COL2A1 (cont.)

Kniest dysplasia -- Kniest dysplasia is caused by mutations in the COL2A1 gene. The mutations cause shorter-than-normal pro-alpha1(II) type II collagen protein chains to be produced. When these chains interact to form triple-helical molecules, these short chains are combined with longer, normal-length chains. The resulting abnormal molecule becomes shorter than normal, causing the signs and symptoms of Kniest dysplasia.

Spondyloepimetaphyseal dysplasia, Strudwick type -- Mutations in the COL2A1 gene can cause spondyloepimetaphyseal dysplasia, Strudwick type. All of the mutations characterized to date in COL2A1 cause an amino acid substitution; specifically, the amino acid glycine is replaced by another amino acid. This change inhibits the formation of stable, triple-stranded, helical collagen molecules. This type of collagen is found primarily in cartilage, the vitreous body of the eye, the inner ear, and the center portion of vertebral discs. Type II collagen is also critical for embryonic development and growth. Because of this critical role, mutations in the COL2A1 gene can result in skeletal and eye aberrations.

Spondyloepiphyseal dysplasia congenita -- Mutations in the COL2A1 gene cause spondyloepimetaphyseal dysplasia congenita. Some mutations cause segments of the gene to be skipped when a protein is being made, resulting in shorter-than-normal pro-alpha1(II) type II collagen chains. Some of these short chains are integrated into mature type II collagen, while other chains are retained inside the cell, making them unusable for collagen production. Other mutations cause an incorrect amino acid replacement in the pro-alpha1(II) type II collagen chain. This mistake changes the function, and sometimes the structure of the collagen, and inhibits the normal production of mature type II collagen. Mutations in the COL2A1 gene can result in the skeletal and eye abnormalities seen in this syndrome.

Stickler syndrome -- Mutations in the COL2A1 gene are the cause of Stickler syndrome, COL2A1. Some of these mutations result in the production of a protein that is too short to be incorporated into a functional type II collagen molecule. Most of the COL2A1 mutations that cause Stickler syndrome however involve a premature termination signal in on copy of the gene. This results in mRNA that is broken down by the cell before a protein can be made. Because of this, cells produce only half of the normal amount of pro-alpha 1(II) type II collagen chains. This shortage results in underproduction of type II collagen in cartilage, the eye, inner ear, and the center portion of vertebral discs, causing the symptoms of Stickler syndrome, COL2A1.

The COL2A1 gene is located on the long (q) arm of chromosome 12 in region 12q13.11-13.2.

Last Editorial Review: 6/9/2016

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