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ERAP1 allotype may successfully identify ankylosing spondylitis
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A functionally distinct allotype of an enzyme called endoplasmic reticulum aminopeptidase 1 was associated with patients with ankylosing spondylitis vs. control participants in a study cohort.
Endoplasmic reticulum aminopeptidase 1 (ERAP1) was genetically sequenced from 17 patients with ankylosing spondylitis (AS) and 19 sex-matched controls who had non-inflammatory rheumatic conditions or non-AS inflammatory conditions such as rheumatoid arthritis and systemic lupus erythematosus. The full-length ERAP1 coding sequence was analyzed and 13 distinct allotypes based on amino acid sequences were revealed. Additional polymorphisms were seen in single nucleotide peptides that were shown previously to be associated with AS.
The researchers developed nomenclature to distinguish ERAP1 molecules using a seven-digit identification system broken into three groups: the first three digits identified coding amino acid differences; the second group of digits distinguished allotypes with conservative nucleotide changes. The third group of digits denoted molecules within allotypes that varied in intronic or untranslated regions.
Fifteen polymorphisms were identified, which included six that were previously described. Two allotypes were more prevalent in control patients and two were more prevalent in AS patients. The majority of samples were heterozygous, and certain allotypes were not found in combination with others. No allotype pair seen in controls was seen in AS patients, according to the researchers. Further assay and cellular trimming studies showed similar results.
“In almost all allotypes identified (71/72), the six variants were co-inherited, forming a backbone, suggestive of an early evolutionary branching based on these variants,” the researchers wrote.
Disclosure: A patent relating to the work has been filed.
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