Alcohol dehydrogenase-2*2 allele is associated with decreased prevalence of fetal alcohol syndrome in the mixed-ancestry population of the Western Cape Province, South Africa
Background: Fetal alcohol syndrome (FAS) is particularly common among the mixed-ancestry population of the Western Cape Province of South Africa and occurs at a frequency of 0.0392-0.0429 (39.2-42.9 of 1000) among 5- to 9-year-old school entrants. While FAS is clearly caused by an environmental insult, studies in twins and mice support a significant genetic contribution to risk for FAS. It is likely that the development of FAS following excessive alcohol exposure is influenced by genetic factors in both the mother and the child. Known polymorphisms of the alcohol dehydrogenase-2 (ADH2) gene resulting in isozymes with different alcohol oxidizing capacities were investigated as possible candidates for influencing the risk for FAS. Methods: Genotyping was undertaken for the ADH2 locus in 56 FAS-affected children, their 56 mothers, and 178 control individuals of mixed ancestry from the same geographic region. The ADH2 alleles were analyzed for the three groups and the allele frequencies of the mother and FAS-affected children were independently compared with the control group. Results: The ADH2*2 allele was found to be significantly more common in the control group than in the mothers of FAS-affected children (p = 0.025 ± 0.004) and in the FAS subjects (p = 0.025 ± 0.004). The ADH2*3 allele frequency was low and was not significantly different between the groups. Conclusion: The ADH2*2 allele is significantly more common in control individuals, suggesting that it may either confer protection or be a marker for a protective effect against FAS among individuals of mixed ancestry in the Western Cape Province of South Africa.