Automated JAK2V617F quantification using a magnetic filtration system and sequence-specific primer-single molecule fluorescence detection

Association between ApoE phenotypes and telomere erosion in Alzheimer's disease

Although several reports suggest that Alzheimer's disease (AD) is associated with shortened telomere length, the clinical relevance of this has not yet been fully elucidated. This study was conducted to clarify the correlation of telomere length with clinical characteristics and ApoE phenotypes in 74 AD patients. Telomere length was determined from genomic DNA extracted from whole blood by quantitative real-time polymerase chain reaction. We found no significant difference in telomere length between the AD and non-dementia elderly control (n = 35) groups. Furthermore, no significant correlation was found among telomere length and the severity of cognitive decline and disease duration, age, or gender difference. However, telomere length was significantly shorter in AD patients with the ApoE4 homozygote than in those with the ApoE4 heterozygote (p < .001) and noncarriers (p < .001). These findings suggest that shortened telomere length may be associated with the ApoE4 homozygote in AD patients.

Sensitive detection and quantification of the JAK2V617F allele by real-time PCR blocking wild-type amplification by using a peptide nucleic acid oligonucleotide

A single G-to-T missense mutation in the gene for the JAK2 tyrosine kinase, leading to a V617F amino acid substitution, is commonly found in several myeloproliferative neoplasms. Reliable quantification of this mutant allele is of increasing clinical and therapeutic interest in predicting and diagnosing this group of neoplasms. Because JAK2V617F is somatically acquired and may be followed by loss of heterozygosity, the percentage of mutant versus wild-type DNA in blood can vary between 0% and almost 100%. Therefore, we developed a real-time PCR assay for detection and quantification of the low-to-high range of the JAK2V617F allele burden. To allow the assay to meet these criteria, amplification of the wild-type JAK2 was blocked with a peptide nucleic acid oligonucleotide. JAK2V617F patient DNA diluted in JAK2 wild-type DNA could be amplified linearly from 0.05% to 100%, with acceptable reproducibility of quantification. The sensitivity of the assay was 0.05% (n = 3 of 3). In 9 of 100 healthy blood donors, a weak positive/background signal was observed in DNA isolated from blood, corresponding to approximately 0.01% JAK2V617F allele. In one healthy individual, we observed this signal in duplicate. The clinical relevance of this finding is not clear. By inhibiting amplification of the wild-type allele, we developed a sensitive and linear real-time PCR assay to detect and quantify JAK2V617F.

Quantitative assay for the detection of the V617F variant in the Janus kinase 2 (JAK2) gene using the Luminex xMAP technology

Background

The availability of clinically valid biomarkers contribute to improve the diagnosis and clinical management of diseases. A valine-to-phenylalanine substitution at position 617 (V617F) in the Janus kinase 2 (JAK2) gene has been recently associated with key signaling abnormalities in the transduction of haemopoietic growth-factor receptors and is now considered as a useful clinical marker of myeloproliferative neoplasms. Several methods have recently been reported to detect the JAK2 V617F point mutation and show variable sensitivity.

Methods

Using the Luminex xMAP technology, we developed a quantitative assay to detect the JAK2V617F variant. The method was based on polymerase chain reaction (PCR) followed by hybridization to specific probes coupled with internally dyed microspheres. The assay comprises 3 steps: genomic DNA extraction, end point PCR reaction, direct hybridization of PCR fragments and quantification. It has been tested with different sources of nucleic acid.

Results

Applied to whole blood samples, this quantitative assay showed a limit of detection of 2%. A highly sensitive allele-specific primer extension reaction performed in parallel allowed to validate the results and to identify the specimens with values below 2%.

Conclusion

Direct hybridization assay using the Luminex xMAP technology allows sensitive quantification of JAK2V617F from blood spots. It is simple and can be easily performed in a clinical setting.

Recurrent der(9;18) in essential thrombocythemia with JAK2 V617F is highly linked to myelofibrosis development

We studied JAK2 mutational status, in combination with cytogenetic analysis in 54 patients with essential thrombocythemia (ET), and attempted to obtain greater insight into the correlation between clinicohematologic features and genetic abnormalities. We found that six ET patients developed myelofibrosis and four of them had JAK2 V617F mutation. It is noteworthy that three of the four ET patients with JAK2 V617F had add(18)(p11). In contrast, the remaining two ET patients who developed myelofibrosis had neither JAK2 V617F nor add(18)(p11). Moreover, none of the ET patients with JAK2 V617F and chromosome changes other than add(18)(p11) developed myelofibrosis. The current results indicate that add(18)(p11), possibly due to der(9;18), may contribute a link to myelofibrosis in JAK2 V617F-positive ET patients, while those with wild-type JAK2 may use another pathway toward myelofibrosis.