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.

Primary ciliary dyskinesia: a genome-wide linkage analysis reveals extensive locus heterogeneity.

Primary ciliary dyskinesia (PCD), or immotile cilia syndrome (ICS), is an autosomal recessive disorder affecting ciliary movement with an incidence of 1 in 20000-30000. Dysmotility to complete immotility of cilia results in a multisystem disease of variable severity with recurrent respiratory tract infections leading to bronchiectasis and male subfertility. Ultrastructural defects are present in ciliated mucosa and spermatozoa. Situs inversus (SI) is found in about half of the patients (Kartagener syndrome). We have collected samples from 61 European and North American families with PCD. A genome-wide linkage search was performed in 31 multiplex families (169 individuals including 70 affecteds) using 188 evenly spaced (19cM average interval) polymorphic markers. Both parametric (recessive model) and non-parametric (identity by descent allele sharing) linkage analyses were used. No major locus for the majority of the families was identified, although the sample was powerful enough to detect linkage if 40% of the families were linked to one locus. These results strongly suggest extensive locus heterogeneity. Potential genomic regions harbouring PCD loci were localised on chromosomes 3p, 4q, 5p, 7p, 8q, 10p, 11q, 13q, 15q, 16p, 17q and 19q. Linkage analysis using PCD families with a dynein arm deficiency provided 'suggestive' evidence for linkage to chromosomal regions 8q, 16pter, while analyses using only PCD families with situs inversus resulted in 'suggestive' scores for chromosomes 8q, and 19q.

A locus for primary ciliary dyskinesia maps to chromosome 19q.

Primary ciliary dyskinesia is an autosomal recessive condition characterised by chronic sinusitis, bronchiectasis, and subfertility. Situs inversus occurs in 50% of cases (Kartagener syndrome). It has an estimated incidence of 1 in 20 000 live births. The clinical phenotype is caused by defective ciliary function associated with a range of ultrastructural abnormalities including absent dynein arms, absent radial spokes, and disturbed ciliary orientation. The molecular genetic basis is unknown. A genome scan was performed in five Arabic families. Using GENEHUNTER, a maximal multipoint lod score (HLOD) of 4.4 was obtained on chromosome 19q13.3-qter at alpha (proportion of linked families) = 0.7. A 15 cM critical region is defined by recombinations at D19S572 and D19S218. These data provide significant evidence for a PCD locus on chromosome 19q and confirm locus heterogeneity.

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.