Characterization of D6S2806 and D6S2879 short tandem repeat loci in HLA-DRB1 region in Iranian population

Genomewide screen analysis has shown the close association of the human leukocyte antigen (HLA)-DRB1 region with susceptibility to multiple sclerosis and a number of autoimmune diseases. Using bioinformatics software, several potential short tandem repeat (STR) markers have been introduced in this region in the major histocompatibility complex data base (dbMHC). In this study, the identity and characteristics of two putative STR markers, D6S2879 and D6S2806, in this region were examined in Iranian population. The loci were genotyped in 85 individuals using polymerase chain reaction followed by polyacrylamide gel electrophoresis and sequencing. Analysis of the allelic frequency showed the presence of six and four alleles for D6S2806 and D6S2879, respectively. Analysis of deviations from Hardy-Weinberg equilibrium (HWE) showed that D6S2806 was in equilibrium (P > 0.05). However, the D6S2879 locus showed a significant deviation from HWE (P < 0.05). Therefore, the D6S2806 locus could be suggested as a marker for linkage analysis and disease-susceptibility investigations in the MHC-DRB1 gene region.

The influence of interstitial collagenase-1 genotype polymorphism on colorectal cancer risk in Iranian population

Interstitial collagenase-1 degrades a variety of extracellular matrix components. A single guanine insertion polymorphism in the promoter has been found that influences on the transcription and expression level of the gene. It is suggested that this polymorphism may enhance susceptibility to some types of cancer. Therefore, this case-control study evaluated the association of this genotype polymorphism with susceptibility to initiation and invasion of colorectal cancer. For this reason, whole blood samples were obtained from 150 CRC patients and 100 control subjects in Tehran. Genomic DNA was extracted and genotyped by PCR-RFLP method. We showed that 2G allele and 2G/2G genotype had higher frequencies in patients (60% and 39%, respectively) than in controls (47% and 23%, respectively). The CRC patients were divided into two groups: with metastasis (M+) and without metastasis (M-) groups. The 2G allele was more frequent in M+ group compared with control group. However, no significantly difference was observed between M-group and control (chi(2) = 0.48, P = 0.78 for 2G/2G genotype). Further stratification analyses showed that only gender (OR = 2.58, 95% CI = 0.89-7.52 for women and OR = 4.12, 95% CI = 1.62-10.42 for men) and smoking (OR = 3.03, 95% CI = 1.28-7.16 for non-smokers and OR = 4.09, 95% CI = 1.18-4.15 for smoker) may modify the risk of colorectal invasion related to 2G/2G genotype. Furthermore, individual with 2G/2G genotype seems to spread metastasis, 3 years earlier than those who were 1G/1G and 1G/2G. In conclusion, to our knowledge, the present epidemiological study for the first time indicates the relationship of 2G/2G genotype polymorphism with invasion risk of colorectal cancer in subgroups of gender and smoking, especially in smoker men.

Unequal sister chromatid exchange in the rDNA array of Saccharomyces cerevisiae

In the yeast Saccharomyces cerevisiae the nucleolar organiser region (NOR) is located on chromosome XII. It contains 100-200 copies of rDNA--a minimum of 20 rDNA genes in tandem--and is termed the RDN locus. Yeast cells may exist in either haploid or diploid form. There are two forms of life cycle: haploid and diploid cells double by mitosis, and diploid cells are reduced to the haploid state by meiosis. Diploid cells have two homologous chromosomes for each of the 16 chromosomes. They are usually of the same size. However, in this study it is shown that homologous chromosomes XII can become different in size due to unequal sister chromatid exchange during mitosis in 'old' cells.