The fifth allele of the human deoxyribonuclease I (DNase I) polymorphism

Significant Association of DNASE1 Variable Number Tandem Repeats and Single Nucleotide Polymorphisms With Gastric Cancer

Introduction: Defects in the apoptotic process are among the most important events involved in carcinogenesis, and defects in DNASE1, as one of the apoptotic machinery components, plays a role in various types of cancer. Previous studies have indicated significant differences in the DNASE1 polymorphisms in different populations. We hypothesized an association of two polymorphic sites in the exon 8 and the intron 4 of the DNASE1 gene with the risk of gastric cancer.

Materials and Methods: The study was carried out on 120 gastric cancer patients and 120 age and sex adjusted controls using PCR and RFLP-PCR.

Results: The genotype GG (rs1053874) in exon 8 of DNASE1 (odds ratio [95% confidence interval]) 4.65 [2.10–10.29], p < 0.001) and genotype 2/3 of variable number tandem repeat (VNTR) in the intron 4 (3.75 [1.56–9.01], p = 0.003) are both linked to gastric cancer.

Conclusion: We propose that both polymorphic sites have a part to play in gastric cancer, and so may be useful diagnosis markers.

Deoxyribonucleases and Their Applications in Biomedicine

Extracellular DNA, also called cell-free DNA, released from dying cells or activated immune cells can be recognized by the immune system as a danger signal causing or enhancing inflammation. The cleavage of extracellular DNA is crucial for limiting the inflammatory response and maintaining homeostasis. Deoxyribonucleases (DNases) as enzymes that degrade DNA are hypothesized to play a key role in this process as a determinant of the variable concentration of extracellular DNA. DNases are divided into two families-DNase I and DNase II, according to their biochemical and biological properties as well as the tissue-specific production. Studies have shown that low DNase activity is both, a biomarker and a pathogenic factor in systemic lupus erythematosus. Interventional experiments proved that administration of exogenous DNase has beneficial effects in inflammatory diseases. Recombinant human DNase reduces mucus viscosity in lungs and is used for the treatment of patients with cystic fibrosis. This review summarizes the currently available published data about DNases, their activity as a potential biomarker and methods used for their assessment. An overview of the experiments with systemic administration of DNase is also included. Whether low-plasma DNase activity is involved in the etiopathogenesis of diseases remains unknown and needs to be elucidated.

Genotyping of five single nucleotide polymorphisms in the OCA2 and HERC2 genes associated with blue-brown eye color in the Japanese population

Human eye color is a polymorphic phenotype influenced by multiple genes. It has recently been reported that three single nucleotide polymorphisms (SNPs) within intron 1 of the OCA2 gene (rs7495174, rs4778241, rs4778138) and two SNPs in intron 86 (rs12913832) and the 3' UTR region (rs1129038) of the HERC2 gene--located in the upstream of the OCA2 locus--have a high statistical association with human eye color. The present study is the first to examine in detail the genotype and haplotype frequencies for these five SNPs in an Asian (Japanese) population (n = 523) comprising solely brown-eyed individuals. Comparison of the genotype and haplotype distributions in Japanese with those in African and European subjects revealed significant differences between Japanese and other populations. Analysis of haplotypes consisting of four SNPs at the HERC2-OCA2 locus (rs12913832/rs7495174/rs4778241/rs4778138) showed that the most frequent haplotype in the Japanese population is A-GAG (0.568), while the frequency of this haplotype is rather low in the European population, even in the brown-eyed group (0.167). The haplotype distribution in the Japanese population was significantly different from that in the brown-eyed European group (F(ST) = 0.18915).

Identification of novel fibronectin fragments detected specifically in juvenile urine

Ugl-Y (young age-related urinary glycoprotein) is an age-specific protein that we have previously identified in urine from healthy subjects under 18 years of age. Isoelectric focusing analysis of Ugl-Y gives a set of three bands, Y1, Y2 and Y3, in the pH region around 3. To determine the complete structure of Ugl-Y, purified Y1 and Y2 from pediatric urine were enzymatically cleaved, and the resulting peptides were analyzed by protein sequencing and/or MALDI-TOF MS. As a result, it was demonstrated that Y1 consists of 189 amino acid residues, and is identical to the region from A723 to R911 of fibronectin, whereas Y2 consists of 181 amino acid residues, and is identical to the region from A723 to R903. Electrophoretic analysis of the lysate prepared from COS-7 cells transfected with Y1- or Y2-expressing vectors gave specific bands corresponding to Y1 or Y2, respectively, showing the validity of the sequences determined. Partial purification of pediatric serum followed by western blotting revealed that Ugl-Y is derived from plasma. Furthermore, Ugl-Y was generated by in vitro digestion of fibronectin by acid protease in extracts of osteoclast cells. These findings suggest that Ugl-Y is probably produced by degradation of fibronectin comprising bone matrix during the process of vigorous bone resorption in children and adolescents. This is the first report on the identification and characterization of juvenile-specific fibronectin fragments excreted into urine.

Deoxyribonuclease I gene polymorphism in Han Chinese population: frequency and effect on glucose and lipid parameters

DNASE1, the encoding gene of deoxyribonuclease I (DNase I), exhibits polymorphisms, including a single nucleotide polymorphism (SNP A2317G) in exon 8 and a 56 bp variable number of tandem repeat, designated as HumDN1 in intron 4. Several different ethnic population studies have revealed both A2317G and HumDN1 demonstrate genetic heterogeneity in the worldwide distribution. Recently, G2317 allele was proposed as an independent risk factor for myocardial infarction in Japanese population. In the present study, we identified A2317G and HumDN1 genotypes in 402 unrelated healthy Han Chinese individuals. At the same time, the impact of different genotypes and diplotypes of DNase I on plasma lipids levels and fasting blood glucose was also illuminated. Polymerase chain reaction and restriction fragment length polymorphism were used for the detection of HumDN1 and A2317G polymorphisms. Plasma glucose and lipids were measured in fasting state by biochemical methods. Three genotypes of A2317G and 9 genotypes of HumDN1 were detected in Han Chinese population. Among them, the most predominate alleles were A2317 (frequency = 53.6%) and HumDN1*3 (frequency = 47.4%) respectively. Linkage disequilibrium between A2317G and HumDN1 polymorphisms was also observed (D' = 0.717). Haplotype A-3, presented in frequency of 46.5%, was most common. Compared to other ethnic populations, Han Chinese had its own unique DNase I gene distribution characteristics. As for the influence of DNase I gene polymorphisms on lipids and glucose levels, no association was found between either genotype or diplotype and these parameters. (all P > 0.05). Results obtained in this study could be used for anthropological investigation, probing into relations between DNase I gene and diseases.

Analysis of genetic polymorphism of deoxyribonuclease I in Ovambo and Turk populations using a genotyping method

Deoxyribonuclease I (DNase I) polymorphism has been used as a valuable marker in genetic and clinical investigations. Six codominant alleles are known for DNase I, DNASE1*1, *2, *3, *4, and the recently discovered alleles *5 and *6. To detect these two new alleles, we added a new DNase I genotyping method based on both an allele-specific amplification and mismatched polymerase chain reaction (PCR). These methods were used to examine the distribution of DNase I genotypes in unrelated individuals from bloodstains of Ovambo and Turkish populations. The DNASE1*1 allele was found to be most dominant in the Ovambos. In contrast, Turks showed the highest allele frequency for DNASE1*2. This study is the first to demonstrate that there is a certain genetic heterogeneity in the worldwide distribution of DNase I polymorphism using the genotyping method of human DNase I polymorphism with PCR.

Clinical applications of DNase I, a genetic marker already used for forensic identification

This review primarily summarizes the clinical applications of deoxyribonuclease I (DNase I). Human DNase I exhibits polymorphism at both the protein and DNA level, and thus is potentially one of the best biochemical markers for forensic practice. Clinically, DNase I activity in serum can be used as a novel diagnostic marker for the early detection of acute myocardial infarction and transient myocardial ischemia. Furthermore, the DNase I gene is considered to be one of the susceptibility genes for gastric and colorectal carcinoma, and myocardial infarction. Over the last decade since the discovery of the utility of its genetic polymorphism for forensic purposes, research on DNase I has expanded into clinical applications.

Molecular, biochemical and immunological analyses of porcine pancreatic DNase I

Deoxyribonuclease I (DNase I) was purified 26500-fold in 39% yield from porcine pancreas to electrophoretic homogeneity using three-step column chromatography. The purified enzyme was inhibited by an antibody specific to the purified enzyme but not by G-actin. A 1303 bp cDNA encoding porcine DNase I was constructed from total RNA from porcine small intestine using a rapid amplification of cDNA ends method, followed by sequencing. Mature porcine DNase I protein was found to consist of 262 amino acids. Unlike all other mammalian DNase I enzymes that are inhibited by G-actin, porcine DNase I has H65 and S114 instead of Y65 and A114, which presumably results in the lack of inhibition. Porcine DNase I was more sensitive to low pH than rat or bovine enzymes. Compared with their primary structures, the amino acid at position 110 was N in porcine enzyme, but S in rat and bovine enzymes. A porcine mutant enzyme in which N was substituted by S alone at position 110 (N110S) became resistant to low pH to a similar extent as the rat and bovine enzymes.

DNase I: structure, function, and use in medicine and forensic science

In this review, available structural data of deoxyribonucleases I (DNases I) from several mammalian species, hen, snake and frog are summarized. Comparative studies on enzymatic and immunological properties and glycosylation are discussed, and several evolutionary conclusions are presented. Over the past decade, the availability of new investigative tools, including sensitive methods of electrophoresis, detection and determination, and genetically modified DNase I models has resulted in a clearer understanding of the molecular mechanisms that connect the function and usefulness of DNase I in medicine and forensic science.

Mammalian deoxyribonucleases I are classified into three types: pancreas, parotid, and pancreas-parotid (mixed), based on differences in their tissue concentrations

Deoxyribonuclease I (DNase I) activities were measured in 14 different tissues from humans and 5 other mammals (bovine, pig, rabbit, rat, and mouse) by using the single radial enzyme diffusion (SRED) method, which is a sensitive and nonradioactive assay for nucleases. The results indicated that these species are classifiable into three groups on the basis of their different tissue distributions of DNase I. In human and pig, the pancreas showed the highest activity of DNase I; in rat and mouse, the parotid glands showed the highest activity; and in bovine and rabbit, both pancreas and parotid glands showed high activity. Therefore we designated human and pig DNase I as pancreas type, rat and mouse DNase I as parotid type, and bovine and rabbit DNase I as pancreas-parotid (or mixed) type. DNase I of the pancreas type was more sensitive to low pH than the other types. DNase I of pancreas type is secreted into the intestinal tract under neutral pH conditions, whereas the other types are secreted from the parotid gland and have to pass through the very acidic conditions in the stomach. Differences in the tissue distribution and acid sensitivity of mammalian DNases I may provide important information about their digestive function from the evolutionary perspective.

Molecular, biochemical and immunological studies of hen pancreatic deoxyribonuclease I

Deoxyribonuclease I (DNase I) was purified from the hen pancreas to electrophoretic homogeneity using six-step column chromatography. The purified enzyme showed a molecular mass of about 33 kDa and maximum activity at pH 7.0. It required divalent cations, Mg2+ and Ca2+, for its activity and was inhibited by EDTA, EGTA and an antibody specific to the purified enzyme but not by G-actin. A 1066-bp cDNA encoding hen DNase I was constructed from the total RNA of a hen pancreas using a combination of the reverse transcriptase-polymerase chain reaction and rapid amplification of cDNA ends methods, followed by sequencing. The cDNA was expressed in Escherichia coli, and the recombinant polypeptide exhibited significant enzyme activity. The mature hen DNase I protein was found to consist of 262 amino acids. In human and bovine DNase I four amino acid residues, Glu-13, Tyr-65, Val-67 and Ala-114 are involved in actin binding, whereas in the hen DNase I these positions were occupied by Asp, Phe, Ser and Phe, respectively. A survey of the DNase I distribution in 15 hen tissues showed that the pancreas had the highest levels of both DNase I enzyme activity and DNase I gene expression. The results of our phylogenetic and immunological analyses indicate that the hen DNase I is not closely related to the mammalian enzymes. This is the first report in which has been described the results of molecular, biochemical and immunological analyses on hen DNase I.

A new allele, DNASE1*6, of human deoxyribonuclease I polymorphism encodes an Arg to Cys substitution responsible for its instability

A new allele, DNASE1*6, of human deoxyribonuclease I (DNase I) has been discovered by isoelectric focusing: its gene product has the most cathodic pI of the six electrophoretic variants. Results of DNA sequencing, mismatched PCR-restriction fragment length polymorphism, and transient transfection of the variant construct showed that the mutant was caused by a C-T transition at nucleotide position 1826, resulting in an Arg to Cys substitution at amino acid position 185 of the mature enzyme. The variant isoenzyme, expressed in COS-7 cells, was more labile than the other types. Instability and an increase in the pI value of the variant suggest that a structural alteration, perhaps due to aberrant formation of a disulfide bond, could occur in the enzyme.

Detection of isozymes of deoxyribonucleases I and II on electrophoresed gels with picogram sensitivity using SYBR Green I

A highly sensitive method for detecting deoxyribonucleases (DNases) I and II on an electrophoresed gel is described. A dried agarose film sheet containing DNA as a substrate and a buffer reagent was placed in contact with the gel surface after electrophoresis (DAFO method, Yasuda et al., Anal. Biochem. 1989, 183, 84-88). After an appropriate incubation period, the film sheet was peeled off and stained with SYBR-Green I (SG), and then the DNase isozyme bands were detected using a fluorescence image analyzer. We could detect pg levels of the DNases (DNase I, 2 pg; DNase II, 2pg), which represents a 32- to 128-fold increase in sensitivity compared with the original DAFO method using ethidium bromide (EB) as the fluorescent dye. A combination of this new detection method and isoelectric focusing electrophoresis in polyacrylamide gel allowed accurate DNase I typing from 1 microL human serum. This new technique has been named SG-DAFO, after its original dried agarose film overlay method using EB (EB-DAFO).

Phenotype 2 of deoxyribonuclease I may be used as a risk factor for gastric carcinoma

BACKGROUND

Human deoxyribonuclease I (DNase I) (EC3.1.21.1) is one of the candidate nucleases that acts in mammalian cells during apoptosis. Genetic polymorphism of DNase I has been classified into 15 phenotypes controlled by 5 autosomal codominant alleles. The purpose of this study was to determine whether DNase I polymorphism is closely related to the incidence of gastric carcinoma.

METHODS

The phenotype distribution was examined using urine samples obtained from unrelated Japanese patients with gastric carcinoma (n = 97) and benign gastric diseases (n = 76). Phenotyping was performed using isoelectric focusing electrophoresis in thin polyacrylamide gel and immunoblotting with an antihuman DNase I antibody.

RESULTS

A close statistical association was found between patients with gastric carcinoma and a high frequency of DNase I phenotype 2. However, there was no significant difference in the phenotype distribution between the group of patients with benign gastric diseases and the controls.

CONCLUSIONS

The findings of the current study suggest that DNase I phenotype 2 may be a marker for gastric carcinoma. Therefore, compared with other phenotypes, DNase I phenotype 2 may have potential for identifying patients who are at risk of harboring or developing gastric carcinoma.

Two novel screening methods for selecting monoclonal antibodies which specifically inhibit DNase I enzyme activity

Two novel screening methods, single radial enzyme diffusion and the DNA-cast polyacrylamide gel electrophoresis, for selecting monoclonal antibodies which detect human deoxyribonuclease I (DNase I) enzyme activity are described. The former was adopted for initial screening to select potential objective antibodies from numerous hybridoma culture supernatants, because it was easy to perform and a powerful mass-screening tool. The latter was utilized for the subsequent precise selection of the antibodies in the supernatants selected after preliminary screening by the former, because it was clearly more accurate and sensitive, although the procedure was slightly more complicated. The consecutive use of these two methods resulted in the isolation of 25 anti-human DNase I antibodies, all of which specifically inhibited the activity of human DNase I.