Lactase persistence genotypes and malaria susceptibility in Fulani of Mali

A Inkeri Lokki,Ville Holmberg,Marita Troye-Blomberg,Elisabeth Israelsson,Seppo Meri,Bakary Maiga,Amagana Dolo,Irma Järvelä,Ogobara K Doumbo

doi:10.1186/1475-2875-10-9

Abstract

BackgroundFulani are a widely spread African ethnic group characterized by lower susceptibility to Plasmodium falciparum, clinical malaria morbidity and higher rate of lactase persistence compared to sympatric tribes. Lactase non-persistence, often called lactose intolerance, is the normal condition where lactase activity in the intestinal wall declines after weaning. Lactase persistence, common in Europe, and in certain African people with traditions of raising cattle, is caused by polymorphisms in the enhancer region approximately 14 kb upstream of the lactase gene.MethodsTo evaluate the relationship between malaria and lactase persistence genotypes, a 400 bp region surrounding the main European C/T-13910 polymorphism upstream of the lactase gene was sequenced. DNA samples used in the study originated from 162 Fulani and 79 Dogon individuals from Mali.ResultsAmong 79 Dogon only one heterozygote of the lactase enhancer polymorphism was detected, whereas all others were homozygous for the ancestral C allele. Among the Fulani, the main European polymorphism at locus C/T-13910 was by far the most common polymorphism, with an allele frequency of 37%. Three other single-nucleotide polymorphisms were found with allele frequencies of 3.7%, 1.9% and 0.6% each. The novel DNA polymorphism T/C-13906 was seen in six heterozygous Fulani. Among the Fulani with lactase non-persistence CC genotypes at the C/T-13910 locus, 24% had malaria parasites detectable by microscopy compared to 18% for lactase persistent genotypes (P = 0.29). Pooling the lactase enhancer polymorphisms to a common presumptive genotype gave 28% microscopy positives for non-persistent and 17% for others (P = 0.11).ConclusionsPlasmodium falciparum parasitaemia in asymptomatic Fulani is more common in individuals with lactase non-persistence genotypes, but this difference is not statistically significant. The potential immunoprotective properties of dietary cow milk as a reason for the partial malaria resistance of Fulani warrant further investigation.

Highlights

Fulani are a widely spread African ethnic group characterized by lower susceptibility to Plasmodium falciparum, clinical malaria morbidity and higher rate of lactase persistence compared to sympatric tribes
In Africa, several polymorphisms in the enhancer region of the lactase gene have been suggested to be associated with lactase persistence (Figure 1)
In Africa several polymorphisms in the enhancer region of the lactase gene have been suggested to be associated with lactase persistence (Figure 1)

Summary

Introduction

Fulani are a widely spread African ethnic group characterized by lower susceptibility to Plasmodium falciparum, clinical malaria morbidity and higher rate of lactase persistence compared to sympatric tribes. Common in Europe, and in certain African people with traditions of raising cattle, is caused by polymorphisms in the enhancer region approximately 14 kb upstream of the lactase gene. During the last 10,000 years protection against malaria and lactase persistence have been two of the strongest selection forces shaping the human genome [1,2]. Lactase persistence, allowing adults to drink milk, has been shown to be beneficial in all regions where the climate and environment have made it possible to herd dairy cattle [1]. Several single nucleotide polymorphisms have been identified to be associated with lactase persistence in the enhancer region residing 13.9 kb upstream of the lactase gene (LCT) at 2q21-22 [3,7,8,9,10]

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