About BRCA1
The BRCA1 gene (BReast CAncer gene 1) on chromosome 17q21 encodes a tumor suppressor protein involved in DNA repair. Mutations in BRCA1 significantly increase the risk of breast, ovarian, and other cancers. BRCA1 spans ~100 kb of genomic DNA with 24 coding exons.
NCBI Gene ID: 672 | RefSeq: NM_007294.4 | Genomic: NC_000017.11 (43044295-43125364)
BRCA1 Primer Design Challenges
- Large gene size: 100+ kb requires careful amplicon selection
- High GC content in some exons: Exons 11 and 16 have 65-70% GC, requiring adjusted parameters
- Known pathogenic SNPs: Over 3,000 variants cataloged in ClinVar; primers must avoid these positions
- Pseudo-genes: BRCA1 has known pseudogenes that can cause non-specific amplification
- Clinical sensitivity: Diagnostic primers require the highest validation standards
Recommended Primer Design Parameters for BRCA1
| Parameter | Standard Exons | GC-Rich Exons (11, 16) |
|---|---|---|
| Primer length | 20-22 nt | 22-25 nt |
| GC content | 45-55% | 50-60% |
| Tm | 58-62°C | 60-65°C |
| Amplicon size | 150-300 bp | 200-350 bp |
| Annealing temp | 58-60°C | 62-65°C |
| PCR additive | Standard | Add 5% DMSO or 1M betaine |
Key SNPs to Avoid in Primer Binding Sites
When designing BRCA1 primers, avoid these high-frequency SNPs in the 3' region:
- rs80357906 (c.5266dupC) — Common pathogenic duplication
- rs80357914 (c.68_69delAG, 185delAG, p.Glu23fs) — Founder's mutation in Ashkenazi Jewish population
- rs28897672 (c.181T>G, p.Cys61Gly) — Exon 5 variant
- c.3756_3759del (p.Ser1253Argfs) — Recurrent Exon 11 deletion (no canonical dbSNP rs; LOVD 3494)
Clinical Validation Required
All BRCA1 primers designed with VigyanLLM are for research use only. Clinical diagnostic applications require additional wet-lab validation, Sanger sequencing confirmation, and regulatory approval before patient use.
Recommended Primer Sequences for BRCA1 — Engine-Designed on NM_007294.4
The three pairs below were produced by VigyanLLM's automatic primer design engine directly against the Homo sapiens BRCA1 RefSeq mRNA NM_007294.4 (7088 nt), under the engine's default constraints: 18–25 nt primers, Tm 57–72 °C (optimum 62 °C), GC 40–60%, and an 80–1500 bp amplicon (optimum 150 bp). Every oligo was then re-checked back against the accession — each forward primer matches the sense strand at its stated 1-based position and each reverse primer matches the reverse complement ending at the amplicon's final base (3 of 3 exact matches for this page).
| Pair | Forward (5′→3′) | Reverse (5′→3′) | Tm fwd / rev | GC fwd / rev | Amplicon |
|---|---|---|---|---|---|
| 1 | 5′-ACTTAGGTGAAGCAGCATCTG-3′ | 5′-TCTAGTTCAGCCATTTCCTGC-3′ | 58.7 / 58.7 °C | 47.6 / 47.6% | 154 bp (nt 4204–4357) |
| 2 | 5′-TCCCTGTTGCTGAAACCATAC-3′ | 5′-ATCAAGTCTTCACTGCCCTTG-3′ | 58.9 / 58.9 °C | 47.6 / 47.6% | 158 bp (nt 6862–7019) |
| 3 | 5′-AGGACAAAGCAGCGGATAC-3′ | 5′-TTCTTGATCTCCCACACTGC-3′ | 58.2 / 58.2 °C | 52.6 / 50.0% | 114 bp (nt 609–722) |
Pair 1 leads with a forward/reverse Tm spread of 0.0 °C, no stable hairpin at 37 °C (ΔG ≥ -0.2 kcal·mol−1 on either oligo), self-dimer Tm at most -1.3 °C, no cross-dimer signal, no pair warnings, and a Primer3 pair-quality score of 100.0/100; the suggested starting annealing temperature is 53.7 °C. Pairs 2 and 3 are alternates from the same run — compare their Tm, GC and product columns above against your chemistry (dye-based or probe), then confirm every candidate in silico and on a gel before use.
Specificity has not been verified.
The automated Primer-BLAST pass that accompanies each design came back inconclusive — no expected amplicon was parsed from the report — so treat specificity as an open question. Confirm each pair with NCBI Primer-BLAST before ordering, and remember that a transcript-based search cannot reveal genomic-repeat or pseudogene off-targets.
How to read this table: these are default whole-transcript designs — they demonstrate what the engine produces under standard constraints and are not positioned over the clinically relevant variants discussed below; to land an amplicon on a specific codon or repeat, design against that region deliberately. Thermodynamics come from Primer3's nearest-neighbor engine (SantaLucia 1998). Example output only: validate each candidate experimentally (gel sizing, efficiency series, melt-curve or probe check) before relying on it.
Design Guidance for BRCA1 Assays
BRCA1 maintains genome integrity through homologous repair of double-strand breaks, and germline variants confer high lifetime risks of breast and ovarian cancer. Two founder variants — 185delAG (c.68_69delAG) and 5382insC (c.5266dupC) — are enriched in Ashkenazi Jewish and other founder populations; both are frameshifts inside the coding sequence.
The genomic locus spans roughly 81 kb and 24 exons, with exon 11 alone about 3.4 kb — so on genomic DNA an amplicon must sit inside a single exon (or straddle a short exon–exon junction) unless you deliberately switch to long-range PCR. On cDNA the spliced transcript NM_007294.4 (7,088 nt) is the template, and primers spanning exon junctions also prevent genomic-DNA carry-over from being amplified. BRCA1 has multiple alternative transcripts — name the RefSeq your assay quantifies. Exon-level deletions and duplications escape ordinary PCR entirely and require an independent method such as MLPA. If you are screening a founder variant, centre the affected base in a short amplicon and keep both primers in variant-free sequence.
Treat these pairs as validated starting candidates, not finished assays: check the binding sites for common variants to avoid allele dropout, re-run specificity against your template type, optimise annealing by gradient around 53.7 °C, confirm a single expected band, and document everything (sequence, lot, efficiency, RefSeq) so the run is reproducible.
References
- NCBI Nucleotide — RefSeq NM_007294.4 (Homo sapiens BRCA1 mRNA).
- NCBI Gene — BRCA1 (Homo sapiens).
- SantaLucia J Jr. A unified view of polymer, dumbbell, and oligonucleotide DNA nearest-neighbor thermodynamics. Proc Natl Acad Sci USA 1998;95:1460–1465.
- Untergasser A, Cutcutache I, Koressaar T, et al. Primer3—new capabilities and interfaces. Nucleic Acids Res 2012;40:W115–W118.
- Ye J, Coulouris G, Zaretskaya I, et al. Primer-BLAST: a tool to design target-specific primers for polymerase chain reaction. Nucleic Acids Res 2009.
- Bustin SA, Benes V, Garson JA, et al. The MIQE guidelines: minimum information for publication of quantitative real-time PCR experiments. Clin Chem 2009;55:611–622.
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