Several mutations in the COL1A1 gene
are responsible for the ‘Arthrochalasia Type’ of Ehlers-Danlos Syndrome (EDS).
These genetic changes lead to the production of defective pro-α1 (I) chain with
missing a critical segment. The absence of this segment interferes with the
assembly and structure of type I collagen molecules and the processing of these
molecules into collagen fibrils.
Tissues that are rich in type I collagen — such as
the skin, bones, and tendons are most affected by this change.
A mutation in the COL1A1 gene has
also been shown to cause the ‘Classic Type’ of Ehlers-Danlos syndrome. This
mutation changes one of the amino acids used to build the pro-α1 (I) chain.
Specifically, this genetic change replaces the amino acid ‘arginine’ with the
amino acid ‘cysteine’ at position 134. The altered protein interferes with
other collagen-building proteins, disrupting the structure of type I collagen
fibrils and trapping collagen in the cell. But researchers believe that this COL1A1 mutation only rarely
underlies the signs and symptoms of classic Ehlers-Danlos syndrome.
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