Osteogenesis Imperfecta (OI) is primarily caused by mutations in genes that affect collagen production. Specifically, about 80-90% of OI cases stem from issues with the type 1 collagen genes, known as COL1A1 and COL1A2.
Understanding the Genetic Basis of OI
These genetic mutations result in the body producing either:
- Abnormally formed collagen: The structure of the collagen is incorrect, making it weak and brittle.
- Too little collagen: The body does not produce a sufficient amount of collagen, leading to reduced bone strength.
Key Genes Involved
Here’s a closer look at the genes and their roles:
| Gene | Function | Effect of Mutation |
|---|---|---|
| COL1A1 | Codes for the alpha-1 chain of type 1 collagen | Can cause the production of abnormal collagen or reduced amounts of normal collagen |
| COL1A2 | Codes for the alpha-2 chain of type 1 collagen | Can cause the production of abnormal collagen or reduced amounts of normal collagen |
These mutations are often autosomal dominant, meaning that only one copy of the mutated gene is needed to cause OI.
Implications of Collagen Defects
Collagen is a crucial protein for bone strength and structural integrity. When collagen is defective or insufficient, it leads to:
- Brittle Bones: Bones that are easily fractured.
- Other Symptoms: Including short stature, blue sclera (whites of the eyes), and hearing loss.
Summary of Causes
In short, genetic mutations in the COL1A1 and COL1A2 genes, which code for type 1 collagen, are the leading cause of OI, leading to abnormal or insufficient collagen production.
These mutations account for most cases of the condition, but other rarer genetic defects can also cause OI.
