The Distribution of delta-Aminolevulinic Acid Dehydratase Genetic Variants in Kazak Population of China

delta-aminolevulinic acid dehydratase (ALAD) catalyzes the second step of heme synthesis. The ALAD gene shows a polymorphism leading to 2 alleles (ALAD1 and ALAD2) and 3 phenotypes (ALAD 1-1, ALAD 1-2 and ALAD 2-2). This polymorphism has been shown to affect lead toxicity and the risk of meningioma. In addition, there is little evidence showing interethnic differences in the distribution of this polymorphism, especially in heterogeneous populations such as the Chinese population. We examined the distribution of genetic variants of the ALAD polymorphism in Han and Kazak Chinese. 938 unrelated Han and 1032 unrelated Kazak individuals were taken into the studies. Genomic DNA was extracted from venous blood and the genotypes for the ALAD polymorphism were determined by polymerase chain reaction followed by restriction fragment length polymorphism digestion and gel electrophoresis. We found a notable interethnic disparity in the distribution of ALAD genotypes and alleles. The ALAD2 allele was more common in Kazak than in Han (P <0.05). Correspondingly, the heterozygote (ALAD 1-2) or homozygote variant (ALAD 2-2) genotypes for this polymorphism were more common in Kazak than in Han (P <0.05). The significant interethnic differences in the distribution of ALAD variants are found between the Han and Kazak population. These findings may help us understand the interethnic disparities in susceptibility to lead toxicity and brain tumors.