An isoform is a slightly different version of the same protein or gene, typically produced by a single gene through a process called alternative splicing or by the existence of closely related genes.
🔑 Definition:
An isoform is one of several structurally similar variants of a protein or gene that may differ in sequence, structure, function, or expression pattern, but originate from the same gene family or locus.
📚 Types of Isoforms:
- Protein Isoforms
Produced when a gene is transcribed and translated in different ways to create variant proteins with distinct functions or behaviors.- Example: Different isoforms of the IκB protein (like IκBα, IκBβ, and IκBε) all inhibit NF-κB, but respond differently to stimuli.
- Gene Isoforms
Often refer to different transcripts from the same gene due to:- Alternative splicing (cutting and rejoining RNA in different ways)
- Alternative promoter usage
- Alternative polyadenylation
⚙️ How Isoforms Arise:
🔄 Alternative Splicing:
- A single gene can produce multiple mRNA transcripts depending on which exons (coding regions) are included.
- This allows one gene to code for many proteins.
🧬 Gene Duplication:
- Sometimes multiple, very similar genes exist in the genome and produce isoforms with subtle differences.
🧠 Why Isoforms Matter:
| Role | Example |
|---|---|
| Functional diversity | Isoforms may localize to different tissues or have different effects. |
| Disease relevance | Some isoforms are overexpressed or underexpressed in cancer or genetic disorders. |
| Drug targeting | Some therapies aim at specific isoforms to avoid side effects. |
🧪 Example:
The p53 gene, a major tumor suppressor, produces multiple isoforms — some promote cell death, while others regulate cell cycle or repair.
📌 Summary:
Isoforms are nature’s way of getting more variety out of fewer genes. They allow a single gene to have multiple roles depending on the tissue, environment, or developmental stage. Understanding isoforms is essential for genetics, personalized medicine, and drug development.