DNA from blood
Mutation assay for the detection of the transition -13910C>T upstream of the human lactase gene using LightCycler® with differentiation from possible neighboring polymorphisms.
The uptake of milk and other lactose-containing food may causes indigestibilities. Such symptoms are often assigned to the syndrome of the hereditary lactose intolerance (LIT) that manifests in adults. The most frequent symptoms are lactose maldigestion, meteorism (tympanites), distension, and diarrhoea (Obermayer-Pietsch, 2004, Journal für Mineralstoffwechsel, 11(3):20-23). Lactose tolerance may be caused by activating mutations in the MCM6 gene (minichromosome maintenance gene) on chromosome 2, near the lactase gene (lactase phlorizin hydrolase gene, LPH gene) (Olds and Sibley, 2003, Hum Mol Genet, 12(18):2333-2340). Activating mutation denotes a mutation where the carrier receives a biological advantage compared to the non-mutated individual. In this example, it is the tolerance towards lactose. The mutation, detectable through this assay, is a base exchange from C (wild type) to T (mutation) at the nucleotide position -13910 upstream of the lactase gene. Homozygous carriers of the mutation have a livelong lactose tolerance. In heterozygous carriers it is supposed that the lactose intolerance may be partially compensated (Obermayer-Pietsch, 2004, Journal für Mineralstoffwechsel, 11(3):20-23; Sibley, 2004, Am J Pharmacogenomics, 4(4):239-245). Wild type carriers develop a lactase deficiency after breastfeed that proceeds with age leading to lactose intolerance. As a consequence of lactase deficiency lactose is not cleaved effectively into the monosaccharides glucose and galactose. Because not-cleaved lactose can not be reabsorbed by the human organism the symptoms mentioned above can typically be found (Srinivasan and Minocha, 1998, Postgraduate Medicine, 104(3):109-111, 115-116, 122-123). The loss of lactase activity usually starts after the ablactating and ends in adult at the status of lactose intolerance. The prevalence of the lactose intolerance varies world-wide strongly between different ethnical groups. In the European population, with a prevalence of less than 30 %, the lactose intolerance is not so widely distributed (Sahi, 1994, Scand J Gastroenterol, 202(29):7-20). In Austria for example, 20-25 % of the people suffer from the primary adult lactose intolerance (ObermayerPietsch, 2004, Journal für Mineralstoffwechsel, 11(3):20-23). There are other possible mutations known in the direct neighborhood of position -13910, for example the mutations -13907C/G, -13913T/C, -13914G/A, and -13915T/G. These mutations may occur more often at individuals of African or Arabic origin (Tag et al, 2007, Clin Chem, 53(1):146-148; Torniainen et. al, 2009, BMC Genet, 10(31)). The importance for lactose tolerance differs depending on the specific mutation.
■ oligomix LIT -13910C>T LT 2
DNA from blood
approx. 1.5 h