Telomere length measurement can distinguish pathogenic from non-pathogenic variants in the shelterin component, TIN2.

Dyskeratosis congenita (DC) is a heterogeneous bone marrow failure syndrome with seven disease-causing genes identified to date, six of which are linked to telomere maintenance. Mutations in one of these genes (TINF2), which encodes a component of the shelterin complex, are associated with particularly short telomeres. Among the 224 consecutive patients with different forms of bone marrow failure (46 with DC, 122 with aplastic anaemia and 57 with some features of DC), we have identified 16 new families with variants in exon 6 of the TINF2 gene, eight of which are novel. We observe that the phenotype associated with these mutations extends to a severe early presentation, not always classified as DC. In addition, we see that some of the variants identified are not associated with short telomeres and are also found in asymptomatic individuals. In the absence of any direct functional assay, the data indicates that the telomere length measurement can inform us as to which variants in TINF2 are pathogenic and which may be non-pathogenic.

Pyridinium crosslinks in the monitoring of patients with bone metastases from carcinoma of the breast.

Assessing the response of bone metastases to systemic therapy remains a difficult clinical problem. The currently available markers of bone disease are limited by the length of time before the changes that accompany regression or progression become evident. The pyridinium crosslinks, pyridinoline (Pyr) and deoxypyridinoline (dPyr), are a recently described group of compounds formed by collagen breakdown. Elevated urinary crosslinks were demonstrated in patients with bone metastases when compared with controls (P<0.0001). Improvements in the sensitivity of the high performance liquid chromatography technique have enabled us to measure these compounds in serum for the first time; Pyr and dPyr were also significantly elevated when compared with controls (P<0.001). We found significant correlations between Pyr and dPyr in serum (p = 0.88; P<0.0001) as well as in urine (p = 0.94; P<0.0001). In addition, a significant relationship existed between serum Pyr and the percentage of bone involved (p = 0.78; P<0.0001). Here we describe or preliminary results using this new assay and consider the role of these markers in the clinical assessment of metastatic bone disease from breast cancer.

Automated solid-phase extraction with high-performance liquid chromatography analysis of pyridinium crosslinks.

An automated solid-phase extraction procedure for free and total pyridinium crosslinks in urine, with on-line HPLC analysis, is described. The pyridinium crosslinks either following hydrolysis in 3 M HCl or free in urine were extracted using a Gilson Aspec system onto extraction cartridges containing an octasilane/cation-exchanger sorbent. After washing, the crosslinks were eluted with 400 microl 100 mM sodium formate, pH 5, and 50 microl was automatically injected onto the analytical HPLC column. Detection was by fluorescence (Ex 295 nm, Em 400 nm). Recoveries were 95-100% with a limit of quantitation (s/n = 5) of 1.97 nmol/liter (nM) for pyridinoline and 2.79 nM for deoxypyridinoline. The interassay coefficient of variation was 6.5% for pyridinoline and 8.2% for deoxypyridinoline. The throughput of the system was up to 70 samples per day. The method correlated well with the established manual cellulose extraction but was substantially simpler and more reliable. A good correlation with an immunoassay for deoxypyridinoline was also obtained.