High resolution melting analysis for detection of variable number of tandem repeats polymorphism of XRCC5

Correlation between thyroglobulin gene polymorphisms and autoimmune thyroid disease

The aim of the present study was to detect thyroglobulin (Tg) gene polymorphisms in a Han Chinese population from the Northern regions of Henan province, China, and to study the correlation between Tg gene polymorphisms and autoimmune thyroid disease (AITD). A total of 270 patients with AITD and 135 healthy controls were enrolled. Genomic DNA was extracted and fluorescence polymerase chain reaction analysis was performed; high‑resolution melting curve analysis (HRMA) was used to detect single‑nucleotide polymorphisms (SNPs) in exons 10, 12 and 33 of the Tg gene. SNPs were then correlated with AITD. Han people from the Northern regions of Henan displayed four Tg exon SNPs: E10SNP24 T/G, E10SNP158 T/C, E12SNP A/G and E33SNP C/T. Several allele and genotype frequencies differed between the AITD group and the healthy control group (Tg E10SNP: Allele T, P<0.01; allele G, P<0.01; and Tg genotype GG, P<0.01; genotype TG, P<0.01. Tg E12SNP: Allele A, P<0.01; allele G, P<0.01; Tg genotype GG, P<0.01; genotype AG, P<0.01). A statistically significant difference in the frequency of selected Tg SNPs haplotypes was also present between AITD patients and healthy controls (P<0.05). There was no significant difference in haplotypes between various types of AITD (hypothyroidism, hyperthyroidism and Hashimoto's disease). The Tg SNP frequency distribution was significantly different between Han populations of the Northern regions of Henan province and the Xi'an regions of Shaanxi province. The results of the present study suggested that specific Tg gene alleles or genotypes were correlated with AITD; specific Tg SNP haplotypes were associated with hypothyroidism, hyperthyroidism and Hashimoto's disease, and the Tg SNP frequency distribution differed depending on the geographical location of the Han Chinese populations.

Susceptibility to gastric cancer and polymorphisms of insertion/deletion at the intron 3 of the XRCC4 and VNTR at the promoter region of the XRCC5

The genes encoding X-ray repair cross-complementing group 4 (XRCC4; OMIM: 194363) and 5 (XRCC5; OMIM: 194364) are involved in repair of DNA double-strand breaks. To investigating the associations between polymorphisms of Insertion/Deletion (I/D, rs28360071) in the intron 3 of the XRCC4 and VNTR in the promoter region of the XRCC5 and risk of gastric cancer, the present study was carried out. We included 159 (56 females, 103 males) with gastric cancer and 242 (75 females, 167 males) healthy blood donors frequency matched for age and gender. Using PCR-based methods, the genotypes of the study polymorphisms were determined. The alleles of VNTR XRCC5 polymorphism divided into two groups: L (0 and 1 repeats) and H (2 and 3 repeats) alleles. For the I/D XRCC4 polymorphism, after stratification of the subjects according to their family history (FH) of cancer, either the ID (OR = 3.19, 95%CI: 1.35-7.50, P = 0.008) or the DD genotypes (OR = 4.62, 95%CI: 1.63-13.0, P = 0.004) among positive FH persons, increased the risk of gastric cancer compared with the reference group (persons who have negative FH and II genotype). For the VNTR XRCC5 polymorphism, the LH + HH genotypes among positive FH persons, increased the risk of gastric cancer compared with the reference group (persons who have negative FH and LL genotype) (OR = 2.88, 95%CI: 1.34-6.18, P = 0.006). Sensitivity analysis showed that the above mentioned associations were not occurred due to the maldistribution of the genotypes among missing data. The present study suggests that both polymorphisms of the XRCC4 and XRCC5 might be risk factors for gastric cancer development especially among persons with positive FH.

Impact of sodium arsenite on chromosomal aberrations with respect to polymorphisms of detoxification and DNA repair genes

Arsenic compounds can increase production of reactive oxygen species. Reactive oxygen species can induce double-strand breaks in DNA, which is a cause of chromosome aberrations (CAs). This study was conducted to determine the association between arsenic exposure and polymorphisms of genes involved in detoxification (glutathione S-transferase T1 [GSTT1], glutathione S-transferase M1 [GSTM1], glutathione S-transferase O2 [GSTO2], catalase [CAT], and NAD(P)H quinone oxidoreductase1 [NQO1]) as well as nonhomologous end joining DNA repair genes (XRCC4, XRCC5, and XRCC6) with induction of chromosomal aberrations. The participants consisted of 123 healthy males who were genotyped using polymerase chain reaction-based methods. Primary cultures of whole blood were treated with sodium arsenite (NaAsO(2); iAs(III); at final concentration 1 µmol/L), mitomycin C (at final concentration 60 ηg/mL; as positive control), or untreated. For each culture, mitotic index (MI), chromatid breaks (CBs), CAs, and total percentage of aberrant cells were determined. The levels of CB and percentage of aberrant cells were significantly higher in the TT genotype of CAT (C-262T polymorphism) than the CC genotype. The CB value in samples with GSTM1 active genotype was significantly higher than the null genotype. The MI in samples with TT genotype of NQO1 (C609T polymorphism) was significantly higher than MI in samples having CC and CT genotypes. There was no association between MI, CB, CA, and percentage of aberrant cells and polymorphisms of XRCC4, XRCC5, and XRCC6.

Association of XRCC5 VNTR polymorphism with the development of chronic myeloid leukemia

Double-strand breaks (DSBs) inducing agents influence the fidelity of DNA repair in both normal cells and leukemic cells, causing major genomic instability. In eukaryotic cells, non-homologous end joining pathway (NHEJ) is the major mechanism for DSB repair. Human X-ray repair cross-complementing 5 (XRCC5) gene encodes for the protein KU86, an important component of NHEJ pathway. Variable number of tandem repeats (VNTR) polymorphism (rs 6147172) in the promoter region of XRCC5 gene was shown to have effect on gene expression and was found to be associated with the development of several cancers. We analyzed VNTR polymorphism of XRCC5 gene in 461 chronic myeloid leukemia (CML) cases and 408 controls by polymerase chain reaction. Our results showed that frequency of 0R/0R genotype was significantly elevated in CML cases compared to that of controls (p = 0.05). Significant difference in the genotype distribution was observed between cases and controls (p = 0.02). The risk of CML development was found to be elevated for individuals carrying lower repeats (1R p = 0.03; 0R p = 0.007). Elevated 0R/0R genotype frequency was found to be significantly associated with early age at onset (≤ 30 years) and slightly elevated in chronic phase and poor hematologic response to imatinib mesylate. The influence of zero repeat on enhanced expression of XRCC5 might confer risk to error-prone repair leading to genomic instability and CML. Hence, the VNTR polymorphism in the promoter region of XRCC5 gene could serve as an important prognostic marker in CML development.

The novel allele (3R) of the VNTR polymorphism in the XRCC5 promoter region dramatically decreases the gene expression

Polymorphism of variable number of tandem repeats (VNTR) in the promoter region of X-ray repair cross-complementing 5 (MIM: 194364, XRCC5; rs6147172) was reported. The aim of the present study is to evaluate the influence of this polymorphism on XRCC5 mRNA levels. Genotypes of XRCC5 VNTR were determined by high resolution of melting analysis (HRMA). The quantitative XRCC5 mRNA expression (compared to ß-actin expression) among 0R/1R, 1R/2R, and 1R/3R genotypes was investigated. There was a negative correlation between the overall number of tandem repeats and XRCC5 expression (r=-0.965, df=7, P<0.001). The mRNA level of XRCC5 decreased as function of number of tandem repeats. The 3R allele of the VNTR polymorphism in the XRCC5 promoter region dramatically decreases the gene expression.