Poly (ADP-ribose) polymerase-1 deficiency does not affect ethylnitrosourea mutagenicity in liver and testis of lacZ transgenic mice.

Poly (ADP-ribose) polymerase-1 (Parp1) has been implicated in DNA base excision repair, single- and double-strand break repair pathways, as well as in cell death by apoptosis or necrosis. We used Parp1(-/-) lacZ plasmid-based transgenic mice to investigate whether Parp1 deficiency influences the in vivo mutagenic and clastogenic response to the alkylating agent N-ethyl-N-Nitrosourea (ENU) in somatic and germ-cell tissues. The comparison of the lacZ mutant frequencies (MFs) between Parp1(+/+) and Parp1(-/-) mice showed that the ablation of Parp1 does not affect the spontaneous or ENU-induced MFs in liver and testis.

Observations on Pyxidium tardigradum (Ciliophora), a protozoan living on Eutardigrada: infestation, morphology and feeding behaviour.

Pyxidium tardigradum is a protozoan that has been reported on a few occasions as an epizoan symphoriont living on eutardigrades. We report here the first records of this species from Kirghizia (the first Asian record), Poland and Portugal. The Portuguese population revealed the largest P.

Mutagenic effects of poly (ADP-ribose) polymerase-1 deficiency in transgenic mice.

Poly (ADP-ribose) polymerase-1 (Parp1) plays a central role in the maintenance of genomic integrity and has been unequivocally associated to DNA base excision repair (BER) but its involvement in double-strand break (DSB) repair pathways remains unclear. In this work, using transgenic Parp1-deficient mice harbouring the lacZ reporter gene, we provide in vivo evidence that Parp1 contributes to the prevention of deletions/insertions in testis following an alkylation insult. In response to N-Methyl-N-Nitrosurea (MNU) treatment no significant difference in the mutant frequency (MF) in the liver and testis could be attributed to Parp1 status, given that both Parp1(+/+) and Parp1(-/-) mice showed a similar significant increase in the overall MF.

Comparative analysis of the mutagenic activity of oxaliplatin and cisplatin in the Hprt gene of CHO cells.

Oxaliplatin is a platinum-derived antitumor drug that is active against cisplatin-resistant tumors and has lower overall toxicity than does cisplatin. DNA adduct formation is believed to mediate the cytotoxic activity of both compounds; however, the adducts may also be responsible for mutagenic and secondary tumorigenic activities. In this study, we have compared the mutagenicity of oxaliplatin and cisplatin in the Hprt gene of CHO-K1 cells.

Molecular cytogenetic characterization of rearrangements involving 12p in leukemia.

Translocations involving the short arm of chromosome 12 are frequent events among patients with various hematologic malignancies. In approximately half of these patients, fluorescence in situ hybridization (FISH) analysis has shown that the breakpoints are clustered within the ETS-variant gene 6 (ETV6) at 12p13, leading to its fusion with a variety of partner genes on different chromosomes. The remaining patients have breakpoints centromeric or telomeric to ETV6 or, less frequently, interstitial 12p13 deletions that invariably involve this gene.

Germline MUTYH (MYH) mutations in Portuguese individuals with multiple colorectal adenomas.

Germinal mutations in the base excision repair (BER) gene MUTYH (MYH) have recently been described in association with predisposition to multiple colorectal adenomas and cancer. In contrast to the classic dominant condition of familial adenomatous polyposis (FAP) due to germinal mutations in the APC gene, the MYH polyposis is an autosomal recessive disease. The identification of individuals affected by MYH polyposis brings new and important implications for the diagnostic, screening, genetic counseling, follow up and therapeutic options in these patients.

Novel MLH1 mutations and a novel MSH2 polymorphism identified by SSCP and DHPLC in Portuguese HNPCC families.

Mismatch repair genes MSH2 and MLH1 are the two major genes implicated in hereditary nonpolyposis colorectal cancer. For the past years, we have successfully searched for mutations in both genes in affected Portuguese families, by SSCP and DNA sequencing analysis but because of the advantages that DHPLC offers, we have established conditions in our laboratory to use this new method. While screening for mutations by both methods, in 35 individuals belonging to HNPCC Portuguese families, 4 novel MLH1 mutations (c.

Quality assessment of genetic markers used for therapy stratification.

Purpose: Therapy stratification based on genetic markers is becoming increasingly important, which makes commitment to the highest possible reliability of the involved markers mandatory. In neuroblastic tumors, amplification of the MYCN gene is an unequivocal marker that indicates aggressive tumor behavior and is consequently used for therapy stratification. To guarantee reliable and standardized quality of genetic features, a quality-assessment study was initiated by the European Neuroblastoma Quality Assessment (ENQUA; connected to International Society of Pediatric Oncology) Group.

Molecular characterization of a familial translocation implicates disruption of HDAC9 and possible position effect on TGFbeta2 in the pathogenesis of Peters' anomaly.

Peters' anomaly (PA) is a congenital defect of the anterior chamber of the eye. We identified a family in which an apparently balanced chromosomal translocation t(1;7) (q41;p21) was associated with PA. Based on this observation, detailed molecular characterizations of the breakpoint regions and candidate genes were carried out.

Mutagenic activity of cisplatin in the lacZ plasmid-based transgenic mouse model.

Cis-diamminedichloroplatinum (II) (cisplatin) is a well characterized antitumor drug used for the treatment of a variety of human cancers. The cytotoxicity of cisplatin is mainly mediated through the formation of DNA adducts, which are also believed to be responsible for the secondary malignancies produced by the drug. The aim of this study was to determine the in vivo mutagenic activity of cisplatin in the lacZ plasmid-based transgenic mouse model.

Molecular characterization of a 7p15-21 homozygous deletion in a Wilms tumor.

Recent molecular studies have shown a relatively high rate of loss of heterozygosity (LOH) at band 7p15-21 in Wilms tumor. We previously reported that the minimal common region of LOH was located between markers D7S517 and D7S503 in bands 7p15-21. We also reported the identification of one Wilms tumor (GOS44) bearing a homozygous, interstitial deletion at a locus within this region.

Low frequency noise and whole-body vibration cause increased levels of sister chromatid exchange in splenocytes of exposed mice.

Chronic exposure to low frequency (LF) noise and whole-body vibration (WBV) induces both physiological and psychological alterations in man. Recently, we have shown that long-term occupational exposure to LF noise and WBV produces genotoxic effects in man expressed as an increase in sister chromatid exchange (SCE) levels in lymphocytes. The objectives of the present study were to investigate whether the observed effect could be reproduced in a murine model and, if so, which of the agents, LF noise alone or in combination with WBV, would be instrumental in the SCE induction.

PCR amplification introduces errors into mononucleotide and dinucleotide repeat sequences.

The polymerase chain reaction (PCR) is used universally for accurate exponential amplification of DNA. We describe a high error rate at mononucleotide and dinucleotide repeat sequence motifs. Subcloning of PCR products allowed sequence analysis of individual DNA molecules from the product pool and revealed that: (1) monothymidine repeats longer than 11 bp are amplified with decreasing accuracy, (2) repeats generally contract during PCR because of the loss of repeat units, (3) Taq and proofreading polymerase Pfu generate similar errors at mononucleotide and dinucleotide repeats, and (4) unlike the parent PCR product pool, individual clones containing a single repeat length produce no "shadow bands".

Translocation (8;17;15;21)(q22;q23;q15;q22) in acute myeloid leukemia (M2). a four-way variant of t(8;21).

We report the results of cytogenetic, fluorescence in situ hybridization (FISH) and molecular analyses in a 15-year-old boy diagnosed with acute myeloid leukemia subtype M2 (AML-M2). Cytogenetic and FISH analyses, the latter with whole chromosome painting probes, revealed a complex translocation involving four chromosomes: t(8;17;15;21)(q22;q23;q15;q22). The observation of breakpoints at 8q22 and 21q22 suggested a rearrangement of the ETO and AML1 genes, respectively.

P73 expression in neuroblastoma: a role in the biology of advanced tumors?

p73, a recently identified gene showing high homology to p53 and mapping to 1p36.33, was presented as a candidate gene for neuroblastoma. In this study the authors evaluate the levels and allelic nature of p73 expression in primary neuroblastomas using reverse transcription-polymerase chain reaction-restriction fragment length polymorphism strategies based on intragenic polymorphisms.

Pathological exon skipping in an HNPCC proband with MLH1 splice acceptor site mutation.

One of the most commonly mutated mismatch repair genes in human nonpolyposis colorectal cancer (HNPCC) is MLH1. We identified a splice site mutation in MLH1 in a colorectal cancer proband (T-to-A at position -11 of intron 1 splice acceptor) and investigated its functional consequences by RT-PCR, using lymphocyte mRNA from the proband, two noncarrying siblings, and one unrelated individual. Subcloning of PCR products followed by sequencing of individual clones revealed increased transcript heterogeneity in the mutation carrier, attributable to the presence of a variety of mRNA forms lacking exon 2, or combinations of exons 2, 4, 6, 9, and 10.

Small GTPase Rac1: structure, localization, and expression of the human gene.

Rac1 is a member of the Rho family of small GTPases involved in signal transduction pathways that control proliferation, adhesion, and migration of cells during embryonic development and invasiveness of tumor cells. Here we present the complete structure of the human RAC1 gene and characterize its expression. The gene comprises 7 exons over a length of 29 kb and is localized to chromosome 7p22.

Mutations in ARHGEF6, encoding a guanine nucleotide exchange factor for Rho GTPases, in patients with X-linked mental retardation.

X-linked forms of mental retardation (XLMR) include a variety of different disorders and may account for up to 25% of all inherited cases of mental retardation. So far, seven X-chromosomal genes mutated in nonspecific mental retardation (MRX) have been identified: FMR2, GDI1, RPS6KA3, IL1RAPL, TM4SF2, OPHN1 and PAK3 (refs 2-9). The products of the latter two have been implicated in regulation of neural plasticity by controlling the activity of small GTPases of the Rho family.

Eleven novel APC mutations identified in Portuguese FAP families.

Germline mutations of the adenomatous polyposis coli (APC) gene are responsible for familial adenomatous polyposis (FAP), an autosomal dominant predisposition to colorectal cancer. In the present study we screened all of the exons of the APC gene in individuals belonging to 85 Portuguese FAP families. We here report eleven novel mutations which are predominantly frameshifts or single base substitutions, resulting in premature stop codons.

Cell type specificity in alternative splicing of the human mismatch repair gene hMSH2.

Human non-polyposis colorectal cancer is caused by germline mutations in the DNA mismatch repair genes hMSH2 and hMHL1. Several alternatively spliced mRNA species of these genes are present in peripheral blood lymphocytes of normal individuals, which can confound RT-PCR based techniques of mutation detection. Using RT-PCR, we compared the pattern of alternative splicing in whole peripheral blood lymphocytes (PBLs), separated T and B cells, lymphoblastoid cell lines (LCLs) from the same individuals, and a variety of tissues.

Loss of heterozygosity at 7p in Wilms' tumour development.

Chromosome 7p alterations have been implicated in the development of Wilms' tumour (WT) by previous studies of tumour cytogenetics, and by our analysis of a constitutional translocation (t(1;7)(q42;p15)) in a child with WT and radial aplasia. We therefore used polymorphic microsatellite markers on 7p for a loss of heterozygosity (LOH) study, and found LOH in seven out of 77 informative WTs (9%). The common region of LOH was 7p15-7p22, which contains the region disrupted by the t(1;7) breakpoint.

Four novel MSH2 / MLH1 gene mutations in portuguese HNPCC families.

Hereditary non-polyposis colorectal cancer (HNPCC) is considered to be determined by germline mutations in the mismatch repair (MMR) genes, especially MSH2 and MLH1. While screening for mutations in these two genes in HNPCC portuguese families, 3 previously unreported MSH2 and 1 MLH1 mutations have been identified in families meeting strict Amsterdam criteria. Hum Mutat 15:116, 2000.

Cloning of a novel human Rac1b splice variant with increased expression in colorectal tumors.

Rac1 is a member of the Ras superfamily of small GTPases involved in signal transduction pathways that induce the formation of lamellipodia, stimulate cell proliferation and activate the JNK/SAPK protein kinase cascade. Here we describe that amplification by RT-PCR of the entire Rac1 coding sequence from a series of human adult and fetal tissues revealed beside the expected Rac1 cDNA, a variant product which contained additional 57 nucleotides between codons 75 and 76. This variant resulted in an in-frame insertion of 19 new amino acids immediately behind the switch II region, including two potential threonine phosphorylation sites for casein kinase II and protein kinase C.

Insertion of the 5' part of BCR within the ABL gene at 9q34 in a Philadelphia-negative chronic myeloid leukemia.

We report a chronic myeloid leukemia patient without evidence of a Philadelphia (Ph) chromosome in whom RT-PCR analysis performed in blast crisis demonstrated the existence of both common b3a2 and b2a2 BCR/ABL fusion transcripts. In situ hybridization studies with BCR- and ABL-specific probes showed location of the BCR/ABL fusion gene on chromosome 9, band q34, instead of at chromosome 22q11, and that it resulted from an insertion of the 5' side of BCR within the ABL gene on chromosome 9. The vast majority of cells showed a BCR/ABL fusion gene on both chromosomes 9, which is equivalent to a double Ph chromosome, thus reinforcing the notion that the critical event in CML is the formation of a functional BCR/ABL fusion gene.