Evidence for duplication of the human salivary amylase gene

Abstract

Isoelectric focusing of human parotid saliva reveals different alpha-amylase patterns reflecting qualitative and quantitative variations. A puzzling pattern, which shows three different amylase gene products, was found in four individuals. Based on this observation a model is presented in which the salivary amylase gene is duplicated. Family studies show that the AMY1*A2 gene forms a haplotype with the normal gene, AMY1*A1, whereas the AMY1*A3 gene still exists in a single form. The absence of homozygote 2-2 in offspring of 1-2 X 1-2 marriages and in population material, and the fact that the variant protein makes up about only 20-30% of the total amylase protein in heterozygotes can be considered as additional evidence supporting the hypothesis. The possibility that cis-acting regulatory variants are involved in the patterns with quantitative variation is discussed.

Variation in gene copy number and polymorphism of the human salivary amylase isoenzyme system in Caucasians

“…AMY1 11 is probably identical with one of the PAGE variants mentioned by Merritt and Karn (1977). The variants AMY1 1, AMY1 2, AMY1 3 and AMY1 5 are in accordance with the numbers used by de Soyza (1978;, Ktihnl and Tischberger (1980), Pronk et al (1982;1984) and Boan and Caeiro (1988). The allozymes A, R1 and R2 in Pronk and Frants (1979) and correspond to our numbers AMY1 1, AMY1 2 and AMY1 3, respectively.…”

“…The phenotypes AA, AR1, AR2, R1R2 and "African variant" of Pronk and Frants (1979) and correspond to our phenotypes AMY1 1, AMY1 1,2, AMY1 1,3, AMY1 3 and AMYI 1QL,9 respectively. Phenotypes 1-2QL, 1-3QL, 1-2QE, 1QL-3 and 1-4 of Pronk et al (1982) are identical to the phenotypes AMY1 1QE,2, AMY1 1QE,3, AMY1 1QL,2, AMY1 1QL,3 and AMY1 1QL,9, respectively these families are shown in Fig. 6.…”

“…As shown by the electrophoretic mobility, the variant products in the phenotypes N, W, C, S and B of correspond to our allozymes AMY1 1, AMY1 3, AMY1 3, AMY1 2 and AMY1 6, respectively. We have not used the designation AMY1 4 in our nomenclature because two different allozymes have been so designated in the literature: AMY1 4 of de Soyza (1978) probably corresponds to our AMY1 6, whereas AMY1 4 of Pronk et al (1982) (called "African variant" in Pronk and Frants 1979) is identical with AMY1 9. AMY1 8 was tentatively used by us to designate a putative new variant, segregating in one Dutch family, and is distinguished by a faint anodal doublet with PAGE (see Fig.…”

“…1 of Groot et al (1989). It serves as a control for the reliability of the PCR-experiments (see also under "Haplotypes encoding AMY1 1") studies (Pronk et al 1982) and DNA analysis (Groot et al 1989). To date, the other allozymes, except for AMY1 3, have always been found together with AMY1 1, making it difficult to establish whether these variants are encoded by a single AMY1 gene or by a haplotype also encoding AMY1 1 (as in AMYI*I,2).…”

“…Based on the observation that some individuals express three different salivary amylase gene products (phenotype AMY1 1,2,3), Pronk et al (1982) postulated a duplication of the salivary amylase gene. The genomic structure of the AMY*l,2 and AMY1*3 haplotypes from a woman with phenotype AMY1 1,2,3 was elucidated by Groot et al (1989).…”