Clearly, genetics is one of the factors that causes DAO Deficiency. In the same family unit, its members share this deficiency and many chronic pathologies that until now were considered “hereditary”.
The enzyme alteration or what the cause of the genetic deficiency is, has not been properly studied yet, but it may be related to the genetic polymorphism of a Dao enzyme nucleotide. According to the National Center for Biotechnology Information (NCBI) data, the gene encoding DAO is a polymorphic gene. The genetic sequence of DAO is found in a fragment located on chromosome 7 (7q34-q36) of the human genome and it consists of 5 exons and 4 introns.
Many differences between the sequence of exons and introns of this gene, due to their genetic polymorphism, have been found. In total, there are 85 single nucleotide polymorphisms located and identified in the DAO human gene (17 in exons, of which 7 have substitution of amino acids).
Among all polymorphisms found in DAO sequence, it has been proved that only one of the 7 polymorphisms, (with reference rs1049793) located in the third exon, has relation with low DAO activity.
Carriers of this polymorphism, present lower DAO activity than controls with significant effect. Preliminary studies suggest that this polymorphism has an overall prevalence close to 0.30% (30% of mutated alleles).
Other studied polymorphisms of the same type of substitution of amino acids, do not show changes in enzyme DAO activity.