Salivary amylase gene copy number: Have humans adapted to high starch diets?

Caldwell, Elizabeth and Von Crammon-Taubadel, Noreen and Weale, Michael E. and Thomas, Mark G. (2004) Salivary amylase gene copy number: Have humans adapted to high starch diets? In: 73rd Annual Meeting of the American Association of Physical Anthropologists, 2004-04-01 - 2004-04-04, Tampa, Florida.

Abstract

The transition to agriculture in the Neolithic period brought about an increase in starch, in the human diet. This study examines whether genetic adaptation to changes in the amount of starch ingested has occurred in humans. Starch digestion begins in the mouth where it is hydrolysed into smaller polysaccharides by the enzyme salivary amylase. Three salivary amylase genes (AMY1A, B & C) and a psuedogene (AMYP1) have been described and are located in tandem on the short arm of chromosome 1. Polymorphic variation has been demonstrated in Caucasian populations in the form of the number of repeats of the AMY1 genes, as follows: (1A-1B-P1)n-1C. This variation results in differing levels salivary amylase enzyme production and, as a result, differences in the efficiency of starch digestion. We have designed a reliable high-throughput PCR based method, using ABI GeneScan technology, to quantify AMY1 gene copy number and to type 6 microsatellite markers closely linked to the AMY gene cluster. Data has been collected for 14 human populations, each with different histories of cereal agriculture and levels of starch in the diet. This data has been analysed using two approaches - a) comparing FST, based on AMY1 repeat number allele frequencies, to a null distribution of FST for neutral markers to gauge evidence for directional selection in different populations; b) examination of intra-allelic variability using microsatellite haplotypes associated with different AMY1 repeat number alleles, to test for differences in selective forces operating on different alleles in the same population.