AMY2 Gene Copy Number Variation as a Marker of Genetic Diversity in Kurds

Abstract
Genetic variation in the human genome ranges from single nucleotide polymorphisms (SNPs) to large chromosomal arrangements. Copy number variations (CNVs) are segments of DNA larger than 1kb in length with variable copies in the genome. The salivary amylase (AMY1) gene is a highly variable region and has been linked to dietary adaptation and body mass index (BMI), whereas the pancreatic amylase (AMY2A and AMY2B) genes are less variable and their functional implications have yet to be explored. In the European population, there are two common types of pancreatic amylase CNVs: a deletion of AMY2A and a duplication of a 116kb region including both AMY2A and AMY2B genes. There is limited information on AMY2 CNVs in non-European populations. This study aims to investigate the frequency of AMY2A/AMY2B duplications in the Kurdish population using a PCR-based duplication junction assay. A total of 186 DNA samples from type 2 diabetic patients and non-diabetic controls were analysed. The assay detects a 424 bp control fragment in all individuals and an additional 323 bp fragment in duplication carrier samples, allowing the differentiation between individuals with four AMY2 copies (duplication-negative) and those with at least six copies (duplication-positive). The results show that 23% of the Kurdish samples were duplication-positive, while 77% did not carry the duplication. The observed frequency in the Kurdish population is higher than that reported in European (12%), African (8.6%), and American (10.9%) populations and rare in East Asian (Chinese and Japanese) populations. The prevalence of duplication carrier samples in the Kurdish population reveals a notable genetic variability in pancreatic amylase genes that aligns with some global populations, possibly reflecting unique historical and dietary influences. These findings emphasise the need for further research on amylase CNVs in the Kurdish population.