Argonaute proteins regulate the timing of the spermatogenic transcriptional program

bioRxiv (Cold Spring Harbor Laboratory) · 2025-01-01 · 1 citations

ABSTRACT Argonaute proteins are best known for their role in microRNA-mediated post-transcriptional gene silencing. Here, we show that AGO3 and AGO4, but not AGO2, localize to the sex chromatin of pachytene spermatocytes where they are required for transcriptional silencing of XY-linked genes, known as Meiotic Sex Chromosome Inactivation (MSCI). Using an Ago413 -/- mouse, we show that AGO3 and AGO4 are key regulators of spermatogenesis, orchestrating expression of meiosis-related genes during prophase I while maintaining silencing of spermiogenesis genes. Premature overexpression of spermiogenesis genes during prophase I in Ago413 -/- mice results in subfertility, altered sperm morphology and reduced fertilization capability. We also identify BRG1, a BAF complex subunit, as an AGO3 interactor. Loss of AGO3 and AGO4 results in increased BRG1 in spermatocytes, suggesting that AGO3 aids in removing BRG1 from the XY chromatin to achieve MSCI and demonstrating a meiotic role for AGO3 in transcriptional control through the chromatin remodeling machinery.

CNTD1 is crucial for crossover formation in female meiosis and for establishing the ovarian reserve

The Journal of Cell Biology · 2025-06-09 · 3 citations

In meiotic prophase I, hundreds of DNA double-strand breaks are formed and subsequently repaired as noncrossovers or crossovers (COs). COs are essential for accurate chromosome segregation during the first meiotic division, and errors in this process result in aneuploidy, birth defects, or infertility. Such errors are more pronounced in females compared with males, indicating that CO regulation and surveillance are sexually dimorphic. We demonstrate here dual roles of cyclin N-terminal domain containing 1 (CNTD1) in ensuring appropriate CO between homologous chromosomes in oocytes and in establishing the pool of follicles in the postnatal ovary. CNTD1-deficient oocytes fail to form COs and exhibit a severely depleted follicle pool shortly after birth, which is temporally distinct from previously reported CO mutants. Further investigation indicates that follicle loss is CHK2-dependent, resulting from inappropriate retention of HORMAD1 and the absence of SKP1. These findings indicate that CNTD1 plays novel roles in CO designation and establishment of the follicular reserve in female mammals.

Meiotic prophase I disruption as a strategy for non-hormonal male contraception using small-molecule inhibitor JQ1

bioRxiv (Cold Spring Harbor Laboratory) · 2025-05-14 · 1 citations

ABSTRACT Long-acting non-hormonal male contraceptives are urgently needed but developing strategies that are both effective and reversible presents significant challenges. Here, we investigated the potential of meiotic prophase I blockade as a promising and potentially reversible approach to male contraception. To do this, we utilized (+)-JQ1, a small-molecule inhibitor of the testis-specific protein, BRDT. Daily injections of (+)-JQ1 for three weeks resulted in disrupted spermatogenesis resulting in loss of spermatozoa and an inability to sire pups. While spermatogenic cells repopulated the testis within six weeks post drug cessation, full fertility restoration required a longer recovery period. We attribute this delay in full recovery to persistent issues with the pachytene transcriptional program, which is crucial for meiotic progression and spermatid development. These findings underscore the potential of pharmacological approaches to disrupt meiotic prophase I as a targeted, reversible male contraceptive strategy, providing new insights into developing effective non-hormonal contraceptive approaches.

Author Reply to Peer Reviews of Argonaute proteins regulate the timing of the spermatogenic transcriptional program

2025-06-10

Chromosome length is not the sole determinant of sexually dimorphic crossover rates during mammalian meiosis: Insights from genetically diverse mouse strains

bioRxiv (Cold Spring Harbor Laboratory) · 2025-12-22 · 1 citations

Meiotic recombination generates crossovers (COs), reciprocal exchanges between homologous chromosomes critical for accurate chromosome segregation. Inappropriate CO frequency and distribution drive aneuploidy in human oocytes, with error rates up to 10-fold higher than in sperm despite females exhibiting higher CO frequencies. COs form in the context of the proteinaceous synaptonemal complex (SC) that tethers homologs during prophase I. SC length strongly correlates with CO number, and sexual dimorphism in recombination has long been attributed to longer SCs in females. However, this model is challenged by wild-derived PWD mice in which males consistently generate more COs despite having shorter SCs. Here, we exploit natural genetic variation among inbred mouse strains to dissect the structural and regulatory basis of sexually dimorphic CO regulation. Using cytological markers of SC assembly (SYCP3), recombination progression (RAD51, MSH4), class I CO designation (HEI10, MLH1/MLH3), and chiasmata, we show that SC length is not the sole predictor of CO number. PWD males exhibit stronger CO interference and higher CO number than females, despite reduced SC length. Notably, females show reduced efficiency in designating recombination intermediate to become COs, whereas PWD males display exceptional proficiency. Unexpectedly, although class II COs are rare, they play a disproportionate role in ensuring that every chromosome pair receives at least one CO, thereby safeguarding against aneuploidy. Together, these findings challenge the prevailing view that SC length is the primary determinant of sexually dimorphic CO rates and instead highlight sex-specific regulation of CO designation and pathway usage as key drivers of recombination outcomes.

Meiosis Overview

Elsevier eBooks · 2025-09-02

Author Response: A TOPBP1 Allele Causing Male Infertility Uncouples XY Silencing Dynamics From Sex Body Formation

2024-01-19

Meiotic sex chromosome inactivation (MSCI) is a critical feature of meiotic prophase I progression in males. While the ATR kinase and its activator TOPBP1 are key drivers of MSCI within the specialized sex body (SB) domain of the nucleus, how they promote silencing remains unclear given their multifaceted meiotic functions that also include DNA repair, chromosome synapsis and SB formation. Here we report a novel mutant mouse harboring mutations in the TOPBP1-BRCT5 domain. Topbp1B5/B5 males are infertile, with impaired MSCI despite displaying grossly normal events of early prophase I, including synapsis and SB formation. Specific ATR-dependent events are disrupted including phosphorylation and localization of the RNA:DNA helicase Senataxin. Topbp1B5/B5 spermatocytes initiate, but cannot maintain ongoing, MSCI. These findings reveal a non-canonical role for the ATR-TOPBP1 signaling axis in MSCI dynamics at advanced stages in pachynema and establish the first mouse mutant that separates ATR signaling and MSCI from SB formation.

Relationships Between Retinal Amyloid Imaging and Amyloid PET in the A4 Trial

Alzheimer s & Dementia · 2024-12-01

Abstract Background Alterations to the retina manifest in patients diagnosed with neurodegenerative diseases such as Alzheimer’s disease (AD). Retinal imaging techniques open the possibility for non‐invasive evaluation of AD pathology. Clinically AD diagnosed patients exhibit retinal amyloid deposits. Few studies monitoring preclinical individuals exist, limiting the assessment of the feasibility of retinal imaging as a biomarker for early‐stage AD risk detection. Method We compared retinal and cerebral amyloid in clinically normal individuals who screened positive for amyloid through positron emission tomography (PET) from the Anti‐Amyloid Treatment in Asymptomatic Alzheimer Disease (A4) as well as a companion cohort of individuals who were negative on amyloid by amyloid PET in the Longitudinal Evaluation of Amyloid Risk and Neurodegeneration (LEARN) study. We quantified the number of curcumin‐positive fluorescent retinal spots from a small subset of participants from both studies to determine retinal amyloid deposition at baseline. Result Participants from the A4 trial exhibited a greater number of retinal spots compared to those from the LEARN study. We report a positive correlation between retinal spots and brain amyloid, as measured by the standardized uptake value ratio (SUVr). Conclusion The results of this small pilot study support the use of retinal fundus imaging for detecting amyloid deposition that is correlated with brain amyloid PET SUVr. A larger sample set is under analysis currently to fully ascertain the relationship between amyloid PET and retinal amyloid both cross‐sectionally and longitudinally.

Supporting Participants in Preclinical Alzheimer’s Trials: Experience from a Research Participant Advisory Board and the A4 Study

Alzheimer s & Dementia · 2024-12-01

Abstract Preclinical Alzheimer’s disease (AD) trials can involve multiple years of follow‐up and burdensome procedures for older individuals. Optimizing the design and conduct of these trials requires input from participants and their families. Since 2020, the Alzheimer’s Clinical Trials Consortium (ACTC) Research Participant Advisory Board has provided input on study attributes including: participant and study partner compensation, consent language, and result communication tools. A key recommendation from the advisory board is to design studies with the option to learn individual research results. Participants find results personally meaningful, even when the clinical relevance of results has not been established. After release of topline study results, A4 research sites were provided reports that included treatment arm assignment and individual research results (cognitive scores, amyloid PET tertile, and Clinical Dementia Rating scale results). Research sites were provided guidance on communicating research results in a training webinar. A survey was subsequently sent to all A4 sites to understand what methods were used to communicate results and support participants. The 42 sites that completed the survey reported sharing results with 445 participants, or 65% of participants active at the end of the study. Participants expressed interest in taking part in other studies and, where eligible, were referred. Those with worsening cognition and function were referred for clinical evaluation and care. Some A4 participants told sites that they expected “something tangible” and “more than a one‐hour meeting” after the many years of participation. The A4 sites that hosted ‘thank you’ events to discuss study‐level results, with separate one‐on‐one sessions to discuss individual results shared these were appreciated by participants. The active involvement of the diverse ACTC Participant Advisory Board has benefited the design of preclinical AD studies. The A4 experience demonstrates that it is feasible to share individual research results, and that a majority of participants will opt to learn. Greater involvement of the Advisory Board at the earliest stages of study design and planning will maximize impact of their feedback, and help researchers move toward the goal of optimized, inclusive trials.

Author Response: A TOPBP1 allele causing male infertility uncouples XY silencing dynamics from sex body formation

2024-02-23