Biallelic IgH rearrangements in patients with indolent lymphoproliferative disorders: molecular and practical implications

We report a group of patients (pts) with indolent lymphoproliferative disorder who had both alleles for the immunoglobulin heavy chain genes rearranged (biIgH). This group of 17 pts consisted of 9 small lymphocytic lymphomas (SLL) and 8 chronic lymphocytic leukemia (CLL). The polymerase chain reaction (PCR) amplification of clonal immunoglobulin heavy (IgH) rearrangement using the complementarity determining region III (CDRIII) constantly retrieved two distinct bands in all PCR informative samples of those pts. To rule out biclonality, we evaluated samples by fluorescein activated cell sorting (FACS) analysis and sequenced the PCR products. We were able to obtain both IgH sequences from 12 patients. FACS suggested biclonality in one case, which also correlated with sequencing results as both IgH rearrangements were in-frame. Recently, we reported a patient who sustained transformation into an aggressive disease after biIgH was detected in the setting of monoclonal disease (Cerny et al., 2003b, Haematologica 88(05):ECR15 B.). We decided to compare clinical characteristics and prognosis of 17 pts with biIgH and 37 pts with monoIgH rearrangements. Although we found some minor differences in disease characteristics between both groups, these did not translate into a significantly different overall survival. Our findings suggest that true biclonal cases of CLL are rare.     

Experimental Trypanosoma cruzi biclonal infection in Triatoma infestans: detection of distinct clonal genotypes using kinetoplast DNA probes

Monitored biclonal densities of parasites were offered to third-stage larvae of Triatoma infestans via an artificial feeding device and 30 days later, the gut contents of the insects were processed for microscopic examination and polymerase chain reaction (PCR) detection of Trypanosoma cruzi kinetoplast DNA [kDNA]). A total of 15 mixtures involving nine different stocks attributed to the 19/20, 32 and 39 major clonal genotypes of Trypanosoma cruzi were used. The presence of each T. cruzi clonal genotype after completion of the cycle through the insects was investigated by hybridising the PCR amplification products with genotype-specific minicircle kDNA probes. Sixty-five out of 90 examined insects (72.2%) were positive for parasites by microscopic examination and 85 (94.4%) were positive by PCR. The results show that almost half of the biclonal infections are not detectable after completion of the cycle, and that there are important differences in detection of such biclonal infections according to the clonal genotypes considered. Moreover, elimination of a clonal genotype by another is a frequent, but not constant, pattern in biclonal infections of T. infestans. The use of PCR and kDNA probes makes it possible to avoid the culture phase, which makes detection of mixed infections much easier in epidemiological surveys. Moreover, the fact that T. infestansdoes not transmit different T. cruzi clonal genotypes with the same efficiency has strong implications for the reliability of xenogiagnosis.     

N-甲基亚硝基脲诱导小鼠胸腺淋巴瘤TCR基因重排分析

目的探讨N-甲基亚硝基脲（MNU）诱导的小鼠胸腺淋巴瘤的单克隆起源。方法采用巢式PCR方法,对8例MNU诱导的胸腺淋巴瘤组织进行T细胞受体β链（TCRβ）和γ链（TCRγ）克隆性基因重排分析,并对TCRγ基因重排的PCR产物直接测序。结果 8例胸腺淋巴瘤检测TCRβ和TCRγ均呈克隆性基因重排。DNA序列测定证实TCRγ基因PCR扩增产物为基因重排产物。结论巢式PCR TCR基因重排检测及DNA序列分析证实,MNU诱导的小鼠胸腺淋巴瘤是来源于T细胞的肿瘤。     

DHPLC mutation analysis of the hereditary nonpolyposis colon cancer (HNPCC) genes hMLH1 and hMSH2

Denaturing high-performance liquid chromatography (DHPLC) is an efficient method for detection of mutations involving a single or few numbers of nucleotides, and it has been successfully used for mutation detection in disease-related genes. Colorectal cancer is one of the most common cancers, and mutations in the genes for hereditary nonpolyposis colon cancer (HNPCC), hMLH1 and hMSH2, also involve mainly point mutations. Sequence analysis is supposed to be a screening method with high sensitivity; however, it is time-consuming and expensive. We therefore decided to test sensitivity and reproducibility of DHPLC for 71 sequence variants in hMLH1 and hMSH2 initially found by sequence analysis in DNA samples of German HNPCC patients. DHPLC conditions of the PCR products were based on the melting pattern of the wild-type sequence of the corresponding PCR fragments. All but one of the 71 mutations was detected using DHPLC (sensitivity of 97%). Running time per sample averaged only 7 min, and the system is highly automated. Thus DHPLC is a rapid and sensitive method for the detection of hMLH1 and hMSH2 sequence variants.     

Use of multiplex terminal restriction fragment length polymorphism for rapid and simultaneous analysis of different components of the soil microbial community

A multiplex terminal restriction fragment length polymorphism (M-TRFLP) fingerprinting method was developed and validated for simultaneous analysis of the diversity and community structure of two or more microbial taxa (up to four taxa). The reproducibility and robustness of the method were examined using soil samples collected from different habitats. DNA was PCR amplified separately from soil samples using individual taxon-specific primers for bacteria, archaea, and fungi. The same samples were also subjected to a multiplex PCR with the primers for all three taxa. The terminal restriction fragment length polymorphism profiles generated for the two sets of PCR products were almost identical not only in terms of the presence of peaks but also in terms of the relative peak intensity. The M-TRFLP method was then used to investigate rhizosphere bacterial, fungal, and rhizobial/agrobacterial communities associated with the dwarf shrub Calluna vulgaris growing in either open moorland, a mature pine forest, or a transition zone between these two habitats containing naturally regenerating pine trees. Rhizosphere microbial communities associated with Vaccinium myrtillus collected from the native pine forest were also investigated. In this study, individual PCR products from the three taxa were also pooled before restriction digestion and fragment size analysis. The terminal restriction fragment length polymorphism profiles obtained with PCR products amplified individually and with multiplexed and pooled PCR products were found to be consistent with each other in terms of the number, position, and relative intensity of peaks. The results presented here confirm that M-TRFLP analysis is a highly reproducible and robust molecular tool for simultaneous investigation of multiple taxa, which allows more complete and higher resolution of microbial communities to be obtained more rapidly and economically.     

Screening strategies for a highly polymorphic gene: DHPLC analysis of the Fanconi anemia group A gene

Introduction: Patients with Fanconi anemia (Fanc) are at risk of developing leukemia. Mutations of the group A gene (FancA) are most common. A multitude of polymorphisms and mutations within the 43 exons of the gene are described. To examine the role of heterozygosity as a risk factor for malignancies, a partially automatized screening method to identify aberrations was needed. We report on our experience with DHPLC (WAVE (Transgenomic)). Methods: PCR amplification of all 43 exons from one individual was performed on one microtiter plate on a gradient thermocycler. DHPLC analysis conditions were established via melting curves, prediction software, and test runs with aberrant samples. PCR products were analyzed twice: native, and after adding a WT-PCR product. Retention patterns were compared with previously identified polymorphic PCR products or mutants. Results and discussion: We have defined the mutation screening conditions for all 43 exons of FancA using DHPLC. So far, 40 different sequence variations have been detected in more than 100 individuals. The native analysis identifies heterozygous individuals, and the second run detects homozygous aberrations. Retention patterns are specific for the underlying sequence aberration, thus reducing sequencing demand and costs. DHPLC is a valuable tool for reproducible recognition of known sequence aberrations and screening for unknown mutations in the highly polymorphic FancA gene.     

Use of Multiplex Terminal Restriction Fragment Length Polymorphism for Rapid and Simultaneous Analysis of Different Components of the Soil Microbial Community▿

A multiplex terminal restriction fragment length polymorphism (M-TRFLP) fingerprinting method was developed and validated for simultaneous analysis of the diversity and community structure of two or more microbial taxa (up to four taxa). The reproducibility and robustness of the method were examined using soil samples collected from different habitats. DNA was PCR amplified separately from soil samples using individual taxon-specific primers for bacteria, archaea, and fungi. The same samples were also subjected to a multiplex PCR with the primers for all three taxa. The terminal restriction fragment length polymorphism profiles generated for the two sets of PCR products were almost identical not only in terms of the presence of peaks but also in terms of the relative peak intensity. The M-TRFLP method was then used to investigate rhizosphere bacterial, fungal, and rhizobial/agrobacterial communities associated with the dwarf shrub Calluna vulgaris growing in either open moorland, a mature pine forest, or a transition zone between these two habitats containing naturally regenerating pine trees. Rhizosphere microbial communities associated with Vaccinium myrtillus collected from the native pine forest were also investigated. In this study, individual PCR products from the three taxa were also pooled before restriction digestion and fragment size analysis. The terminal restriction fragment length polymorphism profiles obtained with PCR products amplified individually and with multiplexed and pooled PCR products were found to be consistent with each other in terms of the number, position, and relative intensity of peaks. The results presented here confirm that M-TRFLP analysis is a highly reproducible and robust molecular tool for simultaneous investigation of multiple taxa, which allows more complete and higher resolution of microbial communities to be obtained more rapidly and economically.     

Evaluation of T-cell receptor gene rearrangements in patients with recurrent patch/plaque (T2) CTCL (mycosis fungoides)

Cutaneous T-cell lymphoma is typically a clonal neoplasm of epidermotropic CD4+ T-lymphocytes that includes the entity mycosis fungoides (MF). After identification of patients with recurrent MF treated with total skin electron beam therapy (TSEBT) at the Yale University School of Medicine, this study attempted to compare T-cell receptor (TCR) gamma gene rearrangements via polymerase chain reaction (PCR) in both original and recurrent skin biopsies from these patients. Between 1974 and 1996, a total of 95 T2 MF patients were treated with TSEB, and four of these were identified for the study. Slides and tissue samples of both primary and recurrent skin biopsies for each patient were confirmed as being consistent with ME DNA for PCR was isolated from paraffin-embedded tissue samples. Using consensus primers that hybridize with conserved regions of the TCR gene, these regions of the genome were amplified. The PCR products were then analyzed by acrylamide gel electrophoresis. Of the primary and recurrent samples from four patients with a median disease-free interval (DFI) of 1222 days, only two showed evidence of a dominant TCR clone. A number of factors, including lack of sequence homology between the primers and the gene segments, the existence of multiple neoplastic cell lines, DNA degradation in the archival samples, and the presence of reactive as well as malignant lymphocytes, may have prevented the detection of dominant TCR rearranged clones in the samples. Despite the results of this study, TCR analysis via PCR and gel electrophoresis continues to be of utility in the evaluation of patients with MF when used in conjunction with other diagnostic modalities and in cases with nonspecific clinical, histopathological, and immunophenotyping findings.     

Denaturing high-performance liquid chromatography is a suitable method for PMM2 mutation screening in carbohydrate-deficient glycoprotein syndrome type IA patients

The phosphomannomutase 2 gene (PMM2; MIM 601785) has been identified as the carbohydrate-deficient glycoprotein syndrome type 1A gene (CDGS type 1A; MIM 212065). The gene spans 8 exons and 741 bp of coding DNA. Previously, we have identified 20 different mutations in the PMM2 gene using mutation screening with single-stranded conformation polymorphism (SSCP) and sequencing of DNA from 61 CDGS type 1A patients. Because eight of these could not be detected by SSCP, we were not satisfied with the sensitivity of the mutation detection technique used. Thus, we wanted to investigate if denaturing high-performance liquid chromatography (DHPLC) was a more suitable mutation screening method for PMM2. DHPLC was set up for PMM2 by optimizing eight different PCR fragments, one for each exon. The mutation detection was optimized empirically with PCR fragments from controls. First, control samples were run at a universal gradient and after modification and shortening of the gradient, also run at 10 different temperatures, 50-70 degrees C with 2-degree intervals, to enable setting of the temperature with the highest resolution. Then, PCR products with known mutations from the previous study were analyzed, and the results were compared to the control chromatograms for aberrations. We detected 19/20 mutations with DHPLC, and several mutations not detected by earlier screening techniques were readily detected by DHPLC. We conclude that DHPLC is a suitable detection technique for a rapid and reliable first scan of CDGS type 1A patients.     

Lymphadenitis and lymphoproliferative lesions associated with the human herpes virus-6 (HHV-6).

A newly described herpes virus, human herpes virus 6, (HHV-6), has been linked to exanthema subitum but beyond this its pathogenetic impact remains to be determined. A large body of evidence links it to various lymphoproliferative disorders and this study was conducted to identify forms of lymphoproliferation linked to HHV-6. We studied biopsy samples from 32 patients with disorders of the lymphatic system for the presence of HHV-6, both by polymerase chain reaction (PCR) and in-situ hybridization (ISH) methods, as well as Epstein-Barr virus (EBV) viral DNA, clonal rearrangements of the antigen receptor genes and bcl-2 genes. All the specimens were studied morphologically and a clinical follow-up of up to 4 years was obtained. Seven of the 32 patients were positive for HHV-6 DNA and the remainder were negative. Two of these HHV-6 positive specimens, both from elderly persons, showed a similar distinct histological pattern diagnosed as malignant B-cell lymphoma of high grade malignancy. Two other HHV-6-positive specimens were reactive lymphadenopathies occurring in younger adults. In addition, one further specimen with evidence of EBV-involvement was from a patient who died 3 months after biopsy with fatal infectious mononucleosis (IM). These five samples had HHV-6 DNA by PCR and ISH. Two specimens without specific histologic abnormalities showed evidence of HHV-6 only by PCR but not by ISH. Both high grade malignant lymphomas showed clonal proliferations, one of monoclonal B-cells and the other of clonal T-cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

Rearrangements of the T cell receptor delta gene in T acute lymphoblastic leukemia cells are distinct from those occurring in B lineage acute lymphoblastic leukemia and preferentially involve one V delta gene segment

Rearrangement of the TCR-delta gene was studied using J delta, C delta, and V delta probes in 61 cases of acute lymphoblastic leukemia (ALL) and several cases of chronic lymphoid neoplasms to define the specificity and the diversity of rearrangements occurring at the delta locus. TCR-delta rearrangements or deletions were found in all T (33 cases) and B lineage (28 cases) ALL but not in any case of B cell chronic proliferations (13 cases). The restriction patterns of rearrangement were clearly distinct between T and B ALL and use of one V delta probe showed that rearrangement of the V delta IDP2 gene segment which is also productively rearranged in the Peer cell line, occurred frequently in T-ALL but never in B lineage ALL. Studies of WT31 and delta TCS1 antibody reactivity showed that at least 4 of 13 CD3+ T-ALL cases expressed the delta protein. CD4 and/or CD8 Ag expression were observed in some of the gamma delta expressing T-ALL. These data show that particular TCR-delta gene rearrangements occur in neoplastic early B cells and that the combinatorial diversity of TCR-delta rearrangements in T cells is higher than initially expected. In addition this study shows that an important proportion of CD3 positive T-ALL cases express the gamma delta heterodimer.     

Molecular profiling of diatom assemblages in tropical lake sediments using taxon-specific PCR and Denaturing High-Performance Liquid Chromatography (PCR-DHPLC)

Here we present a protocol to genetically detect diatoms in sediments of the Kenyan tropical Lake Naivasha, based on taxon-specific PCR amplification of short fragments (approximately 100 bp) of the small subunit ribosomal (SSU) gene and subsequent separation of species-specific PCR products by PCR-based denaturing high-performance liquid chromatography (DHPLC). An evaluation of amplicons differing in primer specificity to diatoms and length of the fragments amplified demonstrated that the number of different diatom sequence types detected after cloning of the PCR products critically depended on the specificity of the primers to diatoms and the length of the amplified fragments whereby shorter fragments yielded more species of diatoms. The DHPLC was able to discriminate between very short amplicons based on the sequence difference, even if the fragments were of identical length and if the amplicons differed only in a small number of nucleotides. Generally, the method identified the dominant sequence types from mixed amplifications. A comparison with microscopic analysis of the sediment samples revealed that the sequence types identified in the molecular assessment corresponded well with the most dominant species. In summary, the PCR-based DHPLC protocol offers a fast, reliable and cost-efficient possibility to study DNA from sediments and other environmental samples with unknown organismic content, even for very short DNA fragments.     

Denaturing high performance liquid chromatography (DHPLC) used in the detection of germline and somatic mutations.

Denaturing high performance liquid chromatography (DHPLC) has been described recently as a method for screening DNA samples for single nucleotide polymorphisms and inherited mutations. Thirty-eight DNAs, 22 of which were heterozygous for previously characterized rearranged transforming gene (RET) or cystic fibrosis transmembrane conductance regulator gene (CFTR) mutations or polymorphisms, were examined using DHPLC analysis to assess the accuracy of this scanning method. Ninety-one per cent (20/22) of the PCR amplicons from specimens with heterozygous RET or CFTR sequence showed elution profiles distinct from corresponding homozygous normal patterns; whether the profiles for two amplicons containing heterozygous RET sequence were distinct from homozygous cases was equivocal. To investigate the usefulness of this method for detecting mutations in tumor DNAs, each of the phosphatase and tensin homologue deleted on chromosome ten gene (PTEN) exons were examined for mutations in 63 malignant gliomas. Seventeen PTEN PCR products from this series of brain tumors showed elution profiles indicating sample heterozygosity and in each instance conventional sequencing confirmed the presence of a mutation. PTEN amplicons containing exons 1, 3 and 5 were sequenced for each of the 63 tumor DNAs to determine whether any mutations may have escaped DHPLC detection, and this analysis identified one such alteration in addition to the eight mutations that DHPLC had revealed. In total, DHPLC identified 37 of 40 (92.5%) PCR products containing defined sequence variation and no alterations were indicated among 196 amplicons containing homozygous normal sequence.     

DHPLC/SURVEYOR Nuclease: A Sensitive, Rapid and Affordable Method to Analyze BRCA1 and BRCA2 Mutations in Breast Cancer Families

Hereditary breast cancer accounts for about 10% of all breast cancers and BRCA1 and BRCA2 genes have been identified as validated susceptibility genes for this pathology. Testing for BRCA gene mutations is usually based on a pre-screening approach, such as the partial denaturation DHPLC method, and capillary direct sequencing. However, this approach is time consuming due to the large size of BRCA1 and BRCA2 genes. Recently, a new low cost and time saving DHPLC protocol has been developed to analyze gene mutations by using SURVEYOR(?) Nuclease digestion and DHPLC analysis. A subset of 90 patients, enrolled in the Genetic Counseling Program of the National Cancer Centre of Bari (Italy), was performed to validate this approach. Previous retrospective analysis showed that 9/90 patients (10%) were mutated in BRCA1 and BRCA2 genes and these data were confirmed by the present approach. DNA samples underwent touchdown PCR and, subsequently, SURVEYOR(?) nuclease digestion. BRCA1 and BRCA2 amplicons were divided into groups depending on amplicon size to allow multiamplicon digestion. The product of this reaction were analyzed on Transgenomic WAVE Nucleic Acid High Sensitivity Fragment Analysis System. The operator who performed the DHPLC surveyor approach did not know the sequencing results at that time. The SURVEYOR(?) Nuclease DHPLC approach was able to detect all alterations with a sensitivity of 95%. Furthermore, in order to save time and reagents, a multiamplicon setting preparation was validated.     

不明原因男性不育人群中睾丸特异性乳酸脱氢酶基因突变的发现及其意义

为了研究睾丸特异性乳酸脱氢酶,即乳酸脱氢酶C4(LDH-C4)基因突变在男性不育发病中的作用,利用LDH-C4特异性底物对100名不明原因男性不育症患者的精子LDH-C4进行活性显色,用变性高效液相色谱(DHPLC)技术对LDH-C4活性低下的患者进行LDHC基因PCR产物的突变筛查,对DHPLC峰形异常的PCR产物进行序列测定.筛选到一组精子LDH-C4活性明显下降的患者,其中1名患者的LDHC基因PCR产物在DHPLC中呈异常洗脱峰.对这一PCR产物进行序列测定,发现患者LDHC基因第5外显子的115位碱基发生了T→A的杂合改变(GenBank登录号GU479375),该突变使LDHC基因的178位密码子由原来的TTG(编码亮氨酸)变为TAG(终止密码子),形成截短的C亚基.T克隆-测序进一步证实了该无义突变的杂合状态.这是在人类LDHC基因上发现的第一个突变,提示LDHC基因突变可能是男性不育发病的原因之一.     

Use of denaturing high-performance liquid chromatography (DHPLC) to characterize the bacterial and fungal airway microbiota of cystic fibrosis patients

The aim of this study was to evaluate the use of denaturing high-performance liquid chromatography (DHPLC) to characterize cystic fibrosis (CF) airway microbiota including both bacteria and fungi. DHPLC conditions were first optimized using a mixture of V6, V7 and V8 region 16S rRNA gene PCR amplicons from 18 bacterial species commonly found in CF patients. Then, the microbial diversity of 4 sputum samples from 4 CF patients was analyzed using cultural methods, cloning/sequencing (for bacteria only) and DHPLC peak fraction collection/sequencing. DHPLC analysis allowed identifying more bacterial and fungal species than the classical culture methods, including well-recognized pathogens such as Pseudomonas aeruginosa. Even if a lower number of bacterial Operational Taxonomic Units (OTUs) was identified by DHPLC, it allowed to find OTUs unidentified by cloning/sequencing. The combination of both techniques permitted to correlate the majority of DHPLC peaks to defined OTUs. Finally, although Aspergillus fumigatus detection using DHPLC can still be improved, this technique clearly allowed to identify a higher number of fungal species versus classical culture-based methods. To conclude, DHPLC provided meaningful additional data concerning pathogenic bacteria and fungi as well as fastidious microorganisms present within the CF respiratory tract. DHPLC can be considered as a complementary technique to culture-dependent analyses in routine microbiological laboratories.     

Application of denaturing high-performance liquid chromatography for rice variety identification and seed purity assessment

Recent DNA sequencing projects and the establishment of high-throughput assays have provided an abundance of sequence information and data on nucleotide polymorphisms in rice. Based on previously identified single-nucleotide polymorphisms (SNPs) and insertions/deletions, we employed denaturing high-performance liquid chromatography (DHPLC) to genotype rice varieties using a chromatographic pattern-based strategy. In this study, 12 amplicons harboring multiple and informative SNPs were screened. PCR products of the 12 amplicons from 47 rice varieties were analyzed by DHPLC and DNA sequencing. Each homozygous sample with a single peak pattern in the initial DHPLC analysis was mixed with zhenshan97 for a second DHPLC analysis. The 12 amplicons were found to be polymorphic across the hybrids, and mixed homozygous samples with 43 distinct DHPLC elution profiles detected. Sequence analysis confirmed that the distinct DHPLC patterns corresponded to different DNA sequences. A set of distinct characteristic profiles in six amplicons differentiated between all of the hybrids, inbred lines, and restorer lines and produced unique a fingerprint for these lines. In addition, we found that the DHPLC pattern of the hybrid was in accordance with the results obtained by DHPLC analysis of a mixed sample of the two parents. These results demonstrate that DHPLC can be efficiently applied for the rapid and automated identification of diverse rice varieties and could possibly be utilized for seed genetic purity testing on a high-throughput scale.     

Determination of loss of heterozygosity in frozen and paraffin embedded tumors by denaturating high-performance liquid chromatography (DHPLC)

Spontaneous renal cell carcinoma (RCC) occurs with a high frequency in Eker rats carrying a germline alteration of the tuberous sclerosis-2 (Tsc-2) tumor suppressor gene. To determine the frequency with which the wild-type allele of the Tsc-2 gene is lost in RCC and the ability of DHPLC to detect loss of heterozygosity (LOH) at this gene locus, fresh-frozen and paraffin-embedded formalin-fixed tumors from heterozygous Eker rats (Tsc-2(Ek/+)) were examined for LOH at the Tsc-2 locus. LOH was determined by quantitation of peak areas of PCR products specific for the mutant and wild-type Tsc-2 alleles. For normal DNA isolated from heterozygous animals, the allele ratio (AR) of mutant to wild-type PCR products was empirically determined to be 1.5+/-0.3 (n=30) and LOH was defined as >2 standard deviations away from this mean, i.e. any AR >2.1. Analysis of 15 spontaneous frozen RCC samples showed LOH in 10/15 samples (66%). Carcinogen-induced tumors exhibited an even higher frequency of LOH, with 6/6 paraffin-embedded, formalin-fixed tumors exhibiting LOH. 100% concordance was observed between the results obtained by DHPLC and traditional methodologies. Therefore, LOH appears to occur with a high frequency in both spontaneous and carcinogen-induced RCC in this animal model and DHPLC is a sensitive and high throughput methodology for detecting this type of genetic alteration.     

Rapid screening of the entire mitochondrial DNA for low-level heteroplasmic mutations

Alterations of the mitochondrial DNA (mtDNA) are implicated in various pathological conditions. In this study, we used denaturing high performance liquid chromatography (DHPLC) as a method to rapidly screen the entire mtDNA for mutations. Overlapping DNA fragments, amplified by one single cycling protocol from frozen pre-formulated PCR mixes, were subjected to DHPLC analysis. Single DHPLC injections of fragments yielded straightforward interpretation of results with a detection limit down to 1% mtDNA heteroplasmy. Furthermore, collection and re-amplification of low degree heteroduplex peak-fractions allowed sequence analysis of mtDNA mutations down to the detection limit of the DHPLC method. In order to demonstrate that the method has diagnostic value, we analyzed and confirmed known mtDNA mutations in patient samples.