Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality in industrialized countries. It is characterized by a progressive airflow limitation resulting from an abnormal inflammatory response of the lungs to inhaled gases and particles. Since oxidative stress is thought to play a role in COPD, and since increased oxidative stress is associated with chromosomal instability in several diseases, we investigated whether such relationship also exists in COPD. Whole blood lymphocytes from 49 COPD patients and 48 age- and sex-matched controls were cultivated in vitro and cytogenetic damage was evaluated by micronucleus (MN) and sister-chromatid-exchange (SCE) assays. In patients with COPD, MN frequency was not significantly different from that of controls. Similarly, SCE frequency did not differ in the two groups suggesting no disturbance in DNA replication. Unlike other diseases characterized by oxidative stress, COPD does not appear to be associated with DNA damage.

Human myotonic dystrophy protein kinase (DMPK), the product of the myotonic dystrophy (DM) locus, is a member of a novel class of multidomain serine -threonine protein kinases, which interacts with members of the Rho family of small GTPases.DMPK has been shown to affect the cell growth, size and shape in different organisms, from fission yeast to man, but its physiological role is still unclear.We examined the effect of the overexpression of two forms of human DMPK, full-length (DMFL) and a C-terminal truncated form (DMT) on the growth and cell morphology of S. cerevisiae, which possesses a DMPK homologous gene (CBK1) important for polarized growth and cell division.We report that the overexpression of either forms of human DMPK did not complement the CBK1 function in the haploid strain WR208-1a, deleted for CBK1.The truncated form, but not the full length one, slowed down growth rate and induced elongation of the haploid wild type strain CBK1.Similar results were obtained in the diploid wild type strain RS112 of S. cerevisiae where also the full-length form was effective.These effects were abolished when either DMFL or DMT were mutated in the ATP binding site (K100R mutation), suggesting that the kinase activity of DMPK is required.Interestingly, DMPK localization in yeast is similar to that of Cbk1 protein suggesting that it might affect a pathway, which regulates cell morphogenesis and progression through cell cycle, possibly involving CBK1.

Insights into the molecular basis of polyglutamine

Myotonic Dystrophy type 1 (DM1) is one of the many inherited human diseases whose molecular defect is the expansion of a trinucleotide DNA sequence. DM1 shares with fragile X syndrome (FMR1), another “unstable triplet syndrome”, several molecular features not present in the remaining triplet diseases. As FMR1 is also characterised by chromosome instability at the site of the expanded triplet, lymphocytes from DM1 patients and healthy donors were cultured for micronucleus (MN) analysis, in order to verify if DM1 is also prone to chromosome instability. A FISH analysis was also carried out to detect the presence of centromeric sequences in the observed MN. The data indicate that DM1 patients present a percentage of centromere-positive MN significantly higher than controls, suggesting that chromosome loss is the main mechanism underlying the origin of the increased spontaneous instability. To further assess the proneness to instability of cells of DM1 patients, cultures from patients and controls were treated in vitro with growing concentrations of two different mutagens: colcemid, a “pure” aneugen compound whose target is tubulin, and mytomicin C, a strong clastogen. The results show that the patient group is significantly less sensitive to colcemid. These data, together with FISH analysis, suggest the presence, in DM1 patients, of an already damaged tubulin, which becomes no more sensitive to the effect of colcemid and which could be the main defect underlying the aneugenic effects in DM1.