Differences in telomere length between homologous chromosomes in humans.

Telomeres are important structures for DNA replication and chromosome stability during cell growth. Telomere length has been correlated with the division potential of human cells and has been found to decrease with age in healthy individuals. Nevertheless, telomere lengths within the same cell are heterogeneous and certain chromosome arms typically have either short or long telomeres. Both the origin and the physiological consequences of this heterogeneity in telomere length remain unknown. In this study we used quantitative telomeric FISH combined with a method to identify the parental origin of chromosomes to show that significant differences in relative telomere intensities are frequently observed between chromosomal homologs in short-term stimulated cultures of peripheral blood lymphocytes. These differences appear to be stable for at least 4 months in vivo, but disappear after prolonged proliferation in vitro. The telomere length differences are also stable during in vitro growth of telomerase-negative fibroblast cells but can be abolished by exogenous telomerase expression in these cells. These findings suggest the existence of a mechanism maintaining differences in telomere length between chromosome homologs that is independent of telomere length itself.

Molecular characterization of germline NF2 gene rearrangements.

Neurofibromatosis type 2 (NF2) is an autosomal dominant disease that causes a predisposition to nervous system tumors. Deleterious point mutations have been found in about 55% of NF2 patients, and large genomic deletions account for approximately 33% of NF2 gene alterations. The majority of these deletions are larger than 50 kb, with a breakpoint usually lying outside the NF2 gene. We identified two cases of intragenic deletion with loss of 1.5 and 40 kb, respectively. In both cases, one boundary of the deletion was located in or at the proximity of an SVA sequence in NF2 intron 4. No sequence identity longer than 5 bases and no signal of specific recombination have been evidenced on either side of the deletion breakpoints. These observations are compatible with a nonhomologous recombination being responsible for the genomic deletions. In a third case, a paracentric inversion of chromosome 22 was found. This chromosomal rearrangement breaks the NF2 gene in two parts and carries the first NF2 exon in a juxta-centromeric position. The variability in position of the deletions and the observation of a new chromosomal rearrangement in the NF2 gene underscore the importance of FISH analysis in the molecular diagnosis of NF2.

NF2 gene in neurofibromatosis type 2 patients.

Neurofibromatosis type 2 (NF2) is an autosomal dominant disorder that predisposes to nervous system tumors. The schwannomin (also termed merlin) protein encoded by the NF2 gene shows a close relationship to the family of cytoskeleton-to-membrane proteins linkers ERM (ezrin-radixin-moesin proteins). Even though penetrance of the disease is >95% and no genetic heterogeneity has been described, point mutations in the NF2 gene have been observed in only 34-66% of the screened NF2 patients, depending on the series. In order to generate tools that would enable an exhaustive alteration screening for the NF2 gene, we have deduced its entire genomic sequence. This knowledge has provided the delineation of a mutation screening strategy which, when applied to a series of 19 NF2 patients, has revealed a high recurrence of large deletions in the gene and has raised the efficiency of mutation detection in NF2 patients to 84% of the cases in this series. The remaining three patients who express two functional NF2 alleles are all sporadic cases, an observation compatible with the presence of mosaicism for NF2 mutation.

Comparison of the enzyme activities between the thickest and the thinnest parts of the abdominal pannus.

OBJECTIVE: According to some reports, there are variations in metabolism in adipocytes from different areas of the body. The purpose of this study was to determine if there are differences in some of the lipid assimilating enzyme activities between the thickest (overhang) and the thinnest (upper margin) parts of the abdominal pannus. METHODS: The abdominal panniculectomy activities of sn-glycerol-3-phosphate dehydrogenase (31 subjects, spectrophotometric method), fatty acid synthetase (14 subjects, spectrophotometric method) and lipoprotein lipase (18 subjects, radioactive method) were determined in the thickest and the thinnest parts of the pannus of lipectomy patients. RESULTS: The enzyme activities were as follows: sn-glycerol-3-phosphate dehydrogenase: thickest: 2083 +/- 227.7 nm/mg/min; thinnest: 2084 +/- 208.3 nm/mg/min (p < 0.098, T = 0.02). Fatty acid synthetase: thickest: 22.0 +/- 3.9 microns/mg/min; thinnest 25.9 +/- 6.9 microns/mg/min (p < 0.36, T = 0.94). Lipoprotein lipase: thickest: 0.70 +/- 0.11% of control; thinnest: 0.61 +/- 0.14% of control (p < 0.47, T = 0.75). Thus no differences in specific enzyme activities were found between the two sites studied. CONCLUSIONS: There was no difference in the activity of the enzymes studied at the thickest and the thinnest part of the pannus.

Activation of the human homologue of the Drosophila sina gene in apoptosis and tumor suppression.

Developmentally regulated genes in Drosophila, which are conserved through evolution, are potential candidates for key functions in biological processes such as cell cycle, programmed cell death, and cancer. We report cloning and characterization of the human homologue of the Drosophila seven in absentia gene (HUMSIAH), which codes for a 282 amino acids putative zinc finger protein. HUMSIAH is localized on human chromosome 16q12-q13. This gene is activated during the physiological program of cell death in the intestinal epithelium. Moreover, human cancer-derived cells selected for suppression of their tumorigenic phenotype exhibit constitutively elevated levels of HUMSIAH mRNA. A similar pattern of expression is also displayed by the p21waf1. These results suggest that mammalian seven in absentia gene, which is a target for activation by p53, may play a role in apoptosis and tumor suppression.

Effect of Abdominal Lipectomy on Lipid Profile, Glucose Handling and Blood Pressure in Patients with Truncal Obesity.

BACKGROUND: Previous studies have found that people with apple (android)-shaped body fat distribution are at risk of developing cardiovascular disease, impaired glucose tolerance and hypertension. METHODS: To investigate the effects of lipectomy, we measured lipid and lipoprotein levels, indices associated with glucose tolerance and blood-pressure. The tests were performed pre-operatively and 3 and 12 months post-operatively in 34 subjects (obese lipectomy patients with android-shaped body fat distribution) and 23 controls (obese breast reduction patients). RESULTS: In subjects, total cholesterol, LDL and blood pressure were significantly lower at 3 months follow-up, but returned to pre-operative levels at 12 months follow-up. Plasma insulin decreased significantly at 3 months follow-up, and continued to decrease at 12 months follow-up. Triglycerides, HDL, fasting blood sugar, glycosylated hemoglobin and C-peptide did not change at 3 and 12 months follow-up. There were no changes in controls. CONCLUSIONS: Lipectomy in patients with truncal obesity may reduce plasma insulin levels, but had no lasting effect on plasma lipids.

Isolation of 10 differentially expressed cDNAs in p53-induced apoptosis: activation of the vertebrate homologue of the drosophila seven in absentia gene.

We report the isolation of 10 differentially expressed cDNAs in the process of apoptosis induced by the p53 tamor suppressor. As a global analytical method, we performed a differential display of mRNA between mouse M1 myeloid leukemia cells and derived clone LTR6 cells, which contain a stably transfected temperature-sensitive mutant of p53. At 32 degrees C wild-type p53 function is activated in LTR6 cells, resulting in programmed cell death. Eight genes are activated (TSAP; tumor suppressor activated pathway), and two are inhibited (TSIP, tumor suppressor inhibited pathway) in their expression. None of the 10 sequences has hitherto been recognized as part of the p53 signaling pathway. Three TSAPs are homologous to known genes. TSAP1 corresponds to phospholipase C beta 4. TSAP2 has a conserved domain homologous to a multiple endocrine neoplasia I (ZFM1) candidate gene. TSAP3 is the mouse homologue of the Drosophila seven in absentia gene. These data provide novel molecules involved in the pathway of wild-type p53 activation. They establish a functional link between a homologue of a conserved developmental Drosophila gene and signal transduction in tumor suppression leading to programmed cell death.