{"gene":"FANCB","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":2005,"finding":"FANCB (previously misidentified as BRCA2/FANCB) was identified as FAAP95, a previously uncharacterized component of the FA core complex that functions upstream of FANCD2 monoubiquitination, placing FANCB in the FA core complex rather than downstream or in a parallel pathway.","method":"Biochemical identification of FAAP95 as the true FANCB protein; pathway placement by epistasis/functional complementation showing FANCB acts upstream of FANCD2 monoubiquitination","journal":"Cell cycle (Georgetown, Tex.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pathway placement established by functional complementation and biochemical analysis, single lab, reviewed/commentary paper summarizing the primary discovery","pmids":["15611632"],"is_preprint":false},{"year":2007,"finding":"FANCB (as a component of the FA core complex) and Mus81 act independently in repairing camptothecin-induced DNA damage during replication; FANCB is required for FANCD2 foci formation after DNA crosslink damage but not for sister chromatid exchanges, gene targeting, or hydroxyurea-induced replication fork repair, while Mus81 handles the latter functions.","method":"Gene knockout of FANCB and/or Mus81 in human Nalm-6 cells; FANCD2 foci assay, Rad51 foci, sister chromatid exchange assay, gene targeting assay, survival assays with MMC, CPT, and HU","journal":"Genes to cells : devoted to molecular & cellular mechanisms","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean gene knockout with multiple orthogonal phenotypic readouts (foci, SCE, survival, gene targeting) in human cells, multiple drug treatments establishing distinct pathway roles","pmids":["17903171"],"is_preprint":false},{"year":2011,"finding":"FancB-mutant mouse embryonic stem cells show hypersensitivity to the crosslinking agent mitomycin C, increased chromosomal abnormalities, reduced sister chromatid exchanges, reduced gene targeting, reduced MMC-induced Rad51 foci, and absent MMC-induced FancD2 foci, confirming FANCB is required for FancD2 monoubiquitination/foci formation and HR repair of ICLs.","method":"FancB knockout mouse ES cells; MMC sensitivity assay, chromosomal aberration analysis, SCE assay, gene targeting assay, immunofluorescence for Rad51 and FancD2 foci","journal":"Mutation research","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO model with multiple orthogonal readouts confirming FANCB role in ICL repair pathway and FANCD2 activation","pmids":["21458466"],"is_preprint":false},{"year":2015,"finding":"FANCB is essential for male germline function: Fancb mutant mice are infertile with primordial germ cell defects and spermatogonial maintenance failure. During meiosis, FANCB localizes to sex chromosomes in an MDC1-dependent manner (MDC1 binds γH2AX to initiate chromosome-wide silencing), is required for FANCD2 localization during meiosis, and regulates H3K9 methylation on sex chromosomes—loss of FANCB decreases H3K9me2 and increases H3K9me3 on sex chromosomes.","method":"Fancb mutant mouse model (first X-linked FA mouse); fertility assays, immunofluorescence for FANCB, FANCD2, MDC1, γH2AX, H3K9me2, H3K9me3 on meiotic chromosomes; spermatogonial analysis","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO mouse model with multiple orthogonal methods (immunofluorescence, epistasis with MDC1, histone modification analysis) establishing novel FANCB function in germline epigenetics","pmids":["26123487"],"is_preprint":false},{"year":2015,"finding":"Fancb-deficient mice have decreased HSC quiescence, reduced progenitor activity in vitro, and reduced repopulating capacity in vivo; Fancb-deficient bone marrow is hypersensitive to MMC and shows impaired recovery from myelotoxic stress; RNA-seq reveals altered expression of genes involved in HSC function and cell cycle regulation in Fancb-deficient HSCs.","method":"Fancb knockout mouse model (Fancb-/y); flow cytometry for HSC populations, colony-forming assays, competitive transplantation assay, MMC bone marrow failure model, 5-FU stress assay, RNA-seq","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO mouse model with multiple orthogonal in vivo and in vitro readouts establishing FANCB role in HSC maintenance","pmids":["26658157"],"is_preprint":false},{"year":2020,"finding":"FANCB protein is indispensable for FANCD2 monoubiquitination (an essential step in ICL repair); FANCB missense variants show variable residual FANCD2 monoubiquitination activity that correlates with clinical severity. Aberrant splicing and transcript destabilization were associated with 2 missense variants. Biochemical reconstitution confirmed that reduced FANCD2 monoubiquitination correlates with earlier disease onset and shorter survival.","method":"Transcript analysis, genetic complementation in FANCB-null cells, biochemical reconstitution of FANCD2 monoubiquitination with FANCB WT and mutant constructs; FANCD2 ubiquitination assay and foci formation assay","journal":"Blood","confidence":"High","confidence_rationale":"Tier 1 / Strong — biochemical reconstitution of FANCD2 monoubiquitination with mutant constructs, genetic complementation, and transcript analysis across multiple patients and variants with functional correlation","pmids":["32106311"],"is_preprint":false},{"year":2017,"finding":"A somatic mosaic intragenic duplication of FANCB covering exon 3 introduces a premature stop codon (p.A319*) in the FANCB protein; lentiviral transduction of FANCB-null cells with the mutant construct confirmed loss of FANCD2 ubiquitination and foci formation activity, while WT FANCB restored these functions.","method":"ArrayCGH for duplication detection; targeted sequencing and PacBio sequencing for breakpoint and aberrant transcript characterization; lentiviral transduction of FANCB-null cells with WT and mutant constructs; FANCD2 ubiquitination and foci formation assays; droplet digital PCR for mosaicism quantitation","journal":"Molecular genetics & genomic medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional complementation with mutant construct in null cells using FANCD2 assays, single lab","pmids":["29193904"],"is_preprint":false},{"year":2011,"finding":"Loss-of-function FANCB mutations (truncating) cause X-linked VACTERL-hydrocephalus syndrome in hemizygous males, and carrier females show highly skewed X-inactivation; increased chromosomal breakage on exposure to DNA cross-linking agents was confirmed in affected cells, consistent with FANCB's role in the FA pathway.","method":"Clinical and molecular characterization of FANCB mutation carriers; chromosome breakage assay with DNA cross-linking agents; X-inactivation analysis","journal":"American journal of medical genetics. Part A","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — chromosome breakage assay directly demonstrating FANCB loss-of-function impairs ICL repair, multiple families, but clinical/molecular characterization study without full biochemical reconstitution","pmids":["21910217"],"is_preprint":false}],"current_model":"FANCB (FAAP95) is an X-linked component of the FA core complex that is required for FANCD2 monoubiquitination in response to DNA interstrand crosslinks; it localizes to sex chromosomes during meiosis in an MDC1/γH2AX-dependent manner, regulates H3K9 methylation on sex chromosomes, maintains hematopoietic stem cell quiescence and repopulating capacity, and its complete loss causes X-linked VACTERL-hydrocephalus syndrome with residual FANCD2 monoubiquitination activity correlating with clinical severity."},"narrative":{"mechanistic_narrative":"FANCB (originally identified as FAAP95) is an X-linked component of the Fanconi anemia (FA) core complex that acts upstream to promote FANCD2 monoubiquitination during the repair of DNA interstrand crosslinks (ICLs) [PMID:15611632, PMID:21458466]. Loss of FANCB abolishes MMC- and crosslink-induced FANCD2 foci formation and reduces RAD51 foci, sister chromatid exchange, and gene targeting, producing crosslinker hypersensitivity and chromosomal instability, while a parallel MUS81-dependent route handles replication-fork repair independently of FANCB [PMID:17903171, PMID:21458466]. Biochemical reconstitution establishes that FANCB protein is indispensable for FANCD2 monoubiquitination, and the degree of residual monoubiquitination conferred by FANCB missense variants correlates with clinical severity [PMID:32106311]. Beyond canonical ICL repair, FANCB has dedicated germline and stem-cell roles: during male meiosis it localizes to the sex chromosomes in an MDC1/γH2AX-dependent manner, is required for meiotic FANCD2 localization, and shapes sex-chromosome H3K9 methylation (decreasing H3K9me2 and increasing H3K9me3 upon loss), with FANCB-mutant mice showing primordial germ cell defects and spermatogonial failure [PMID:26123487]; it also maintains hematopoietic stem cell quiescence and repopulating capacity [PMID:26658157]. Truncating loss-of-function FANCB mutations cause X-linked VACTERL-hydrocephalus syndrome in hemizygous males, with carrier females showing skewed X-inactivation [PMID:21910217].","teleology":[{"year":2005,"claim":"Established the molecular identity and pathway position of FANCB by showing the true FANCB protein is FAAP95, a core-complex member acting upstream of FANCD2, resolving prior confusion with BRCA2.","evidence":"Biochemical identification of FAAP95 with epistasis/complementation placing FANCB upstream of FANCD2 monoubiquitination","pmids":["15611632"],"confidence":"Medium","gaps":["Did not define the biochemical activity FANCB contributes to monoubiquitination","Core-complex subunit interactions not mapped at the structural level"]},{"year":2007,"claim":"Distinguished FANCB's ICL-repair function from a parallel replication-fork pathway, showing FANCB is required for FANCD2 foci but not for SCE, gene targeting, or HU-induced fork repair, which depend on MUS81.","evidence":"FANCB and/or MUS81 knockout in human Nalm-6 cells with FANCD2/RAD51 foci, SCE, gene-targeting, and MMC/CPT/HU survival assays","pmids":["17903171"],"confidence":"High","gaps":["Mechanism by which FANCB selectively channels crosslink versus fork lesions not resolved"]},{"year":2011,"claim":"Confirmed in a clean mammalian knockout that FANCB is required for FancD2 monoubiquitination/foci and homologous-recombination repair of ICLs.","evidence":"Fancb-knockout mouse ES cells assayed for MMC sensitivity, chromosomal aberrations, SCE, gene targeting, and Rad51/FancD2 foci","pmids":["21458466"],"confidence":"High","gaps":["Did not address tissue-specific or developmental roles in vivo"]},{"year":2011,"claim":"Linked FANCB loss-of-function directly to human disease, defining truncating mutations as the cause of X-linked VACTERL-hydrocephalus syndrome.","evidence":"Clinical/molecular characterization of carriers with chromosome breakage assays and X-inactivation analysis across multiple families","pmids":["21910217"],"confidence":"Medium","gaps":["No biochemical reconstitution to quantify residual activity of specific variants","Genotype-phenotype mechanism not yet established"]},{"year":2015,"claim":"Revealed a meiotic, epigenetic role for FANCB beyond ICL repair: recruitment to sex chromosomes via MDC1/γH2AX and control of sex-chromosome H3K9 methylation and germ cell maintenance.","evidence":"First X-linked FA (Fancb mutant) mouse with fertility assays, immunofluorescence for FANCB/FANCD2/MDC1/γH2AX/H3K9me2/H3K9me3, and spermatogonial analysis","pmids":["26123487"],"confidence":"High","gaps":["Molecular mechanism linking FANCB to H3K9 methyltransferase/demethylase activity unknown","Whether the meiotic role requires FANCD2 monoubiquitination not dissected"]},{"year":2015,"claim":"Demonstrated a hematopoietic stem cell role, showing FANCB maintains HSC quiescence, progenitor activity, and repopulating capacity under stress.","evidence":"Fancb-/y mouse with HSC flow cytometry, colony-forming and competitive transplantation assays, MMC/5-FU stress models, and RNA-seq","pmids":["26658157"],"confidence":"High","gaps":["Whether HSC defects derive from ICL-repair failure or a distinct FANCB function not separated"]},{"year":2017,"claim":"Used a patient mosaic intragenic duplication (p.A319*) to confirm by complementation that FANCB truncation abolishes FANCD2 ubiquitination and foci while WT rescues.","evidence":"ArrayCGH/PacBio breakpoint mapping and lentiviral complementation of FANCB-null cells with WT/mutant constructs; FANCD2 ubiquitination/foci assays; ddPCR mosaicism","pmids":["29193904"],"confidence":"Medium","gaps":["Single-lab complementation","Functional consequence of mosaicism in patient tissues not quantified"]},{"year":2020,"claim":"Quantitatively connected FANCB biochemistry to clinical severity, showing residual FANCD2 monoubiquitination activity of missense variants correlates with disease onset and survival.","evidence":"Transcript analysis, genetic complementation in FANCB-null cells, and biochemical reconstitution of FANCD2 monoubiquitination with WT/mutant FANCB across patients","pmids":["32106311"],"confidence":"High","gaps":["Structural basis for how individual residues support the monoubiquitination reaction unresolved"]},{"year":null,"claim":"The biochemical activity FANCB contributes within the core complex and the molecular link between FANCB and sex-chromosome H3K9 methylation remain undefined.","evidence":"","pmids":[],"confidence":"High","gaps":["No structural model of FANCB within the FA core complex","Mechanism connecting FANCB to histone methylation machinery not identified","Whether HSC and germline roles are separable from ICL repair not resolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,2,5]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[1,2]},{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[3]}],"pathway":[{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[1,2,5]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[3]}],"complexes":["FA core complex"],"partners":["FANCD2","MDC1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8NB91","full_name":"Fanconi anemia group B protein","aliases":["Fanconi anemia-associated polypeptide of 95 kDa","FAAP95"],"length_aa":859,"mass_kda":97.7,"function":"DNA repair protein required for FANCD2 ubiquitination","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q8NB91/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/FANCB","classification":"Not Classified","n_dependent_lines":8,"n_total_lines":1208,"dependency_fraction":0.006622516556291391},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"FANCA","stoichiometry":4.0}],"url":"https://opencell.sf.czbiohub.org/search/FANCB","total_profiled":1310},"omim":[{"mim_id":"611301","title":"FA CORE COMPLEX-ASSOCIATED PROTEIN 100; FAAP100","url":"https://www.omim.org/entry/611301"},{"mim_id":"608111","title":"FANCL GENE; FANCL","url":"https://www.omim.org/entry/608111"},{"mim_id":"314390","title":"VACTERL ASSOCIATION, X-LINKED, WITH OR WITHOUT HYDROCEPHALUS; VACTERLX","url":"https://www.omim.org/entry/314390"},{"mim_id":"300515","title":"FANCB GENE; FANCB","url":"https://www.omim.org/entry/300515"},{"mim_id":"300514","title":"FANCONI ANEMIA, COMPLEMENTATION GROUP B; FANCB","url":"https://www.omim.org/entry/300514"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"bone marrow","ntpm":2.3},{"tissue":"lymphoid tissue","ntpm":1.7}],"url":"https://www.proteinatlas.org/search/FANCB"},"hgnc":{"alias_symbol":["FAB","FLJ34064","FAAP95"],"prev_symbol":[]},"alphafold":{"accession":"Q8NB91","domains":[{"cath_id":"2.40.128","chopping":"10-136","consensus_level":"medium","plddt":82.27,"start":10,"end":136},{"cath_id":"-","chopping":"474-534_573-749","consensus_level":"medium","plddt":76.5971,"start":474,"end":749},{"cath_id":"1.10.287","chopping":"750-781_828-859","consensus_level":"medium","plddt":69.0806,"start":750,"end":859}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NB91","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NB91-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NB91-F1-predicted_aligned_error_v6.png","plddt_mean":71.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=FANCB","jax_strain_url":"https://www.jax.org/strain/search?query=FANCB"},"sequence":{"accession":"Q8NB91","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8NB91.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8NB91/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NB91"}},"corpus_meta":[{"pmid":"188440","id":"PMC_188440","title":"Proposals for the classification of the acute leukaemias. French-American-British (FAB) co-operative group.","date":"1976","source":"British journal of haematology","url":"https://pubmed.ncbi.nlm.nih.gov/188440","citation_count":5532,"is_preprint":false},{"pmid":"12610629","id":"PMC_12610629","title":"Structure of the extracellular region of HER2 alone and in complex with the Herceptin Fab.","date":"2003","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/12610629","citation_count":1238,"is_preprint":false},{"pmid":"1369317","id":"PMC_1369317","title":"Renaturation, purification and characterization of recombinant Fab-fragments produced in Escherichia coli.","date":"1991","source":"Bio/technology (Nature Publishing Company)","url":"https://pubmed.ncbi.nlm.nih.gov/1369317","citation_count":365,"is_preprint":false},{"pmid":"9604927","id":"PMC_9604927","title":"The Drosophila Fab-7 chromosomal element conveys epigenetic inheritance during mitosis and meiosis.","date":"1998","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/9604927","citation_count":296,"is_preprint":false},{"pmid":"23479652","id":"PMC_23479652","title":"Efficient generation of stable bispecific IgG1 by controlled Fab-arm exchange.","date":"2013","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/23479652","citation_count":284,"is_preprint":false},{"pmid":"1749770","id":"PMC_1749770","title":"An autoantibody to single-stranded DNA: comparison of the three-dimensional structures of the unliganded Fab and a deoxynucleotide-Fab complex.","date":"1991","source":"Proteins","url":"https://pubmed.ncbi.nlm.nih.gov/1749770","citation_count":280,"is_preprint":false},{"pmid":"3422031","id":"PMC_3422031","title":"HL-60 cell line was derived from a patient with FAB-M2 and not FAB-M3.","date":"1988","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/3422031","citation_count":248,"is_preprint":false},{"pmid":"2665768","id":"PMC_2665768","title":"Implications of a Fab-like structure for the T-cell receptor.","date":"1989","source":"Immunology today","url":"https://pubmed.ncbi.nlm.nih.gov/2665768","citation_count":219,"is_preprint":false},{"pmid":"6572076","id":"PMC_6572076","title":"A comparison of surface marker analysis and FAB classification in acute myeloid leukemia.","date":"1983","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/6572076","citation_count":166,"is_preprint":false},{"pmid":"3312833","id":"PMC_3312833","title":"Classification of acute myeloid leukemias--a comparison of FAB and immunophenotyping.","date":"1987","source":"Leukemia","url":"https://pubmed.ncbi.nlm.nih.gov/3312833","citation_count":161,"is_preprint":false},{"pmid":"15696168","id":"PMC_15696168","title":"Crystal structure of a soluble CD28-Fab complex.","date":"2005","source":"Nature immunology","url":"https://pubmed.ncbi.nlm.nih.gov/15696168","citation_count":158,"is_preprint":false},{"pmid":"1436040","id":"PMC_1436040","title":"Crystal structure of a streptococcal protein G domain bound to an Fab fragment.","date":"1992","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/1436040","citation_count":147,"is_preprint":false},{"pmid":"6661227","id":"PMC_6661227","title":"FAB-mapping of recombinant-DNA protein products.","date":"1983","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/6661227","citation_count":139,"is_preprint":false},{"pmid":"8496956","id":"PMC_8496956","title":"Three-dimensional structure of an anti-steroid Fab' and progesterone-Fab' complex.","date":"1993","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/8496956","citation_count":130,"is_preprint":false},{"pmid":"9514577","id":"PMC_9514577","title":"All individual domains of staphylococcal protein A show Fab binding.","date":"1998","source":"FEMS immunology and medical microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/9514577","citation_count":125,"is_preprint":false},{"pmid":"11172718","id":"PMC_11172718","title":"Drosophila chromosome condensation proteins Topoisomerase II and Barren colocalize with Polycomb and maintain Fab-7 PRE silencing.","date":"2001","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/11172718","citation_count":101,"is_preprint":false},{"pmid":"17346344","id":"PMC_17346344","title":"Single chain Fab (scFab) fragment.","date":"2007","source":"BMC biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/17346344","citation_count":98,"is_preprint":false},{"pmid":"7528131","id":"PMC_7528131","title":"Abciximab (c7E3 Fab). A review of its pharmacology and therapeutic potential in ischaemic heart disease.","date":"1994","source":"Drugs","url":"https://pubmed.ncbi.nlm.nih.gov/7528131","citation_count":98,"is_preprint":false},{"pmid":"31017822","id":"PMC_31017822","title":"Safety and Tolerability, Pharmacokinetics, and Pharmacodynamics of ACT017, an Antiplatelet GPVI (Glycoprotein VI) Fab.","date":"2019","source":"Arteriosclerosis, thrombosis, and vascular biology","url":"https://pubmed.ncbi.nlm.nih.gov/31017822","citation_count":98,"is_preprint":false},{"pmid":"10545917","id":"PMC_10545917","title":"Polymerizable Fab' antibody fragments for targeting of anticancer drugs.","date":"1999","source":"Nature biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/10545917","citation_count":95,"is_preprint":false},{"pmid":"8609731","id":"PMC_8609731","title":"Cytogenetic analysis of B cell chronic lymphoid leukemias classified according to morphologic and immunophenotypic (FAB) criteria.","date":"1995","source":"Leukemia","url":"https://pubmed.ncbi.nlm.nih.gov/8609731","citation_count":94,"is_preprint":false},{"pmid":"1369462","id":"PMC_1369462","title":"Fab assembly and enrichment in a monovalent phage display system.","date":"1991","source":"Bio/technology (Nature Publishing Company)","url":"https://pubmed.ncbi.nlm.nih.gov/1369462","citation_count":93,"is_preprint":false},{"pmid":"12661007","id":"PMC_12661007","title":"Mutations of CEBPA in acute myeloid leukemia FAB types M1 and M2.","date":"2003","source":"Genes, chromosomes & cancer","url":"https://pubmed.ncbi.nlm.nih.gov/12661007","citation_count":92,"is_preprint":false},{"pmid":"30397147","id":"PMC_30397147","title":"Site-selective chemoenzymatic glycoengineering of Fab and Fc glycans of a therapeutic antibody.","date":"2018","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/30397147","citation_count":84,"is_preprint":false},{"pmid":"34019795","id":"PMC_34019795","title":"Fab-dimerized glycan-reactive antibodies are a structural category of natural antibodies.","date":"2021","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/34019795","citation_count":83,"is_preprint":false},{"pmid":"18302019","id":"PMC_18302019","title":"Analysis of FANCB and FANCN/PALB2 fanconi anemia genes in BRCA1/2-negative Spanish breast cancer families.","date":"2008","source":"Breast cancer research and treatment","url":"https://pubmed.ncbi.nlm.nih.gov/18302019","citation_count":78,"is_preprint":false},{"pmid":"15554746","id":"PMC_15554746","title":"Fab antibody fragments: some applications in clinical toxicology.","date":"2004","source":"Drug safety","url":"https://pubmed.ncbi.nlm.nih.gov/15554746","citation_count":75,"is_preprint":false},{"pmid":"29273204","id":"PMC_29273204","title":"Locking the Elbow: Improved Antibody Fab Fragments as Chaperones for Structure Determination.","date":"2017","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/29273204","citation_count":70,"is_preprint":false},{"pmid":"15739883","id":"PMC_15739883","title":"An artificial protein L for the purification of immunoglobulins and fab fragments by affinity chromatography.","date":"2005","source":"Journal of chromatography. A","url":"https://pubmed.ncbi.nlm.nih.gov/15739883","citation_count":62,"is_preprint":false},{"pmid":"3131664","id":"PMC_3131664","title":"Streptococcal protein G has affinity for both Fab- and Fc-fragments of human IgG.","date":"1988","source":"Molecular immunology","url":"https://pubmed.ncbi.nlm.nih.gov/3131664","citation_count":57,"is_preprint":false},{"pmid":"26123487","id":"PMC_26123487","title":"FANCB is essential in the male germline and regulates H3K9 methylation on the sex chromosomes during meiosis.","date":"2015","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/26123487","citation_count":54,"is_preprint":false},{"pmid":"14574700","id":"PMC_14574700","title":"Higher expression of Fab antibody fragments in a CHO cell line at reduced temperature.","date":"2003","source":"Biotechnology and bioengineering","url":"https://pubmed.ncbi.nlm.nih.gov/14574700","citation_count":49,"is_preprint":false},{"pmid":"18426914","id":"PMC_18426914","title":"Functional interaction between the Fab-7 and Fab-8 boundaries and the upstream promoter region in the Drosophila Abd-B gene.","date":"2008","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/18426914","citation_count":49,"is_preprint":false},{"pmid":"26303531","id":"PMC_26303531","title":"Functional Requirements for Fab-7 Boundary Activity in the Bithorax Complex.","date":"2015","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/26303531","citation_count":47,"is_preprint":false},{"pmid":"25481745","id":"PMC_25481745","title":"An improved single-chain Fab platform for efficient display and recombinant expression.","date":"2014","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/25481745","citation_count":46,"is_preprint":false},{"pmid":"15611632","id":"PMC_15611632","title":"New advances in the DNA damage response network of Fanconi anemia and BRCA proteins. FAAP95 replaces BRCA2 as the true FANCB protein.","date":"2005","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/15611632","citation_count":45,"is_preprint":false},{"pmid":"36241613","id":"PMC_36241613","title":"The Fab region of IgG impairs the internalization pathway of FcRn upon Fc engagement.","date":"2022","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/36241613","citation_count":45,"is_preprint":false},{"pmid":"31420591","id":"PMC_31420591","title":"The Fab portion of immunoglobulin G contributes to its binding to Fcγ receptor III.","date":"2019","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/31420591","citation_count":44,"is_preprint":false},{"pmid":"9310834","id":"PMC_9310834","title":"Diverse Fab specific for acetylcholine receptor epitopes from a myasthenia gravis thymus combinatorial library.","date":"1997","source":"International immunology","url":"https://pubmed.ncbi.nlm.nih.gov/9310834","citation_count":39,"is_preprint":false},{"pmid":"21910217","id":"PMC_21910217","title":"X-linked VACTERL with hydrocephalus syndrome: further delineation of the phenotype caused by FANCB mutations.","date":"2011","source":"American journal of medical genetics. Part A","url":"https://pubmed.ncbi.nlm.nih.gov/21910217","citation_count":36,"is_preprint":false},{"pmid":"36716825","id":"PMC_36716825","title":"Differences in IgG autoantibody Fab glycosylation across autoimmune diseases.","date":"2023","source":"The Journal of allergy and clinical immunology","url":"https://pubmed.ncbi.nlm.nih.gov/36716825","citation_count":36,"is_preprint":false},{"pmid":"11024187","id":"PMC_11024187","title":"Amplification of IgG VH and VL (Fab) from single human plasma cells and B cells.","date":"2000","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/11024187","citation_count":36,"is_preprint":false},{"pmid":"3484662","id":"PMC_3484662","title":"The French-American-British (FAB) classification of leukemia. The Pediatric Oncology Group experience with lymphocytic leukemia.","date":"1986","source":"Cancer","url":"https://pubmed.ncbi.nlm.nih.gov/3484662","citation_count":33,"is_preprint":false},{"pmid":"24586053","id":"PMC_24586053","title":"In vitro Fab display: a cell-free system for IgG discovery.","date":"2014","source":"Protein engineering, design & selection : PEDS","url":"https://pubmed.ncbi.nlm.nih.gov/24586053","citation_count":31,"is_preprint":false},{"pmid":"29708852","id":"PMC_29708852","title":"Fab is the most efficient format to express functional antibodies by yeast surface display.","date":"2018","source":"mAbs","url":"https://pubmed.ncbi.nlm.nih.gov/29708852","citation_count":30,"is_preprint":false},{"pmid":"29309709","id":"PMC_29309709","title":"Affinity maturation of a portable Fab-RNA module for chaperone-assisted RNA crystallography.","date":"2018","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/29309709","citation_count":29,"is_preprint":false},{"pmid":"31231932","id":"PMC_31231932","title":"Microbioreactor Cultivations of Fab-Producing Escherichia coli Reveal Genome-Integrated Systems as Suitable for Prospective Studies on Direct Fab Expression Effects.","date":"2019","source":"Biotechnology journal","url":"https://pubmed.ncbi.nlm.nih.gov/31231932","citation_count":28,"is_preprint":false},{"pmid":"25505012","id":"PMC_25505012","title":"Fab fragment glycosylated IgG may play a central role in placental immune evasion.","date":"2014","source":"Human reproduction (Oxford, England)","url":"https://pubmed.ncbi.nlm.nih.gov/25505012","citation_count":28,"is_preprint":false},{"pmid":"9770525","id":"PMC_9770525","title":"Crystal structure of Taq DNA polymerase in complex with an inhibitory Fab: the Fab is directed against an intermediate in the helix-coil dynamics of the enzyme.","date":"1998","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/9770525","citation_count":28,"is_preprint":false},{"pmid":"29193904","id":"PMC_29193904","title":"Somatic mosaicism of an intragenic FANCB duplication in both fibroblast and peripheral blood cells observed in a Fanconi anemia patient leads to milder phenotype.","date":"2017","source":"Molecular genetics & genomic medicine","url":"https://pubmed.ncbi.nlm.nih.gov/29193904","citation_count":27,"is_preprint":false},{"pmid":"39150906","id":"PMC_39150906","title":"The humanized platelet glycoprotein VI Fab inhibitor EMA601 protects from arterial thrombosis and ischaemic stroke in mice.","date":"2024","source":"European heart journal","url":"https://pubmed.ncbi.nlm.nih.gov/39150906","citation_count":26,"is_preprint":false},{"pmid":"32106311","id":"PMC_32106311","title":"Association of clinical severity with FANCB variant type in Fanconi anemia.","date":"2020","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/32106311","citation_count":26,"is_preprint":false},{"pmid":"24445201","id":"PMC_24445201","title":"Anticomplementary activity of horse IgG and F(ab')2 antivenoms.","date":"2014","source":"The American journal of tropical medicine and hygiene","url":"https://pubmed.ncbi.nlm.nih.gov/24445201","citation_count":25,"is_preprint":false},{"pmid":"16118414","id":"PMC_16118414","title":"Construction of human naïve Fab library and characterization of anti-met Fab fragment generated from the library.","date":"2005","source":"Molecular biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/16118414","citation_count":25,"is_preprint":false},{"pmid":"19235139","id":"PMC_19235139","title":"E. coli expression and purification of Fab antibody fragments.","date":"2009","source":"Current protocols in protein science","url":"https://pubmed.ncbi.nlm.nih.gov/19235139","citation_count":24,"is_preprint":false},{"pmid":"30887174","id":"PMC_30887174","title":"A general platform for efficient extracellular expression and purification of Fab from Escherichia coli.","date":"2019","source":"Applied microbiology and biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/30887174","citation_count":23,"is_preprint":false},{"pmid":"28965821","id":"PMC_28965821","title":"Biophysical characterization and structure of the Fab fragment from the NIST reference antibody, RM 8671.","date":"2017","source":"Biologicals : journal of the International Association of Biological Standardization","url":"https://pubmed.ncbi.nlm.nih.gov/28965821","citation_count":23,"is_preprint":false},{"pmid":"31563513","id":"PMC_31563513","title":"Characterization of Native Reversible Self-Association of a Monoclonal Antibody Mediated by Fab-Fab Interaction.","date":"2019","source":"Journal of pharmaceutical sciences","url":"https://pubmed.ncbi.nlm.nih.gov/31563513","citation_count":23,"is_preprint":false},{"pmid":"17903171","id":"PMC_17903171","title":"Human Mus81 and FANCB independently contribute to repair of DNA damage during replication.","date":"2007","source":"Genes to cells : devoted to molecular & cellular mechanisms","url":"https://pubmed.ncbi.nlm.nih.gov/17903171","citation_count":22,"is_preprint":false},{"pmid":"24782039","id":"PMC_24782039","title":"Derivatization of antibody Fab fragments: a designer enzyme for native protein modification.","date":"2014","source":"Chembiochem : a European journal of chemical biology","url":"https://pubmed.ncbi.nlm.nih.gov/24782039","citation_count":22,"is_preprint":false},{"pmid":"23050123","id":"PMC_23050123","title":"In vitro selection of fab fragments by mRNA display and gene-linking emulsion PCR.","date":"2012","source":"Journal of nucleic acids","url":"https://pubmed.ncbi.nlm.nih.gov/23050123","citation_count":21,"is_preprint":false},{"pmid":"20086088","id":"PMC_20086088","title":"Evaluation of Fab and F(ab')2 fragments and isotype variants of a recombinant human monoclonal antibody against Shiga toxin 2.","date":"2010","source":"Infection and immunity","url":"https://pubmed.ncbi.nlm.nih.gov/20086088","citation_count":21,"is_preprint":false},{"pmid":"6194337","id":"PMC_6194337","title":"The biological properties of immunoglobulin G and its split products [F(ab')2 and Fab].","date":"1983","source":"Klinische Wochenschrift","url":"https://pubmed.ncbi.nlm.nih.gov/6194337","citation_count":20,"is_preprint":false},{"pmid":"35328000","id":"PMC_35328000","title":"The Genome of Rhyzopertha dominica (Fab.) (Coleoptera: Bostrichidae): Adaptation for Success.","date":"2022","source":"Genes","url":"https://pubmed.ncbi.nlm.nih.gov/35328000","citation_count":19,"is_preprint":false},{"pmid":"29909010","id":"PMC_29909010","title":"Introduction of a glycosylation site in the constant region decreases the aggregation of adalimumab Fab.","date":"2018","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/29909010","citation_count":19,"is_preprint":false},{"pmid":"36480251","id":"PMC_36480251","title":"IgG Fab Glycans Hinder FcRn-Mediated Placental Transport.","date":"2023","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/36480251","citation_count":18,"is_preprint":false},{"pmid":"19789273","id":"PMC_19789273","title":"Bicistronic DNA display for in vitro selection of Fab fragments.","date":"2009","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/19789273","citation_count":18,"is_preprint":false},{"pmid":"32372058","id":"PMC_32372058","title":"High-Throughput Generation of Bipod (Fab × scFv) Bispecific Antibodies Exploits Differential Chain Expression and Affinity Capture.","date":"2020","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/32372058","citation_count":18,"is_preprint":false},{"pmid":"31551239","id":"PMC_31551239","title":"Distinct Elements Confer the Blocking and Bypass Functions of the Bithorax Fab-8 Boundary.","date":"2019","source":"Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/31551239","citation_count":18,"is_preprint":false},{"pmid":"29566240","id":"PMC_29566240","title":"Identification of high affinity HER2 binding antibodies using CHO Fab surface display.","date":"2018","source":"Protein engineering, design & selection : PEDS","url":"https://pubmed.ncbi.nlm.nih.gov/29566240","citation_count":18,"is_preprint":false},{"pmid":"29549023","id":"PMC_29549023","title":"Impact of surfactants on the target recognition of Fab-conjugated PLGA nanoparticles.","date":"2018","source":"European journal of pharmaceutics and biopharmaceutics : official journal of Arbeitsgemeinschaft fur Pharmazeutische Verfahrenstechnik e.V","url":"https://pubmed.ncbi.nlm.nih.gov/29549023","citation_count":18,"is_preprint":false},{"pmid":"26658157","id":"PMC_26658157","title":"Fancb deficiency impairs hematopoietic stem cell function.","date":"2015","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/26658157","citation_count":17,"is_preprint":false},{"pmid":"33116155","id":"PMC_33116155","title":"Improvement of Certolizumab Fab' properties by PASylation technology.","date":"2020","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/33116155","citation_count":17,"is_preprint":false},{"pmid":"2996809","id":"PMC_2996809","title":"Thyroid stimulation by (Fab)2 and Fab fragments of TSH receptor antibody.","date":"1985","source":"Clinical endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/2996809","citation_count":17,"is_preprint":false},{"pmid":"29205853","id":"PMC_29205853","title":"Comparative Study of In Situ Loaded Antibody and PEG-Fab NIPAAM Gels.","date":"2017","source":"Macromolecular bioscience","url":"https://pubmed.ncbi.nlm.nih.gov/29205853","citation_count":17,"is_preprint":false},{"pmid":"30980702","id":"PMC_30980702","title":"Characterization of Disulfide Bond Rebridged Fab-Drug Conjugates Prepared Using a Dual Maleimide Pyrrolobenzodiazepine Cytotoxic Payload.","date":"2019","source":"ChemMedChem","url":"https://pubmed.ncbi.nlm.nih.gov/30980702","citation_count":17,"is_preprint":false},{"pmid":"25849503","id":"PMC_25849503","title":"Structure of the omalizumab Fab.","date":"2015","source":"Acta crystallographica. Section F, Structural biology communications","url":"https://pubmed.ncbi.nlm.nih.gov/25849503","citation_count":16,"is_preprint":false},{"pmid":"33666254","id":"PMC_33666254","title":"Humanized Anti-DNABII Fab Fragments Plus Ofloxacin Eradicated Biofilms in Experimental Otitis Media.","date":"2021","source":"The Laryngoscope","url":"https://pubmed.ncbi.nlm.nih.gov/33666254","citation_count":16,"is_preprint":false},{"pmid":"28906004","id":"PMC_28906004","title":"Acute myeloid leukaemia (FAB AML-M4Eo) with cryptic insertion of cbfb resulting in cbfb-Myh11 fusion.","date":"2015","source":"Hematological oncology","url":"https://pubmed.ncbi.nlm.nih.gov/28906004","citation_count":16,"is_preprint":false},{"pmid":"28630449","id":"PMC_28630449","title":"Effect of DNA sequence of Fab fragment on yield characteristics and cell growth of E. coli.","date":"2017","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/28630449","citation_count":16,"is_preprint":false},{"pmid":"29232309","id":"PMC_29232309","title":"A Bispecific Antibody Based on Pertuzumab Fab Has Potent Antitumor Activity.","date":"2018","source":"Journal of immunotherapy (Hagerstown, Md. : 1997)","url":"https://pubmed.ncbi.nlm.nih.gov/29232309","citation_count":16,"is_preprint":false},{"pmid":"21458466","id":"PMC_21458466","title":"The phenotype of FancB-mutant mouse embryonic stem cells.","date":"2011","source":"Mutation research","url":"https://pubmed.ncbi.nlm.nih.gov/21458466","citation_count":15,"is_preprint":false},{"pmid":"29126850","id":"PMC_29126850","title":"PSMA-targeted bispecific Fab conjugates that engage T cells.","date":"2017","source":"Bioorganic & medicinal chemistry letters","url":"https://pubmed.ncbi.nlm.nih.gov/29126850","citation_count":15,"is_preprint":false},{"pmid":"24290808","id":"PMC_24290808","title":"Choice of labeling and cell line influences interactions between the Fab fragment AbD15179 and its target antigen CD44v6.","date":"2013","source":"Nuclear medicine and biology","url":"https://pubmed.ncbi.nlm.nih.gov/24290808","citation_count":15,"is_preprint":false},{"pmid":"23109335","id":"PMC_23109335","title":"IgG Fab fragments forming bivalent complexes by a conformational mechanism that is reversible by osmolytes.","date":"2012","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/23109335","citation_count":15,"is_preprint":false},{"pmid":"8511605","id":"PMC_8511605","title":"Imaging of colorectal carcinoma with technetium-99m radiolabeled Fab' fragments.","date":"1993","source":"Seminars in nuclear medicine","url":"https://pubmed.ncbi.nlm.nih.gov/8511605","citation_count":15,"is_preprint":false},{"pmid":"9753066","id":"PMC_9753066","title":"Coexpression of erythroid and megakaryocytic genes in acute erythroblastic (FAB M6) and megakaryoblastic (FAB M7) leukaemias.","date":"1998","source":"British journal of haematology","url":"https://pubmed.ncbi.nlm.nih.gov/9753066","citation_count":15,"is_preprint":false},{"pmid":"7927988","id":"PMC_7927988","title":"Immunoglobulin Fab fragment-binding proteins.","date":"1994","source":"International journal of immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/7927988","citation_count":14,"is_preprint":false},{"pmid":"17579273","id":"PMC_17579273","title":"Construction of human Fab (gamma1/kappa) library and identification of human monoclonal Fab possessing neutralizing potency against Japanese encephalitis virus.","date":"2007","source":"Microbiology and immunology","url":"https://pubmed.ncbi.nlm.nih.gov/17579273","citation_count":14,"is_preprint":false},{"pmid":"22019510","id":"PMC_22019510","title":"A novel fragment of antigen binding (Fab) surface display platform using glycoengineered Pichia pastoris.","date":"2011","source":"Journal of immunological methods","url":"https://pubmed.ncbi.nlm.nih.gov/22019510","citation_count":14,"is_preprint":false},{"pmid":"20600082","id":"PMC_20600082","title":"Antibody Fab display and selection through fusion to the pIX coat protein of filamentous phage.","date":"2010","source":"Journal of immunological methods","url":"https://pubmed.ncbi.nlm.nih.gov/20600082","citation_count":13,"is_preprint":false},{"pmid":"36107737","id":"PMC_36107737","title":"Neuropeptidomes of Tenebrio molitor L. and Zophobas atratus Fab. (Coleoptera, Polyphaga: Tenebrionidae).","date":"2022","source":"Journal of proteome research","url":"https://pubmed.ncbi.nlm.nih.gov/36107737","citation_count":13,"is_preprint":false},{"pmid":"32284303","id":"PMC_32284303","title":"Production of an antibody Fab fragment using 2A peptide in insect cells.","date":"2020","source":"Journal of bioscience and bioengineering","url":"https://pubmed.ncbi.nlm.nih.gov/32284303","citation_count":13,"is_preprint":false},{"pmid":"16740365","id":"PMC_16740365","title":"Antibodies and Fab fragments protect Cu,Zn-SOD against methylglyoxal-induced inactivation.","date":"2006","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/16740365","citation_count":13,"is_preprint":false},{"pmid":"2584225","id":"PMC_2584225","title":"Crystallization and preliminary X-ray diffraction data of an anti-angiotensin II Fab and of the peptide-Fab complex.","date":"1989","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/2584225","citation_count":13,"is_preprint":false},{"pmid":"28756139","id":"PMC_28756139","title":"A universal phage display system for the seamless construction of Fab libraries.","date":"2017","source":"Journal of immunological methods","url":"https://pubmed.ncbi.nlm.nih.gov/28756139","citation_count":12,"is_preprint":false},{"pmid":"9032079","id":"PMC_9032079","title":"Not just another Fab: the crystal structure of a TcR-MHC-peptide complex.","date":"1997","source":"Structure (London, England : 1993)","url":"https://pubmed.ncbi.nlm.nih.gov/9032079","citation_count":12,"is_preprint":false},{"pmid":"14769869","id":"PMC_14769869","title":"Expression, purification, and characterization of humanized anti-HBs Fab fragment.","date":"2003","source":"Journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/14769869","citation_count":11,"is_preprint":false},{"pmid":"37405421","id":"PMC_37405421","title":"A Researcher's Perspective on Unconventional Lab-to-Fab for 2D Semiconductor Devices.","date":"2023","source":"ACS nano","url":"https://pubmed.ncbi.nlm.nih.gov/37405421","citation_count":11,"is_preprint":false},{"pmid":"24065833","id":"PMC_24065833","title":"A dual host vector for Fab phage display and expression of native IgG in mammalian cells.","date":"2013","source":"Protein engineering, design & selection : PEDS","url":"https://pubmed.ncbi.nlm.nih.gov/24065833","citation_count":11,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":45369,"output_tokens":2391,"usd":0.085986,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9494,"output_tokens":3038,"usd":0.06171,"stage2_stop_reason":"end_turn"},"total_usd":0.147696,"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\": 2005,\n      \"finding\": \"FANCB (previously misidentified as BRCA2/FANCB) was identified as FAAP95, a previously uncharacterized component of the FA core complex that functions upstream of FANCD2 monoubiquitination, placing FANCB in the FA core complex rather than downstream or in a parallel pathway.\",\n      \"method\": \"Biochemical identification of FAAP95 as the true FANCB protein; pathway placement by epistasis/functional complementation showing FANCB acts upstream of FANCD2 monoubiquitination\",\n      \"journal\": \"Cell cycle (Georgetown, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pathway placement established by functional complementation and biochemical analysis, single lab, reviewed/commentary paper summarizing the primary discovery\",\n      \"pmids\": [\"15611632\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"FANCB (as a component of the FA core complex) and Mus81 act independently in repairing camptothecin-induced DNA damage during replication; FANCB is required for FANCD2 foci formation after DNA crosslink damage but not for sister chromatid exchanges, gene targeting, or hydroxyurea-induced replication fork repair, while Mus81 handles the latter functions.\",\n      \"method\": \"Gene knockout of FANCB and/or Mus81 in human Nalm-6 cells; FANCD2 foci assay, Rad51 foci, sister chromatid exchange assay, gene targeting assay, survival assays with MMC, CPT, and HU\",\n      \"journal\": \"Genes to cells : devoted to molecular & cellular mechanisms\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean gene knockout with multiple orthogonal phenotypic readouts (foci, SCE, survival, gene targeting) in human cells, multiple drug treatments establishing distinct pathway roles\",\n      \"pmids\": [\"17903171\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"FancB-mutant mouse embryonic stem cells show hypersensitivity to the crosslinking agent mitomycin C, increased chromosomal abnormalities, reduced sister chromatid exchanges, reduced gene targeting, reduced MMC-induced Rad51 foci, and absent MMC-induced FancD2 foci, confirming FANCB is required for FancD2 monoubiquitination/foci formation and HR repair of ICLs.\",\n      \"method\": \"FancB knockout mouse ES cells; MMC sensitivity assay, chromosomal aberration analysis, SCE assay, gene targeting assay, immunofluorescence for Rad51 and FancD2 foci\",\n      \"journal\": \"Mutation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO model with multiple orthogonal readouts confirming FANCB role in ICL repair pathway and FANCD2 activation\",\n      \"pmids\": [\"21458466\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"FANCB is essential for male germline function: Fancb mutant mice are infertile with primordial germ cell defects and spermatogonial maintenance failure. During meiosis, FANCB localizes to sex chromosomes in an MDC1-dependent manner (MDC1 binds γH2AX to initiate chromosome-wide silencing), is required for FANCD2 localization during meiosis, and regulates H3K9 methylation on sex chromosomes—loss of FANCB decreases H3K9me2 and increases H3K9me3 on sex chromosomes.\",\n      \"method\": \"Fancb mutant mouse model (first X-linked FA mouse); fertility assays, immunofluorescence for FANCB, FANCD2, MDC1, γH2AX, H3K9me2, H3K9me3 on meiotic chromosomes; spermatogonial analysis\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO mouse model with multiple orthogonal methods (immunofluorescence, epistasis with MDC1, histone modification analysis) establishing novel FANCB function in germline epigenetics\",\n      \"pmids\": [\"26123487\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Fancb-deficient mice have decreased HSC quiescence, reduced progenitor activity in vitro, and reduced repopulating capacity in vivo; Fancb-deficient bone marrow is hypersensitive to MMC and shows impaired recovery from myelotoxic stress; RNA-seq reveals altered expression of genes involved in HSC function and cell cycle regulation in Fancb-deficient HSCs.\",\n      \"method\": \"Fancb knockout mouse model (Fancb-/y); flow cytometry for HSC populations, colony-forming assays, competitive transplantation assay, MMC bone marrow failure model, 5-FU stress assay, RNA-seq\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO mouse model with multiple orthogonal in vivo and in vitro readouts establishing FANCB role in HSC maintenance\",\n      \"pmids\": [\"26658157\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"FANCB protein is indispensable for FANCD2 monoubiquitination (an essential step in ICL repair); FANCB missense variants show variable residual FANCD2 monoubiquitination activity that correlates with clinical severity. Aberrant splicing and transcript destabilization were associated with 2 missense variants. Biochemical reconstitution confirmed that reduced FANCD2 monoubiquitination correlates with earlier disease onset and shorter survival.\",\n      \"method\": \"Transcript analysis, genetic complementation in FANCB-null cells, biochemical reconstitution of FANCD2 monoubiquitination with FANCB WT and mutant constructs; FANCD2 ubiquitination assay and foci formation assay\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — biochemical reconstitution of FANCD2 monoubiquitination with mutant constructs, genetic complementation, and transcript analysis across multiple patients and variants with functional correlation\",\n      \"pmids\": [\"32106311\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"A somatic mosaic intragenic duplication of FANCB covering exon 3 introduces a premature stop codon (p.A319*) in the FANCB protein; lentiviral transduction of FANCB-null cells with the mutant construct confirmed loss of FANCD2 ubiquitination and foci formation activity, while WT FANCB restored these functions.\",\n      \"method\": \"ArrayCGH for duplication detection; targeted sequencing and PacBio sequencing for breakpoint and aberrant transcript characterization; lentiviral transduction of FANCB-null cells with WT and mutant constructs; FANCD2 ubiquitination and foci formation assays; droplet digital PCR for mosaicism quantitation\",\n      \"journal\": \"Molecular genetics & genomic medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional complementation with mutant construct in null cells using FANCD2 assays, single lab\",\n      \"pmids\": [\"29193904\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Loss-of-function FANCB mutations (truncating) cause X-linked VACTERL-hydrocephalus syndrome in hemizygous males, and carrier females show highly skewed X-inactivation; increased chromosomal breakage on exposure to DNA cross-linking agents was confirmed in affected cells, consistent with FANCB's role in the FA pathway.\",\n      \"method\": \"Clinical and molecular characterization of FANCB mutation carriers; chromosome breakage assay with DNA cross-linking agents; X-inactivation analysis\",\n      \"journal\": \"American journal of medical genetics. Part A\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — chromosome breakage assay directly demonstrating FANCB loss-of-function impairs ICL repair, multiple families, but clinical/molecular characterization study without full biochemical reconstitution\",\n      \"pmids\": [\"21910217\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"FANCB (FAAP95) is an X-linked component of the FA core complex that is required for FANCD2 monoubiquitination in response to DNA interstrand crosslinks; it localizes to sex chromosomes during meiosis in an MDC1/γH2AX-dependent manner, regulates H3K9 methylation on sex chromosomes, maintains hematopoietic stem cell quiescence and repopulating capacity, and its complete loss causes X-linked VACTERL-hydrocephalus syndrome with residual FANCD2 monoubiquitination activity correlating with clinical severity.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"FANCB (originally identified as FAAP95) is an X-linked component of the Fanconi anemia (FA) core complex that acts upstream to promote FANCD2 monoubiquitination during the repair of DNA interstrand crosslinks (ICLs) [#0, #2]. Loss of FANCB abolishes MMC- and crosslink-induced FANCD2 foci formation and reduces RAD51 foci, sister chromatid exchange, and gene targeting, producing crosslinker hypersensitivity and chromosomal instability, while a parallel MUS81-dependent route handles replication-fork repair independently of FANCB [#1, #2]. Biochemical reconstitution establishes that FANCB protein is indispensable for FANCD2 monoubiquitination, and the degree of residual monoubiquitination conferred by FANCB missense variants correlates with clinical severity [#5]. Beyond canonical ICL repair, FANCB has dedicated germline and stem-cell roles: during male meiosis it localizes to the sex chromosomes in an MDC1/\\u03b3H2AX-dependent manner, is required for meiotic FANCD2 localization, and shapes sex-chromosome H3K9 methylation (decreasing H3K9me2 and increasing H3K9me3 upon loss), with FANCB-mutant mice showing primordial germ cell defects and spermatogonial failure [#3]; it also maintains hematopoietic stem cell quiescence and repopulating capacity [#4]. Truncating loss-of-function FANCB mutations cause X-linked VACTERL-hydrocephalus syndrome in hemizygous males, with carrier females showing skewed X-inactivation [#7].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Established the molecular identity and pathway position of FANCB by showing the true FANCB protein is FAAP95, a core-complex member acting upstream of FANCD2, resolving prior confusion with BRCA2.\",\n      \"evidence\": \"Biochemical identification of FAAP95 with epistasis/complementation placing FANCB upstream of FANCD2 monoubiquitination\",\n      \"pmids\": [\"15611632\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Did not define the biochemical activity FANCB contributes to monoubiquitination\", \"Core-complex subunit interactions not mapped at the structural level\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Distinguished FANCB's ICL-repair function from a parallel replication-fork pathway, showing FANCB is required for FANCD2 foci but not for SCE, gene targeting, or HU-induced fork repair, which depend on MUS81.\",\n      \"evidence\": \"FANCB and/or MUS81 knockout in human Nalm-6 cells with FANCD2/RAD51 foci, SCE, gene-targeting, and MMC/CPT/HU survival assays\",\n      \"pmids\": [\"17903171\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Mechanism by which FANCB selectively channels crosslink versus fork lesions not resolved\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Confirmed in a clean mammalian knockout that FANCB is required for FancD2 monoubiquitination/foci and homologous-recombination repair of ICLs.\",\n      \"evidence\": \"Fancb-knockout mouse ES cells assayed for MMC sensitivity, chromosomal aberrations, SCE, gene targeting, and Rad51/FancD2 foci\",\n      \"pmids\": [\"21458466\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Did not address tissue-specific or developmental roles in vivo\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Linked FANCB loss-of-function directly to human disease, defining truncating mutations as the cause of X-linked VACTERL-hydrocephalus syndrome.\",\n      \"evidence\": \"Clinical/molecular characterization of carriers with chromosome breakage assays and X-inactivation analysis across multiple families\",\n      \"pmids\": [\"21910217\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"No biochemical reconstitution to quantify residual activity of specific variants\", \"Genotype-phenotype mechanism not yet established\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Revealed a meiotic, epigenetic role for FANCB beyond ICL repair: recruitment to sex chromosomes via MDC1/\\u03b3H2AX and control of sex-chromosome H3K9 methylation and germ cell maintenance.\",\n      \"evidence\": \"First X-linked FA (Fancb mutant) mouse with fertility assays, immunofluorescence for FANCB/FANCD2/MDC1/\\u03b3H2AX/H3K9me2/H3K9me3, and spermatogonial analysis\",\n      \"pmids\": [\"26123487\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Molecular mechanism linking FANCB to H3K9 methyltransferase/demethylase activity unknown\", \"Whether the meiotic role requires FANCD2 monoubiquitination not dissected\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Demonstrated a hematopoietic stem cell role, showing FANCB maintains HSC quiescence, progenitor activity, and repopulating capacity under stress.\",\n      \"evidence\": \"Fancb-/y mouse with HSC flow cytometry, colony-forming and competitive transplantation assays, MMC/5-FU stress models, and RNA-seq\",\n      \"pmids\": [\"26658157\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Whether HSC defects derive from ICL-repair failure or a distinct FANCB function not separated\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Used a patient mosaic intragenic duplication (p.A319*) to confirm by complementation that FANCB truncation abolishes FANCD2 ubiquitination and foci while WT rescues.\",\n      \"evidence\": \"ArrayCGH/PacBio breakpoint mapping and lentiviral complementation of FANCB-null cells with WT/mutant constructs; FANCD2 ubiquitination/foci assays; ddPCR mosaicism\",\n      \"pmids\": [\"29193904\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Single-lab complementation\", \"Functional consequence of mosaicism in patient tissues not quantified\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Quantitatively connected FANCB biochemistry to clinical severity, showing residual FANCD2 monoubiquitination activity of missense variants correlates with disease onset and survival.\",\n      \"evidence\": \"Transcript analysis, genetic complementation in FANCB-null cells, and biochemical reconstitution of FANCD2 monoubiquitination with WT/mutant FANCB across patients\",\n      \"pmids\": [\"32106311\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Structural basis for how individual residues support the monoubiquitination reaction unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The biochemical activity FANCB contributes within the core complex and the molecular link between FANCB and sex-chromosome H3K9 methylation remain undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"No structural model of FANCB within the FA core complex\", \"Mechanism connecting FANCB to histone methylation machinery not identified\", \"Whether HSC and germline roles are separable from ICL repair not resolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 2, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [1, 2, 5]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"complexes\": [\"FA core complex\"],\n    \"partners\": [\"FANCD2\", \"MDC1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"faith_supported":5,"faith_total":5,"faith_pct":100.0}}