NOD2 and Crohn’s Disease: What rs2066844 Means

Oct 3

4 min read

A single DNA marker cannot tell you whether you have Crohn’s disease. But NOD2 rs2066844 is one well-studied genetic clue about how the immune system recognizes bacteria in the gut. Also known as R702W, this variant has been associated with differences in Crohn’s disease susceptibility [R].

Here’s what the variant does, what the CC, CT, and TT results mean, and why none of them can diagnose or rule out Crohn’s disease.

Explore your NOD2 rs2066844 result in the free GeneExplorer.

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What Does the NOD2 Gene Do?

The NOD2 gene provides instructions for making a protein involved in innate immune defense. NOD2 helps certain immune cells and intestinal cells—including Paneth cells—recognize fragments of bacterial cell walls. One of the fragments it recognizes is muramyl dipeptide (MDP), a component of bacterial peptidoglycan [R] [R].

After recognizing MDP, NOD2 can activate signaling pathways involved in immune responses. NOD2 is also connected to autophagy, a process cells use to capture and break down microbes and damaged cell material [R].

This bacterial-sensing role helps explain why NOD2 has been studied in Crohn’s disease. The intestine is constantly exposed to microbes, and Crohn’s disease involves a complex interaction between immune responses, intestinal biology, genetics, and environmental factors. NOD2 is only one part of that system [R].

What Is NOD2 rs2066844 (R702W)?

rs2066844 is a single-letter DNA change in the NOD2 gene, written as c.2104C>T. It changes the amino acid at position 702 of the NOD2 protein from arginine to tryptophan, which is why it is also called R702W or Arg702Tr [R].

In the forward-strand notation used for this report, the T allele is the variant allele associated with increased Crohn’s disease susceptibility. Functional studies suggest that Crohn’s-associated NOD2 variants, including R702W, can respond less effectively to bacterial components such as MDP in laboratory models. The precise way this contributes to disease in people is still being studied [R, R].

NOD2 has other Crohn’s-associated variants too. A result for rs2066844 covers this one position, not every variant in NOD2 or every genetic factor linked to Crohn’s disease [R].

What Do CC, CT, and TT Mean?

These genotype labels show how many copies of the T allele appear at rs2066844:

Genotype	What it means at this marker
CC	No T allele at rs2066844. This does not rule out Crohn’s disease or other genetic influences.
CT	One copy of the T allele associated with increased susceptibility.
TT	Two copies of the T allele at this position. This is associated with higher susceptibility.

The table describes one SNP only. A CC result does not mean someone cannot develop Crohn’s disease, and a CT or TT result does not mean they will.

What Does Research Say About rs2066844 and Crohn’s Risk?

A 2021 study analyzed genetic and electronic health record data from the DiscovEHR cohort. In its genotype model, the researchers reported an odds ratio of 1.30 for people with one R702W copy and 4.02 for people with two copies, compared with the reference genotype [R].

These are cohort-level odds estimates, not a personal probability. The study’s adult comparison included 50,305 controls and 984 people identified with inflammatory bowel disease (IBD) through health records. The authors noted that this was not a pure Crohn’s disease cohort, although the ten people with two R702W copies identified among its IBD cases had Crohn’s diagnoses. The estimate for two copies was based on a small number of cases and has a wider confidence interval [R].

An odds ratio is not the same as an individual’s absolute chance of developing a condition. Your personal health cannot be predicted from this SNP alone, and the study’s figures should not be read as a forecast for any one person.

Why One NOD2 Result Is Not the Whole Story

Crohn’s disease is influenced by many genetic and non-genetic factors. NOD2 is one of several genes involved in intestinal immune function; other studied genes include IL23R, ATG16L1, and IRGM. Researchers have identified many genetic variants associated with Crohn’s disease, and their effects vary [R].

A single rs2066844 result also does not show which microbes are present in your gut, measure current inflammation, or reveal whether your NOD2 protein is functioning a particular way. DNA can offer clues about inherited tendencies, but it is not a microbiome test or a measure of current gut health. For more context, read our guide to gut health, the microbiome, and genetics and explore IL23R and inflammatory signaling.

Can NOD2 rs2066844 Diagnose Crohn’s Disease?

No. Crohn’s disease is diagnosed using a person’s health history, examination, and appropriate medical tests. Depending on the situation, clinicians may use blood or stool tests, endoscopy, biopsies, or imaging. A consumer DNA marker by itself cannot diagnose Crohn’s disease or rule it out [R].

If you have persistent digestive symptoms or concerns about a genetic result, discuss them with a qualified healthcare professional.

Frequently Asked Questions

Does having the T allele mean I will develop Crohn’s disease?

No. The T allele is associated with susceptibility, but it does not determine whether someone will develop Crohn’s disease. Many people with a risk-associated variant do not develop the condition, and people without this variant can still develop it.

Does a CC result mean I cannot get Crohn’s disease?

No. CC means that the T allele is not present at rs2066844. It says nothing about other NOD2 variants, other genes, or non-genetic factors that may contribute to Crohn’s disease.

Is NOD2 the same as Crohn’s disease?

No. NOD2 is a gene involved in immune signaling. Some variants in NOD2 are associated with Crohn’s susceptibility, but the gene is only one part of the broader biology of the disease.

Does this result tell me about my gut microbiome?

No. rs2066844 is a DNA marker. It does not identify the microbes in your gut or measure microbiome balance.

Explore NOD2 in Free GeneExplorer

GeneExplorer can check supported raw DNA files for NOD2 rs2066844 and show whether your result includes zero, one, or two copies of the T allele. Read more on the NOD2 GeneExplorer page, or start with free GeneExplorer.