Telomere aggregates in hepatitis C patients

Aneuploidy and asynchronous replication in non-alcholic fatty liver disease and cryptogenic cirrhosis

BACKGROUND/AIMS

Non-alcoholic fatty liver disease (NAFLD) and cryptogenic cirrhosis (CC), which is largely a late sequela of NAFLD, are considered pre-neoplastic conditions that might progress to hepatocellular carcinoma. Aneuploidy, telomere aggregates and synchronization of replication were evaluated as markers of genetic instability in these patients.

METHODOLOGY

Peripheral blood lymphocytes from 22 patients with NAFLD, 20 patients with CC and 20 age-matched healthy controls were analyzed. To determine random aneuploidy, we used the fluorescence in situ hybridization (FISH) with probes for chromosomes 9 and 18. The rate of aneuploidy was inferred from the fraction of cells revealing one, three or more hybridization signals per cell. Aggregate size was divided into three fusion groups of 2-5, 6-10 and 11-15 telomeres, relative to the size of a single telomere. The replication pattern was determined by FISH in two pairs of alleles, 15qter and 13qter. Asynchrony was determined by the presence of one single and one set of double dots in the same cell.

RESULTS

Significantly higher random aneuploidy rate was found in the CC patients than in the control group, and to a lesser degree in NAFLD patients. Telomere aggregates were insignificantly higher in both groups. Only patients with CC showed significantly higher rate of asynchronous replication with proportionately more cells with two single dots among the normal cells (p<0.001).

CONCLUSIONS

These results likely reflect changes in gene replication and cell cycle progression in these conditions, possibly correlating with their malignant potential.

Role of progerin-induced telomere dysfunction in HGPS premature cellular senescence

Hutchinson-Gilford Progeria Syndrome (HGPS) is a premature-aging syndrome caused by a dominant mutation in the gene encoding lamin A, which leads to an aberrantly spliced and processed protein termed progerin. Previous studies have shown that progerin induces early senescence associated with increased DNA-damage signaling and that telomerase extends HGPS cellular lifespan. We demonstrate that telomerase extends HGPS cellular lifespan by decreasing progerin-induced DNA-damage signaling and activation of p53 and Rb pathways that otherwise mediate the onset of premature senescence. We show further that progerin-induced DNA-damage signaling is localized to telomeres and is associated with telomere aggregates and chromosomal aberrations. Telomerase amelioration of DNA-damage signaling is relatively rapid, requires both its catalytic and DNA-binding functions, and correlates in time with the acquisition by HGPS cells of the ability to proliferate. All of these findings establish that HGPS premature cellular senescence results from progerin-induced telomere dysfunction.

Telomeres are shorter in placental trophoblasts of pregnancies complicated with intrauterine growth restriction (IUGR)

OBJECTIVE

Telomeres are nucleoprotein structures located at the termini of chromosomes, and protect them from fusion and degradation. Telomeres are progressively shortened with each mitotic cycle and by environmental factors. We hypothesized that antepartum stress can lead to accelerated telomere shortening in placental trophoblasts, and plays a role in intrauterine growth restriction (IUGR).

METHODS

Placental biopsies were derived from 16 pregnancies complicated with IUGR and from 13 uncomplicated pregnancies. Fluorescence-in-situ protocol was used to determine telomere length. Immunohistochemistry for hTERT was performed to assess telomerase activity. Clinical and histopathological characteristics were collected to ensure that IUGR was secondary to placental insufficiency. Fluorescence-in-situ-hybridization was used to rule out aneuploidy as a reason for shortened telomeres.

RESULTS

The number and intensity of telomeres staining and telomerase activity were significantly lower in the IUGR placentas. No aneuploidy was detected for the chromosomes checked in the placental biopsies.

CONCLUSIONS

Telomeres are shorter in trophoblasts of IUGR placentas.

TERC telomerase subunit gene copy number in different disease stages of non-hodgkin lymphoma and in hepatitis C

ABSTRACT Focal amplification of specific regions of the genome creates high copy number and expression of oncogenes in tumors. By applying fluorescence in situ hybridization (FISH) to leukocytes of hepatitis C (HCV) patients and non-Hodgkin lymphoma (NHL) patients, we estimated gene dosage of the TERC gene at 3q26.3. Higher TERC copy numbers were found in NHL at diagnosis compared to HCV patient groups. Higher TERC copy numbers were also observed in NHL patient at diagnosis and relapse compared to patients in remission. We believe that the TERC gene amplification is involved in the process of genetic instability leading to tumor genesis such as in NHL.

Telomere aggregates in trisomy 21 amniocytes

Trisomy 21 is the most common chromosomal abnormality among persons with intellectual disability, with a live birth rate of 1 in 800-1,000. As such, this abnormality may serve as a model for human disorders that result from supernumerary copies of a genomic region. Down syndrome carries an increased risk of developing acute leukemia and other malignancies. Telomeres of tumor cells nuclei tend to form aggregates (TA). This study evaluated TA formation in amniocytes from trisomy 21 pregnancies, compared with amniocytes from normal euploid pregnancies. A commercially available peptide nucleic acid telomere kit was used to evaluate TA formation, using two-dimensional fluorescence microscopy. Significantly higher frequencies of TA were found in trisomy 21 amniocytes than in amniocytes from normal pregnancies. The TAs found in trisomy 21 amniocytes apparently represent an additional parameter that reflects the high genetic instability of this syndrome and its recognized predisposition to develop leukemia and other malignancies.