Background: Adult-type hypolactasia (lactase non-persistence) is a common cause of gastrointestinal symptoms. Several DNA sequence variants have been identified for the lactase-persistence/non-persistence (LP/LNP), the most common being the C to T residing -13910 bp upstream of the lactase gene (LCT). We have analysed sequence variants of LP/LNP in subjects originating from Northern Russia.
Methods: A total of 148 subjects with gastrointestinal complaints were genotyped covering about 400 bp around the -13910C/T variant using direct PCR-sequencing. All patients were interviewed about milk-related symptoms using the questionnaire. Disaccharidase activities were measured from intestinal biopsy specimens of the index person.
Results: The prevalence of the -13910C/C genotype among 148 patients was 28.4%. A G to A variant residing 13914 bp upstream from the LCT gene (-13914G>A) was identified in one participant carrying the -13910C/C genotype. In two biopsy specimens her lactase activity was above the generally accepted cut off level for adult-type hypolactasia, 10U/g protein. Three other family members also carried the -13914G>A genotype. Among eight family members five had the LNP genotype -13910C/C.
Conclusion: A rare variant G to A residing 13914 bp upstream of the LCT gene was identified in a subject carrying the more frequent variant -13910C/C. The -13914G>A variant in heterozygous state was associated with increased lactase activity, suggesting that the increased lactase activity is most likely to be associated with the -13914G>A variant. Further studies need to be done to confirm the functional role of this variant.