The T/G−13915 variant upstream of the lactase gene (LCT) is the founder allele of lactase persistence in an urban Saudi population
- F Imtiaz1,
- E Savilahti2,
- A Sarnesto2,
- D Trabzuni1,
- K Al-Kahtani1,
- I Kagevi1,
- M S Rashed1,
- B F Meyer1,
- I Järvelä3,4
- 1King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
- 2Hospital for Children and Adolescents, University of Helsinki, Finland
- 3Laboratory of Molecular Genetics, Helsinki University Central Hospital, Laboratory Services, Helsinki, Finland
- 4Department of Medical Genetics, University of Helsinki, Helsinki, Finland
- Correspondence to: Dr Irma Järvelä University of Helsinki, Department of Medical Genetics, Haartmaninkatu 8, PO Box 63, FIN-00290 Helsinki, Finland;
- Received 11 May 2007
- Accepted 13 July 2007
- Revised 1 July 2007
Background: The prevalence of lactase persistence is high in Saudi Arabia.
Objective: To identify a DNA variant for the lactase persistence/non-persistence trait in adult Arabs in Saudi Arabia.
Methods: We sequenced DNA from 432 anonymous neonatal blood donors from five different regions of Saudi Arabia to cover the 400 bp region surrounding the previously identified lactase persistence/non-persistence variant C/T−13910 residing in intron 13 of the MCM6 gene.
Results: Two anonymous blood donors carried the C/T−13910 genotype. One variant, T/G −13915, residing 5 bp upstream of the C/T−13910 variant, was present in 332 of 432 (76.9%) of the neonatal samples, compatible with previous prevalence figures of lactase persistence in urban Saudi populations. Determination of disaccharidase activities in 25 intestinal biopsy samples showed a highly significant correlation between lactase activity and the T/G−13915 genotypes (p<0.001; Fisher exact test) as well as between the L:S ratio and the aforementioned genotypes (p<0.001; Fisher exact test).
Conclusion: The T/G−13915 variant is the founder mutation of lactase persistence in an urban Saudi population. The results obtained here have implications for genetic testing of adult-type hypolactasia and to analysis of human evolution, the origin of cattle domestication and migrations of the populations in the Arabian peninsula.
- LCT, lactase gene
- L:S, lactase:sucrase ratio
- LTT, indirect lactose tolerance test
- OMIM, Online Mendelian Inheritance in Man
- SNP, single-nucleotide polymorphism
Competing interests: None declared.