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      Frequency of adult type-associated lactase persistence LCT-13910C/T genotypes in the Czech/Slav and Czech Roma/Gypsy populations

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          Abstract

          Lactase non-persistence (leading to primary lactose intolerance) is a genetically dependent inability to digest lactose in adulthood. As part of the human adaptation to dairying, the human lactase LCT-13910C/T mutation (which propagates adult expression of lactase) developed, spread and participated in the adaptation to dairying. This variant is associated with lactase activity persistence, and its carriers are able to digest lactose. We compared the frequencies of lactase 13910C/T (rs4988235) genotypes in Czechs/Slavs (N = 288) and Czech Gypsies/Roma (N = 300), two ethnically different groups where this polymorphism has not yet been analysed. Allelic frequencies significantly differed between the populations (p < 0.0001). In Czechs/Slavs, the lactase persistence T allele was present in 76% of the individuals, which is in agreement with frequencies among geographically neighbouring populations. In the Czech Gypsy/Roma population, only 27% of the adults were carriers of at least one lactase persistence allele, similar to the Indian population. In agreement with this result, dairy product consumption was reported by 70.5% of Czechs/Slavs and 39.0% of the Czech Gypsy/Roma population. Both in the Czech Gypsy/Roma and in the Czech/Slavs populations, the presence of carriers of the lactase persistence allele was similar in subjects self-reporting the consumption of unfermented/fresh milk, in comparison to the others.

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          Lactose intolerance: diagnosis, genetic, and clinical factors

          Most people are born with the ability to digest lactose, the major carbohydrate in milk and the main source of nutrition until weaning. Approximately 75% of the world’s population loses this ability at some point, while others can digest lactose into adulthood. This review discusses the lactase-persistence alleles that have arisen in different populations around the world, diagnosis of lactose intolerance, and its symptomatology and management.
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            Population Genomics of Human Adaptation.

            Recent advances in genotyping technologies have facilitated genome-wide scans for natural selection. Identification of targets of natural selection will shed light on processes of human adaptation and evolution and could be important for identifying variation that influences both normal human phenotypic variation as well as disease susceptibility. Here we focus on studies of natural selection in modern humans who originated ~200,000 years go in Africa and migrated across the globe ~50,000 - 100,000 years ago. Movement into new environments, as well as changes in culture and technology including plant and animal domestication, resulted in local adaptation to diverse environments. We summarize statistical approaches for detecting targets of natural selection and for distinguishing the effects of demographic history from natural selection. On a genome-wide scale, immune-related genes appear to be major targets of positive selection. Genes associated with reproduction and fertility also appear to be fast evolving. Additional examples of recent human adaptation include genes associated with lactase persistence, eccrine glands, and response to hypoxia. Lastly, we emphasize the need to supplement scans of selection with functional studies to demonstrate the physiologic impact of candidate loci.
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              The T 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.

              The ability to digest the milk sugar lactose as an adult (lactase persistence) is a variable genetic trait in human populations. The lactase-persistence phenotype is found at low frequencies in the majority of populations in sub-Saharan Africa that have been tested, but, in some populations, particularly pastoral groups, it is significantly more frequent. Recently, a CT polymorphism located 13.9 kb upstream of exon 1 of the lactase gene (LCT) was shown in a Finnish population to be closely associated with the lactase-persistence phenotype (Enattah et al. 2002). We typed this polymorphism in 1,671 individuals from 20 distinct cultural groups in seven African countries. It was possible to match seven of the groups tested with groups from the literature for whom phenotypic information is available. In five of these groups, the published frequencies of lactase persistence are >/=25%. We found the T allele to be so rare that it cannot explain the frequency of the lactase-persistence phenotype throughout Africa. By use of a statistical procedure to take phenotyping and sampling errors into account, the T-allele frequency was shown to be significantly different from that predicted in five of the African groups. Only the Fulbe and Hausa from Cameroon possessed the T allele at a level consistent with phenotypic observations (as well as an Irish sample used for comparison). We conclude that the C-13.9kbT polymorphism is not a predictor of lactase persistence in sub-Saharan Africans. We also present Y-chromosome data that are consistent with previously reported evidence for a back-migration event into Cameroon, and we comment on the implications for the introgression of the -13.9kb*T allele.
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                Author and article information

                Journal
                Genet Mol Biol
                Genet. Mol. Biol
                gmb
                Genetics and Molecular Biology
                Sociedade Brasileira de Genética
                1415-4757
                1678-4685
                11 May 2017
                Apr-Jun 2017
                : 40
                : 2
                : 450-452
                Affiliations
                [1 ]Centre for Experimental Medicine, Institute for Clinical and Experimental Medicine, Prague, Czech Republic
                [2 ]Department of Preventive Cardiology, Institute for Clinical and Experimental Medicine, Prague, Czech Republic
                [3 ]University of South Bohemia in České Budějovice, Faculty of Health and Social Studies, České Budějovice, Czech Republic
                [4 ]Czech Technical University of Prague, Faculty of Biotechnical Enginnering, Kladno, Czech Republic
                Author notes
                Send correspondence to Jaroslav A. Hubacek. Centre for Experimental Medicine, Institute for Clinical and Experimental Medicine (IKEM-DEM), Videnska 1958/9, 140 21 Prague 4, Czech Republic. E-mail: jahb@ 123456ikem.cz
                Article
                S1415-47572017005013101
                10.1590/1678-4685-GMB-2016-0071
                5488455
                28497837
                7f38fd85-65bb-4ff3-b5c4-2a60ed998150
                Copyright © 2017, Sociedade Brasileira de Genética.

                License information: This is an open-access article distributed under the terms of the Creative Commons Attribution License (type CC-BY), which permits unrestricted use, distribution and reproduction in any medium, provided the original article is properly cited.

                History
                : 18 March 2016
                : 27 July 2016
                Page count
                Figures: 0, Tables: 1, Equations: 0, References: 22, Pages: 3
                Categories
                Human and Medical Genetics

                Molecular biology
                lactose,lactase persistence,polymorphism,czech/slav,czech gypsy/roma
                Molecular biology
                lactose, lactase persistence, polymorphism, czech/slav, czech gypsy/roma

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