Lactase persistence evolutionary genetics pdf

A news article on the search for a lactose tolerance mutation in. Kotze,5 muntaser ibrahim,6 thomas nyambo,7 sabah a. Lactose intolerance is inherited in an autosomal recessive pattern, that means that one copy of the lactase persistence allele is enough to confer the ability to digest lactose as an adult. The lactase nonpersistence phenotype is common in adult humans 65%, ingram et al. Absence of the lactasepersistenceassociated allele in. Lactase persistence lp, the dominant mendelian trait conferring the ability to digest the milk sugar lactose in adults, has risen to high frequency in central and northern europeans in the last 20,000 years. The evolution of lactase persistence humans are relatively unique among mammal species in that some of their adult population retains the ability to digest lactose, a sugar found in milk. Lactase is the enzyme responsible for the digestion of the milk sugar lactose and its production decreases after the weaning phase in most mammals, including most humans. Author summary most adults worldwide do not produce the enzyme lactase and so are unable to digest the milk sugar lactose.

This activity focuses on the genetic changes that gave rise to lactase persistence an example of recent human evolution. Convergent adaptation of human lactase persistence in. Lactose digestion and the evolutionary genetics of lactase persistence. Just 10,000 years ago, no one past infancy could digest milk sugar, called lactose. Lactase persistence lp is a trait in which lactose can be digested throughout adulthood, while lactase nonpersistence lnp can cause lactose intolerance and influence dairy consumption. The distribution of these different lactase phenotypes in human populations is highly variable and is controlled by a polymorphic element cisacting to the lactase gene. The evolutionary genetics of lactase persistence in seven. Combining genetics, chemistry, and anthropology, this story provides a compelling example of the coevolution of human gene regulation and human culture. Symptoms may include abdominal pain, bloating, diarrhea, gas, and nausea. Lactase persistence is common in people of european ancestry as well as some african, middle eastern and southern asian groups, but is rare or absent elsewhere in the world. A singlenucleotide variant, ct910, located 14 kb upstream of the lactase gene lct, has been shown to be completely correlated with lactase persistence lp in northern europeans. As expected, lactase persistence is strongly correlated with the dairying history of the population.

The mutation leading to lactase persistence in this population is different from the one found in lactasepersistent individuals from europe. Genetic origins of lactase persistence and the spread of. Babies always made lactase, the enzyme that breaks down this. This genetically determined trait differs in frequency worldwide and is due to cisacting. Students explore the evidence for lactasepersistence mutations that arose within the last. Lactase persistence and milk consumption in europe an interdisciplinary approach involving genetics and archaeology michela leonardi ag palaeogenetik, institute of anthropology, johannes gutenberg university, mainz, d human evolutionary ecology group, department of anthropology, university college london, london, uk m. Pdf lactose digestion and the evolutionary genetics of lactase. A worldwide correlation of lactase persistence phenotype. Some humans, however, continue to produce lactase throughout adulthood, a trait known as lactase persistence.

The genetic basis of lp has been investigated in many populations in the world. These symptoms typically start thirty minutes to two hours after eating or drinking milkbased food. Age estimates based on the intraallelic microsatellite. The levels of haplotype diversity within the lineages defined by two singlenucleotide polymorphisms snps. Understanding the genetics of lactase persistence is vital to knowing how it is inherited between populations. Lp is prevalent in europe, with the highest frequencies in the northwest of the continent 0.

It is thought that selection has played a major role in maintaining. Lactose digestion and the evolutionary genetics of lactase. Sarah tishkoff and colleagues investigated lactase persistence in east africa. The enzyme lactase that is located in the villus enterocytes of the small intestine is responsible for digestion of lactose in milk.

The frequency of this allele rose rapidly in europe after transition from huntergatherer to agriculturalist lifestyles and the introduction of milkable domestic species from anatolia some 8000 years ago. Milk is rich in lactose roughly 40 gramsliter for cows milk, which serves as the major carbohydrate energy source for infants and young animals. Lactase persistence is the continued activity of the enzyme lactase in adulthood. Genetic diversity in human populations is the result of a relatively recent biological and cultural evolution, so that most of the human genetic background can be. Resequencing of a second phenotyped cohort revealed the presence of many variant alleles at the locus, the occurrence of which is significantly higher in persistent individuals. The evolutionary genetics of lactase persistence in africa and the middle east. The evolutionary genetics of lactase persistence in africa.

Primary research open access the evolutionary genetics of lactase persistence in seven ethnic groups across the iranian plateau hadi charati1,2, minsheng peng1,2,3, wei chen4, xingyan yang5, roghayeh jabbari ori6, mohsen aghajanpourmir7,8, ali esmailizadeh1,6 and. The expression of lactase which digests lactose from milk in humans is generally lost after weaning, but selected mutations influencing the promoter of the lactase gene have spread into the human populations. A putative causal nucleotide change has been identified and occurs on the background of a very extended haplotype that is frequent in northern europeans, where lactase persistence is frequent. Persistence of lactase into adulthood varies in frequency worldwide and is attributable to several different single nucleotide changes in an enhancer of the lct gene. Lactase persistencethe ability of adults to digest the lactose in milkvaries widely in frequency across. Lactase persistence and milk consumption in europe an. Lactase persists into adult life in some, but not all, people.

Pdf genetics of lactase persistence fresh lessons in. Current estimates for the age of lactase persistenceassociated alleles bracket those for the origins of animal domestication and the culturally transmitted practice of dairying. When natural selection favors a beneficial allele, such as the lactasepersistence allele red band, that allele is more likely to be passed on from one generation to the next. However, the mechanism and evolutionary significance of this variation have proved more elusive, and continue to excite the interest of investigators from different disciplines. Lactase persistence is one of the clearest examples of niche construction in humans. The ability of adult humans to digest the milk sugar lactose lactase persistence is a dominant mendelian trait that has been a subject of extensive genetic, medical and evolutionary research.

Nonpersistence or persistence of lactase expression into adult life being a polymorphic trait has been attributed to various single nucleotide polymorphisms in the enhancer region surrounding. Since lactases only function is the digestion of lactose in milk, in most mammal species, the activity of the enzyme is dramatically reduced after weaning. It follows a mendelian autosomal heritance regulated by cisacting elements of the lactase gene lct. Nearly every allele associates with an independent haplotype, providing strong evidence that multiple unrelated evolutionary events gave rise to lactase persistence. Genetics of lactase persistence and lactose intolerance. Those affected vary in the amount of lactose they can tolerate before symptoms develop. Series of studies revealed five regulatory variants that are located in the 14 kb upstream of lct in. Studies of lactase persistence suggest that positive. Population genetics of lactase persistence and lactose.

Tishkoff1,9 in humans, the ability to digest lactose, the sugar in milk, declines after weaning because of. Evidence of stillongoing convergence evolution of the. This is considered a classical example of geneculture coevolution, and several studies suggested that the lactase gene has been under strong directional evolutionary selective. Genetics of lactase persistence fresh lessons in the history of milk drinking edward hollox 1 european journal of human genetics volume. Iran has a long history of pastoralism and the daily consumption of dairy products. Genetics of lactase persistence fresh lessons in the history of milk drinking edward hollox 1 european journal of human genetics volume , pages 267 269 2005. Lactase persistence is a genetic trait, which varies in frequency in different populations of the world. Lactase persistence behaves as a dominant trait because half levels of lactase activity are suf. Convergent adaptation of human lactase persistence in africa and europe. In the first column, the red band indicates a genetic variant or mutation associated with lactase persistencethe lactasepersistence allele. A snp in the gene encoding lactase lct ct910 is associated with the ability to digest milk as adults lactase persistence in europeans, but the genetic basis of lactase persistence in. Here, we analyzed the background of the alleles carrying the critical variant in 1,611 dna samples from 37 populations. Lactase activity is high and vital during infancy, but in most mammals, including most humans, lactase activity declines after the weaning phase.

The enzyme, lactase, is restricted to the small intestine where it digests lactose in the milk of suckling mammals. Some have argued for the culturehistorical hypothesis. Article genetic origins of lactase persistence and the spread of pastoralism in africa alessia ranciaro, 1, michael c. In humans, the ability to digest lactose, the sugar in milk, declines after weaning because of decreasing levels of the enzyme lactasephlorizin hydrolase, encoded by lct. Evidence for selection overview this activity focuses on the genetic changes that gave rise to lactase persistence an example of recent human evolution. Evolution of lactase persistence royal society publishing. It has been known for some 40 years that lactase production persists into adult life in some people but not in others. Genetic diversity of lactase persistence in east african. In some human populations, though, lactase persistence has recently evolved as an adaptation to the consumption of nonhuman milk and dairy products beyond. They express lactase and can consume fresh milk throughout life.

Pdf the evolutionary genetics of lactase persistence in. Many people in populations that have a long history of dairying have the trait of lactase persistence. Our data show that the t910 variant is found on two different, highly divergent. The origin of lactase persistence coincides with a cultural shift in human populations who began to use the milk of other mammals as food. The frequency of this allele rose rapidly in europe after transition from huntergatherer to agriculturalist lifestyles and the introduction of milkable. Lactose intolerance lactase nonpersistence lactose intolerance is a deficit in the ability to digest lactose, and is due to a relative lack of the lactase enzyme in the small intestine.

This trait is likely to have conferred a selective advantage in individuals who consume appreciable amounts of unfermented milk. Lactase persistence, the ability to digest the milk sugar lactose in adulthood, is highly associated with a t allele situated,910 bp upstream from the actual lactase gene in europeans. Genetics of lactase persistence fresh lessons in the history of milk drinking article pdf available in european journal of humangenetics 3. Hirbo,1 wenya ko, 10 alain froment,2 paolo anagnostou,3,4 maritha j. Microsatellite variation and evolution of human lactase. Clearly, the availability of fresh animal milk created an environment that selected for lactase persistence. Lactose intolerance is when a person has symptoms due to a decreased ability to digest lactose, a sugar found in dairy products. Ingram cj, mulcare ca, itan y, thomas mg, swallow dm. Key words milk, polymorphism, population distribution, developmental decline, functional dna element s abstract the enzyme lactase that is. One of these is at particularly high frequencies in europeans and several others have been found elsewhere. Lactose is the main carbohydrate disaccharide sugar in animal milk, including. Lactase persistence, the ability to drink milk as an adult and the opposite of lactose intolerance, is a trait that arose in humans as a direct result of our domestication of other mammals. As a primary factor in human evolution, natural selection is an important component of genetic research. A kidfriendly description of sarah tishkoffs genetic studies from the university of maryland.

The evolutionary genetics of lactase persistence in seven ethnic. Lactose digestion and the evolutionary genetics of lactase persistence article pdf available in human genetics 1246. Both genetic changes occur in the regulatory region of the lactase gene. This ability is the result of a mutation that occurred thousands of years ago, and that must have conferred some adaptive advantage to those with the trait. This dominantly inherited genetic trait is known as lactase persistence. Lactase, the enzyme responsible for milk digestion, is expressed in the small intestine of nearly all neonate mammals, and normally downregulates following weaning. In other healthy humans, lactase activity persists at a high level throughout adult life, enabling them to digest. The ability to digest dietary lactose is associated with lactase persistence lp in the intestinal lumen in human. Likewise, the cultural practices of dairying and milk drinking have. However, most people in europe and many from other populations continue to produce lactase throughout their life lactase persistence. Lactose digestion and the evolutionary genetics of lactase persistence ingram from npb npb 2 at university of california, davis. Pdf lactose digestion and the evolutionary genetics of. However, some individuals maintain high enzyme amounts and are able to digest lactose into adulthood i.

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