ONLINE MUTATION REPORT

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 Järvelä^3,4

¹ King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
² Hospital for Children and Adolescents, University of Helsinki, Finland
³ Laboratory of Molecular Genetics, Helsinki University Central Hospital, Laboratory Services, Helsinki, Finland
⁴ Department of Medical Genetics, University of Helsinki, Helsinki, Finland

Correspondence to:
Correspondence to:
Dr Irma Järvelä
University of Helsinki, Department of Medical Genetics, Haartmaninkatu 8, PO Box 63, FIN-00290 Helsinki, Finland; irma.jarvela{at}kolumbus.fi

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.

Abbreviations: LCT, lactase gene; L:S, lactase:sucrase ratio; LTT, indirect lactose tolerance test; OMIM, Online Mendelian Inheritance in Man; SNP, single-nucleotide polymorphism

Keywords: DNA-variant; lactase persistence; lactase non persistence; lactase activity; Urban Saudi population

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