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COL18A1 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

COL18A1 gene

The COL18A1 gene is responsible for producing collagen XVIII, a protein essential for the structure of basement membranes and eye development.

Overview

The COL18A1 gene provides instructions for making the protein that forms collagen XVIII. This collagen is found in basement membranes, which are thin, sheet-like structures that separate and support cells throughout the body. There are three versions (isoforms) of the collagen XVIII alpha 1 subunit, which vary in length and distribution; the short version is found throughout the body, including the eye, while the two longer versions are primarily located in the liver.

Additionally, a fragment of collagen XVIII can be processed into a protein called endostatin, which acts as an anti-angiogenic factor by blocking the formation of new blood vessels (angiogenesis). While the exact function of collagen XVIII is not fully understood, all isoforms appear to be involved in the normal development of the eye.

Health Conditions Related to Genetic Changes

Knobloch syndrome

At least a dozen mutations in the COL18A1 gene have been identified in people with Knobloch syndrome, a condition characterized by severe vision problems and an occipital encephalocele (a skull defect). These mutations generally lead to the loss of collagen XVIII, either by creating an abnormally short genetic blueprint or by replacing single amino acids. The loss of one or all isoforms of this protein is believed to cause the signs and symptoms of the syndrome.

Genomic Location

The COL18A1 gene is found on chromosome 21.

Frequently Asked Questions

Knobloch syndrome typically causes severe myopia (nearsightedness) that can be so extreme it leads to retinal detachment. Many patients also develop optic nerve atrophy, cataracts, or retinal vascular abnormalities, which can worsen vision over time. Regular ophthalmologic exams are essential to monitor and manage these changes early. How is a COL18A1 mutation diagnosed in a patient suspected of Knobloch syndrome?::Diagnosis usually involves a combination of clinical evaluation (looking for severe myopia, occipital encephalocele, or other brain abnormalities) and genetic testing. A targeted gene panel or whole exome sequencing that includes COL18A1 is performed, and any identified variants are compared against known pathogenic mutations. Is Knobloch syndrome inherited in an autosomal recessive or dominant pattern?::Most reported cases are autosomal recessive, meaning both parents carry one mutated copy of COL18A1. However, rare de novo mutations can occur, so genetic counseling is recommended for families to understand recurrence risk. Can prenatal testing detect COL18A1 mutations for families at risk of Knobloch syndrome?::Yes. If a pathogenic variant has been identified in a family, chorionic villus sampling or amniocentesis can be used to test the fetus for that specific mutation. Noninvasive prenatal testing (cell-free DNA) is not yet reliable for COL18A1.
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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