Allelic Frequency of a 24-bp Duplication in Exon 10 of the CHIT1 Gene in the General Iranian Population.

Abstract

The human chitinase chitotriosidase enzyme, which is encoded by the CHIT1 gene, is produced by macrophages, and may be important in immune responses to chitin-containing organisms, such as fungi. Plasma chitotriosidase activity is used to diagnose and monitor some forms of lysosomal storage disorders, such as Gaucher's and Niemann-Pick disease. However, homozygous duplication of a 24-bp region in exon 10 of the CHIT1 gene eliminates enzyme activity and may complicate disease monitoring. The high prevalence of this mutation highlights the need to determine its frequency in different populations and screen patients for this mutation to verify whether chitotriosidase activity is a reliable marker of lysosomal storage disease. This study investigated the allele frequency of the 24-bp duplication in the general Iranian population. To identify the 24-bp duplication in exon 10 of the CHIT1 gene (H allele), genotyping of DNA extracted from peripheral blood leukocytes of 577 healthy Iranians was performed using polymerase chain reaction (PCR) amplification and high resolution melting (HRM) PCR techniques. In this study, heterozygous and homozygous duplications were detected in 183 (31.7%) and 35 (6.1%) subjects, respectively. In addition, the allelic frequency was 21.9% (95% confidence interval). Our study indicates that genotype analysis by HRM-PCR is a fast, reliable, and highly accurate screening approach for identifying the 24-bp duplication in CHIT1 exon 10. Due to the wide range of duplication frequencies among different ethnic groups, new biomarkers are necessary for assessing genetic characteristics of lysosomal storage disorders in different populations.