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COL9A1 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

COL9A1 gene

The COL9A1 gene provides instructions for creating a vital component of type IX collagen, a protein essential for the structure and support of cartilage and other connective tissues.

Normal Function

The COL9A1 gene provides instructions for making part of a large molecule called type IX collagen. Collagens are a family of proteins that strengthen and support connective tissues, such as skin, bone, cartilage, tendons, and ligaments. In particular, type IX collagen is an important component of cartilage, which is a tough, flexible tissue that makes up much of the skeleton during early development. Most cartilage is later converted to bone, except for the cartilage that continues to cover and protect the ends of bones and is present in the nose and external ears.

Type IX collagen is made up of three proteins that are produced from three distinct genes: one α1(IX) chain, which is produced from the COL9A1 gene, one α2(IX) chain, which is produced from the COL9A2 gene, and one α3(IX) chain, which is produced from the COL9A3 gene. Type IX collagen is more flexible than other types of collagen molecules and is closely associated with type II collagen. Researchers believe that the flexible nature of type IX collagen allows it to act as a bridge that connects type II collagen with other cartilage components. Studies have shown that type IX collagen also interacts with the proteins produced from the MATN3 and COMP genes.

Health Conditions Related to Genetic Changes

Multiple epiphyseal dysplasia

At least one mutation in the COL9A1 gene has been found to cause dominant multiple epiphyseal dysplasia, a disorder of cartilage and bone development that primarily affects the ends of the long bones in the arms and legs (epiphyses). The identified mutation, called a splice-site mutation, involves the addition of one DNA building block (nucleotide) near an area of the gene called exon 8 (written as 1-bp ins, IVS8, T, +3). This mutation disrupts the way the gene's instructions are used to make the α1(IX) chain, resulting in a deletion of several protein building blocks (amino acids). It is not known how this mutation in COL9A1 causes the signs and symptoms of dominant multiple epiphyseal dysplasia.

Stickler syndrome

MedlinePlus Genetics provides information about Stickler syndrome.

Other Names for This Gene

  • alpha 1 type IX collagen
  • cartilage-specific short collagen
  • collagen IX, alpha-1 polypeptide
  • collagen type IX alpha 1
  • collagen, type IX, alpha 1
  • DJ149L1.1.2
  • FLJ40263
  • MED

Frequently Asked Questions

The earliest signs often include mild joint pain during or after activity, especially in the knees, hips, or ankles, and a subtle limp. Children may also experience occasional swelling of the joint ends (epiphyses) and reduced stamina for sports. Watch for persistent pain that interferes with school activities, difficulty climbing stairs, or a noticeable decrease in height growth velocity, and bring these concerns to a pediatric orthopedist. How is the diagnosis of COL9A1‑related multiple epiphyseal dysplasia confirmed?::Diagnosis combines clinical evaluation, radiographic findings (irregular, flattened epiphyses on X‑ray), and molecular genetic testing. After a clinician suspects the disorder based on symptoms and imaging, a blood sample is sent for targeted sequencing of the COL9A1 gene (or a multigene panel for skeletal dysplasias). A pathogenic variant confirms the diagnosis. Prenatal testing is possible if the familial variant is known. Are there lifestyle or treatment measures that can slow joint degeneration in COL9A1‑related disease?::While the genetic defect cannot be reversed, several strategies can mitigate wear‑and‑tear: maintain a healthy weight to reduce joint load; engage in low‑impact aerobic exercise (swimming, cycling) to strengthen surrounding muscles; use orthotic shoe inserts or custom braces to improve joint alignment; and consider periodic NSAID therapy under physician guidance for pain control. In some cases, orthopedic surgeons may recommend corrective osteotomies or joint‑preserving procedures when deformities become severe. My sister, who carries the same COL9A1 mutation, is planning to have children. What is the inheritance risk for her offspring?::COL9A1 mutations that cause dominant multiple epiphyseal dysplasia follow an autosomal‑dominant pattern. Each child has a 50 % chance of inheriting the pathogenic variant. The severity can vary even within the same family, so a child who inherits the mutation may have milder, similar, or more pronounced symptoms. Genetic counseling before conception is recommended to discuss testing options and family planning.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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