Denaturing High-performance Liquid Chromatography Profiles Research Articles

Clonal Evolution of Gene Mutations Involving DNA Methylation in the Progression of CMML to Secondary AML

Abstract Background and Aim: The molecular pathogenesis of progression of chronic myelomonocytic leukemia (CMML) to secondary acute myeloid leukemia (sAML) remains incompletely understood. Genemutations involving DNA methylation in the transformation of CMML to sAML were investigated in matched paired CMML/sAML bone marrow samples to determine the roles of TET2, DNMT3A, IDH1 and IDH2 mutations in the evolution of CMML to sAML. Material and Methods: 106 CMML (63 CMML-1 and 43 CMML-2) patients were analyzed for TET2, DNMT3A, IDH1, and IDH2 mutations at the initial diagnosis. 33 patients had paired CMML/sAML bone marrow samples for comparative analyses. Mutational analysis of TET2 was performed by PCR followed by direct sequencing for PCR products amplified with primer pairs covering the whole coding sequences (exons 3-11). DNMT3A mutations (exons 2-23) were screened by denaturing high-performance liquid chromatography (DHPLC) with adding GC-clamps to the primers to facilitate mutation detection.Samples with abnormal DHPLC profile were then directly sequenced. The hot spots of IDH1 and IDH2 genes on exon 4 were PCR-amplified from gDNA and subjected for direct sequencing. Additional gene mutations were analyzed by PCR-based assays with direct sequencing. The allele burden of gene mutations was measured at both CMML and sAML phases by pyrosequencing with a detection sensitivity of 5%. Results: The frequencies of TET2, DNMT3A, IDH1 and IDH2 in 106 CMML patients were 39.8% (41/103), 8.5% (9/106), 0% (0/106), and 7.5% (8/106), respectively. These epigenetic gene mutations were mostly mutually exclusive. Of the 31 paired CMML/sAML samples examined for DNMT3A, 4 had DNMT3A mutations at diagnosis; the mutation status, patterns and allele burden remained unchanged at sAML phases. None of 33 patients acquired IDH1 mutation and one acquired IDH2 mutation during sAML progression. Of the 30 patients with paired samples analyzed for TET2 mutation, 12 patients had TET2 mutations at both CMML and sAML phases; 10 patients retained the same TET2 mutations with stable allele burden, one patient had clonal expansion of TET2 mutation, and the other patient acquired 3rdTET2 mutation at sAML progression along with expansion of a preexisted TET2 mutant clone and one stable TET2 mutant subclone. Another patient harboring TET2 mutation at CMML diagnosis lost themutation at sAML progression. Acquisition of additional gene mutations during sAML evolution was detected in 5 TET2-mutated patients, including RUNX1, CEBPA, FLT3- ITD, JAK2 V617F, NPM1, SRSF2, and CSF3R, either alone or in combination. Conclusions: Our results showed that TET2 and DNMT3A mutational status and allele burden remained unchanged during the progression of CMML to sAML except that rare patients might have expansion or emergence of TET2 subclone at sAML phase. Acquisition of additional gene mutations occurred in half of TET2-mutated patients during the progression of CMML to sAML. Grant support: NHRI- EX103-10003NI and MOHW103-TD-B-111-09 Disclosures No relevant conflicts of interest to declare.

Application of Denaturing High-Performance Liquid Chromatography for Monitoring Sulfate-Reducing Bacteria in Oil Fields

Sulfate-reducing bacteria (SRB) participate in microbially induced corrosion (MIC) of equipment and H2S-driven reservoir souring in oil field sites. Successful management of industrial processes requires methods that allow robust monitoring of microbial communities. This study investigated the applicability of denaturing high-performance liquid chromatography (DHPLC) targeting the dissimilatory sulfite reductase ß-subunit (dsrB) gene for monitoring SRB communities in oil field samples from the North Sea, the United States, and Brazil. Fifteen of the 28 screened samples gave a positive result in real-time PCR assays, containing 9 × 10(1) to 6 × 10(5) dsrB gene copies ml(-1). DHPLC and denaturing gradient gel electrophoresis (DGGE) community profiles of the PCR-positive samples shared an overall similarity; both methods revealed the same samples to have the lowest and highest diversity. The SRB communities were diverse, and different dsrB compositions were detected at different geographical locations. The identified dsrB gene sequences belonged to several phylogenetic groups, such as Desulfovibrio, Desulfococcus, Desulfomicrobium, Desulfobulbus, Desulfotignum, Desulfonatronovibrio, and Desulfonauticus. DHPLC showed an advantage over DGGE in that the community profiles were very reproducible from run to run, and the resolved gene fragments could be collected using an automated fraction collector and sequenced without a further purification step. DGGE, on the other hand, included casting of gradient gels, and several rounds of rerunning, excising, and reamplification of bands were needed for successful sequencing. In summary, DHPLC proved to be a suitable tool for routine monitoring of the diversity of SRB communities in oil field samples.

Prenatal and post-natal screening of β-thalassemia and hemoglobin E genes in Thailand using denaturing high performance liquid chromatography

We have developed methods based on PCR and denaturing high performance liquid chromatography (DHPLC) for rapid identifications of common β-thalassemia mutations found in Thailand. The β-globin gene was separately amplified by PCR on four different fragments covering eight most common β-thalassemia mutations including nucleotide -28 A-G, codon 17 (A-T), IVSI-1 (G-T), IVSI-5 (G-C), codon 26 (G-A or Hb E), codons 41/42 (-TTCT), codons 71/72 (+A) and IVSII-654 (C-T). After PCR amplification, heteroduplex was generated by denaturation at 95 °C for 5 min followed by a slow reduction in temperature to 25 °C at 0.03 °C/s. Analysis of heteroduplex was done on an automated WAVE Nucleic Acid Fragment Analysis System. Specific DHPLC profile for each mutation was demonstrated which could be used in screening for all eight β-thalassemia mutations. Further validation was done on 42 pre- and post-natal DNA samples which demonstrated 100 % accuracy as compared to the result obtained with conventional PCR assays. In a remaining case with an unknown mutation, a different DHPLC profile was noted on one of the amplified fragment. Further DNA sequencing of this fragment revealed a T-G transversion at the IVSI-116, a previously un-described mutation in Thai population. The DHPLC assay developed should prove useful for rapid screening of known and unknown β-thalassemia mutations during carrier screening and pre-natal diagnosis which would facilitate an ongoing prevention and control program of thalassemia.

Bacterial Diversity in an Amazonian Mangrove Ecosystem

Mangroves form a transition zone among terrestrial, marine, and freshwater environments, and they host a striking diversity of macro- and microorganisms. In recent years, increasing anthropogenic impacts have caused widespread degradation of mangrove environments. To analyze the bacterial diversity of Salina Lake, an artificial body of water located in the mangroves of eastern Amazonia, total DNA was extracted from sediment and water samples that were collected from three sites (P1, P2, P3) located within the lake. The 16S rRNA gene was partially amplified, separated using the Denaturing High Performance Liquid Chromatography (DHPLC) method, and sequenced. The DHPLC profiles were quite distinct for the different aquatic and sedimentary bacterial communities. The most abundant groups (> 70%) at all sampled locations were Proteobacteria and unclassified bacteria, but other phyla were also identified, including Bacteroidetes, Cyanobacteria, Acidobacteria, Firmicutes, Actinobacteria, Chloroflexi, Siprochaetes and TM7 . A total of 24, 15, and 23 OTUs (Operational Taxonomic Units) were observed in the water samples from P1, P2, and P3, respectively, whereas the sediment samples returned 29, 34, and 52 OTUs. This is the first analysis performed on the bacterial diversity of Salina Lake, which was created by the construction of a highway within a protected mangrove area.

Mutations in the gyrA and parC genes and in vitro activities of fluoroquinolones in 114 clinical isolates of Pseudomonas aeruginosa derived from urinary tract infections and their rapid detection by denaturing high-performance liquid chromatography

Fluoroquinolone (FQ) resistance in Pseudomonas aeruginosa has spread. The purpose of this study was to investigate the correlation between representative FQ, i.e. levofloxacin (LVX), resistance and mutations in the gyrA and parC genes of P. aeruginosa clinical isolates from the urine of urinary tract infection patients and their rapid detection by denaturing high-performance liquid chromatography (DHPLC). The susceptibility to LVX of 114 clinical isolates was measured and the quinolone resistance-determining regions (QRDRs) in the gyrA and parC genes of these isolates were sequenced. DHPLC was undertaken to correlate the distinctive chromatograms with their DNA mutation patterns. Among 114 isolates tested, 22 isolates (19.3%) were resistant to LVX. Six amino acid mutations were detected (Thr83Ile, Asp87Tyr and Asp87Asn in gyrA and Ser87Leu, Ser87Trp and Glu91Arg in parC), existing alone or in combination. There were 10 kinds of mutation patterns. The presence of two or more kinds of mutation significantly correlated with LVX resistance compared with the wild-type or a single mutation (P<0.0001). DHPLC data identified the number of amino acid mutations with reproducibility distinguishable by peak number and profile of the DHPLC chromatogram. In conclusion, two or more mutations in gyrA and parC were significantly related to LVX resistance in P. aeruginosa. DHPLC facilitated the detection of resistant alleles, providing a rapid (5min per sample), economical (96 samples per run) and reliable technique for characterising LVX resistance in P. aeruginosa. This rapid detection system could forecast LVX resistance by the DHPLC profile.

Detection of a novel splicing mutation causing analbuminemia in a Libyan family

Background and objectivesAnalbuminemia is a very rare autosomal recessive disorder. It is an allelic heterogeneous defect caused by a variety of mutations within the albumin gene.We describe in this report two new cases of analbuminemia in Libyans. Design and methodsThe 14 coding exons of the human serum albumin (HSA) gene and their intron–exon junctions were PCR amplified. The products were screened for mutations by Denaturing High Performance Liquid Chromatography (DHPLC). Samples with altered DHPLC profiles were sequenced. ResultsDNA sequencing revealed the presence of a novol homozygous G➔T transition in the first base of intron 11 (c.1428+1G>T), in both children. This mutation destroys the GT consensus donor sequence found at the 5′ end of most intervening sequences and would cause the defective pre-mRNA splicing. ConclusionMolecular diagnosis based on DHPLC and DNA sequencing represents a powerful tool to study molecular defects causing analbuminemia.

Application of Denaturing High-Performance Liquid Chromatography (DHPLC) for the Identification of Fish: A New Way To Determine the Composition of Processed Food Containing Multiple Species

The identification of fish species in transformed food products is difficult because the existing methods are not adapted to heat-processed products containing more than one species. Using a common to all vertebrates region of the cytochrome b gene, we have developed a denaturing high-performance liquid chromatography (DHPLC) fingerprinting method, which allowed us to identify most of the species in commercial crab sticks. Whole fish and fillets were used for the creation of a library of referent DHPLC profiles. Crab sticks generated complex DHPLC profiles in which the number of contained fish species can be estimated by the number of major fluorescence peaks. The identity of some of the species was predicted by comparison of the peaks with the referent profiles, and others were identified after collection of the peak fractions, reamplification, and sequencing. DHPLC appears to be a quick and efficient method to analyze the species composition of complex heat-processed fish products.

Molecular monitoring of fungal communities in air samples by denaturing high-performance liquid chromatography (D-HPLC)

To describe a new molecular technique for the assessment of fungal diversity in the air. Air samples were collected every week in a henhouse in France during a 15-week period. After air sampling, the collecting membrane was diluted, and the liquid was used for subsequent cultivation and molecular analysis: PCR-temperature temporal gradient electrophoresis (TTGE), which has already been used for the identification of fungal species in air samples and PCR-denaturing high-performance liquid chromatography (D-HPLC), a new technique for the analysis of complex microbial populations. D-HPLC profiles were reproducible from run-to-run, and several fungal organisms could be identified at the species level by sequencing. PCR-D-HPLC enabled the identification of fungal species (both Ascomycota and Basidiomycota) that may be encountered in air. The new technique allowed the detection of more fungal species than did the PCR-TTGE technique. However, some fungal species were detected only by PCR-TTGE, suggesting that PCR-D-HPLC and PCR-TTGE are complementary. PCR-D-HPLC represents a considerable saving in time over currently available procedures for detection and identification of fungal organisms in air. However, the fungal diversity detected by PCR-D-HPLC or by PCR-TTGE was lower than that revealed by culture.

Detection of genomic DNA methylation with denaturing high performance liquid chromatography

DNA methylation contributes to the epigenetic control of gene expression. Variations in the methylation status can result in the silencing of genes. DNA methyltransferase converts cytosine to 5-methyl cytosine in CpG islands located in the promoter regions of genes. When CpG islands are hypermethylated, the gene is repressed/silenced, and similarly when it is hypomethylated, transcription can take place and the gene is expressed. The classical methods to detect DNA methylation require labor-intensive and time-consuming steps. As a result of large-scale expression profiling studies, high-throughput techniques are needed to screen for alterations in the methylation patterns. Denaturing high performance liquid chromatography (DHPLC) is a reliable, highly sensitive technique for mutation discovery. In the present study we examined the suitability of DHPLC technology to detect alterations in methylation pattern of the promoter regions of several genes. We report reliable and reproducible results in distinguishing methylated and unmethylated promoter regions of human PCDHGB6, c-MYC, MGMT1, CDKN2A/p16, and ATM genes. These DHPLC profiles were independently confirmed with bisulfite genomic sequencing. In conclusion, DHPLC technology serves as a rapid screening tool to monitor the genomic DNA methylation and could be used to increase the throughput efficiency of methylation analysis.

Unique spectrum of SPAST variants in Estonian HSP patients: presence of benign missense changes but lack of exonic rearrangements

BackgroundHereditary spastic paraplegia (HSP) is a clinically and genetically heterogeneous disorder that can be an autosomal-dominant, autosomal-recessive, or X-linked disease. The most common autosomal-dominant form of the disease derives from mutations in the SPAST gene.MethodsThe aim of this study was to analyze 49 patients diagnosed with HSP from the Estonian population for sequence variants of the SPAST gene and to describe the associated phenotypes. Healthy control individuals (n = 100) with no family history of HSP were also analyzed. All patient samples were screened using denaturing high performance liquid chromatography (DHPLC) and multiplex ligation-dependent probe amplification (MLPA) assay. Samples with abnormal DHPLC and MLPA profiles were sequenced, with the same regions sequenced in control samples.ResultsSequence variants of SPAST were identified in 19/49 HSP patients (38.8%), twelve among them had pathogenic mutations. Within the latter group there was one sporadic case. Eight patients had pure, and four - complex HSP. The twelve variants were identified: seven pathogenic (c.1174-1G>C, c.1185delA, c.1276C>T, c.1352_1356delGAGAA, c.1378C>A, c.1518_1519insTC, c.1841_1842insA) and five non-pathogenic (c.131C>T, c.484G>A, c.685A>G, c.1245+202delG, c.1245+215G>C). Only 2 of these mutations had previously been described (c.131C>T, c.1245+202delG). Three mutations, c.1174-1G>C, c.1276 C>T, c.1378C>A, showed intrafamilial segregation.ConclusionThis study identified new variants of the SPAST gene which included benign missense variants and short insertions/deletions. No large rearrangements were found. Based on these data, 7 new pathogenic variants of HSP are associated with clinical phenotypes.

Clinical features and hMSH2/hMLH1 germ-line mutations in Chinese patients with hereditary nonpolyposis colorectal cancer

At least five mismatch repair (MMR) genes, including hMSH2, hMLH1, hPMS, hPMS2, and hMSH6/GTBP, are associated with hereditary nonpolyposis colorectal cancer (HNPCC). More than 90% of families with HNPCC harbor the hMSH2 and hMLH1 gene mutations. We have analyzed the clinical features of HNPCC among Chinese patients and report the results of screening for mutations in the hMSH2 and hMLH1 genes. The data concerning gender, site of colorectal cancer (CRC), age at diagnosis, history of synchronous and/or metachronous colorectal cancer, instance of extracolonic cancers, and histopathology of tumors for 126 patients from 28 independent families with HNPCC were collected. Fifteen of the families met the Amsterdam I criteria, and 13 met the Japanese clinical criteria for diagnosis. Genomic DNA was extracted from the peripheral lymphocytes. Polymerase chain reaction (PCR) and denaturing high-performance liquid chromatography (DHPLC) were used to screen the coding region of the hMSH2 and hMLH1 genes. Samples showing abnormal DHPLC profiles were sequenced. One hundred and seventy malignant neoplasms were found in the 126 patients, of whom 23 had multiple cancers. Ninety-eight of the patients (77.8%) had colorectal cancers, with an average age at onset of 45.9 years and a right-sided predominance. Eight hMSH2 or hMLH1 gene sequence variations were found in 12 families, and a germ-line G204X nonsense mutation in the third exon of hMSH2 was found, representing the first mutation in an MMR gene ever found in people of Chinese Mongolian ethnicity. HNPCC is a typical autosomally dominant hereditary disease, characterized by early onset, a predominance of proximal colorectal cancer, and multiple synchronous and metachronous colorectal cancers. DHPLC is a powerful tool for detecting mutations in the hMSH2 and hMLH1 genes. Mutations in the first nine exons of the hMLH1 gene were more common in Chinese patients.

Pitfalls in the Denaturing High-Performance Liquid Chromatography Analysis of Mitochondrial DNA Mutation

Denaturing high-performance liquid chromatography (DHPLC) purification of heteroduplexes has been reported as a method to increase sensitivity of the detection of low-level heteroplasmy by DNA sequencing, and DHPLC profiling has been suggested as a method to allow the correlation of a characteristic chromatographic profile with a specific sequence alteration. Herein we report pitfalls associated with the use of DHPLC for these purposes. We show that the purified heteroduplex fraction does not contain a 50:50 mix of wild-type and mutant DNA in DNA samples containing low-level mutations, and that with a commonly used protocol, DNA sequencing gave false negative results at the 1% mutation level, potentially leading to misdiagnosis. We improved the protocol to detect low levels of mutations and evaluated the sensitivity of DNA sequencing in the detection of mutation in these fractions. We also studied the DHPLC profiles of several mutations in the tRNALeu(UUR) region of mitochondrial DNA and found a characteristic profile in only one of five mutants tested, whereas four other mutants showed identical chromatographic profiles.

Putative role of specific JAG1 gene exons in modulating clinical features in patients with leukoencephalopathy

The aim of this study was to investigate the possible role of JAG1 gene mutations in modulating clinical features in patients with CADASIL-like phenotype which resulted negative for NOTCH3 gene mutations. Sixty-six CADASIL-like patients without NOTCH3 gene mutations were investigated for 5 out of 26 exons of the JAG1 gene, whose mutations were implicated in central nervous system vascular abnormalities. PCR was performed with primers specific for exons 3, 4, 13, 23 and 24 comprising the intron–exon boundaries. Amplicons were then analyzed by denaturing high performance liquid chromatography (DHPLC). The exons showing a variant DHPLC profile were directly sequenced. The sequence of exons 3, 4 and 23 revealed the presence of four already described polymorphisms in JAG1. 1001C/T (g.16015 C > T) in exon 4 was found in 9 patients, IVS23 + 18delT (g.33147 delT) in 29 patients, IVS3-15T/C (g.15852 T > C) in 17 patients, IVS2-43C/T (g.10532 C > T) in 1 patient; both the polymorphism 1001C/T and IVS3-15T/C were found in 3 patients. No mutations were found. These data demonstrate absence of correlation between mutations in specific JAG1 gene exons and clinical features in patients with CADASIL-like phenotype.

Mutation detection of ABCD1 gene in the molecular diagnosis of X-linked adrenoleukodystrophy by denaturing HPLC

目的 对4个肾上腺脑白质营养不良(ALD)家系进行基因突变分析.方法 应用变性HPLC技术检测了4个ALD家系的ABCD1基因,并通过核苷酸序列分析确证突变位点.结果 所有患儿的母亲,患儿2、患儿3、患儿4弟弟及其表弟与正常对照的PCR产物混合物,均出现变性HPLC洗脱双峰,而正常对照均为单峰,提示相应基因片段存在突变位点.上述出现异源双峰的PCR产物经直接测序,证实了相关突变的存在:患儿1母亲为fs Glu 471突变携带者;患儿2存在S108X突变;患儿3存在R617C突变;患儿4弟弟和表弟均存在A141T突变.结论 变性HPLC能有效地检测ABCD1基因突变,并为进一步地基因突变筛查与产前诊断提供依据。

Mutation screening of mismatch repair gene Mlh3 in familial esophageal cancer

To shed light on the possible role of mismatch repair gene Mlh3 in familial esophageal cancer (FEC). A total of 66 members from 10 families suggestive of a genetic predisposition to hereditary esophageal cancer were screened for germline mutations in Mlh3 with denaturing high performance liquid chromatography (DHPLC), a newly developed method of comparative sequencing based on heteroduplex detection. For all samples exhibiting abnormal DHPLC profiles, sequence changes were evaluated by cycle sequencing. For any mutation in family members, we conducted a segregation study to compare its prevalence in sporadic esophageal cancer patients and normal controls. Exons of Mlh3 in all samples were successfully examined. Overall, 4 missense mutations and 3 polymorphisms were identified in 4 families. Mlh3 missense mutations in families 9 and 10 might be pathogenic, but had a reduced penetrance. While in families 1 and 7, there was no sufficient evidence supporting the monogenic explanations of esophageal cancers in families. The mutations were found in 33% of high-risk families and 50% of low-risk families. Mlh3 is a high risk gene with a reduced penetrance in some families. However, it acts as a low risk gene for esophageal cancer in most families. Mutations of Mlh3 may work together with other genes in an accumulated manner and result in an increased risk of esophageal tumor. DHPLC is a robust and sensitive technique for screening gene mutations.

Denaturing HPLC-based approach for detection of COL7A1 gene mutations causing dystrophic epidermolysis bullosa

Dystrophic epidermolysis bullosa (DEB) is a rare clinically heterogeneous genodermatosis due to genetic defects in type VII collagen gene ( COL7A1). Identification of COL7A1 mutations is a challenge since this gene comprises 118 exons and more than 300 mutations scattered over the gene have been reported. Here, we describe for the first time the use of denaturing high performance liquid chromatography (DHPLC) for COL7A1 mutation detection. To validate the method, exon-specific DHPLC conditions were applied to screen DNA samples from patients carrying known COL7A1 mutations. Abnormal DHPLC profiles were obtained for all known mutations. Subsequent DHPLC analysis of 17 DEB families of unknown genotype allowed the identification of 21 distinct mutations, 9 of which were novel. The DHPLC mutation detection rate was significantly higher compared with our mutation scanning rate with conventional techniques (97% vs 86%), indicating DHPLC as the method of choice for COL7A1 molecular characterization in DEB patients.

Denaturing high-performance liquid chromatography in the detection of ABCA1 gene mutations in familial HDL deficiency

Mutations in the ABCA1 gene are the cause of familial high density lipoprotein deficiency (FHD). Because these mutations are spread over the entire gene, their detection requires the sequencing of all 50 exons. The aim of this study was to validate denaturing high-performance liquid chromatography (DHPLC) in mutation detection as an alternative to systematic sequencing. Exons of the ABCA1 gene were amplified using primers employed for sequencing. Temperatures for DHPLC were deducted from a software and empirically defined for each amplicon. To assess DHPLC reliability, we tested 30 sequence variants found in FHD patients and controls. Combined DHPLC and sequencing was applied to the genotyping of new FHD patients. Most of the amplicons required from two to five temperature conditions to obtain partially denatured DNA over the entire amplicon length. Twenty-nine of the variants found by sequencing were detected by DHPLC (97% sensitivity). The detection of the last variant (in exon 40) required different primers and amplification conditions. DHPLC and sequencing analysis of new FHD patients revealed that all amplicons showing a heteroduplex DHPLC profile contained sequence variants. No variants were detected in amplicons with a homoduplex profile. DHPLC is a sensitive and reliable method for the detection of ABCA1 gene mutations.

High capacity and low cost detection of prion protein gene variant alleles by denaturing HPLC

Mutations in the human prion protein gene ( PRNP) are responsible for hereditary diseases called transmissible spongiform encephalopathies (TSE) and a polymorphic site at codon 129 determines sensitivity to infectious forms of these maladies. More recently, codon 129 has been related to cognition performance in the elderly, in Alzheimer disease (AD) and in Down syndrome. Furthermore, a rare polymorphism at codon 171 was described in 23% of patients with mesial temporal lobe epilepsy related to hippocampal sclerosis (MTLE-HS), the most common form of surgically remediable epileptic syndrome. Thus, a method that permits fast and efficient screening of PRNP mutations and polymorphisms in patients, in high risk populations, and in family members is desirable. In the present study, we established the conditions for analysis of the PRNP open reading frame using denaturing high-performance liquid chromatography (DHPLC), whereby unpurified PCR products were subjected to denaturing and reannealing steps leading to heteroduplex formation. We described specific profiles for the PRNP polymorphisms at codons 129 (M/V), 117 (A/A silent), 219 (E/K), 171 (N/S), and the octarepeat deletion using amplified DNA from 562 samples. The chromatograms for TSE-associated mutations at codons 102 (P/L), 183 (T/A), and 210 (V/I) were also determined. Specificity of the DHPLC profile for each PRNP variant allele was confirmed in 100% of the samples by direct and cloned DNA sequencing in addition to endonuclease digestion when applicable. Therefore, the present study shows that DHPLC is a rapid, highly accurate and efficient technique for the detection of PRNP genetic variants.

Clinical features and hMSH2/hMLH1 germline mutation screening of Chinese hereditary nonpolyposis colorectal cancer patients

To analyze the clinical features of hereditary nonpolyposis colorectal cancer (HNPCC) among Chinese and report the results of screening of hMSH2 and hMLH1 gene mutations. The data concerning sex, site of colorectal cancer (CRC), age of diagnosis, history of synchronous and/or metachronous colorectal cancer, instance of extracolonic cancers, and histopathology of tumors of 126 patients from 28 independent families of HNPCC in China were collected, of which 15 met the Amsterdam criteriaI and 13 met the Japanese clinical diagnosis criteria. The genomic DNA was extracted from the peripheral lymphocytes. Polymerase chain reaction (PCR) and denaturing high-performance liquid chromatography (DHPLC) were used to screen the coding region of hMSH2 and hMLH1 genes. Samples showing abnormal DHPLC profiles were sequenced by a 377 DNA sequencer. One hundred and seventy malignant neoplasms were found in the 126 patients, in which 23 of multiple cancers were found. Ninety-eight of the 126 patients (77.8%) had colorectal cancers, with an average age of onset of 45.9 years and a right-sided predominance. Eight hMSH2 or hMLH1 gene sequence variations were found in 12 families, and a germline G204X nonsense mutation in the third exon of hMSH2 was found for the first time, the first mismatch repair gene (MMR) mutation ever found in Chinese Mongolian people. HNPCC is a typical auto-dominant hereditary disease, characterized by early onset, proximal predominance of colorectal cancer, multiple synchronous and metachronous colorectal cancers, and an excess of extra-colonic cancers. Frequent gastric cancer occurrence and less synchronous colorectal cancers are notable features in Chinese HNPCC patients. DHPLC is a powerful tool in hMSH2 and hMLH1 gene mutation screening. Three novel mutations have been found. hMLH1 gene mutations, especially those of the first nine exons, are more common than hMSH2 gene mutations in Chinese patients.

Clinical features and mismatch repair gene mutation screening in Chinese patients with hereditary nonpolyposis colorectal carcinoma.

Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominantly-inherited cancer-susceptibility syndrome that confers an increased risk for colorectal cancer and a variety of other tumors at a young age. It has been associated with germline mutations in five mismatch repair (MMR) genes (hMSH2, hMLH1, hPMS1, hPMS2, and hMSH6/GTBP). The great majority of germline mutations were found in hMSH2 and hMLH1. The purpose of this study was to analyze the clinical features of Chinese HNPCC patients and to screen hMSH2 and hMLH1 gene mutations. Twenty-eight independent Chinese families were collected, of which 15 met Amsterdam criteria I and 13 met the Japanese clinical diagnosis criteria. The data were recorded including sex, site of colorectal cancer (CRC), age of diagnosis, history of synchronous and/or metachronous CRC, instance of extracolonic cancers, and histopathology of tumors. Peripheral blood samples were collected from all pedigrees after formal written consents were signed. PCR and denaturing high-performance liquid chromatography (DHPLC) were used to screen the coding regions of hMSH2 and hMLH1 genes. The samples showing abnormal DHPLC profiles were sequenced by a 377 DNA sequencer. One hundred and seventy malignant neoplasms were found in one hundred and twenty-six patients (multiple cancer in twenty-three), including one hundred and twenty-seven CRCs, fifteen gastric, seven endometrial, and five esophageal cancers. Seventy-seven point eight percent of the patients had CRCs, sharing the features of early occurrence (average age of onset, 45.9 years) and of the right-sided predominance reported in the literature. In Chinese HNPCC patients, gastric cancer occurred more frequently, accounting for 11.9% of all cancers patients and ranking second in the spectrum of HNPCC predisposing cancers. Synchronous CRCs occurred less frequently, only accounting for 3.1% of the total CRCs. Twenty percent of the colorectal patients had metachronous CRCs within 10 years after operation. Eight hMSH2 or hMLH1 gene sequence variations were found in twelve families, including the first Mongolian kindred with a hMSH2 gene mutation. HNPCC is characterized by an early-age onset, proximal predominance of CRC, multiple metachronous CRCs, and an excess of extra-colonic cancers. Frequent gastric cancer occurrence and less synchronous CRCs are the remarkable features in Chinese HNPCC patients. DHPLC is a powerful tool in hMSH2 and hMLH1 gene mutation screening. hMLH1 gene mutations, especially of the first nine exons, have been found more common than hMSH2 gene mutations in Chinese patients. Three of seven mutations have been found to be novel, and the germline G204X nonsense mutation in the third exon of hMSH2 has become the first MMR gene mutation found in Chinese Mongolian people.