How is "Hay Fever" encoded by the genome?
Are you one of the millions of people who dread the coming of spring because it means you will be too busy sneezing to enjoy the nice weather? Hay fever is one of the most common types of allergies. The word “hay” is misleading, as people with hay fever can be allergic to the pollen of hundreds of different types of grasses, flowers, and weeds.
The official medical name for hay fever is seasonal allergic rhinitis. There are several factors that contribute to the development of hay fever, and research shows that the genes you inherit from your parents are one of them.
Is Hay Fever Genetic?
For people who have hay fever, the arrival of spring is not always a happy event. Hay fever is usually worse between late March and September, especially when it's warm, humid, windy, and pollen count is at its highest. The prevalence of hay fever varies among populations and has environmental and genetic risk factors. Family and twin studies have estimated that the contribution of genetic factors for hay fever is 33-91%.
Comorbidity between asthma, hay fever, and eczema is common, and previous genome-wide association studies have, apart from identifying a large number of genetic variants associated with risk of diseases, also found evidence of genetic overlap between the diseases. Many of the identified target genes were predicted to influence the function of immune cells, and only six loci were identified to have disease-specific effects. Many previous GWA studies for asthma, hay fever, and eczema have been conducted in different cohorts that were subsequently analyzed to increase statistical significance.
The aim for the particular study was to explain a larger part of the genetic background of self- reported asthma, hay fever, and eczema and identify possible novel disease-specific effects. In total, 136,545 Caucasians from the UK biobank were enrolled. Although the phenotypes in the UK Biobank are self-reported, the questions are well defined and identical for all participants. Hay fever and eczema could not be separated for most participants since they had primarily answered yes or no on whether they had either hay fever or eczema. However, to investigate hay fever and eczema individually, hay fever (N cases = 18,915) and eczema (N cases = 7,884) were also separately analyzed in a smaller subset of UK Biobank participants. A total of 27 and 18 loci were identified for hay fever and eczema respectively, among which rs3918226 in the NOS3 gene, rs1330303 in the BNC2 gene and rs12343737 in the TNC gene were associated with hay fever. Moreover, the EAGLE consortium GWA summary statistics which consists of 21,000 atopic dermatitis 733 (eczema) cases and 96,000 controls, were used to replicate novel loci for hay fever/eczema, and eczema analyzed separately.
Interestingly, one of the strongest associations for hay fever/eczema found within the FLG locus was more significantly associated with eczema when this phenotype was analyzed separately. In contrast, this variant was not associated with hay fever when hay fever was analyzed separately. It was, however, associated with asthma. This agrees with the previous GWA study (Ferreira et al) where an SNP at the FLG locus was shown to be specifically associated with eczema. However, a different study has shown that mutations within the FLG locus are associated with eczema starting in the first year of life, and later these mutations are associated with both asthma and hay fever. This is an example of the typical progression of allergic diseases that often begin early in life, commonly referred to as the atopic march. If you would like to know more about this research, you can read the study:
https://pubmed.ncbi.nlm.nih.gov/31361310/
Learn About Your Genetic Traits on Genomelink
Along with asthma and eczema, the genetic tendency to develop seasonal allergic rhinitis is called atopy. If you have an atopic disease like hay fever, your immune system produces immunoglobulin E (lgE) antibodies in an effort to bind the allergens. Unfortunately, an overproduction of lgE is what causes the symptoms associated with allergies. A 2018 study led by researcher Johannes Waage identified 41 individual genes that increase a person’s risk for developing hay fever. Twenty of those genes were previously unidentified. Genetics aren’t the only risk factor for seasonal allergies. People who are consistently exposed to other common allergens such as pet hair, dust, mold, or air pollution have an increased risk of developing hay fever and perennial allergic rhinitis (allergies that are present throughout the year).
Having a genetic link to hay fever or other conditions doesn’t mean you will definitely develop that condition, but it does mean you are at a higher risk than others. The more you understand about your physical and mental well-being through genetic testing, the more opportunities you have to protect your health. Learning about your ancestry is fun and informative, but your ancestry DNA test can tell you so much more about your heritage. Upload the raw data from your DNA testing kit to Genomelink to learn more.
Are you interested in learning more about your genetic tendency for hay fever? You can log in to your Genomelink TRAITS to see this new genetic trait.
