Source 1primary paper2026MED
Toolkit/IscB cytosine base editors
IscB cytosine base editors
Also known as: IscB-CBEs
Taxonomy: Mechanism Branch / Architecture. Workflows sit above the mechanism and technique branches rather than replacing them.
Summary
Beyond gene knockout systems, we develop cytosine base editors (CBEs) and adenine base editors (ABEs) from pIscB-v3.
Usefulness & Problems
Why this is useful
IscB-CBEs are cytosine base editors developed from the pIscB-v3 platform. The abstract places them as an extension beyond knockout editing.; C-to-T base editing in rice
Source:
IscB-CBEs are cytosine base editors developed from the pIscB-v3 platform. The abstract places them as an extension beyond knockout editing.
Source:
C-to-T base editing in rice
Problem solved
They provide a compact IscB-based route to base editing in rice.; extends pIscB-v3 beyond gene knockout into base editing
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They provide a compact IscB-based route to base editing in rice.
Source:
extends pIscB-v3 beyond gene knockout into base editing
Problem links
extends pIscB-v3 beyond gene knockout into base editing
LiteratureThey provide a compact IscB-based route to base editing in rice.
Source:
They provide a compact IscB-based route to base editing in rice.
Published Workflows
Objective: Engineer and identify high-activity hypercompact IscB systems for rice genome editing and extend the lead system into compact base editors.
Why it works: The workflow first screens for a high-activity IscB configuration in rice, then uses the best-performing compact nuclease platform as the parent scaffold for cytosine and adenine base editor development.
RNA-guided DNA cleavage by IscBcytosine deamination for C-to-T conversionadenine deamination for A-to-G conversionvariant screeningcomponent combination optimizationeditor fusion design
Stages
- 1.Screening IscB variants for rice activity(broad_screen)
The study first screens IscB variants to identify a rice-compatible high-activity lead system.
Selection: high activity in rice
- 2.Characterization of lead nuclease performance(secondary_characterization)
After identifying a lead IscB system, the authors further characterize its performance properties in rice.
Selection: editing efficiency, edited line recovery, specificity, and TAM compatibility
- 3.Development and comparison of IscB-derived base editors(functional_characterization)
The lead pIscB-v3 platform is extended beyond knockout editing into compact base editor formats.
Selection: base editing performance of derived CBE and ABE architectures
- 4.Deaminase-module optimization within IscB base editors(hit_picking)
The study compares deaminase choices and fusion architectures to improve IscB-derived base editing performance.
Selection: superior deaminase-module performance for base conversion
Taxonomy & Function
Primary hierarchy
Mechanism Branch
Architecture: A reusable architecture pattern for arranging parts into an engineered system.
Techniques
No technique tags yet.
Target processes
editingImplementation Constraints
cofactor dependency: cofactor requirement unknownencoding mode: genetically encodedimplementation constraint: context specific validationoperating role: regulator
These editors are derived from pIscB-v3 and require a deaminase component, with Sdd7 and APOBEC3A explicitly discussed in the abstract.; derived from pIscB-v3
Independent follow-up evidence is still limited. Validation breadth across biological contexts is still narrow. Independent reuse still looks limited, so the evidence base may be fragile. No canonical validation observations are stored yet, so context-specific performance remains under-specified.
Validation
Cell-freeBacteriaMammalianMouseHumanTherapeuticIndep. Replication
Supporting Sources
Ranked Claims
Sdd7 outperformed human APOBEC3A in IscB cytosine base editors for C-to-T conversion in rice.
We find that the ssDNA-targeting SCP1.201 family deaminase Sdd7 outperformed human APOBEC3A in IscB-CBEs for C-to-T conversions in rice.
Adding an extra TadA-8e copy to either terminus of TadA8e-nIscB significantly enhanced A-to-G conversion activity.
However, fusing an extra copy of TadA-8e to either terminus of TadA8e-nIsc significantly enhances A-to-G conversions.
pIscB-v3 achieved an average editing efficiency of 17.61% across ten endogenous targets in rice.
The average editing efficiency of pIscB-v3 is 17.61% from ten endogenous targets
average editing efficiency 17.61 %
Sdd7-nIscB achieved precise edits in rice lines with an average frequency of 22.92% and a maximum frequency of 47.92%.
The Sdd7-nIscB achieves precise edits in 22.92% of lines on average, with a maximum frequency of 47.92%.
average precise edit frequency 22.92 %maximum precise edit frequency 47.92 %
pIscB-v3 produced edited lines in up to 83.33% of T0 generation plants, with 33.33% homozygous and bi-allelic mutations.
we obtain edited lines in up to 83.33% of T0 generation with 33.33% of homozygous and bi-allelic mutations
edited lines in T0 generation 83.33 %homozygous and bi-allelic mutations 33.33 %
pIscB-v3 showed superior mutagenesis efficiency compared with other tested systems in rice.
A version of pIscB-v3, combining enOgeuIscB and c9RNA-v13, demonstrated superior mutagenesis efficiency compared to other systems.
TadA8e-nIscB exhibited limited activity in rice.
Additionally, TadA8e-nIscB exhibits limited activity.
The study demonstrates that IscB can support an efficient and versatile miniature plant genome editing toolkit for crop breeding.
Collectively, our results demonstrate the robust capabilities of IscB to develop an efficient and versatile miniature plant genome editing toolkit to substantially facilitate crop breeding.
pIscB-v3 exhibited high editing specificity and relaxed target-adjacent motif compatibility in rice.
Further analysis reveals that pIscB-v3 exhibits high editing specificity and relaxed target-adjacent motif (TAM) compatibility in rice.
Approval Evidence
1 source2 linked approval claimsfirst-pass slug iscb-cytosine-base-editors
Beyond gene knockout systems, we develop cytosine base editors (CBEs) and adenine base editors (ABEs) from pIscB-v3.
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comparative performancesupports
Sdd7 outperformed human APOBEC3A in IscB cytosine base editors for C-to-T conversion in rice.
We find that the ssDNA-targeting SCP1.201 family deaminase Sdd7 outperformed human APOBEC3A in IscB-CBEs for C-to-T conversions in rice.
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platform scopesupports
The study demonstrates that IscB can support an efficient and versatile miniature plant genome editing toolkit for crop breeding.
Collectively, our results demonstrate the robust capabilities of IscB to develop an efficient and versatile miniature plant genome editing toolkit to substantially facilitate crop breeding.
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Comparisons
Source-stated alternatives
The abstract explicitly compares Sdd7 and human APOBEC3A within the IscB-CBE context.
Source:
The abstract explicitly compares Sdd7 and human APOBEC3A within the IscB-CBE context.
Source-backed strengths
We find that the ssDNA-targeting SCP1.201 family deaminase Sdd7 outperformed human APOBEC3A in IscB-CBEs for C-to-T conversions in rice. A version of pIscB-v3, combining enOgeuIscB and c9RNA-v13, demonstrated superior mutagenesis efficiency compared to other systems. Additionally, TadA8e-nIscB exhibits limited activity.
Source:
We find that the ssDNA-targeting SCP1.201 family deaminase Sdd7 outperformed human APOBEC3A in IscB-CBEs for C-to-T conversions in rice.
Source:
A version of pIscB-v3, combining enOgeuIscB and c9RNA-v13, demonstrated superior mutagenesis efficiency compared to other systems.
Source:
Additionally, TadA8e-nIscB exhibits limited activity.
Compared with microfluidic organ-on-chip platforms
IscB cytosine base editors and microfluidic organ-on-chip platforms address a similar problem space because they share editing.
Shared frame: same top-level item type; shared target processes: editing
Strengths here: looks easier to implement in practice.
Compared with synthetic promoters
IscB cytosine base editors and synthetic promoters address a similar problem space because they share editing.
Shared frame: same top-level item type; shared target processes: editing
Relative tradeoffs: appears more independently replicated; looks easier to implement in practice.
Compared with Z7-E78-ABE
IscB cytosine base editors and Z7-E78-ABE address a similar problem space because they share editing.
Shared frame: same top-level item type; shared target processes: editing
Ranked Citations
- 1.