About APOE
The APOE gene (apolipoprotein E) on chromosome 19q13.32 encodes a glycoprotein involved in lipid metabolism and cholesterol transport. The APOE ε4 allele is the strongest genetic risk factor for late-onset Alzheimer's disease. APOE spans ~3.6 kb with 4 coding exons, making it one of the smallest clinically important genes for primer design.
NCBI Gene ID: 348 | RefSeq: NM_000041.4 | Genomic: NC_000019.10 (44905791-44909393)
APOE Primer Design Challenges
- Allele discrimination: ε2 (rs7412) and ε4 (rs429358) differ by single nucleotides in exons 4, requiring allele-specific primers or RFLP-based design
- Small gene size: Only ~3.6 kb limits intronic primer placement options between exons
- GC-rich regions: Exon 4 has ~60% GC content around the ε2/ε3/ε4 polymorphic sites
- High sequence homology: APOE promoter region shares homology with APOC1 pseudogene nearby
- Multiplex compatibility: Genotyping assays often require multiplex PCR with internal controls
Recommended Primer Design Parameters for APOE
| Parameter | Standard Exons (1–3) | Exon 4 (Genotyping) |
|---|---|---|
| Primer length | 20-22 nt | 22-26 nt |
| GC content | 45-55% | 50-60% |
| Tm | 58-62°C | 60-66°C |
| Amplicon size | 150-300 bp | 200-300 bp |
| Annealing temp | 58-60°C | 62-65°C (for allele-specific) |
| PCR additive | Standard | 3-5% DMSO for GC-rich regions |
Key SNPs to Avoid in Primer Binding Sites
When designing APOE primers, account for these defining polymorphisms:
- rs429358 (c.388T>C, p.Cys130Arg) — Defines ε4 allele; critical for Alzheimer's risk genotyping
- rs7412 (c.526C>T, p.Arg176Cys) — Defines ε2 allele; protective against Alzheimer's
- rs440446 — Promoter variant affecting gene expression levels
- rs405509 (T>G promoter SNP) — Associated with altered APOE expression
- rs769449 — Intron 1 variant in LD with ε4, useful for tagging
Clinical Validation Required
All APOE 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.
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Pre-configured with APOE-specific parameters. Enter exon number or genomic coordinates.
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