Lactase persistence

Burger, J., Kirchner, M., Bramanti, B., Haak, W. and Thomas, M.G. (2007). Absence of the lactase-persistence-associated allele in early Neolithic Europeans. Proceedings of the National Academy of Sciences, USA 104 3736-3741. 

Interestingly, the lactase-persistent phenotype found in some pastoral groups in sub-Saharan Africa is not correlated with the -13910 (T) genotype as it is in northern European populations.This implies that the -13910 SNP is not a causative mutation or not the only causative mutation influencing lactase persistence. There is speculation that other variants may be involved in this region of the DNA and are yet to be identified (Bersaglieri et al., 2004 Mulcare et al.,2004 OMIM). 

Enattah NS, Forsblom C, Rasinpera H, et al., The FinnDiane Study Group The genetic variant of lactase persistence C (-13910)T as a risk factor for type I and II diabetes in the Finnish population. Pur J Clin Nutr 1-4,2004. 

Mulcare CA,Weale ME, Jones AL, et al. TheT allele of a single-nucleotide polymorphism 13.9 kb upstream of the lactase gene (LCT)(C-13.9kbT) does not predict or cause the lactase-persistence phenotype in Africans. Am J Hum Genet 74 1102-1110, 2004. 

Thomas S, Walker-Smith JA, Senewiratne B, et al. Age dependency of the lactase persistence and lactase restriction phenotypes among children in Sri Lanka and Britain. J Trop Pediatr. 36 80-85,1990. 

Troelsen JT, Olsen J, Moller J, et al. An upstream polymorphism associated with lactase persistence has increased enhancer activity. Gastroenterology 125 1686-1694,2003. 

Rossi M, Maiuri L, Fusco MI, Salvati VM, Fuccio A, Auricchio S, Mantei N, Zecca L, Gloor SM, Semenza G. Lactase persistence versus decline in human adults multifactorial events are involved in down-regulation after weaning. Gastroenterology 1997 112 1506-1514. 

Deficiency of the enzyme lactase is common. Indeed, it is only in people of north European origin that lactase persists after childhood. In most other people, and in a number of Europeans, lactase is gradually lost through adolescence — alactasia (see Problem 4.2). In the absence of lactase, lactose cannot be absorbed. It remains in the intestinal lumen, where it is a substrate for bacterial fermentation to lactate (section... 

Weinberg RB. Apolipoprotein A-IV-2 allele Association of its worldwide distribution with adult persistence of lactase and speculation on its function and origin. Genet Epidemiol. 1999, 17 285-297. 

A common malabsorption syndrome, lactose intolerance, is characterized by nausea, diarrhea, and flatulence after ingesting dairy products or other foods containing lactose. One of the causes of lactose intolerance is a low level of lactase, which decreases after infancy in most of the world s population (nonpersistant lactase or adult hypolactasia). However, lactase activity remains high in some populations (persistent lactase), including Northwestern Europeans and their descendants. 

Lactase (intestinal) (EC 3.2.1.23). Lactase is present in infancy when it is required for digestion of lactose in the mother s milk. The enzyme then decreases markedly with age, so that abdominal pain and diarrhea result from drinking milk, due to failure to hydrolyse lactose in the intestinal mucosa and lactose malabsorption. Condition prevalent throughout the world, and hereditary persistence of high intestinal lactase activity prevails only on Northern European populations (and those derived from them) and certain Arab and Hamitic races. 

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