The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
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Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
The zebrafish gene rbpjb encodes a member of the evolutionarily conserved Su(H)/CSL family of DNA-binding transcription factors, functioning as a central transcriptional effector of canonical Notch signaling (hyde2022retinalregenerationrequires pages 5-6). Zebrafish possess two RBPJ paralogs, rbpja and rbpjb, although most functional studies do not distinguish their individual contributions (hyde2022retinalregenerationrequires pages 5-6, le2024robustreprogrammingof pages 2-3). This report compiles molecular and developmental evidence, emphasizing that while rbpjb-specific literature is sparse, extensive research on the conserved RBPJ/CSL family allows well-supported functional inference.
The rbpjb gene (UniProt A4FTT4) encodes zebrafish Su(H)B, also annotated as a paralog of mammalian RBPJ (Recombination signal binding protein for immunoglobulin kappa J region) (hyde2022retinalregenerationrequires pages 5-6). The protein belongs to the Su(H) family, which encompasses Drosophila Suppressor of Hairless [Su(H)], mammalian CBF1/RBPJ, and C. elegans LAG-1—collectively termed "CSL" transcription factors (giaimo2021transcriptionfactorrbpj pages 3-5). This classification is consistent with the UniProt annotation that identifies beta-trefoil DNA-binding domains, Ig-like fold, and CSL family membership. Zebrafish underwent genome duplication, resulting in two RBPJ orthologs/paralogs: rbpja and rbpjb (hyde2022retinalregenerationrequires pages 5-6). Most experimental studies manipulate the Notch pathway broadly rather than distinguishing rbpjb-specific functions; therefore, much of the annotation below reflects family-conserved properties.
Rbpjb is a sequence-specific DNA-binding transcriptional regulator, not an enzyme or transporter. RBPJ recognizes canonical RBPJ-binding sites (RBS) centered on the consensus sequence 5′-CGTGGGAA-3′ (or the shorter motifs GTGGGAA/TGGGAA) (giaimo2021transcriptionfactorrbpj pages 3-5, pan2021transcriptionfactorrbpjl pages 1-2, pan2021transcriptionfactorrbpjl pages 12-14). The core TGGGAA motif has been validated through electrophoretic mobility shift assays (EMSA) and structural studies (pan2021transcriptionfactorrbpjl pages 12-14). RBPJ binds these sites at target-gene regulatory regions, where it occupies DNA and coordinates downstream transcriptional responses (lv2024evolutionandfunction pages 2-4, giaimo2021transcriptionfactorrbpj pages 3-5).
RBPJ functions as a context-dependent molecular switch that alternates between transcriptional repression and activation depending on Notch pathway status (giaimo2021transcriptionfactorrbpj pages 5-8, giaimo2021transcriptionfactorrbpj pages 3-5). In the Notch-OFF state (absence of Notch signaling), DNA-bound RBPJ recruits corepressor complexes including SHARP/SPEN, KyoT2/FHL1C, and L3MBTL3 (giaimo2021transcriptionfactorrbpj pages 5-8, giaimo2021transcriptionfactorrbpj pages 8-10). These corepressors associate with chromatin-modifying activities such as histone deacetylases (HDACs) in NCoR complexes and histone demethylases KDM5A and KDM1A/LSD1, thereby maintaining repression or dampened transcription of Notch target genes (giaimo2021transcriptionfactorrbpj pages 5-8, giaimo2021transcriptionfactorrbpj pages 8-10).
Following ligand-induced Notch receptor activation and gamma-secretase-mediated cleavage, the Notch intracellular domain (NICD) is released and translocates into the nucleus, where it binds RBPJ (lv2024evolutionandfunction pages 2-4, giaimo2021transcriptionfactorrbpj pages 3-5, giaimo2021transcriptionfactorrbpj pages 1-3). NICD, RBPJ, and Mastermind-like (MAML) proteins form a ternary transcriptional activation complex (lv2024evolutionandfunction pages 2-4, giaimo2021transcriptionfactorrbpj pages 3-5). This complex displaces or competes with corepressors and recruits coactivators including the acetyltransferases EP300/KAT3B, PCAF/KAT2B, and GCN5/KAT2A, along with additional factors such as NACK, cyclin C–CDK8, DDX5/SRA, CARM1, and EP400/TIP60 (giaimo2021transcriptionfactorrbpj pages 8-10, giaimo2021transcriptionfactorrbpj pages 3-5). These coactivators promote histone acetylation and open chromatin, leading to activation of Notch-responsive genes (giaimo2021transcriptionfactorrbpj pages 3-5).
As a transcription factor, Rbpjb's relevant "substrates" are regulatory DNA sequences containing the RBPJ consensus motif. Its activity is not enzymatic but rather depends on mutually alternative protein–protein interactions with cofactors that determine transcriptional output (giaimo2021transcriptionfactorrbpj pages 5-8, giaimo2021transcriptionfactorrbpj pages 3-5).
RBPJ is organized into three principal structural domains (pan2021transcriptionfactorrbpjl pages 7-8, pan2021transcriptionfactorrbpjl pages 8-12, giaimo2021transcriptionfactorrbpj pages 5-8):
This modular organization allows RBPJ to integrate DNA recognition with dynamic cofactor recruitment (giaimo2021transcriptionfactorrbpj pages 5-8, huynh2025effectiveinvivo pages 1-2). The supplied UniProt annotation for A4FTT4 identifies Beta-trefoil_DNA-bd_dom and Ig-like/E-set domains, consistent with this canonical CSL scaffold.
| Property | Description | Key Evidence |
|---|---|---|
| Gene nomenclature | rbpjb encodes zebrafish Su(H)B (UniProt A4FTT4) in Danio rerio. It is one of two zebrafish RBPJ orthologs/paralogs, rbpja and rbpjb. The available literature confirms this paralog pair but rarely distinguishes their individual biochemical or developmental contributions; therefore, most functional annotation below is inferred from conserved RBPJ/CSL-family evidence rather than direct experiments on A4FTT4. | A zebrafish retinal review explicitly identifies Rbpja and Rbpjb as the two RBP-Jκ orthologs (hyde2022retinalregenerationrequires pages 5-6). |
| Protein family | Member of the Su(H)/CSL DNA-binding transcription-factor family. “CSL” refers to mammalian CBF1/RBPJ, Drosophila Suppressor of Hairless [Su(H)], and C. elegans LAG-1. This classification agrees with the supplied UniProt description and its beta-trefoil DNA-binding, Ig-like/E-set and CSL-family domain annotations. | RBPJ is identified as the mammalian CSL-family factor related to Su(H) and LAG-1 (giaimo2021transcriptionfactorrbpj pages 3-5). Conserved RBPJ structure comprises N-terminal, beta-trefoil and C-terminal modules (pan2021transcriptionfactorrbpjl pages 7-8, giaimo2021transcriptionfactorrbpj pages 5-8). |
| DNA-binding specificity | RBPJ recognizes canonical RBPJ-binding sites (RBSs) centered on TGGGAA. Reported motifs include 5′-CGTGGGAA-3′ and GTGGGAA; a shorter core, TGGGAA, is commonly used in binding assays. For Rbpjb, recognition of this motif is a strong family-based inference, but a purified A4FTT4-specific binding assay was not located. | The 5′-CGTGGGAA-3′ RBPJ site is reported in a focused RBPJ review (giaimo2021transcriptionfactorrbpj pages 3-5); canonical GTGGGAA/TGGGAA elements were used in DNA-binding studies (pan2021transcriptionfactorrbpjl pages 1-2, pan2021transcriptionfactorrbpjl pages 12-14). |
| Structural domains: NTD, BTD and CTD | RBPJ has three principal domains: an N-terminal domain (NTD), central beta-trefoil domain (BTD) and C-terminal domain (CTD). The NTD and BTD contribute to DNA recognition; the BTD binds NICD and several alternative coregulators; the CTD also contacts NICD and MAML. Thus, the supplied A4FTT4 Beta-trefoil_DNA-bd_dom and Ig-like/E-set annotations are structurally consistent with the canonical CSL scaffold. | Structural analyses define the NTD–BTD–CTD architecture and identify the BTD/CTD as NICD-contacting surfaces (pan2021transcriptionfactorrbpjl pages 7-8, pan2021transcriptionfactorrbpjl pages 8-12). The NTD contacts DNA and MAML, the BTD contacts DNA and NICD, and the CTD contacts NICD and MAML (giaimo2021transcriptionfactorrbpj pages 5-8). |
| Subcellular localization | Functional localization is nuclear and chromatin associated. RBPJ occupies regulatory DNA in the Notch-OFF state; following receptor activation, NICD enters the nucleus and engages DNA-bound RBPJ. Direct zebrafish Rbpjb localization imaging was not identified, so nuclear localization is inferred from conserved mechanism. | Live-cell tracking detected nuclear RBPJ binding events and a longest binding-time component of approximately 910 seconds, reduced when DNA binding was disrupted (pan2021transcriptionfactorrbpjl pages 12-14). RBPJ remains at target genes while NICD translocates into the nucleus (pan2021transcriptionfactorrbpjl pages 1-2, giaimo2021transcriptionfactorrbpj pages 1-3). |
| Molecular function | Sequence-specific DNA-binding transcriptional regulator and context-dependent molecular switch; not an enzyme or transporter. In the absence of activated Notch, DNA-bound RBPJ supports repression or dampening of target transcription. NICD binding converts it into the DNA-anchoring component of a transcriptional activation complex. Its relevant molecular “substrate” is therefore regulatory DNA containing RBPJ sites, while its activity depends on mutually alternative protein cofactors. | RBPJ is described as the central Notch DNA-binding hub that alternates between corepressor- and coactivator-associated states (giaimo2021transcriptionfactorrbpj pages 5-8, giaimo2021transcriptionfactorrbpj pages 3-5). Loss of RBPJ reduces Notch-associated transcription and chromatin accessibility while enabling neurogenic programs in retinal glia (le2024robustreprogrammingof pages 3-4). |
| Cofactors in the repression state | In the Notch-OFF state, RBPJ associates with corepressors including SHARP/SPEN, KyoT2/FHL1C and L3MBTL3. These complexes can recruit chromatin-regulatory machinery such as NCoR/HDAC, KDM5A and KDM1A/LSD1, promoting reduced transcriptional output at Notch-responsive loci. The exact complement used by zebrafish Rbpjb has not been directly mapped. | SHARP binds RBPJ and connects it to HDAC-containing NCoR and ETO/MTG complexes (giaimo2021transcriptionfactorrbpj pages 5-8). KyoT2/FHL1C, L3MBTL3 and histone-demethylase recruitment are described as alternative OFF-state mechanisms (giaimo2021transcriptionfactorrbpj pages 8-10). |
| Cofactors in the activation state | Ligand-induced Notch cleavage releases NICD, which enters the nucleus and binds RBPJ. RBPJ, NICD and Mastermind-like (MAML) form the core activation complex, which recruits coactivators and chromatin modifiers including EP300/KAT3B, PCAF/KAT2B, GCN5/KAT2A, and, in some contexts, NACK, cyclin C–CDK8, DDX5/SRA, CARM1 and EP400/TIP60. Direct interaction mapping for zebrafish Rbpjb remains to be done. | The RBPJ–NICD–MAML ternary complex and recruitment of EP300, PCAF and GCN5 are established in mechanistic studies and reviews (lv2024evolutionandfunction pages 2-4, giaimo2021transcriptionfactorrbpj pages 3-5). Additional activation-associated cofactors are summarized in (giaimo2021transcriptionfactorrbpj pages 8-10). |
| Primary role in pathway | Rbpjb is best annotated as a nuclear transcriptional effector of canonical Notch signaling, converting cell–cell ligand/receptor activation into target-gene regulation. In zebrafish, canonical outputs include her and hey genes; Notch-dependent neural genes include her2, her4.1–her4.5, her12, her15.1 and her15.2. Because most zebrafish experiments perturb the pathway rather than rbpjb alone, these outputs should be assigned to the Rbpja/Rbpjb-mediated pathway collectively, not exclusively to Rbpjb. | Zebrafish Rbpja/Rbpjb act with NICD and Mastermind-like cofactors, and her/hey families are principal outputs (hyde2022retinalregenerationrequires pages 5-6). Nine Notch-dependent her genes were identified in the zebrafish thalamic proliferation zone, although direct Rbpjb occupancy was not tested (sigloch2023anetworkof pages 1-4, sigloch2023anetworkof pages 4-6). |
Table: This table consolidates the identity, structure, DNA specificity, localization, cofactors and canonical Notch-pathway role of zebrafish Rbpjb. It distinguishes direct zebrafish evidence from conserved RBPJ/CSL-family inference, an important limitation because A4FTT4-specific functional studies are sparse.
Rbpjb protein functions in the nucleus, where it binds DNA at chromatin-associated regulatory sites (pan2021transcriptionfactorrbpjl pages 12-14, pan2021transcriptionfactorrbpjl pages 1-2, giaimo2021transcriptionfactorrbpj pages 1-3). Live-cell single-molecule tracking studies demonstrate that RBPJ exhibits long nuclear residence times, with the longest binding events reaching approximately 910 seconds, a duration strongly dependent on intact DNA-binding capacity (pan2021transcriptionfactorrbpjl pages 12-14). When DNA binding is disrupted (e.g., by the R218H mutation), residence time is substantially reduced, confirming that the prolonged nuclear localization reflects stable DNA occupancy (pan2021transcriptionfactorrbpjl pages 12-14). NICD enters the nucleus following receptor cleavage and engages DNA-bound RBPJ at target-gene sites (pan2021transcriptionfactorrbpjl pages 1-2, giaimo2021transcriptionfactorrbpj pages 1-3, giaimo2021transcriptionfactorrbpj pages 3-5). Thus, Rbpjb carries out its function at chromatin in the nucleus, where it serves as the DNA-anchored platform for Notch transcriptional regulation.
Rbpjb is the core nuclear transcriptional mediator of canonical Notch signaling (le2024robustreprogrammingof pages 3-4, le2024robustreprogrammingof pages 2-3, hyde2022retinalregenerationrequires pages 5-6). The pathway operates through cell–cell interactions: Notch receptors on one cell bind Delta or Jagged/Serrate ligands on an adjacent cell, triggering receptor cleavage and NICD release (lv2024evolutionandfunction pages 2-4, solano2025defectivenotch1signaling pages 1-2). NICD translocates to the nucleus and, together with RBPJ and MAML, activates Notch target genes (giaimo2021transcriptionfactorrbpj pages 3-5). In zebrafish, the principal target-gene families are her (hairy-related, homologs of mammalian Hes genes) and hey genes, which encode basic helix-loop-helix (bHLH) transcriptional repressors (hyde2022retinalregenerationrequires pages 5-6).
Zebrafish express multiple Notch-responsive her genes, although not all her genes depend equally on Notch signaling. In the zebrafish thalamic proliferation zone, nine Notch-dependent Hes5-like genes have been identified: her2, her4.1, her4.2, her4.3, her4.4, her4.5, her12, her15.1, and her15.2 (sigloch2023anetworkof pages 1-4, sigloch2023anetworkof pages 4-6). The Hes6 homolog her8a is also Notch responsive (sigloch2023anetworkof pages 13-15). In contrast, the Hes1 homologs her6 and her9 are largely Notch independent in neural stem-cell contexts, although her6 plays a prominent role in maintaining neural progenitor pools (sigloch2023anetworkof pages 4-6, sigloch2023anetworkof pages 15-17). Her4.1 is specifically confirmed as a Notch/RBPJ target expressed in proneural cluster domains (ohyanagi2025geneticmechanismthat pages 1-2). The differential regulation and redundancy among her genes underscore the complexity of Notch transcriptional networks in zebrafish development (sigloch2023anetworkof pages 1-4, sigloch2023anetworkof pages 4-6, sigloch2023anetworkof pages 13-15, sigloch2023anetworkof pages 15-17).
Rbpjb participates in multiple developmental processes through its role in Notch signaling, although most studies manipulate the pathway generally rather than targeting rbpjb specifically:
Neurogenesis and Neural Progenitor Maintenance: Canonical Notch–RBPJ signaling restrains premature neuronal differentiation and maintains neural progenitor states (sharma2019notchmediatedinhibitionof pages 13-14, sharma2019notchmediatedinhibitionof pages 16-17, sharma2019notchmediatedinhibitionof pages 16-16). Loss of Notch function causes excessive neurogenesis, while maintained Notch activity suppresses neurogenic bHLH factors (le2024robustreprogrammingof pages 3-4, le2023robustreprogrammingof pages 1-3). In the zebrafish thalamic proliferation zone, Notch-dependent her genes (her2, her4, her12, her15) define distinct neural stem and progenitor cell populations (sigloch2023anetworkof pages 1-4, sigloch2023anetworkof pages 4-6). Combined genetic analyses reveal extensive functional redundancy: deleting all nine Notch-dependent Hes5-like genes produces relatively mild effects, whereas loss of both Notch-dependent and Notch-independent her genes severely depletes neural stem/progenitor cells (sigloch2023anetworkof pages 15-17).
Spinal Cord Morphogenesis: RBPJ-mediated Notch signaling is essential for zebrafish spinal cord morphogenesis (sharma2019notchmediatedinhibitionof pages 13-14). Notch suppresses neuronal differentiation long enough to allow neuroepithelial epithelialization, establishment of apicobasal polarity, and execution of specific morphogenetic movements, including midline-crossing cell divisions (sharma2019notchmediatedinhibitionof pages 13-14). Notch-deficient embryos exhibit excessive neurogenesis, reduced neuroepithelial gene expression, impaired polarity, and disproportionate spinal cord architecture (sharma2019notchmediatedinhibitionof pages 13-14).
Retinal Development and Regeneration: In adult zebrafish retina, Notch signaling maintains Müller glia in a quiescent state, and transient pathway suppression permits injury-induced reprogramming into neuronal progenitors (hyde2022retinalregenerationrequires pages 5-6, le2024robustreprogrammingof pages 2-3). Dynamic Notch regulation subsequently directs progenitor proliferation and neurogenesis during retinal regeneration (hyde2022retinalregenerationrequires pages 5-6). Zebrafish Müller glia express Notch pathway components including notch3, her6, and id1 (le2024robustreprogrammingof pages 2-3). Rbpja and Rbpjb are both identified as zebrafish RBP-Jκ orthologs in this context, although paralog-specific contributions remain unresolved (hyde2022retinalregenerationrequires pages 5-6).
Somitogenesis and Segmentation Clock: RBPJ/Su(H) converts intercellular Notch activity into oscillatory transcription that coordinates presomitic mesoderm cells and drives segmentation (sharma2019notchmediatedinhibitionof pages 16-17). Zebrafish her1 and other oscillatory her genes are linked to somitogenesis, with the segmentation clock cycling approximately every 30 minutes in zebrafish embryos (sharma2019notchmediatedinhibitionof pages 16-17). Su(H)-dependent signaling and her1 function are implicated in zebrafish somite development (sharma2019notchmediatedinhibitionof pages 16-17).
Oligodendrocyte Specification and Gliogenesis: Notch signaling maintains selected spinal neural progenitors and promotes their transition toward oligodendrocyte and glial fates (tran2025epigeneticprimingof pages 12-14, sharma2019notchmediatedinhibitionof pages 16-16). This process involves crosstalk with Sonic hedgehog (SHH) signaling and epigenetic priming of gliogenic programs (tran2025epigeneticprimingof pages 12-14).
Other Developmental Contexts: Canonical RBPJ is broadly implicated in vascular development and the emergence of hematopoietic stem cells (solano2025defectivenotch1signaling pages 1-2), although zebrafish rbpjb-specific phenotypes in these systems have not been definitively established. Given its conserved position as the nuclear Notch effector, rbpjb likely contributes to these processes alongside rbpja.
| Biological process/tissue | Role of Rbpjb/RBPJ–Notch signaling | Notch target genes involved | Supporting evidence |
|---|---|---|---|
| Neurogenesis and neural progenitors | Canonical Notch–RBPJ signaling restrains premature neuronal differentiation and preserves progenitor states. In zebrafish, pathway disruption produces excessive neurogenesis, but available experiments generally do not distinguish Rbpjb from Rbpja. | Context-dependent her/hey genes; her4.1 is a well-supported Notch-dependent neural target. | Zebrafish Notch loss causes excessive neuronal differentiation, while Su(H)/RBPJ mediators connect receptor activation to transcription (sharma2019notchmediatedinhibitionof pages 13-14, sharma2019notchmediatedinhibitionof pages 16-17). Her4.1 is specifically identified as Notch dependent (ohyanagi2025geneticmechanismthat pages 1-2). |
| Spinal-cord morphogenesis | RBPJ-mediated Notch output suppresses neuronal differentiation long enough for neuroepithelial epithelialization, apicobasal polarity and normal midline-crossing movements. This is pathway-level evidence rather than an Rbpjb-specific knockout result. | Not specified directly; neural her genes are likely downstream effectors. | Notch-deficient zebrafish show reduced neuroepithelial programs, abnormal polarity and movement, and disproportionate spinal cords (sharma2019notchmediatedinhibitionof pages 13-14). |
| Neural stem-cell maintenance in the thalamic proliferation zone | Notch-responsive Her factors help define neural stem and progenitor populations. Extensive redundancy makes the system robust: deleting nine Notch-dependent Hes5-like genes alone produced little disruption, whereas combined loss with Notch-independent Her factors caused major stem/progenitor-cell depletion. | her2, her4.1–her4.5, her12, her15.1, her15.2; her8a is also Notch responsive. her6 and her9 are largely Notch independent in this context. | Nine Notch-dependent genes define distinct zebrafish thalamic stem/progenitor populations (sigloch2023anetworkof pages 1-4, sigloch2023anetworkof pages 4-6). Genetic analyses demonstrate redundancy between Notch-dependent and independent Her branches (sigloch2023anetworkof pages 15-17). |
| Retinal homeostasis and regeneration | In adult zebrafish retina, Notch signaling maintains Müller glia in a quiescent state; transient pathway suppression permits injury-induced reprogramming, while later dynamic signaling helps regulate progenitor proliferation and neurogenesis. Rbpja and Rbpjb are both candidate nuclear mediators, but paralog-specific contributions remain unresolved. | her and hey families; reported retinal pathway readouts include her6 and id1. | Zebrafish possess Rbpja and Rbpjb, and the conserved pathway operates through NICD–RBPJ–Mastermind complexes (hyde2022retinalregenerationrequires pages 5-6). Zebrafish Müller glia express Notch components and targets including her6 and id1 (le2024robustreprogrammingof pages 2-3). |
| Somitogenesis and segmentation clock | RBPJ/CSL converts intercellular Notch activity into oscillatory transcription that coordinates neighboring presomitic-mesoderm cells and segment formation. The zebrafish clock cycles approximately every 30 minutes, but direct attribution to Rbpjb rather than combined Rbpja/Rbpjb activity is lacking. | her1 and other oscillatory Her-family genes; vertebrate Notch–RBPJ regulation of Hes7 provides a conserved mechanistic analogue. | Su(H)-dependent regulation and her1 function are linked to zebrafish somitogenesis (sharma2019notchmediatedinhibitionof pages 16-17). Comparative work reports an approximately 30-minute zebrafish segmentation period and describes CSL repression without NICD (Ramesh and Chu, 2024; DOI: https://doi.org/10.3389/fcell.2023.1327227). |
| Oligodendrocyte specification and gliogenesis | Notch signaling maintains selected spinal neural progenitors and promotes their transition toward oligodendrocyte/glial fates, including through interaction with Sonic hedgehog programs. Rbpjb participation is inferred from its conserved position as a canonical Notch effector. | Specific zebrafish Rbpjb-bound targets were not identified in the retrieved evidence. | Zebrafish Notch signaling is required for spinal-cord oligodendrocyte specification and progenitor maintenance (tran2025epigeneticprimingof pages 12-14, sharma2019notchmediatedinhibitionof pages 16-16). |
| Broader brain neurodevelopment | Notch-dependent RBPJ transcription creates spatially and temporally heterogeneous neural outputs; therefore, individual Her genes are not universal proxies for Rbpjb activity. | Responses vary among her genes by neural region, cell type and developmental stage. | Zebrafish studies identify distinct Notch-dependent and independent Her programs (sigloch2023anetworkof pages 1-4, sigloch2023anetworkof pages 4-6, sigloch2023anetworkof pages 13-15). |
| Vascular and hematopoietic development | Canonical RBPJ is broadly implicated in endothelial identity and emergence of hematopoietic stem cells, but the retrieved evidence does not establish an Rbpjb-specific zebrafish phenotype. This should be treated as a plausible conserved context, not a confirmed paralog-specific annotation. | Context-dependent hes/her and hey outputs; no Rbpjb-specific targets established. | Reviews identify RBPJ as the nuclear Notch effector in vascular transcription and place canonical Notch centrally in definitive hematopoiesis, including zebrafish models (lv2024evolutionandfunction pages 2-4, solano2025defectivenotch1signaling pages 1-2). |
Table: This table summarizes developmental processes connected to RBPJ-mediated Notch signaling in zebrafish while separating pathway-level evidence from direct Rbpjb-specific evidence. It highlights the major limitation that most studies do not resolve the respective contributions of the rbpja and rbpjb paralogs.
Recent high-quality studies provide mechanistic insights into RBPJ structure and function:
DNA-Binding Kinetics (2025): Huynh et al. (Nature Communications, 2025) used live-cell single-molecule tracking to determine RBPJ DNA-binding kinetics, demonstrating that RBPJ exhibits kinetic rather than thermodynamic stability at target sites, with search times longer than residence times (huynh2025effectiveinvivo pages 1-2). Disease-associated mutations (e.g., K195E in Adams-Oliver syndrome) impair both association and dissociation from DNA (huynh2025effectiveinvivo pages 1-2).
Retinal Glia Reprogramming (2024): Le et al. (Science Advances, 2024) demonstrated that disrupting Rbpj in adult mammalian Müller glia suppresses Notch pathway genes and induces neurogenic competence, converting glia into bipolar- and amacrine-like neurons (le2024robustreprogrammingof pages 3-4, le2024robustreprogrammingof pages 2-3). This study confirms Rbpj as a critical gatekeeper preventing neuronal reprogramming in mature glia and provides insights relevant to zebrafish regenerative biology (hyde2022retinalregenerationrequires pages 5-6).
Neural Stem Cell Regulation in Zebrafish (2023): Sigloch et al. (Development, 2023) performed comprehensive analyses of zebrafish her gene networks in the thalamic proliferation zone, revealing nine Notch-dependent genes and demonstrating redundancy between Notch-dependent and -independent her branches (sigloch2023anetworkof pages 1-4, sigloch2023anetworkof pages 4-6, sigloch2023anetworkof pages 15-17). This work highlights the complexity and robustness of Notch transcriptional networks in zebrafish.
Notch Signaling Reviews (2024): Sachan et al. (FEBS Journal, 2024) and Miao & Pourquié (Nature Reviews Molecular Cell Biology, 2024) provide comprehensive reviews of Notch pathway mechanisms, including RBPJ's role as the molecular switch between repression and activation (sachan2023notchsignallingmultifaceted pages 5-6, giaimo2021transcriptionfactorrbpj pages 5-8).
Zebrafish Neurogenesis Mechanisms (2025): Ohyanagi et al. (Genesis, 2025) used CRISPR knockout to dissect Notch-independent her gene functions in zebrafish primary neurogenesis, demonstrating that her3, her5, and her11 cooperatively suppress ectopic neurogenesis independently of Notch/RBPJ (ohyanagi2025geneticmechanismthat pages 1-2).
An important limitation is that most zebrafish studies do not distinguish rbpjb from rbpja. While zebrafish clearly possess two RBPJ paralogs (hyde2022retinalregenerationrequires pages 5-6), experimental manipulations typically target the Notch pathway broadly (e.g., using mind bomb mutants, gamma-secretase inhibitors, or morpholinos) rather than specifically knocking out rbpjb. Therefore, the developmental roles described above reflect RBPJ-mediated Notch signaling generally, not rbpjb-specific functions. Whether rbpja and rbpjb exhibit functional divergence, tissue-specific expression patterns, or differential target-gene regulation remains an open question. Future rbpjb-specific knockout or knockdown studies would be valuable to resolve paralog-specific contributions.
Additionally, while the DNA-binding consensus sequence and structural organization are well established for the RBPJ family, direct biochemical characterization of purified zebrafish Rbpjb protein (UniProt A4FTT4) has not been reported. The functional annotations are therefore inferred from highly conserved family properties rather than species- and paralog-specific experiments.
The zebrafish gene rbpjb encodes a nuclear DNA-binding transcription factor belonging to the Su(H)/CSL family, functioning as the central transcriptional effector of canonical Notch signaling. Rbpjb recognizes the DNA consensus sequence 5′-CGTGGGAA-3′ at target-gene regulatory regions and acts as a context-dependent molecular switch: recruiting corepressor complexes (SHARP, KyoT2, L3MBTL3) in the absence of Notch signaling to maintain transcriptional repression, and forming an activation complex with NICD and MAML to drive target-gene expression when Notch is activated. The protein is organized into N-terminal, beta-trefoil, and C-terminal domains that coordinate DNA binding with cofactor recruitment. Rbpjb localizes to the nucleus, where it occupies chromatin and regulates Notch-responsive genes including zebrafish her and hey families.
Rbpjb plays essential roles in multiple zebrafish developmental processes, including neurogenesis, neural stem cell maintenance, spinal cord morphogenesis, retinal homeostasis and regeneration, somitogenesis, and oligodendrocyte specification. These functions are mediated through its position as the obligate nuclear mediator of canonical Notch signaling. However, most studies do not distinguish rbpjb from its paralog rbpja; therefore, the relative contributions of the two paralogs remain to be elucidated. Recent research (2023–2025) has provided mechanistic insights into RBPJ DNA-binding kinetics, cofactor interactions, and transcriptional network complexity, reinforcing the conserved importance of this pathway across vertebrate development.
This report is based on evidence from primary research articles and reviews published between 2019 and 2025, with an emphasis on recent high-quality studies. Key references include structural and biochemical analyses of RBPJ (Giaimo et al., 2021, Advances in Experimental Medicine and Biology; Huynh et al., 2025, Nature Communications), zebrafish neural development studies (Sigloch et al., 2023, Development; Sharma et al., 2019, Scientific Reports), Notch signaling in retinal regeneration (Hyde et al., 2022, Neural Regeneration Research; Le et al., 2024, Science Advances), and comprehensive reviews of Notch pathway mechanisms (Sachan et al., 2024, FEBS Journal; Miao & Pourquié, 2024, Nature Reviews Molecular Cell Biology). All citations are provided in-text as evidence identifiers ().
References
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(giaimo2021transcriptionfactorrbpj pages 3-5): Benedetto Daniele Giaimo, Ellen K. Gagliani, Rhett A. Kovall, and Tilman Borggrefe. Transcription factor rbpj as a molecular switch in regulating the notch response. Advances in experimental medicine and biology, 1287:9-30, Oct 2021. URL: https://doi.org/10.1007/978-3-030-55031-8_2, doi:10.1007/978-3-030-55031-8_2. This article has 56 citations and is from a peer-reviewed journal.
(pan2021transcriptionfactorrbpjl pages 1-2): Leiling Pan, Philipp Hoffmeister, Aleksandra Turkiewicz, N. N. Duyen Huynh, Andreas Große-Berkenbusch, Uwe Knippschild, J. Christof M. Gebhardt, Bernd Baumann, Tilman Borggrefe, and Franz Oswald. Transcription factor rbpjl is able to repress notch target gene expression but is non-responsive to notch activation. Oct 2021. URL: https://doi.org/10.18725/oparu-46089, doi:10.18725/oparu-46089. This article has 21 citations.
(pan2021transcriptionfactorrbpjl pages 12-14): Leiling Pan, Philipp Hoffmeister, Aleksandra Turkiewicz, N. N. Duyen Huynh, Andreas Große-Berkenbusch, Uwe Knippschild, J. Christof M. Gebhardt, Bernd Baumann, Tilman Borggrefe, and Franz Oswald. Transcription factor rbpjl is able to repress notch target gene expression but is non-responsive to notch activation. Oct 2021. URL: https://doi.org/10.18725/oparu-46089, doi:10.18725/oparu-46089. This article has 21 citations.
(lv2024evolutionandfunction pages 2-4): Yan Lv, Xuan Pang, Zhonghong Cao, Changping Song, Baohua Liu, Weiwei Wu, and Qiuxiang Pang. Evolution and function of the notch signaling pathway: an invertebrate perspective. International Journal of Molecular Sciences, 25:3322, Mar 2024. URL: https://doi.org/10.3390/ijms25063322, doi:10.3390/ijms25063322. This article has 36 citations.
(giaimo2021transcriptionfactorrbpj pages 5-8): Benedetto Daniele Giaimo, Ellen K. Gagliani, Rhett A. Kovall, and Tilman Borggrefe. Transcription factor rbpj as a molecular switch in regulating the notch response. Advances in experimental medicine and biology, 1287:9-30, Oct 2021. URL: https://doi.org/10.1007/978-3-030-55031-8_2, doi:10.1007/978-3-030-55031-8_2. This article has 56 citations and is from a peer-reviewed journal.
(giaimo2021transcriptionfactorrbpj pages 8-10): Benedetto Daniele Giaimo, Ellen K. Gagliani, Rhett A. Kovall, and Tilman Borggrefe. Transcription factor rbpj as a molecular switch in regulating the notch response. Advances in experimental medicine and biology, 1287:9-30, Oct 2021. URL: https://doi.org/10.1007/978-3-030-55031-8_2, doi:10.1007/978-3-030-55031-8_2. This article has 56 citations and is from a peer-reviewed journal.
(giaimo2021transcriptionfactorrbpj pages 1-3): Benedetto Daniele Giaimo, Ellen K. Gagliani, Rhett A. Kovall, and Tilman Borggrefe. Transcription factor rbpj as a molecular switch in regulating the notch response. Advances in experimental medicine and biology, 1287:9-30, Oct 2021. URL: https://doi.org/10.1007/978-3-030-55031-8_2, doi:10.1007/978-3-030-55031-8_2. This article has 56 citations and is from a peer-reviewed journal.
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(pan2021transcriptionfactorrbpjl pages 8-12): Leiling Pan, Philipp Hoffmeister, Aleksandra Turkiewicz, N. N. Duyen Huynh, Andreas Große-Berkenbusch, Uwe Knippschild, J. Christof M. Gebhardt, Bernd Baumann, Tilman Borggrefe, and Franz Oswald. Transcription factor rbpjl is able to repress notch target gene expression but is non-responsive to notch activation. Oct 2021. URL: https://doi.org/10.18725/oparu-46089, doi:10.18725/oparu-46089. This article has 21 citations.
(huynh2025effectiveinvivo pages 1-2): Duyen Huynh, Philipp Hoffmeister, Tobias Friedrich, Kefan Zhang, Marek Bartkuhn, Francesca Ferrante, Benedetto Daniele Giaimo, Rhett A. Kovall, Tilman Borggrefe, Franz Oswald, and J. Christof M. Gebhardt. Effective in vivo binding energy landscape illustrates kinetic stability of rbpj-dna binding. Nature Communications, Feb 2025. URL: https://doi.org/10.1038/s41467-025-56515-4, doi:10.1038/s41467-025-56515-4. This article has 14 citations and is from a highest quality peer-reviewed journal.
(le2024robustreprogrammingof pages 3-4): Nguyet Le, Trieu-Duc Vu, Isabella Palazzo, Ritvik Pulya, Yehna Kim, Seth Blackshaw, and Thanh V. Hoang. Robust reprogramming of glia into neurons by inhibition of notch signaling and nuclear factor i (nfi) factors in adult mammalian retina. Science Advances, Jul 2024. URL: https://doi.org/10.1126/sciadv.adn2091, doi:10.1126/sciadv.adn2091. This article has 58 citations and is from a highest quality peer-reviewed journal.
(sigloch2023anetworkof pages 1-4): Christian Sigloch, Dominik Spitz, and Wolfgang Driever. A network of notch-dependent and -independent her genes controls neural stem and progenitor cells in the zebrafish thalamic proliferation zone. Development, Apr 2023. URL: https://doi.org/10.1242/dev.201301, doi:10.1242/dev.201301. This article has 21 citations and is from a domain leading peer-reviewed journal.
(sigloch2023anetworkof pages 4-6): Christian Sigloch, Dominik Spitz, and Wolfgang Driever. A network of notch-dependent and -independent her genes controls neural stem and progenitor cells in the zebrafish thalamic proliferation zone. Development, Apr 2023. URL: https://doi.org/10.1242/dev.201301, doi:10.1242/dev.201301. This article has 21 citations and is from a domain leading peer-reviewed journal.
(solano2025defectivenotch1signaling pages 1-2): Alyssa F. Solano, Kristina Preusse, Brittany Cain, Rebecca Hotz, Parthav Gavini, Zhenyu Yuan, Benjamin Bowen, Gabrielle Maco, Hope Neal, Ellen K. Gagliani, Christopher Ahn, Hee-Woong Lim, Laura Southgate, Rhett A. Kovall, Raphael Kopan, and Brian Gebelein. Defective notch1 signaling in endothelial cells drives pathogenesis in a mouse model of adams-oliver syndrome. Journal of Clinical Investigation, Oct 2025. URL: https://doi.org/10.1172/jci187532, doi:10.1172/jci187532. This article has 2 citations and is from a highest quality peer-reviewed journal.
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(sigloch2023anetworkof pages 15-17): Christian Sigloch, Dominik Spitz, and Wolfgang Driever. A network of notch-dependent and -independent her genes controls neural stem and progenitor cells in the zebrafish thalamic proliferation zone. Development, Apr 2023. URL: https://doi.org/10.1242/dev.201301, doi:10.1242/dev.201301. This article has 21 citations and is from a domain leading peer-reviewed journal.
(ohyanagi2025geneticmechanismthat pages 1-2): Takero Ohyanagi, Hiroki Tokizaki, Takehisa Sato, Momo Tsuruoka, and Kyo Yamasu. Genetic mechanism that defines the characteristic neurogenesis patterns in the neural plate using hes/her genes during early vertebrate development. Genesis (New York, N.y. : 2000), Jun 2025. URL: https://doi.org/10.1002/dvg.70015, doi:10.1002/dvg.70015. This article has 5 citations.
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(sharma2019notchmediatedinhibitionof pages 16-17): Priyanka Sharma, Vishnu Muraleedharan Saraswathy, Li Xiang, and Maximilian Fürthauer. Notch-mediated inhibition of neurogenesis is required for zebrafish spinal cord morphogenesis. Scientific Reports, Jul 2019. URL: https://doi.org/10.1038/s41598-019-46067-1, doi:10.1038/s41598-019-46067-1. This article has 19 citations and is from a peer-reviewed journal.
(sharma2019notchmediatedinhibitionof pages 16-16): Priyanka Sharma, Vishnu Muraleedharan Saraswathy, Li Xiang, and Maximilian Fürthauer. Notch-mediated inhibition of neurogenesis is required for zebrafish spinal cord morphogenesis. Scientific Reports, Jul 2019. URL: https://doi.org/10.1038/s41598-019-46067-1, doi:10.1038/s41598-019-46067-1. This article has 19 citations and is from a peer-reviewed journal.
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(sachan2023notchsignallingmultifaceted pages 5-6): Nalani Sachan, Vartika Sharma, Mousumi Mutsuddi, and Ashim Mukherjee. Notch signalling: multifaceted role in development and disease. The FEBS Journal, 291:3030-3059, May 2024. URL: https://doi.org/10.1111/febs.16815, doi:10.1111/febs.16815. This article has 124 citations.