What is the Difference Between COL1A1 and COL1A2

COL1A1 and COL1A2 are two genes that, respectively, encode the two α1 chains and a single α2 chain in the Type I collagen. Type I collagen is a fibrillar collagen and the most abundant type in the body. It is a heterotrimer and is the key structural protein in several tissues.

The key difference between COL1A1 and COL1A2 is their function. COL1A1 produces proalpha-1 chain of type I collagen, while COL1A2 produces proalpha-2 chain of type I collagen.

CONTENTS

1. Overview and Key Difference
2. What is COL1A1  
3. What is COL1A2
4. Similarities – COL1A1 and COL1A2
5. COL1A1 vs COL1A2 in Tabular Form
6. Summary – COL1A1 vs COL1A2
7. FAQ – COL1A1 and COL1A2

What is COL1A1?

The COL1A1 is a gene located on the long (q) arm of chromosome 17 between positions 21.3 and 22.1. This gene is responsible for the production of a chain in the type 1 collagen called proalpha-1 chain or pro α1 (I). There are two proalpha-1 chains in type 1 collagen heterotrimer. Two pro-alpha1(I) chains and a pro-alpha2(I) chain (produced by the COL1A2 gene) combine to make a molecule of type I procollagen. Moreover, type I procollagen is processed by other enzymes outside the cell in order to convert it into a complete type I collagen molecule.

Figure 01: COL1A1

Mutations in the COL1A1 gene are linked to conditions such as Ehlers–Danlos syndrome vascular type, Ehlers–Danlos syndrome arthrochalasia type, Ehlers–Danlos syndrome classical type, osteogenesis imperfecta type I, type II, type III, and type IV, and osteoporosis.

What is COL1A2?

COL1A2 gene normally provides instructions for making a part of a large molecule called type I collagen. A part of type I collagen called the pro-α2(I) chain is produced from the COL1A2 gene. The location of this gene is chromosome 7q21.3.

Figure 02: COL1A2

Furthermore, people with certain COL1A2 mutations have signs and symptoms of both osteogenesis imperfecta and arthrochalasia type of Ehlers-Danlos syndrome. These genetic mutations may include duplications of a large part of the gene, deletions of a major segment of the pro-α2(I) chain or genetic changes that produce an abnormally shortened version of the pro-α2(I) chain.

Similarities Between COL1A1 and COL1A2

1. COL1A1 and COL1A2 are two genes that make 2 pro chains of type 1 collagen.
2. Both these two genes work collectively.
3. The functions of these genes help provide structure to the skin, bones, tendons, and ligaments.
4. Mutations in these genes result in different disorders.

Difference Between COL1A1 and COL1A2

Definition

1. COL1A1 is a gene that provides instructions for making part of a type I collagen called the pro-α1(I) chain.
2. COL1A2 is a gene that provides instructions for making part of a type I collagen called the pro-α2(I) chain.

Number of Chains Produced

1. COL1A1 gene produces two pro-α1(I) chain of type I collagen heterotrimer.
2. COL1A2gene produces one pro-α2(I) chain of type I collagen heterotrimer.

Location

1. The location of COL1A1 gene is chromosome 17q between 21.3 and 22.1 positions.
2. The location of COL1A2gene is chromosome7q21.3.

Length and Exons

1. The COL1A1 gene is 18 kb in length and consists of 52 exons.
2. The COL1A2 gene is 36.67 kb in length and consists of 52 exons.

Encodes for

1. The protein of COL1A1gene consists of 1464 amino acids and 140-kDa in size.
2. The protein of COL1A2 gene consists of 1366 amino acids and 129 kDa in size.

Diseases Associated With

1. Mutations in the COL1A1 gene result in conditions such as Ehlers–Danlos syndrome vascular type, Ehlers–Danlos syndrome arthrochalasia type, Ehlers–Danlos syndrome classical type, osteogenesis imperfecta type I, osteogenesis imperfecta type II, osteogenesis imperfecta type III, osteogenesis imperfecta type IV and osteoporosis.
2. Mutations in COL1A2 result in osteogenesis imperfecta and arthrochalasis form of Ehlers-Danlos syndrome.

The following table summarizes the difference between COL1A1 and COL1A2.

Summary – COL1A1 vs COL1A2

Type 1 collagen is a protein found in skin, tendons, ligaments, and bone. Most supplements of type 1 collagen come from cows. Type I collagen molecule is a heterotrimeric molecule. COL1A1 and COL1A2 are two genes that make 2 pro chains of type 1 collagen. COL1A1 provides instructions for making two pro-α1(I) chains of type 1 collagen, while COL1A2 provides instructions for making one pro-α2(I) chain of type 1 collagen. This is the summary of the difference between COL1A1 and COL1A2.

FAQ: COL1A1 and COL1A2

1. What does the COL1A1 gene do?

• The COL1A1 gene provides instructions for making part of a large structural protein called type I collagen. This part is a pro-α1(I) chain. There are two pro-α1(I) chains in type 1 collagen protein. Moreover, type 1 collagen strengthens and supports many tissues in the body, including bone, tendon, cartilage, skin, and the white part of the eye.

2. What is COL1A1Ehlers-Danlos syndrome?

• Ehlers-Danlos syndrome refers to a group of disorders that affect the connective tissues that support the skin, blood vessels, bones, and other organs. Several forms of Ehlers-Danlos syndrome are caused by mutations in the COL1A1 gene, which occur in one copy of the gene in each cell.

3. What are the main symptoms of the Ehlers-Danlos syndrome?

• There are various types of Ehlers-Danlos syndrome. However, the most common signs and symptoms of this syndrome include overly flexible joints, stretchy skin, and fragile skin. Moreover, people with vascular Ehlers-Danlos syndrome often have distinctive facial features of a thin upper lip, thin nose, small earlobes, and prominent eyes.

4. What is the function of COL1A2 gene?

• COL1A2 gene is located in chromosome 7q21.3. The COL1A2 gene normally provides instructions for making a component of type I collagen called the pro-α2(I) chain. There is only one chain of pro-α2(I) in type 1 collagen heterotrimer.

5. What diseases are caused by COL1A2 gene mutation?

• It has been found that heterozygous mutations in the COL1A2 gene, which encodes the alpha2 chain of type I collagen, generally result in either osteogenesis imperfecta or the arthrochalasis form of Ehlers-Danlos syndrome.

Reference:

1. “COL1A2 Gene: Medlineplus Genetics.” MedlinePlus, U.S. National Library of Medicine.
2. “COL1A1 Collagen Type I Alpha 1 Chain [Homo Sapiens (Human)] – Gene.” National Center for Biotechnology Information, U.S. National Library of Medicine.

Image Courtesy:

1. “PBB GE COL1A1 202312 s at fs” By Genomics Institute of the Novartis Research Foundation (CC BY-SA 3.0) via Commons Wikimedia
2. “PBB GE COL1A2 202403 s at fs” By Genomics Institute of the Novartis Research Foundation (CC BY-SA 3.0) via Commons Wikimedia

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