes, where NRY expansion occurred recently or is on-going, offer an opportunity to study the causes of this process. Here, we used the plant Silene latifolia, where sex chromosomes evolved ~11 million years ago, to study the location of the boundary between the NRY and the recombining pseudoautosomal region (PAR). The previous work devoted to the NRY/PAR boundary in S. latifolia was based on a handful of genes with locations approximately known from the genetic map. Here, we report the analysis of 86 pseudoautosomal and sex-linked genes adjacent to the S. latifolia NRY/PAR boundary to establish the location of the boundary more precisely. We take advantage of the dense genetic map and polymorphism data from wild populations to identify 20 partially sex-linked genes located in the “fuzzy boundary”, that rarely recombines in male meiosis. Genes proximal to this fuzzy boundary show no evidence of recombination in males, while the genes distal to this partially-sex-linked region are actively recombining in males. Our results provide a more accurate location for the PAR boundary in S. latifolia, which will help to elucidate the causes of PAR boundary shifts leading to NRY expansion over time.

Ensuring meiotic DNA break formation in the mouse pseudoautosomal region.

Sex chromosomes in males of most eutherian species share only a diminutive homologous segment, the pseudoautosomal region (PAR), wherein double-strand break (DSB) formation, pairing, and crossing over must occur for correct meiotic segregation1,2. How cells ensure PAR recombination is unknown. Here we delineate an unexpected dynamic ultrastructure of the PAR and identify controlling cis- and trans-acting factors that make this the hottest area of DSB formation in the male mouse genome. Before break formation, multiple DSB-promoting factors hyper-accumulate in the PAR, its chromosome axes elongate, and the sister chromatids separate. These phenomena are linked to heterochromatic mo-2 minisatellite arrays and require MEI4 and ANKRD31 proteins but not axis components REC8 or HORMAD1. We propose that the repetitive PAR sequence confers unique chromatin and higher order structures crucial for recombination. Chromosome synapsis triggers collapse of the elongated PAR structure and, remarkably, oocytes can be reprogrammed to display spermatocyte-like PAR DSB levels simply by delaying or preventing synapsis. Thus, sexually dimorphic behavior of the PAR rests in part on kinetic differences between the sexes for a race between maturation of PAR structure, DSB formation, and completion of pairing and synapsis. Our findings establish a mechanistic paradigm of sex chromosome recombination during meiosis.

Genes that escape from X-chromosome inactivation: Potential contributors to Klinefelter syndrome.

One of the two X chromosomes in females is epigenetically inactivated, thereby compensating for the dosage difference in X‐linked genes between XX females and XY males. Not all X‐linked genes are completely inactivated, however, with 12% of genes escaping X chromosome inactivation and another 15% of genes varying in their X chromosome inactivation status across individuals, tissues or cells. Expression of these genes from the second and otherwise inactive X chromosome may underlie sex differences between males and females, and feature in many of the symptoms of XXY Klinefelter males, who have both an inactive X and a Y chromosome. We review the approaches used to identify genes that escape from X‐chromosome inactivation and discuss the nature of their sex‐biased expression. These genes are enriched on the short arm of the X chromosome, and, in addition to genes in the pseudoautosomal regions, include genes with and without Y‐chromosomal counterparts. We highlight candidate escape genes for some of the features of Klinefelter syndrome and discuss our current understanding of the mechanisms underlying silencing and escape on the X chromosome as well as additional differences between the X in males and females that may contribute to Klinefelter syndrome.

A triple “no” to the enrichment of immune genes at X files

Abstract Objective As sex bias in immune function has been contributed partly to a preponderance of immune system-related genes (ISRG) on the X-chromosome, we performed a comparative study to verify this viewpoint. Methods The comparative study consisted of three complementary strategies: Results The X chromosome had less ISRG than the median of the autosomal chromosomes. Among X-linked genes, ISRG ranked 4th after genes dedicated to the reproductive and nervous systems or to development, proliferation and apoptosis (not ranking genes dedicated to basal metabolism nor genes of unknown function). On the Y chromosome, ISRG ranked 2nd, and at the pseudoautosomal region 1st. Various epigenetic controllers, X-linked MSL3 and Y-linked KDM5D and UTY, were preferentially expressed in leukocytes and deserve further attention with respect to a possible role in sex biased expression or its neutralisation. Conclusions The X chromosome is not enriched for ISRG. Thus, gene-related causes for sex bias in immune responses cannot be due to the X-linked ISRG number, but may be due to 1) particular sex chromosome-linked genes, 2) sex-biased regulation of the expression of ISRG in leukocytes and/or lymphoid organs. (Funding: UDEM, UIN19592)

Detection of SHOX gene deletions in Egyptian children with idiopathic short stature using FISH

The short stature homeobox-containing (SHOX) gene, mapped on the pseudoautosomal region of the X and Y chromosomes, strongly affects human height. Therefore, SHOX haploinsufficiency has been reported to cause idiopathic short stature (ISS) and the short stature seen in patients with Turner's syndrome, Leri-Weill dyschondrosteosis, and Langer mesomelic dysplasia. SHOX deletions are responsible for approximately 80% of isolated haploinsufficiency. Aiming to evaluate the prevalence of SHOX gene deletions in the Egyptian patients with unexplained short stature, the present study used FISH analysis to investigate SHOX deletions in 25 patients with ISS. Despite the tiny sample size and the limitations of the used analysis technique, our findings emphasize the importance of including SHOX mutation analysis in the genetic workup of ISS cases. Furthermore, this study could not confirm a correlation of SHOX deletions with any specific clinical feature or an anthropometric measurement.

Gene mapping and genomic prediction of bull fertility using sex chromosome markers

Service sire has been recognized as an important factor affecting dairy herd fertility. Our group has reported promising results on gene mapping and genomic prediction of dairy bull fertility using autosomal SNP markers. Little is known, however, about the genetic contribution of sex chromosomes, which are enriched in genes related to sexual development and reproduction. As such, the main goal of this study was to investigate the effect of SNP markers on X and Y chromosomes (BTAX and BTAY, respectively) on sire conception rate (SCR) in US Holstein bulls. The analysis included a total of 5,014 bulls with SCR records and genotypes for roughly 291k SNP located on the autosomes, 1.5k SNP located on the pseudoautosomal region (PAR), 13.7k BTAX-specific SNP, and 24 BTAY-specific SNP. We first performed genomic scans of the sex chromosomes, and then we evaluated the genomic prediction of SCR including BTAX SNP markers in the predictive models. Two markers located on PAR and 3 markers located on the X-specific region showed significant associations with sire fertility. Interestingly, these regions harbor genes, such as FAM9B, TBL1X, and PIH1D3, that are directly implicated in testosterone concentration, spermatogenesis, and sperm motility. On the other hand, BTAY showed very low genetic variability, and none of the segregating markers were associated with SCR. Notably, model predictive ability was largely improved by including BTAX markers. Indeed, the combination of autosomal with BTAX SNP delivered predictive correlations around 0.343, representing an increase in accuracy of about 7.5% compared with the standard whole autosomal genome approach. Overall, this study provides evidence of the importance of both PAR and X-specific regions in male fertility in dairy cattle. These findings may help to improve conception rates in dairy herds through accurate genome-guided decisions on bull fertility.

Evolution of the Autism-Associated Neuroligin-4 Gene Reveals Broad Erosion of Pseudoautosomal Regions in Rodents.

Variants in genes encoding synaptic adhesion proteins of the neuroligin family, most notably neuroligin-4, are a significant cause of autism spectrum disorders in humans. Although human neuroligin-4 is encoded by two genes, NLGN4X and NLGN4Y, that are localized on the X-specific and male-specific regions of the two sex chromosomes, the chromosomal localization and full genomic sequence of the mouse Nlgn4 gene remain elusive. Here, we analyzed the neuroligin-4 genes of numerous rodent species by direct sequencing and bioinformatics, generated complete drafts of multiple rodent neuroligin-4 genes, and examined their evolution. Surprisingly, we find that the murine Nlgn4 gene is localized to the pseudoautosomal region (PAR) of the sex chromosomes, different from its human orthologs. We show that the sequence differences between various neuroligin-4 proteins are restricted to hotspots in which rodent neuroligin-4 proteins contain short repetitive sequence insertions compared with neuroligin-4 proteins from other species, whereas all other protein sequences are highly conserved. Evolutionarily, these sequence insertions initiate in the clade eumuroidea of the infraorder myomorpha and are additionally associated with dramatic changes in noncoding sequences and gene size. Importantly, these changes are not exclusively restricted to neuroligin-4 genes but reflect major evolutionary changes that substantially altered or even deleted genes from the PARs of both sex chromosomes. Our results show that despite the fact that the PAR in rodents and the neuroligin-4 genes within the rodent PAR underwent massive evolutionary changes, neuroligin-4 proteins maintained a highly conserved core structure, consistent with a substantial evolutionary pressure preserving its physiological function.

SeXY chromosomes and the immune system: reflections after a comparative study

BackgroundSex bias in immune function has been contributed in part to a preponderance of immune system-related genes (ISRG) on the X-chromosome. We verified whether ISRG are more abundant on the X chromosome as compared to autosomal chromosomes and reflected on the impact of our findings.MethodsConsulting freely accessible databases, we performed a comparative study consisting of three complementary strategies. First, among coding X/Y-linked genes, the abundance of ISRG was compared to the abundance of genes dedicated to other systems. Genes were assigned considering three criteria: disease, tissue expression, and function (DEF approach). In addition, we carried out two genome-wide approaches to compare the contribution of sex and autosomal chromosomes to immune genes defined by an elevated expression in lymphatic tissues (LTEEG approach) or annotation to an immune system process, GO:0002376 (GO approach).ResultsThe X chromosome had less immune genes than the median of the autosomal chromosomes. Among X-linked genes, ISRG ranked fourth after the reproductive and nervous systems and genes dedicated to development, proliferation and apoptosis. On the Y chromosome, ISRG ranked second, and at the pseudoautosomal region (PAR) first. According to studies on the expression of X-linked genes in a variety of (mostly non-lymphatic) tissues, almost two-thirds of ISRG are expressed without sex bias, and the remaining ISRG presented female and male bias with similar frequency. Various epigenetic controllers, X-linked MSL3 and Y-linked KDM5D and UTY, were preferentially expressed in leukocytes and deserve further attention for a possible role in sex biased expression or its neutralisation.ConclusionsThe X chromosome is not enriched for ISRG, though particular X-linked genes may be responsible for sex differences in certain immune responses. So far, there is insufficient information on sex-biased expression of X/Y-linked ISRG in leukocytes to draw general conclusions on the impact of X/Y-linked ISRG in immune function. More research on the regulation of the expression X-linked genes is required with attention to 1) female and male mechanisms that may either augment or diminish sex biased expression and 2) tissue-specific expression studies.

Variant calling on the GRCh38 assembly with the data from phase three of the 1000 Genomes Project.

We present a set of biallelic SNVs and INDELs, from 2,548 samples spanning 26 populations from the 1000 Genomes Project, called de novo on GRCh38. We believe this will be a useful reference resource for those using GRCh38. It represents an improvement over the "lift-overs" of the 1000 Genomes Project data that have been available to date by encompassing all of the GRCh38 primary assembly autosomes and pseudo-autosomal regions, including novel, medically relevant loci. Here, we describe how the data set was created and benchmark our call set against that produced by the final phase of the 1000 Genomes Project on GRCh37 and the lift-over of that data to GRCh38.

Characterization of chromatin at structurally abnormal inactive X chromosomes reveals potential evidence of a rare hybrid active and inactive isodicentric X chromosome.

X chromosome structural abnormalities are relatively common in Turner syndrome patients, in particular X isochromosomes. Reports over the last five decades examining asynchronous DNA replication between the normal X and isochromosome have clearly established that the structurally abnormal chromosome is the inactive X chromosome (Xi). Here the organization of chromatin at a deleted X chromosome, an Xq isochromosome, and two isodicentric chromosomes were examined. Consistent with previous differential staining methods, at interphase, the X isochromosome and isodicentric X chromosomes frequently formed bipartite Barr bodies, observed by fluorescence microscopy using numerous independent bona fide markers of Xi heterochromatin. At metaphase, with the exception of the pseudoautosomal region and the duplicated locus of the macrosatellite DXZ4 (if present on the abnormal X chromosome based on break points), euchromatin markers were absent from the Xi, whereas histone variant macroH2A formed reproducible banded mirror-image chromosomes. Unexpectedly, the isodicentric chromosome in 46,X,idic(X)(q28) cells, which carry a near full-length q-arm-to-q-arm fused chromosome, showed at interphase very rare instances of Xi chromatin bodies that were separated by large distances in the nucleus. Further examination using immunofluorescence and FISH support the possibility that these rare cells may represent ones in which one half of the isodicentric chromosome is active and the other half is inactive.

Identifying sex-linked markers in Litoria aurea: a novel approach to understanding sex chromosome evolution in an amphibian

Few taxa exhibit the variability of sex-determining modes as amphibians. However, due to the presence of homomorphic sex chromosomes in many species, this phenomenon has been difficult to study. The Australian frog, Litoria aurea, has been relatively well studied over the past 20 years due to widespread declines largely attributable to chytrid fungus. However, it has been subject to few molecular studies and its mode of sex determination remained unknown. We applied DArTseq™ to develop sex-linked single nucleotide polymorphisms (SNPs) and restriction fragment presence/absence (PA) markers in 44 phenotypically sexed L. aurea individuals from the Molonglo River in NSW, Australia. We conclusively identified a male heterogametic (XX-XY) sex determination mode in this species, identifying 11 perfectly sex-linked SNP and six strongly sex-linked PA markers. We identified a further 47 moderately sex-linked SNP loci, likely serving as evidence indicative of XY recombination. Furthermore, within these 47 loci, a group of nine males were found to have a feminised Y chromosome that significantly differed to all other males. We postulate ancestral sex-reversal as a means for the evolution of this now pseudoautosomal region on the Y chromosome. Our findings present new evidence for the ‘fountain of youth’ hypothesis for the retention of homomorphic sex chromosomes in amphibians and describe a novel approach for the study of sex chromosome evolution in amphibia.

Paircounting

X inactivation presents two longstanding puzzles: the counting and choice of X chromosomes. Here, we consider counting and choice in the context of pairing, both of the X and of the autosomes.

Effect of Concomitant Deletions of CDKN2A/B, PAX5 and Pseudoautosomal Region Genes along with IKZF1 Deletions (IKZF1-Plus) on Outcome in BCR-ABL1 Negative Pediatric B-Cell Acute Lymphoblastic Leukemia

Effect of Concomitant Deletions of CDKN2A/B, PAX5 and Pseudoautosomal Region Genes along with IKZF1 Deletions (IKZF1-Plus) on Outcome in BCR-ABL1 Negative Pediatric B-Cell Acute Lymphoblastic Leukemia

Evolutionary Dynamics of Sex Chromosomes of Paleognathous Birds.

Standard models of sex chromosome evolution propose that recombination suppression leads to the degeneration of the heterogametic chromosome, as is seen for the Y chromosome in mammals and the W chromosome in most birds. Unlike other birds, paleognaths (ratites and tinamous) possess large nondegenerate regions on their sex chromosomes (PARs or pseudoautosomal regions). It remains unclear why these large PARs are retained over >100 Myr, and how this retention impacts the evolution of sex chromosomes within this system. To address this puzzle, we analyzed Z chromosome evolution and gene expression across 12 paleognaths, several of whose genomes have recently been sequenced. We confirm at the genomic level that most paleognaths retain large PARs. As in other birds, we find that all paleognaths have incomplete dosage compensation on the regions of the Z chromosome homologous to degenerated portions of the W (differentiated regions), but we find no evidence for enrichments of male-biased genes in PARs. We find limited evidence for increased evolutionary rates (faster-Z) either across the chromosome or in differentiated regions for most paleognaths with large PARs, but do recover signals of faster-Z evolution in tinamou species with mostly degenerated W chromosomes, similar to the pattern seen in neognaths. Unexpectedly, in some species, PAR-linked genes evolve faster on average than genes on autosomes, suggested by diverse genomic features to be due to reduced efficacy of selection in paleognath PARs. Our analysis shows that paleognath Z chromosomes are atypical at the genomic level, but the evolutionary forces maintaining largely homomorphic sex chromosomes in these species remain elusive.

Opposite Expression Patterns of Spry3 and p75NTR in Cerebellar Vermis Suggest a Male-Specific Mechanism of Autism Pathogenesis.

Autism is a genetically complex neurobehavioral disorder with a population prevalence of more than 1%. Cerebellar abnormalities, including Purkinje cell deficits in the vermis, are consistently reported, and rodent models of cerebellar dysfunction exhibit features analogous to human autism. We previously analyzed the regulation and expression of the pseudoautosomal region 2 gene SPRY3, which is adjacent to X chromosome-linked TMLHE, a known autism susceptibility gene. SPRY3 is a regulator of branching morphogenesis and is strongly expressed in Purkinje cells. We previously showed that mouse Spry3 is not expressed in cerebellar vermis lobules VI–VII and X, regions which exhibit significant Purkinje cell loss or abnormalities in autism. However, these lobules have relatively high expression of p75NTR, which encodes a neurotrophin receptor implicated in autism. We propose a mechanism whereby inappropriate SPRY3 expression in these lobules could interact with TrkB and p75NTR signaling pathways resulting in Purkinje cell pathology. We report preliminary characterization of X and Y chromosome-linked regulatory sequences upstream of SPRY3, which are polymorphic in the general population. We suggest that an OREG-annotated region on chromosome Yq12 ∼60 kb from SPRY3 acts as a silencer of Y-linked SPRY3 expression. Deletion of a β-satellite repeat, or alterations in chromatin structure in this region due to trans-acting factors, could affect the proposed silencing function, leading to reactivation and inappropriate expression of Y-linked SPRY3. This proposed male-specific mechanism could contribute to the male bias in autism prevalence.

DNA Methylation Status of SHOX-Flanking CpG Islands in Healthy Individuals and Short Stature Patients with Pseudoautosomal Copy Number Variations

SHOX resides in the short arm pseudoautosomal region (PAR1) of the sex chromosomes and escapes X inactivation. SHOX haploinsufficiency underlies idiopathic short stature (ISS) and Leri-Weill dyschondrosteosis (LWD). A substantial percentage of cases with SHOX haploinsufficiency arise from pseudoautosomal copy number variations (CNVs) involving putative enhancer regions of SHOX. Our previous study using peripheral blood samples showed that some CpG dinucleotides adjacent to SHOX exon 1 were hypomethylated in a healthy woman and methylated in a woman with gross X chromosomal rearrangements. However, it remains unknown whether submicroscopic pseudoautosomal CNVs cause aberrant DNA methylation of SHOX-flanking CpG islands. In this study, we examined the DNA methylation status of SHOX-flanking CpG islands in 50 healthy individuals and 10 ISS/LWD patients with pseudoautosomal CNVs. In silico analysis detected 3 CpG islands within the 20-kb region from the translation start site of SHOX. Pyrosequencing and bisulfite sequencing of genomic DNA samples revealed that these CpG islands were barely methylated in peripheral blood cells and cultured chondrocytes of healthy individuals, as well as in peripheral blood cells of ISS/LWD patients with pseudoautosomal CNVs. These results, in conjunction with our previous findings, indicate that the DNA methylation status of SHOX-flanking CpG islands can be affected by gross X-chromosomal abnormalities, but not by submicroscopic CNVs in PAR1. Such CNVs likely disturb SHOX expression through DNA methylation-independent mechanisms, which need to be determined in future studies.

The distribution of epigenetic histone marks differs between the X and Y chromosomes in Silene latifolia.

Contrasting patterns of histone modifications between the X and Y chromosome in Silene latifolia show euchromatic histone mark depletion on the Y chromosome and indicate hyperactivation of one X chromosome in females. Silene latifolia (white campion) is a dioecious plant with heteromorphic sex chromosomes (24, XX in females and 24, XY in males), and a genetically degenerated Y chromosome that is 1.4 times larger than the X chromosome. Although the two sex chromosomes differ in their DNA content, information about epigenetic histone marks and evidence of their function are scarce. We performed immunolabeling experiments using antibodies specific for active and suppressive histone modifications as well as pericentromere-specific histone modifications. We show that the Y chromosome is partially depleted of histone modifications important for transcriptionally active chromatin, and carries these marks only in the pseudo-autosomal region, but that it is not enriched for suppressive and pericentromere histone marks. We also show that two of the active marks are specifically enriched in one of the X chromosomes in females and in the X chromosome in males. Our data support recent findings that genetic imprinting mediates dosage compensation of sex chromosomes in S. latifolia.

A 105\xa0kb interstitial insertion in the Xq27.1 palindrome from pseudoautosomal region PAR1 causes a novel X-linked recessive compound phenotype

BackgroundGenomic disorders present a wide spectrum of unrelated clinical entities that result from genomic rearrangements. Interstitial insertions requiring three points of breakage are rare genomic rearrangement events. The pseudoautosomal region PAR1, homologous between the Xp22 and Yp11 loci, has a high crossover and recombination rate. A 180 bp human-specific palindrome at Xq27.1 appears to be a hotspot for genomic rearrangement, and several genetic diseases/phenotypes associated with Xq27.1 palindrome-driven genomic rearrangement have been reported. Here we investigate a Chinese family with an extremely rare X-linked compound phenotype that remains undiagnosed. We attempt to identify underlying genetic causes by an integrated genome analysis.MethodsA five-generation Chinese family with a distinct X-linked compound phenotype was recruited. Peripheral blood samples were collected and genomic DNA was extracted. Systemic physical and lab examinations were performed to evaluate the phenotype. An integrated genomic analysis was performed. Genotyping and linkage analysis were conducted to map the disease locus. Whole exome sequencing was performed to detect mutations in coding region. Whole genome sequencing was used to detect single nucleotide variations, small insertions, small deletions, or large structural variations. Copy number variation scanning was also performed on the genome scale. Interstitial insertion was confirmed by gap-PCR and quantitative-PCR, and breakpoint junctions were identified by genome walking and direct sequencing. Expression of products of genes nearby to the Xq27.1 palindrome was measured in peripheral blood from patients and unrelated controls via quantitative-PCR.ResultsThe identified compound phenotype of genu varum, cubitus valgus, and everted lipsdoes not match any reported clinical entities. Fine mapping and linkage analysis identified a candidate interval of 4 Mb on the X chromosome. No potential coding region mutations were detected. A 105 kb genomic fragment of PAR1 containing no coding genes was duplicated and inserted into the center of a human-specific palindrome at Xq27.1. The interstitial insertion fully cosegregated with the family phenotype. No expression of FGF13 or SOX3 was detected in peripheral blood from the proband or unrelated controls.ConclusionWe report an extremely rare phenotype associated with an infrequently-seen genomic rearrangement. The novel compound phenotype is X-linked and characterized by genu varum, cubitus valgus, and everted lips. A 105 kb interstitial insertion of a PAR1 fragment into the Xq27.1 palindrome is associated with the phenotype in the family. The present study identified the underlying genetic cause of the phenotype, expanding the spectrum of known human-specific Xq27.1 palindrome insertion events and associated phenotypes.

Instability of the Pseudoautosomal Boundary in House Mice.

Faithful segregation of homologous chromosomes at meiosis requires pairing and recombination. In taxa with dimorphic sex chromosomes, pairing between them in the heterogametic sex is limited to a narrow interval of residual sequence homology known as the pseudoautosomal region (PAR). Failure to form the obligate crossover in the PAR is associated with male infertility in house mice (Mus musculus) and humans. Yet despite this apparent functional constraint, the boundary and organization of the PAR is highly variable in mammals, and even between subspecies of mice. Here, we estimate the genetic map in a previously documented expansion of the PAR in the M. musculus castaneus subspecies and show that the local recombination rate is 100-fold higher than the autosomal background. We identify an independent shift in the PAR boundary in the M. musculus musculus subspecies and show that it involves a complex rearrangement, but still recombines in heterozygous males. Finally, we demonstrate pervasive copy-number variation at the PAR boundary in wild populations of M. m. domesticus, M. m. musculus, and M. m. castaneus Our results suggest that the intensity of recombination activity in the PAR, coupled with relatively weak constraints on its sequence, permit the generation and maintenance of unusual levels of polymorphism in the population of unknown functional significance.

REC114 Partner ANKRD31 Controls Number, Timing, and Location of Meiotic DNA Breaks.

Double-strand breaks (DSBs) initiate the homologous recombination that is crucial for meiotic chromosome pairing and segregation. Here, we unveil mouse ANKRD31 as a lynchpin governing multiple aspects of DSB formation. Spermatocytes lacking ANKRD31 have altered DSB locations and fail to target DSBs to the pseudoautosomal regions (PARs) of sex chromosomes. They also have delayed and/or fewer recombination sites but, paradoxically, more DSBs, suggesting DSB dysregulation. Unrepaired DSBs and pairing failures-stochastic on autosomes, nearly absolute on X and Y-cause meiotic arrest and sterility in males. Ankrd31-deficient females have reduced oocyte reserves. A crystal structure defines a pleckstrin homology (PH) domain in REC114 and its direct intermolecular contacts with ANKRD31. Invivo, ANKRD31 stabilizes REC114 association with the PAR and elsewhere. Our findings inform a model in which ANKRD31 is a scaffold anchoring REC114 and other factors to specific genomic locations, thereby regulating DSB formation.