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- Title
A novel polymorphism associated with lactose tolerance in Africa: multiple causes for lactase persistence?
- Authors
Ingram, Catherine J E; Elamin, Mohamed F; Mulcare, Charlotte A; Weale, Michael E; Tarekegn, Ayele; Raga, Tamiru Oljira; Bekele, Endashaw; Elamin, Farouk M; Thomas, Mark G; Bradman, Neil; Swallow, Dallas M
- Abstract
Persistence or non-persistence of lactase expression into adult life is a polymorphic trait that has been attributed to a single nucleotide polymorphism (C-13910T) in an enhancer element 13.9 kb upstream of the lactase gene (LCT). The -13910*T allele occurs at very high frequency in northern Europeans as part of a very long haplotype (known as A), and promotes binding of the transcription factor Oct-1. However, -13910*T is at very low frequency in many African milk drinking pastoralist groups where lactase persistence phenotype has been reported at high frequency. We report here for the first time, a cohort study of lactose digester and non-digester Sudanese volunteers and show there is no association of -13910*T or the A haplotype with lactase persistence. We support this finding with new genotype/phenotype frequency comparisons in pastoralist groups of eastern African and Middle Eastern origin. Resequencing revealed three new SNPs in close proximity to -13910*T, two of which are within the Oct-1 binding site. The most frequent of these (-13915*G) is associated with lactose tolerance in the cohort study, providing evidence for a cis-acting effect. Despite its location, -13915*G abolishes, rather than enhances Oct-1 binding, indicating that this particular interaction is unlikely to be involved in lactase persistence. This study reveals the complexity of this phenotypic polymorphism and highlights the limitations of C-13910T as a diagnostic test for lactase persistence status, at least for people with non-European ancestry.
- Publication
Human genetics, 2007, Vol 120, Issue 6, p779
- ISSN
0340-6717
- Publication type
Journal Article
- DOI
10.1007/s00439-006-0291-1