Base Editing Analysis
CRISPResso2 for Base Editing
bash
# Analyze base editing with expected outcome
CRISPResso --fastq_r1 reads.fq.gz \
--amplicon_seq ATGCGATCGATCGATCGATCGATCG \
--guide_seq TCGATCGATCGATCGAT \
--expected_hdr_amplicon_seq ATGCGATCGATCGTTCGATCGATCG \
--base_editor_output \
-o results/
Key Metrics
| Metric | Description |
|---|---|
| Editing efficiency | % reads with target base change |
| Bystander edits | Unintended edits in editing window |
| Indel frequency | Insertions/deletions (should be low) |
| Purity | Target edit without bystanders |
Base Editor Types
Cytosine Base Editors (CBE)
bash
# C->T conversion (or G->A on opposite strand)
CRISPResso --fastq_r1 reads.fq.gz \
--amplicon_seq $AMPLICON \
--guide_seq $GUIDE \
--base_editor_output \
--conversion_nuc_from C \
--conversion_nuc_to T
Adenine Base Editors (ABE)
bash
# A->G conversion (or T->C on opposite strand)
CRISPResso --fastq_r1 reads.fq.gz \
--amplicon_seq $AMPLICON \
--guide_seq $GUIDE \
--base_editor_output \
--conversion_nuc_from A \
--conversion_nuc_to G
Prime Editing Analysis
bash
# Prime editing with pegRNA
CRISPResso --fastq_r1 reads.fq.gz \
--amplicon_seq $AMPLICON \
--guide_seq $SPACER \
--expected_hdr_amplicon_seq $EDITED_AMPLICON \
--prime_editing_pegRNA_extension_seq $EXTENSION \
-o prime_edit_results/
Editing Window Analysis
python
import pandas as pd
# Load CRISPResso quantification
quant = pd.read_csv('CRISPResso_output/Quantification_window_nucleotide_percentage_table.txt',
sep='\t')
# Calculate per-position editing
editing_window = quant[(quant['Position'] >= -5) & (quant['Position'] <= 5)]
Quality Thresholds
- •Editing efficiency: >30% considered good for most applications
- •Indel rate: <5% ideal for base editors
- •Bystander rate: depends on application; <10% often acceptable
Related Skills
- •crispr-screens/crispresso-editing - General editing QC
- •crispr-screens/library-design - Guide design considerations
- •variant-calling/vcf-basics - Downstream variant analysis