Affinage

HORMAD2

HORMA domain-containing protein 2 · UniProt Q8N7B1

Length
307 aa
Mass
35.3 kDa
Annotated
2026-06-10
37 papers in source corpus 14 papers cited in narrative 14 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 4/5 claims corpus-supported (80%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

HORMAD2 is a meiosis-specific HORMA-domain protein that marks unsynapsed chromosome axes and operates the asynapsis surveillance checkpoint that eliminates oocytes and spermatocytes failing to complete homologous synapsis (PMID:22549958, PMID:23039116). It preferentially decorates unsynapsed axes throughout meiotic prophase and is removed from axes upon synapsis (PMID:19851446), being recruited to the axis via a conserved 'safety-belt' interaction in which its C-terminal closure motif (sharing a Ser-Glu-Pro sequence) docks into the HORMA domain of HORMAD1 (PMID:25446517, PMID:37794593); HORMAD1 and SYCP2 are its principal axis-associated partners, positioning it peripherally around the SYCP3/SYCP2 axial core (PMID:31444302, PMID:38401263). On unsynapsed axes HORMAD2 is required for the local accumulation of ATR kinase activity that builds the surveillance signal, a function genetically separable from the DSB-repair checkpoint (PMID:22549958, PMID:23039116, PMID:39961811). HORMAD2 is itself phosphorylated during prophase I as an ATR target, dependent on the 9-1-1 subunit RAD1 and on BRCA1/SYCP3, coupling it to the meiotic silencing of unsynapsed chromatin (MSUC) machinery (PMID:22346761, PMID:35133274). Synapsis-coupled removal of HORMAD2 is driven by the TRIP13 AAA-ATPase acting on its N-terminal region (PMID:19851446, PMID:32473092, PMID:38401263); when removal fails, retained HORMAD2 (with HORMAD1) aberrantly recruits BRCA1 through an N-terminal HORMA-domain interface and activates the checkpoint to eliminate oocytes, and Hormad2 deletion is epistatic to Trip13, rescuing Trip13-mutant fertility (PMID:28844861, PMID:40050306).

Mechanistic history

Synthesis pass · year-by-year structured walk · 12 steps
  1. 2009 High

    Established that HORMAD2 is an unsynapsed-axis marker whose distribution is reciprocal to synaptonemal complex components and is controlled by TRIP13, framing it as a dynamic axis component rather than a static structural protein.

    Evidence Immunofluorescence in wild-type and TRIP13-deficient/DSB-processing-mutant mouse meiocytes with SC co-localization

    PMID:19851446

    Open questions at the time
    • Did not define the molecular basis of axis recruitment
    • Did not establish a functional consequence of HORMAD2 presence
  2. 2012 High

    Defined HORMAD2's core function: recruiting ATR activity to unsynapsed axes to drive an asynapsis surveillance checkpoint mechanistically distinct from DSB surveillance, with sex-specific consequences for germ cell elimination.

    Evidence Hormad2 knockout mice; ATR/γH2AX/SYCP immunofluorescence; epistasis with Spo11−/− and Dmc1−/−; gene-dosage oocyte counting

    PMID:22549958 PMID:23039116

    Open questions at the time
    • Did not identify how HORMAD2 physically recruits ATR
    • Did not resolve the downstream effector causing germ cell death
  3. 2012 Medium

    Linked HORMAD2 to the MSUC silencing pathway by showing it is phosphorylated in prophase I in a BRCA1/SYCP3- and recombination-initiation-dependent manner.

    Evidence Phospho-specific western blot/IF in Spo11, BRCA1, and SYCP3 mutant spermatocytes

    PMID:22346761

    Open questions at the time
    • Phosphorylation site identity not fully resolved
    • Direct kinase responsible not established in this study
    • Causal role of the phosphorylation in MSUC not tested by mutagenesis
  4. 2014 Medium

    Provided the molecular mechanism of axis recruitment by demonstrating a conserved HORMA domain–closure motif 'safety-belt' interaction between HORMAD1 and HORMAD2's C-terminus.

    Evidence Biochemical pulldowns, sequence analysis, and structural data from C. elegans orthologs

    PMID:25446517

    Open questions at the time
    • Mammalian interaction validated biochemically in a single study
    • No structure of the mammalian complex
  5. 2017 High

    Placed HORMAD2 in a defined checkpoint hierarchy — downstream of TRIP13 and upstream of CHK2 — by showing Hormad2 deletion rescues Trip13-mutant female fertility and that HORMAD1/2 on unsynapsed axes trigger CHK2-dependent oocyte elimination above a DSB threshold.

    Evidence Genetic epistasis (Hormad2 deletion in Trip13 hypomorph), oocyte counting, DSB-marker IF, CHK2 pathway analysis

    PMID:28844861

    Open questions at the time
    • Did not define the molecular link between retained HORMAD and checkpoint kinase activation
    • Did not resolve the intersister recombination inhibition mechanism
  6. 2019 Medium

    Resolved the nanoscale architecture of HORMAD2 on the axis, showing it is arrayed peripherally around the compact SYCP3/SYCP2 axial core.

    Evidence Expansion microscopy + 2-color STORM (ExSTORM) at 10–20 nm resolution in mouse spermatocytes

    PMID:31444302

    Open questions at the time
    • No functional mutagenesis tied to the positioning
    • Single lab structural observation
  7. 2020 Medium

    Extended TRIP13-dependent HORMAD2 disassembly to human cells, showing pathogenic TRIP13 variants reduce TRIP13 abundance and cause HORMAD2 to accumulate.

    Evidence HeLa overexpression and patient-derived lymphoblastoid cells; western blot for HORMAD2

    PMID:32473092

    Open questions at the time
    • Cellular context is not meiotic
    • Direct enzymatic action of TRIP13 on HORMAD2 not reconstituted here
  8. 2022 Medium

    Positioned the 9-1-1 complex upstream of HORMAD2 modification by showing RAD1 is required for HORMAD2 phosphorylation as an ATR target during meiosis.

    Evidence Testis-specific Rad1 knockout mice; phospho-HORMAD2 and ATR-target IF/western blot

    PMID:35133274

    Open questions at the time
    • Direct biochemical phosphorylation not shown
    • Phosphosite still undefined
    • Single lab
  9. 2022 Medium

    Connected HORMAD2 checkpoint signaling to aneuploidy risk by showing non-homologous synapsis maintains pachytene-like HORMAD2 levels and thereby evades the asynapsis checkpoint.

    Evidence HORMAD2 IF quantification on Prdm9-deficient rat oocyte chromosome spreads

    PMID:35596034

    Open questions at the time
    • Correlative protein quantification without functional rescue
    • Mechanism of checkpoint evasion not directly tested
  10. 2023 High

    Provided high-resolution structural confirmation that human HORMAD2 binds HORMAD1's HORMA domain via a shared Ser-Glu-Pro closure motif, and tied this interaction to HR repair function.

    Evidence X-ray crystallography of human HORMAD1, peptide-binding assays, cell-based HR repair reporter

    PMID:37794593

    Open questions at the time
    • HR repair assay performed in non-meiotic cell context
    • No structure of full-length HORMAD2
  11. 2024 High

    Identified HORMAD2's in vivo interactors and showed its N-terminus is required for TRIP13-mediated removal, with mislocalization to the SC central region upon N-terminal tagging.

    Evidence N-terminal knock-in tagging in mice; Co-IP/mass spectrometry; super-resolution microscopy; fertility and sperm count

    PMID:38401263

    Open questions at the time
    • Did not map the precise TRIP13 engagement residues
    • Reduced sperm count mechanism not fully resolved
  12. 2025 High

    Defined the effector mechanism of the retained-HORMAD checkpoint: HORMAD2 (with HORMAD1) recruits BRCA1 via an N-terminal HORMA-domain interface to trigger oocyte elimination, and confirmed HORMAD2's apoptotic role is specific to asynapsis surveillance.

    Evidence Reciprocal Co-IP; N-terminal-tagged HORMAD knock-in mice; BRCA1 IF; oocyte counting; squash immunohistochemistry with Spo11/Dmc1 double mutants

    PMID:39961811 PMID:40050306

    Open questions at the time
    • HORMAD2 contributes to but binds BRCA1 only weakly — relative contribution vs HORMAD1 not quantified
    • Downstream apoptotic execution steps not detailed

Open questions

Synthesis pass · forward-looking unresolved questions
  • How HORMAD2 phosphorylation, its peripheral axial positioning, and the N-terminal BRCA1/TRIP13 interface are mechanistically integrated to convert an unsynapsed axis into a committed elimination signal remains unresolved.
  • HORMAD2 phosphosite identity and its functional requirement remain undefined
  • Direct biochemical reconstitution of TRIP13-mediated HORMAD2 removal is lacking
  • The precise structural interface and quantitative contribution of HORMAD2 to BRCA1 recruitment is unresolved

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0060089 molecular transducer activity 3
Localization
GO:0005694 chromosome 3 GO:0000228 nuclear chromosome 2
Pathway
R-HSA-1474165 Reproduction 3 R-HSA-5357801 Programmed Cell Death 3 R-HSA-8953897 Cellular responses to stimuli 3
Complex memberships
synaptonemal complex axis / lateral element

Evidence

Reading pass · 14 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2009 HORMAD2 preferentially associates with unsynapsed chromosome axes throughout meiotic prophase and is depleted from synapsed axes; TRIP13 AAA-ATPase is required for the reciprocal distribution of HORMADs and SYCP1/SC-component along chromosome axes, indicating TRIP13 promotes HORMAD2 removal from synapsed chromatin. Immunofluorescence analysis of wild-type and mutant (TRIP13-deficient, DSB-processing mutant) mouse spermatocytes/oocytes; co-localization with SC markers PLoS genetics High 19851446
2012 HORMAD2 is required for accumulation of the checkpoint kinase ATR along unsynapsed chromosome axes (but not at DNA DSBs or DSB-associated chromatin loops), and this HORMAD2-dependent ATR recruitment constitutes a distinct asynapsis surveillance mechanism; HORMAD2 knockout eliminates asynaptic Spo11−/− oocytes but not DSB-repair-defective Dmc1−/− oocytes, demonstrating that asynapsis surveillance and DSB surveillance are mechanistically distinct. Hormad2 knockout mouse generation; immunofluorescence for ATR on meiotic chromosomes; genetic epistasis using Spo11−/− and Dmc1−/− double mutants; oocyte counting Genes & development High 22549958
2012 HORMAD2 deficiency impairs proper recruitment of ATR activity to unsynapsed chromosomes; in males, loss of HORMAD2 causes partial dissociation of the sex body (ATR- and γH2AX-enriched domain) from elongated sex chromosome axes leading to spermatocyte loss; in females, HORMAD2-dependent pseudo-sex body formation (likely via local ATR concentration) drives elimination of asynaptic Spo11-deficient oocytes. Hormad2 knockout mouse; immunofluorescence for ATR, γH2AX, SYCP1, SYCP3; Hormad2/Spo11 double-mutant analysis; oocyte counting in a gene-dosage series Genes to cells : devoted to molecular & cellular mechanisms High 23039116
2012 HORMAD2 is post-translationally phosphorylated during meiotic prophase I; phosphorylation of HORMAD2 depends on BRCA1 and SYCP3 for normal levels, and is dramatically reduced in the absence of meiotic recombination initiation; reduced HORMAD2 phosphorylation is associated with impaired targeting of the MSUC (meiotic silencing of unsynapsed chromatin) machinery to unsynapsed chromosomes. Western blot and immunofluorescence with phospho-specific analysis; genetic requirement tested in Spo11, BRCA1, and SYCP3 mutant spermatocytes PLoS genetics Medium 22346761
2014 Mammalian HORMAD1 binds a cognate peptide motif found at the C-terminus of HORMAD2, indicating that HORMAD2 is recruited to the chromosome axis via a 'safety-belt' HORMA domain–closure motif interaction conserved from C. elegans to mammals. Biochemical binding assays (pulldown); structural analysis of C. elegans orthologs; sequence analysis identifying conserved closure motif in HORMAD2 C-terminus Developmental cell Medium 25446517
2017 HORMAD1/2 on unsynapsed chromosome axes inhibit repair of spontaneous DSBs by intersister recombination; when a threshold (~10) of late-prophase spontaneous DSBs accumulates on unsynapsed axes bearing HORMAD1/2, the CHK2-dependent DNA damage checkpoint is triggered to eliminate oocytes; Hormad2 deletion rescued fertility of Trip13-mutant females (which cannot remove HORMADs from synapsed chromosomes), establishing that HORMAD2 is epistatic to TRIP13 in this checkpoint pathway. Genetic epistasis: Hormad2 deletion in Trip13 hypomorphic females; oocyte counting; immunofluorescence for DSB markers; CHK2 pathway analysis Molecular cell High 28844861
2019 Using expansion microscopy coupled with 2-color STORM (ExSTORM) at 10–20 nm resolution in mouse spermatocytes, HORMAD2 was shown to be arrayed around the SYCP3/SYCP2 C-terminus filament core of the meiotic chromosome axis, positioned peripherally relative to the compact axial core. Expansion microscopy + 2-color STORM (ExSTORM) super-resolution imaging of mouse spermatocytes Proceedings of the National Academy of Sciences of the United States of America Medium 31444302
2020 TRIP13 pathogenic variants reduce TRIP13 protein abundance and cause HORMAD2 to accumulate (fail to be removed) in HeLa cells and patient-derived lymphoblastoid cells, establishing that TRIP13 enzymatic activity is required for HORMAD2 disassembly in a human cellular context. In vitro cell assays (HeLa overexpression); patient-derived lymphoblastoid cells; western blot for HORMAD2 levels American journal of human genetics Medium 32473092
2022 RAD1 (shared subunit of all 9-1-1 complexes) is required for phosphorylation of HORMAD2 as an ATR target during meiosis; testis-specific Rad1 disruption impaired HORMAD2 phosphorylation along with other ATR targets (H2AX, CHK1), placing 9-1-1 complexes upstream of ATR-mediated HORMAD2 modification. Testis-specific Rad1 knockout mice; immunofluorescence and western blot for phospho-HORMAD2 and other ATR targets on meiotic chromosomes eLife Medium 35133274
2022 In Prdm9-deficient rat oocytes, non-homologous synapsis (NHS) is accompanied by HORMAD2 levels similar to those on pachytene chromosomes with homologous synapsis; this indicates that NHS bypasses the HORMAD2-based asynapsis signal and allows oocytes to evade meiotic checkpoints, linking HORMAD2 checkpoint evasion to subsequent aneuploidy. Immunofluorescence for HORMAD2 on rat oocyte chromosome spreads; comparison between homologous-synapsed and non-homologously-synapsed pachytene chromosomes in Prdm9-deficient animals Mammalian genome Medium 35596034
2023 The crystal structure of human HORMAD1 reveals a self-closed conformation via intramolecular HORMA domain–closure motif interaction; structural and biochemical data show that a peptide from HORMAD2 binds HORMAD1 in the same mode as HORMAD1's own closure motif, with both sharing a conserved Ser-Glu-Pro sequence; this HORMAD1–HORMAD2 interaction contributes to HORMAD1-dependent homologous recombination repair in cell-based assays. X-ray crystallography of human HORMAD1; peptide-binding biochemical assays; cell-based HR repair reporter assays Structure (London, England : 1993) High 37794593
2024 N-terminal tagging (3×FLAG-HA) of HORMAD2 prevents its timely removal from synapsed chromosome axes by TRIP13; co-immunoprecipitation coupled with mass spectrometry identified HORMAD1 and SYCP2 as HORMAD2-associated proteins in the testis; super-resolution microscopy showed that N-terminally tagged HORMAD2 redistributes to the central region of the synaptonemal complex rather than the lateral elements, without blocking meiosis but reducing sperm count in males. N-terminal knock-in tagging in mice; co-IP + mass spectrometry; super-resolution microscopy; fertility and sperm count assays Reproduction (Cambridge, England) High 38401263
2025 When HORMAD1 and HORMAD2 are retained on synapsed chromosome axes (in TRIP13-deficient contexts), they recruit BRCA1 and activate the chromosome asynapsis checkpoint, triggering oocyte elimination; mechanistically, HORMAD1 co-immunoprecipitates with BRCA1 via an interface on its HORMA domain near the N-terminus (not through the canonical closure-motif binding mode), while HORMAD2 co-immunoprecipitates with BRCA1 weakly but also contributes to BRCA1 recruitment; N-terminal tagging of HORMAD1/2 retains them on synapsed axes but abolishes BRCA1 recruitment and oocyte elimination, confirming the N-terminal interface is required. Co-immunoprecipitation; N-terminal-tagged HORMAD knock-in mice; immunofluorescence for BRCA1 on meiotic chromosomes; oocyte counting in multiple genetic backgrounds Nature communications High 40050306
2025 Using a squash immunohistochemical method for perinatal mouse ovaries, asynapsis-induced oocyte apoptosis (but not DNA damage-induced apoptosis) was shown to be significantly dependent on HORMAD2 in double-mutant analysis, confirming HORMAD2's specific role in the asynapsis surveillance pathway distinct from the DNA damage checkpoint. Squash immunohistochemistry; double-mutant analysis (Hormad2 × Spo11 and Hormad2 × Dmc1); apoptosis kinetics measurement in perinatal ovaries Histochemistry and cell biology Medium 39961811

Source papers

Stage 0 corpus · 37 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2009 Mouse HORMAD1 and HORMAD2, two conserved meiotic chromosomal proteins, are depleted from synapsed chromosome axes with the help of TRIP13 AAA-ATPase. PLoS genetics 333 19851446
2012 Meiotic DNA double-strand breaks and chromosome asynapsis in mice are monitored by distinct HORMAD2-independent and -dependent mechanisms. Genes & development 122 22549958
2012 Pathogenesis of immunoglobulin A nephropathy: recent insight from genetic studies. Annual review of medicine 107 23072577
2014 The chromosome axis controls meiotic events through a hierarchical assembly of HORMA domain proteins. Developmental cell 105 25446517
2020 Bi-allelic Missense Pathogenic Variants in TRIP13 Cause Female Infertility Characterized by Oocyte Maturation Arrest. American journal of human genetics 102 32473092
2017 The DNA Damage Checkpoint Eliminates Mouse Oocytes with Chromosome Synapsis Failure. Molecular cell 101 28844861
2019 Molecular organization of mammalian meiotic chromosome axis revealed by expansion STORM microscopy. Proceedings of the National Academy of Sciences of the United States of America 86 31444302
2012 HORMAD2 is essential for synapsis surveillance during meiotic prophase via the recruitment of ATR activity. Genes to cells : devoted to molecular & cellular mechanisms 65 23039116
2012 Phosphorylation of chromosome core components may serve as axis marks for the status of chromosomal events during mammalian meiosis. PLoS genetics 63 22346761
2018 The Cancer/Testes (CT) Antigen HORMAD1 promotes Homologous Recombinational DNA Repair and Radioresistance in Lung adenocarcinoma cells. Scientific reports 47 30333500
2015 MTMR3 risk allele enhances innate receptor-induced signaling and cytokines by decreasing autophagy and increasing caspase-1 activation. Proceedings of the National Academy of Sciences of the United States of America 44 26240347
2020 Dynamic Shifts in the HIV Proviral Landscape During Long Term Combination Antiretroviral Therapy: Implications for Persistence and Control of HIV Infections. Viruses 37 31991737
2020 State changes of the HORMA protein ASY1 are mediated by an interplay between its closure motif and PCH2. Nucleic acids research 34 32558910
2016 Genome-wide association study identifies variants in HORMAD2 associated with tonsillectomy. Journal of medical genetics 29 27941131
2019 Identification of susceptibility locus shared by IgA nephropathy and inflammatory bowel disease in a Chinese Han population. Journal of human genetics 28 31857673
2012 HORMAD2/CT46.2, a novel cancer/testis gene, is ectopically expressed in lung cancer tissues. Molecular human reproduction 28 22893617
2020 Prdm9 Intersubspecific Interactions in Hybrid Male Sterility of House Mouse. Molecular biology and evolution 23 32642764
2023 MTMR3 risk alleles enhance Toll Like Receptor 9-induced IgA immunity in IgA nephropathy. Kidney international 17 37414396
2016 SOHLH2 is essential for synaptonemal complex formation during spermatogenesis in early postnatal mouse testes. Scientific reports 14 26869299
2021 Genome-wide DNA methylation and RNA expression differences correlate with invasiveness in melanoma cell lines. Epigenomics 13 33781093
2024 WGCNA combined with machine learning to explore potential biomarkers and treatment strategies for acute liver failure, with experimental validation. iLIVER 8 40635857
2023 Structural and biochemical insights into the interaction mechanism underlying HORMAD1 and its partner proteins. Structure (London, England : 1993) 8 37794593
2022 Multiple 9-1-1 complexes promote homolog synapsis, DSB repair, and ATR signaling during mammalian meiosis. eLife 8 35133274
2022 Genic and chromosomal components of Prdm9-driven hybrid male sterility in mice (Mus musculus). Genetics 7 35924978
2015 A rare Robertsonian translocation rob(14;22) carrier with azoospermia, meiotic defects, and testicular sperm aneuploidy. Systems biology in reproductive medicine 6 26043179
2025 Aberrant activation of chromosome asynapsis checkpoint triggers oocyte elimination. Nature communications 5 40050306
2017 A strategy to apply quantitative epistasis analysis on developmental traits. BMC genetics 5 28506208
2014 Dosage compensation of an aneuploid genome in mouse spermatogenic cells. Biology of reproduction 5 24790161
2025 Genome-wide association study of pulpal and apical diseases. Nature communications 4 40701953
2023 Mucosal Immune Defence Gene Polymorphisms as Relevant Players in the Pathogenesis of IgA Vasculitis? International journal of molecular sciences 4 37685869
2024 A homozygous stop codon in HORMAD2 in a patient with recurrent digynic triploid miscarriage. Molecular genetics & genomic medicine 3 38400599
2022 Prdm9 deficiency of rat oocytes causes synapsis among non-homologous chromosomes and aneuploidy. Mammalian genome : official journal of the International Mammalian Genome Society 2 35596034
2025 A simple immunohistochemical method for perinatal mammalian ovaries revealed different kinetics of oocyte apoptosis caused by DNA damage and asynapsis. Histochemistry and cell biology 1 39961811
2024 The N-terminal modification of HORMAD2 causes its ectopic persistence on synapsed chromosomes without meiotic blockade. Reproduction (Cambridge, England) 1 38401263
2026 Aberrant signaling in tonsillar B cells producing pathogenic O-glycoforms of IgA1 in IgA nephropathy. Frontiers in immunology 0 41694356
2026 The synaptonemal complex: structure, function, and clinical implications†. Biology of reproduction 0 42059593
2026 Hybrid male sterility in house mice: meiotic checkpoints, chromosomal asynapsis, and the Prdm9-Mir465 incompatibility†. Biology of reproduction 0 42251751

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