{"gene":"DONSON","run_date":"2026-06-09T23:54:42","timeline":{"discoveries":[{"year":2017,"finding":"DONSON is a replisome component that stabilizes replication forks during genome replication. Loss of DONSON leads to severe replication-associated DNA damage from nucleolytic cleavage of stalled replication forks, and ATR-dependent signaling in response to replication stress is impaired in DONSON-deficient cells, resulting in decreased checkpoint activity and chromosomal instability.","method":"Genetic identification of biallelic mutations in patients, cell-based replication assays, DNA damage marker analysis, ATR signaling assays in DONSON-deficient cells","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (patient cell lines, replication fork assays, checkpoint signaling analysis), replicated across 29 patient-derived samples","pmids":["28191891"],"is_preprint":false},{"year":2017,"finding":"DONSON is expressed in progenitor cells of embryonic human brain and other proliferating tissues, co-expressed with components of the DNA replication machinery, and Donson is essential for early embryonic development in mice, indicating an essential conserved role in the cell cycle.","method":"RNA-seq transcriptome analysis, aberrant splicing detection, mouse embryonic lethality upon Donson disruption, co-expression analysis with replication factors","journal":"Genome research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mouse knockout lethality phenotype plus human expression co-regulation data, single study","pmids":["28630177"],"is_preprint":false},{"year":2019,"finding":"Missense variants in DONSON associated with Meier-Gorlin syndrome all disrupted the nuclear localization of DONSON, establishing that proper nuclear localization is required for DONSON function.","method":"Linked-read whole genome sequencing, nuclear localization assays of missense variants in patient-derived cells","journal":"Journal of medical genetics","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct localization experiment across multiple variants, single lab, functional consequence inferred from patient phenotype","pmids":["31784481"],"is_preprint":false},{"year":2020,"finding":"DONSON-bound replisomes are more frequent in early S phase and associate with euchromatin regions, whereas FANCM-bound replisomes predominate in late S phase and heterochromatin, identifying two distinct replisome populations distinguished by chromatin domain and replication timing.","method":"iPOND (isolation of proteins on nascent DNA), ChIP-seq of DONSON- and FANCM-associated DNA, replication timing analysis","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — iPOND combined with ChIP-seq providing orthogonal genome-wide evidence for distinct replisome populations, rigorous controls","pmids":["32769987"],"is_preprint":false},{"year":2021,"finding":"Conditional deletion of Donson in progenitors of cortical glutamatergic neurons (Emx1-Cre) caused extensive apoptosis in the early dorsomedial neuroepithelium, preventing formation of the neocortex and hippocampus. Deletion in subpallial progenitors (Nkx2.1-Cre) ablated 75% of Nkx2.1-derived cortical GABAergic neurons, establishing Donson as essential for early telencephalic neuroepithelium progenitors.","method":"Conditional knockout mouse models (Emx1-Cre, Tbr2-Cre, Nkx2.1-Cre), histology, immunofluorescence, apoptosis assays","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple Cre-driver conditional knockouts with specific cellular phenotypic readouts, orthogonal methods in single rigorous study","pmids":["33739968"],"is_preprint":false},{"year":2023,"finding":"DONSON scaffolds a vertebrate pre-loading complex (pre-LC) containing GINS, TOPBP1, and DNA pol ε, and docks this pre-LC onto MCM2-7 to deliver GINS to its binding site during CMG helicase assembly at replication initiation. A patient-derived DONSON mutation compromises CMG assembly and recapitulates microcephalic dwarfism in mice.","method":"AlphaFold-based protein-protein interaction screening followed by experimental validation (Co-IP, pulldown), mouse patient-mutation knock-in model, CMG assembly assays","journal":"Science (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 2 / Strong — in silico prediction validated by multiple biochemical experiments and in vivo mouse model, multiple orthogonal methods","pmids":["37590370"],"is_preprint":false},{"year":2023,"finding":"DONSON is required for CMG (CDC45-MCM-GINS) helicase assembly during S-phase in mammalian cells. DONSON binds directly but transiently to CDC45-MCM-GINS during S-phase and is dispensable for MCM2-7 loading onto chromatin during G1-phase, but essential for CDC45-MCM-GINS assembly during S-phase.","method":"Rapid protein depletion (auxin-inducible degron) in mouse embryonic stem cells, co-immunoprecipitation, chromatin fractionation, S-phase specific helicase assembly assays","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — rapid depletion combined with reciprocal Co-IP and chromatin fractionation, orthogonal methods distinguishing G1 vs S-phase roles","pmids":["37781960"],"is_preprint":false},{"year":2023,"finding":"DONSON is essential for replisome assembly in vertebrates. DONSON physically interacts with GINS and Pol ε via its conserved N-terminal PGY and NPF motifs. DONSON's chromatin association during replication initiation requires the pre-replicative complex, TopBP1, and kinase activities of S-CDK and DDK. Both S-CDK and DDK require DONSON to trigger replication initiation.","method":"Xenopus laevis cell-free replication system, immunodepletion/add-back experiments, co-immunoprecipitation, motif mutagenesis (PGY and NPF motifs), kinase inhibitor experiments","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution in Xenopus cell-free system combined with mutagenesis of defined interaction motifs and kinase dependency experiments","pmids":["37458194"],"is_preprint":false},{"year":2023,"finding":"DONSON is required for Cdc45 and GINS association with Mcm2-7 complexes and helicase activation during replication initiation. DONSON interacts with the initiation factor TopBP1 in a CDK-dependent manner. Following initiation, DONSON also forms part of the replisome during the elongation stage of DNA replication.","method":"Xenopus laevis egg extract cell-free system, immunodepletion, co-immunoprecipitation, chromatin association assays, CDK inhibitor experiments","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 / Strong — cell-free reconstitution system with immunodepletion and CDK-dependency experiments, orthogonal co-IP and chromatin assays","pmids":["37638758"],"is_preprint":false},{"year":2023,"finding":"Cryo-EM of proteins from replicating Xenopus egg extracts identified a double CMG complex bridged by a DONSON dimer. DONSON dimerization reconfigures the MCM motors in the double CMG. Tethering elements mediating complex formation are essential for replication, and primordial dwarfism patient mutations disrupting DONSON dimerization affect GINS and MCM engagement in human cells and DNA synthesis in Xenopus egg extracts.","method":"Cryo-electron microscopy (cryo-EM) of native complexes from Xenopus egg extracts, mutagenesis of dimerization interface, human cell complementation assays, Xenopus DNA synthesis assays","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structure combined with mutagenesis and functional validation in two systems (human cells and Xenopus extracts)","pmids":["37820732"],"is_preprint":false}],"current_model":"DONSON is a metazoan-specific replication factor that acts at two stages: during replication initiation, it scaffolds a vertebrate pre-loading complex (containing GINS, TOPBP1, and DNA pol ε) and docks it onto MCM2-7 to drive CMG helicase assembly in a CDK- and DDK-dependent manner, functioning as the functional ortholog of yeast Sld2; and during elongation, it is a replisome component that stabilizes replication forks, prevents nucleolytic cleavage of stalled forks, and supports ATR-dependent checkpoint signaling—with DONSON-bound replisomes preferentially associating with early-replicating euchromatin—such that biallelic loss-of-function mutations cause microcephalic dwarfism syndromes including Meier-Gorlin syndrome."},"narrative":{"mechanistic_narrative":"DONSON is a metazoan replication factor that operates at the heart of the cell cycle by driving assembly and stabilization of the replicative CMG helicase [PMID:28191891, PMID:37781960]. At replication initiation it scaffolds a vertebrate pre-loading complex containing GINS, TOPBP1, and DNA polymerase ε, engaging these partners through its conserved N-terminal PGY and NPF motifs, and docks this complex onto MCM2-7 to deliver GINS during CMG (CDC45-MCM-GINS) assembly [PMID:37590370, PMID:37458194]. This activity is gated by cell-cycle kinases: DONSON's chromatin loading requires the pre-replicative complex and TOPBP1, and both S-CDK and DDK depend on DONSON to trigger initiation, with DONSON binding TOPBP1 in a CDK-dependent manner [PMID:37458194, PMID:37638758]. DONSON binds CDC45-MCM-GINS transiently during S phase and is dispensable for G1 MCM2-7 loading but essential for S-phase helicase activation [PMID:37781960]. Structurally, a DONSON dimer bridges two CMG complexes and reconfigures the MCM motors, and patient mutations that disrupt dimerization impair GINS/MCM engagement and DNA synthesis [PMID:37820732]. Beyond initiation, DONSON persists as a replisome component that stabilizes forks, prevents nucleolytic cleavage of stalled forks, and supports ATR-dependent checkpoint signaling, with DONSON-bound replisomes preferentially associating with early-replicating euchromatin [PMID:28191891, PMID:32769987, PMID:37638758]. DONSON is essential for proliferating progenitors, including telencephalic neuroepithelium, and biallelic loss-of-function or localization-disrupting mutations cause microcephalic dwarfism syndromes including Meier-Gorlin syndrome [PMID:28630177, PMID:31784481, PMID:33739968, PMID:37590370].","teleology":[{"year":2017,"claim":"Established DONSON as a genome-stability factor by linking it to replisome function and fork protection, answering whether the gene had a direct role in replication rather than a peripheral one.","evidence":"Patient biallelic mutation identification with replication fork and ATR checkpoint assays in DONSON-deficient cells","pmids":["28191891"],"confidence":"High","gaps":["Did not define the molecular step DONSON catalyzes at the fork","No direct biochemical partner identified"]},{"year":2017,"claim":"Placed DONSON within the proliferating-progenitor and replication-factor expression program and showed it is essential for development, framing why its loss produces growth/brain phenotypes.","evidence":"Human brain RNA-seq co-expression analysis and Donson mouse embryonic lethality","pmids":["28630177"],"confidence":"Medium","gaps":["Correlative co-expression, not a direct mechanistic role","Lethality stage does not pinpoint the affected cell-cycle step"]},{"year":2019,"claim":"Showed that Meier-Gorlin-associated missense variants converge on disrupted nuclear localization, establishing that nuclear access is a functional requirement.","evidence":"Whole genome sequencing and nuclear localization assays of variants in patient-derived cells","pmids":["31784481"],"confidence":"Medium","gaps":["Localization signal/mechanism of nuclear import not mapped","Functional consequence inferred from phenotype, not biochemistry"]},{"year":2020,"claim":"Distinguished two replisome populations by chromatin domain and timing, showing DONSON-bound replisomes are an early-S/euchromatin-associated class.","evidence":"iPOND combined with ChIP-seq and replication timing analysis","pmids":["32769987"],"confidence":"High","gaps":["Does not explain what specifies DONSON to early-replicating regions","Functional consequence of the two populations unresolved"]},{"year":2021,"claim":"Defined the cell-type basis of the neurological phenotype, showing DONSON is required in telencephalic neuroepithelial progenitors.","evidence":"Conditional Cre-driver knockout mice with histology and apoptosis assays","pmids":["33739968"],"confidence":"High","gaps":["Does not connect progenitor loss to a specific replication defect at molecular resolution"]},{"year":2023,"claim":"Resolved DONSON's core mechanism: it scaffolds a pre-loading complex (GINS, TOPBP1, Pol ε) and delivers GINS to MCM2-7 to assemble CMG, defining it as an initiation factor and explaining the dwarfism phenotype.","evidence":"AlphaFold-guided interaction screening with Co-IP/pulldown validation, CMG assembly assays, and patient-mutation knock-in mice; corroborated by Xenopus cell-free reconstitution mapping PGY/NPF motifs and S-CDK/DDK dependence; degron depletion separating G1 from S-phase roles","pmids":["37590370","37458194","37638758","37781960"],"confidence":"High","gaps":["Precise order of GINS handoff and motor engagement not fully resolved","Mechanism coupling initiation role to later fork-protection role unclear"]},{"year":2023,"claim":"Provided structural mechanism: a DONSON dimer bridges two CMG complexes and reconfigures MCM motors, and dimerization-disrupting patient mutations impair helicase engagement and DNA synthesis.","evidence":"Cryo-EM of native double-CMG complexes from Xenopus egg extracts with dimerization-interface mutagenesis and validation in human cells and Xenopus extracts","pmids":["37820732"],"confidence":"High","gaps":["Functional purpose of the double-CMG configuration in vivo not fully defined","Whether dimerization is required at every origin is unknown"]},{"year":null,"claim":"How DONSON's transient initiation-stage helicase-assembly role is mechanistically linked to its persistent elongation-stage fork-protection and ATR-signaling functions remains unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No mechanism connecting CMG assembly to fork stabilization","Determinants of DONSON-replisome targeting to early euchromatin unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[5,7,9]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[9]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[2]},{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[3,8]}],"pathway":[{"term_id":"R-HSA-69306","term_label":"DNA Replication","supporting_discovery_ids":[5,6,7]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[1,6]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[0]}],"complexes":["pre-loading complex (pre-LC)","CMG helicase","replisome","double CMG"],"partners":["GINS","TOPBP1","POLE","MCM2-7","CDC45"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NYP3","full_name":"Protein downstream neighbor of Son","aliases":["B17"],"length_aa":566,"mass_kda":62.7,"function":"Replisome component that maintains genome stability by protecting stalled or damaged replication forks. After the induction of replication stress, required for the stabilization of stalled replication forks, the efficient activation of the intra-S-phase and G/2M cell-cycle checkpoints and the maintenance of genome stability","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q9NYP3/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/DONSON","classification":"Common Essential","n_dependent_lines":1206,"n_total_lines":1208,"dependency_fraction":0.9983443708609272},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"PSMG1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/DONSON","total_profiled":1310},"omim":[{"mim_id":"621528","title":"MEIER-GORLIN SYNDROME 10; MGORS10","url":"https://www.omim.org/entry/621528"},{"mim_id":"617604","title":"MICROCEPHALY, SHORT STATURE, AND LIMB ABNORMALITIES; MISSLA","url":"https://www.omim.org/entry/617604"},{"mim_id":"611428","title":"DOWNSTREAM NEIGHBOR OF SON; DONSON","url":"https://www.omim.org/entry/611428"},{"mim_id":"251230","title":"MICROCEPHALY-MICROMELIA SYNDROME; MIMIS","url":"https://www.omim.org/entry/251230"},{"mim_id":"224690","title":"MEIER-GORLIN SYNDROME 1; MGORS1","url":"https://www.omim.org/entry/224690"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Cell Junctions","reliability":"Approved"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/DONSON"},"hgnc":{"alias_symbol":["B17","C2TA","DKFZP434M035"],"prev_symbol":["C21orf60"]},"alphafold":{"accession":"Q9NYP3","domains":[{"cath_id":"-","chopping":"150-221_449-566","consensus_level":"medium","plddt":88.2803,"start":150,"end":566},{"cath_id":"-","chopping":"239-330_394-446","consensus_level":"medium","plddt":90.9003,"start":239,"end":446}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NYP3","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NYP3-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NYP3-F1-predicted_aligned_error_v6.png","plddt_mean":72.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=DONSON","jax_strain_url":"https://www.jax.org/strain/search?query=DONSON"},"sequence":{"accession":"Q9NYP3","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NYP3.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NYP3/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NYP3"}},"corpus_meta":[{"pmid":"30922402","id":"PMC_30922402","title":"Circular RNA circ-DONSON facilitates gastric cancer growth and invasion via NURF complex dependent activation of transcription factor SOX4.","date":"2019","source":"Molecular cancer","url":"https://pubmed.ncbi.nlm.nih.gov/30922402","citation_count":204,"is_preprint":false},{"pmid":"28191891","id":"PMC_28191891","title":"Mutations in DONSON disrupt replication fork stability and cause microcephalic dwarfism.","date":"2017","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/28191891","citation_count":96,"is_preprint":false},{"pmid":"37590370","id":"PMC_37590370","title":"In silico protein interaction screening uncovers DONSON's role in replication initiation.","date":"2023","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/37590370","citation_count":89,"is_preprint":false},{"pmid":"28630177","id":"PMC_28630177","title":"Integrated genome and transcriptome sequencing identifies a noncoding mutation in the genome replication factor DONSON as the cause of microcephaly-micromelia syndrome.","date":"2017","source":"Genome research","url":"https://pubmed.ncbi.nlm.nih.gov/28630177","citation_count":39,"is_preprint":false},{"pmid":"32581651","id":"PMC_32581651","title":"CircRNA DONSON contributes to cisplatin resistance in gastric cancer cells by regulating miR-802/BMI1 axis.","date":"2020","source":"Cancer cell international","url":"https://pubmed.ncbi.nlm.nih.gov/32581651","citation_count":38,"is_preprint":false},{"pmid":"32769987","id":"PMC_32769987","title":"DONSON and FANCM associate with different replisomes distinguished by replication timing and chromatin domain.","date":"2020","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/32769987","citation_count":36,"is_preprint":false},{"pmid":"37820732","id":"PMC_37820732","title":"The structural mechanism of dimeric DONSON in replicative helicase activation.","date":"2023","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/37820732","citation_count":35,"is_preprint":false},{"pmid":"31784481","id":"PMC_31784481","title":"Linked-read genome sequencing identifies biallelic pathogenic variants in DONSON as a novel cause of Meier-Gorlin syndrome.","date":"2019","source":"Journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/31784481","citation_count":34,"is_preprint":false},{"pmid":"37458194","id":"PMC_37458194","title":"Novel role of DONSON in CMG helicase assembly during vertebrate DNA replication initiation.","date":"2023","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/37458194","citation_count":32,"is_preprint":false},{"pmid":"37638758","id":"PMC_37638758","title":"DONSON facilitates Cdc45 and GINS chromatin association and is essential for DNA replication initiation.","date":"2023","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/37638758","citation_count":29,"is_preprint":false},{"pmid":"10950926","id":"PMC_10950926","title":"Organization and conservation of the GART/SON/DONSON locus in mouse and human genomes.","date":"2000","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/10950926","citation_count":28,"is_preprint":false},{"pmid":"37781960","id":"PMC_37781960","title":"DONSON is required for CMG helicase assembly in the mammalian cell cycle.","date":"2023","source":"EMBO reports","url":"https://pubmed.ncbi.nlm.nih.gov/37781960","citation_count":22,"is_preprint":false},{"pmid":"31407851","id":"PMC_31407851","title":"Biallelic and De Novo Variants in DONSON Reveal a Clinical Spectrum of Cell Cycle-opathies with Microcephaly, Dwarfism and Skeletal Abnormalities.","date":"2019","source":"American journal of medical genetics. Part A","url":"https://pubmed.ncbi.nlm.nih.gov/31407851","citation_count":19,"is_preprint":false},{"pmid":"34853591","id":"PMC_34853591","title":"Circ-DONSON Knockdown Inhibits Cell Proliferation and Radioresistance of Breast Cancer Cells via Regulating SOX4.","date":"2021","source":"Journal of oncology","url":"https://pubmed.ncbi.nlm.nih.gov/34853591","citation_count":11,"is_preprint":false},{"pmid":"34409524","id":"PMC_34409524","title":"Circ-DONSON Facilitates the Malignant Progression of Gastric Cancer Depending on the Regulation of miR-149-5p/LDHA Axis.","date":"2021","source":"Biochemical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/34409524","citation_count":10,"is_preprint":false},{"pmid":"35298084","id":"PMC_35298084","title":"Microcephalic primordial dwarfism with predominant Meier-Gorlin phenotype, ichthyosis, and multiple joint deformities-Further expansion of DONSON Cell Cycle-opathy phenotypic spectrum.","date":"2022","source":"American journal of medical genetics. Part A","url":"https://pubmed.ncbi.nlm.nih.gov/35298084","citation_count":8,"is_preprint":false},{"pmid":"33228112","id":"PMC_33228112","title":"Downstream Neighbor of SON (DONSON) Expression Is Enhanced in Phenotypically Aggressive Prostate Cancers.","date":"2020","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/33228112","citation_count":7,"is_preprint":false},{"pmid":"32805676","id":"PMC_32805676","title":"Downstream neighbor of SON (DONSON) is associated with unfavorable survival across diverse cancers with oncogenic properties in clear cell renal cell carcinoma.","date":"2020","source":"Translational oncology","url":"https://pubmed.ncbi.nlm.nih.gov/32805676","citation_count":7,"is_preprint":false},{"pmid":"38159447","id":"PMC_38159447","title":"DONSON: Slding in 2 the limelight.","date":"2023","source":"DNA repair","url":"https://pubmed.ncbi.nlm.nih.gov/38159447","citation_count":6,"is_preprint":false},{"pmid":"32016978","id":"PMC_32016978","title":"Circ-DONSON promotes malignant progression of glioma through modulating FOXO3.","date":"2020","source":"European review for medical and pharmacological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/32016978","citation_count":6,"is_preprint":false},{"pmid":"31191207","id":"PMC_31191207","title":"Further Delineation of the Microcephaly-Micromelia Syndrome Associated with Loss-of-Function Variants in DONSON.","date":"2019","source":"Molecular syndromology","url":"https://pubmed.ncbi.nlm.nih.gov/31191207","citation_count":5,"is_preprint":false},{"pmid":"33739968","id":"PMC_33739968","title":"The microcephaly gene Donson is essential for progenitors of cortical glutamatergic and GABAergic neurons.","date":"2021","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/33739968","citation_count":1,"is_preprint":false},{"pmid":"41612845","id":"PMC_41612845","title":"Meier-Gorlin syndrome due to a recurrent DONSON variant in a Turkish family: first report of thumb aplasia and long-term growth data.","date":"2026","source":"Journal of pediatric endocrinology & metabolism : JPEM","url":"https://pubmed.ncbi.nlm.nih.gov/41612845","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":13460,"output_tokens":2629,"usd":0.039907,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9845,"output_tokens":2751,"usd":0.059,"stage2_stop_reason":"end_turn"},"total_usd":0.098907,"stage1_batch_id":"msgbatch_01AsR7g8dGTEiEw9U83bJeWn","stage2_batch_id":"msgbatch_01YV5ZyxtFNUZEjxRcpd9jzb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2017,\n      \"finding\": \"DONSON is a replisome component that stabilizes replication forks during genome replication. Loss of DONSON leads to severe replication-associated DNA damage from nucleolytic cleavage of stalled replication forks, and ATR-dependent signaling in response to replication stress is impaired in DONSON-deficient cells, resulting in decreased checkpoint activity and chromosomal instability.\",\n      \"method\": \"Genetic identification of biallelic mutations in patients, cell-based replication assays, DNA damage marker analysis, ATR signaling assays in DONSON-deficient cells\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (patient cell lines, replication fork assays, checkpoint signaling analysis), replicated across 29 patient-derived samples\",\n      \"pmids\": [\"28191891\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"DONSON is expressed in progenitor cells of embryonic human brain and other proliferating tissues, co-expressed with components of the DNA replication machinery, and Donson is essential for early embryonic development in mice, indicating an essential conserved role in the cell cycle.\",\n      \"method\": \"RNA-seq transcriptome analysis, aberrant splicing detection, mouse embryonic lethality upon Donson disruption, co-expression analysis with replication factors\",\n      \"journal\": \"Genome research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mouse knockout lethality phenotype plus human expression co-regulation data, single study\",\n      \"pmids\": [\"28630177\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Missense variants in DONSON associated with Meier-Gorlin syndrome all disrupted the nuclear localization of DONSON, establishing that proper nuclear localization is required for DONSON function.\",\n      \"method\": \"Linked-read whole genome sequencing, nuclear localization assays of missense variants in patient-derived cells\",\n      \"journal\": \"Journal of medical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct localization experiment across multiple variants, single lab, functional consequence inferred from patient phenotype\",\n      \"pmids\": [\"31784481\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"DONSON-bound replisomes are more frequent in early S phase and associate with euchromatin regions, whereas FANCM-bound replisomes predominate in late S phase and heterochromatin, identifying two distinct replisome populations distinguished by chromatin domain and replication timing.\",\n      \"method\": \"iPOND (isolation of proteins on nascent DNA), ChIP-seq of DONSON- and FANCM-associated DNA, replication timing analysis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — iPOND combined with ChIP-seq providing orthogonal genome-wide evidence for distinct replisome populations, rigorous controls\",\n      \"pmids\": [\"32769987\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Conditional deletion of Donson in progenitors of cortical glutamatergic neurons (Emx1-Cre) caused extensive apoptosis in the early dorsomedial neuroepithelium, preventing formation of the neocortex and hippocampus. Deletion in subpallial progenitors (Nkx2.1-Cre) ablated 75% of Nkx2.1-derived cortical GABAergic neurons, establishing Donson as essential for early telencephalic neuroepithelium progenitors.\",\n      \"method\": \"Conditional knockout mouse models (Emx1-Cre, Tbr2-Cre, Nkx2.1-Cre), histology, immunofluorescence, apoptosis assays\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple Cre-driver conditional knockouts with specific cellular phenotypic readouts, orthogonal methods in single rigorous study\",\n      \"pmids\": [\"33739968\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"DONSON scaffolds a vertebrate pre-loading complex (pre-LC) containing GINS, TOPBP1, and DNA pol ε, and docks this pre-LC onto MCM2-7 to deliver GINS to its binding site during CMG helicase assembly at replication initiation. A patient-derived DONSON mutation compromises CMG assembly and recapitulates microcephalic dwarfism in mice.\",\n      \"method\": \"AlphaFold-based protein-protein interaction screening followed by experimental validation (Co-IP, pulldown), mouse patient-mutation knock-in model, CMG assembly assays\",\n      \"journal\": \"Science (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in silico prediction validated by multiple biochemical experiments and in vivo mouse model, multiple orthogonal methods\",\n      \"pmids\": [\"37590370\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"DONSON is required for CMG (CDC45-MCM-GINS) helicase assembly during S-phase in mammalian cells. DONSON binds directly but transiently to CDC45-MCM-GINS during S-phase and is dispensable for MCM2-7 loading onto chromatin during G1-phase, but essential for CDC45-MCM-GINS assembly during S-phase.\",\n      \"method\": \"Rapid protein depletion (auxin-inducible degron) in mouse embryonic stem cells, co-immunoprecipitation, chromatin fractionation, S-phase specific helicase assembly assays\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — rapid depletion combined with reciprocal Co-IP and chromatin fractionation, orthogonal methods distinguishing G1 vs S-phase roles\",\n      \"pmids\": [\"37781960\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"DONSON is essential for replisome assembly in vertebrates. DONSON physically interacts with GINS and Pol ε via its conserved N-terminal PGY and NPF motifs. DONSON's chromatin association during replication initiation requires the pre-replicative complex, TopBP1, and kinase activities of S-CDK and DDK. Both S-CDK and DDK require DONSON to trigger replication initiation.\",\n      \"method\": \"Xenopus laevis cell-free replication system, immunodepletion/add-back experiments, co-immunoprecipitation, motif mutagenesis (PGY and NPF motifs), kinase inhibitor experiments\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution in Xenopus cell-free system combined with mutagenesis of defined interaction motifs and kinase dependency experiments\",\n      \"pmids\": [\"37458194\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"DONSON is required for Cdc45 and GINS association with Mcm2-7 complexes and helicase activation during replication initiation. DONSON interacts with the initiation factor TopBP1 in a CDK-dependent manner. Following initiation, DONSON also forms part of the replisome during the elongation stage of DNA replication.\",\n      \"method\": \"Xenopus laevis egg extract cell-free system, immunodepletion, co-immunoprecipitation, chromatin association assays, CDK inhibitor experiments\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cell-free reconstitution system with immunodepletion and CDK-dependency experiments, orthogonal co-IP and chromatin assays\",\n      \"pmids\": [\"37638758\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Cryo-EM of proteins from replicating Xenopus egg extracts identified a double CMG complex bridged by a DONSON dimer. DONSON dimerization reconfigures the MCM motors in the double CMG. Tethering elements mediating complex formation are essential for replication, and primordial dwarfism patient mutations disrupting DONSON dimerization affect GINS and MCM engagement in human cells and DNA synthesis in Xenopus egg extracts.\",\n      \"method\": \"Cryo-electron microscopy (cryo-EM) of native complexes from Xenopus egg extracts, mutagenesis of dimerization interface, human cell complementation assays, Xenopus DNA synthesis assays\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structure combined with mutagenesis and functional validation in two systems (human cells and Xenopus extracts)\",\n      \"pmids\": [\"37820732\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"DONSON is a metazoan-specific replication factor that acts at two stages: during replication initiation, it scaffolds a vertebrate pre-loading complex (containing GINS, TOPBP1, and DNA pol ε) and docks it onto MCM2-7 to drive CMG helicase assembly in a CDK- and DDK-dependent manner, functioning as the functional ortholog of yeast Sld2; and during elongation, it is a replisome component that stabilizes replication forks, prevents nucleolytic cleavage of stalled forks, and supports ATR-dependent checkpoint signaling—with DONSON-bound replisomes preferentially associating with early-replicating euchromatin—such that biallelic loss-of-function mutations cause microcephalic dwarfism syndromes including Meier-Gorlin syndrome.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"DONSON is a metazoan replication factor that operates at the heart of the cell cycle by driving assembly and stabilization of the replicative CMG helicase [#0, #6]. At replication initiation it scaffolds a vertebrate pre-loading complex containing GINS, TOPBP1, and DNA polymerase \\u03b5, engaging these partners through its conserved N-terminal PGY and NPF motifs, and docks this complex onto MCM2-7 to deliver GINS during CMG (CDC45-MCM-GINS) assembly [#5, #7]. This activity is gated by cell-cycle kinases: DONSON's chromatin loading requires the pre-replicative complex and TOPBP1, and both S-CDK and DDK depend on DONSON to trigger initiation, with DONSON binding TOPBP1 in a CDK-dependent manner [#7, #8]. DONSON binds CDC45-MCM-GINS transiently during S phase and is dispensable for G1 MCM2-7 loading but essential for S-phase helicase activation [#6]. Structurally, a DONSON dimer bridges two CMG complexes and reconfigures the MCM motors, and patient mutations that disrupt dimerization impair GINS/MCM engagement and DNA synthesis [#9]. Beyond initiation, DONSON persists as a replisome component that stabilizes forks, prevents nucleolytic cleavage of stalled forks, and supports ATR-dependent checkpoint signaling, with DONSON-bound replisomes preferentially associating with early-replicating euchromatin [#0, #3, #8]. DONSON is essential for proliferating progenitors, including telencephalic neuroepithelium, and biallelic loss-of-function or localization-disrupting mutations cause microcephalic dwarfism syndromes including Meier-Gorlin syndrome [#1, #2, #4, #5].\",\n  \"teleology\": [\n    {\n      \"year\": 2017,\n      \"claim\": \"Established DONSON as a genome-stability factor by linking it to replisome function and fork protection, answering whether the gene had a direct role in replication rather than a peripheral one.\",\n      \"evidence\": \"Patient biallelic mutation identification with replication fork and ATR checkpoint assays in DONSON-deficient cells\",\n      \"pmids\": [\"28191891\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the molecular step DONSON catalyzes at the fork\", \"No direct biochemical partner identified\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Placed DONSON within the proliferating-progenitor and replication-factor expression program and showed it is essential for development, framing why its loss produces growth/brain phenotypes.\",\n      \"evidence\": \"Human brain RNA-seq co-expression analysis and Donson mouse embryonic lethality\",\n      \"pmids\": [\"28630177\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Correlative co-expression, not a direct mechanistic role\", \"Lethality stage does not pinpoint the affected cell-cycle step\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Showed that Meier-Gorlin-associated missense variants converge on disrupted nuclear localization, establishing that nuclear access is a functional requirement.\",\n      \"evidence\": \"Whole genome sequencing and nuclear localization assays of variants in patient-derived cells\",\n      \"pmids\": [\"31784481\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Localization signal/mechanism of nuclear import not mapped\", \"Functional consequence inferred from phenotype, not biochemistry\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Distinguished two replisome populations by chromatin domain and timing, showing DONSON-bound replisomes are an early-S/euchromatin-associated class.\",\n      \"evidence\": \"iPOND combined with ChIP-seq and replication timing analysis\",\n      \"pmids\": [\"32769987\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not explain what specifies DONSON to early-replicating regions\", \"Functional consequence of the two populations unresolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Defined the cell-type basis of the neurological phenotype, showing DONSON is required in telencephalic neuroepithelial progenitors.\",\n      \"evidence\": \"Conditional Cre-driver knockout mice with histology and apoptosis assays\",\n      \"pmids\": [\"33739968\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not connect progenitor loss to a specific replication defect at molecular resolution\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Resolved DONSON's core mechanism: it scaffolds a pre-loading complex (GINS, TOPBP1, Pol \\u03b5) and delivers GINS to MCM2-7 to assemble CMG, defining it as an initiation factor and explaining the dwarfism phenotype.\",\n      \"evidence\": \"AlphaFold-guided interaction screening with Co-IP/pulldown validation, CMG assembly assays, and patient-mutation knock-in mice; corroborated by Xenopus cell-free reconstitution mapping PGY/NPF motifs and S-CDK/DDK dependence; degron depletion separating G1 from S-phase roles\",\n      \"pmids\": [\"37590370\", \"37458194\", \"37638758\", \"37781960\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise order of GINS handoff and motor engagement not fully resolved\", \"Mechanism coupling initiation role to later fork-protection role unclear\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Provided structural mechanism: a DONSON dimer bridges two CMG complexes and reconfigures MCM motors, and dimerization-disrupting patient mutations impair helicase engagement and DNA synthesis.\",\n      \"evidence\": \"Cryo-EM of native double-CMG complexes from Xenopus egg extracts with dimerization-interface mutagenesis and validation in human cells and Xenopus extracts\",\n      \"pmids\": [\"37820732\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional purpose of the double-CMG configuration in vivo not fully defined\", \"Whether dimerization is required at every origin is unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How DONSON's transient initiation-stage helicase-assembly role is mechanistically linked to its persistent elongation-stage fork-protection and ATR-signaling functions remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No mechanism connecting CMG assembly to fork stabilization\", \"Determinants of DONSON-replisome targeting to early euchromatin unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [5, 7, 9]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [3, 8]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-69306\", \"supporting_discovery_ids\": [5, 6, 7]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [1, 6]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"complexes\": [\"pre-loading complex (pre-LC)\", \"CMG helicase\", \"replisome\", \"double CMG\"],\n    \"partners\": [\"GINS\", \"TOPBP1\", \"POLE\", \"MCM2-7\", \"CDC45\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}