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Biomedical subjects

N Ramoz

Publications and source records attributed to N Ramoz.

9 recordsLinked to original sources
PubMed2004

Linkage analysis for autism in a subset families with obsessive-compulsive behaviors: evidence for an autism susceptibility gene on chromosome 1 and further support for susceptibility genes on chromosome 6 and 19.

Although there is considerable evidence for a strong genetic component to idiopathic autism, several genome-wide screens for susceptibility genes have been carried out with limited concordance of linked loci, reflecting numerous genes of weak effect and/or sample heterogeneity. In the current study, linkage analysis was carried out in a sample of 62 autism-affected relative pairs with more severe obsessive-compulsive behaviors, selected from a larger (n=115) set of autism-affected relative pairs as a means of reducing sample heterogeneity. Obsessive-compulsive behaviors were assessed using the Autism Diagnostic Interview-Revised (ADI-R). In the sample with more severe obsessive-compulsive behaviors, multipoint NPL scores above 2 were observed on chromosomes 1, 4, 5, 6, 10, 11 and 19, with the strongest evidence for linkage on chromosome 1 at the marker D1S1656, where the multipoint NPL score was 3.06, and the two-point NPL score was 3.21. In follow-up analyses, analyzing the subset of families (n=35) where the patients had the most severe obsessive-compulsive behaviors generated a multipoint NPL score of 2.76, and a two-point NPL score of 2.79, indicating that the bulk of evidence for linkage was derived from the families most severely affected with obsessive-compulsive behaviors. The data suggest that there is an autism susceptibility gene on chromosome 1 and provide further support for the presence of autism susceptibility genes on chromosomes 6 and 19.

Autistic Disorder↗
PubMed2001

Mutation and abnormal expression of the p53 gene in the viral skin carcinogenesis of epidermodysplasia verruciformis.

Patients suffering from epidermodysplasia verruciformis are prone to nonmelanoma skin cancers, due to an inherited abnormal susceptibility to the oncogenic human papillomavirus type 5. Genotoxic sunlight ultraviolet B radiations are likely to be a cofactor. Lesions of two human-papillomavirus-type-5-infected epidermodysplasia verruciformis patients collected during an 8 y period were retrospectively studied for p53 mutations in exons 5 through 8 by a polymerase chain reaction single-strand conformation polymorphism technique and/or by DNA sequencing of amplified exons. Mutations were detected in 11 of 26 (42.3%) specimens, including five (62.5%) squamous cell carcinomas, three (33.3%) Bowen's carcinomas in situ, two (40%) actinic keratoses, and one (33%) benign lesion. The nine mutations characterized by sequencing were shown to be missense and to affect mutational hotspots in human cancers. Five were C-->T transitions at dicytidine sites considered as ultraviolet signature mutations. Two were transversions (C-->G and C-->A) at dicytidine sites and two were C-->T transitions at nondipyrimidine sites. A marked p53 immunoreactivity was disclosed in 72.7% of 11 invasive carcinomas, 55.6% of nine carcinomas in situ, 37.5% of eight actinic keratoses, and one of three benign lesions. This includes 81.8% of 11 specimens with a p53 mutation but also 50% of 14 specimens with no mutation detected. A dysfunction of the p53 gene is thus likely to play a part in epidermodysplasia verruciformis carcinogenesis, either due to ultraviolet-B-induced p53 mutations, as in nonmelanoma skin cancers in the general population, or involving other mutagens or mechanisms. The part played by human papillomavirus type 5 proteins expressed in epidermodysplasia verruciformis keratinocytes remains to be determined.

Adult↗
PubMed2000

Evidence for a nonallelic heterogeneity of epidermodysplasia verruciformis with two susceptibility loci mapped to chromosome regions 2p21-p24 and 17q25.

Epidermodysplasia verruciformis is a rare genodermatosis associated with a high risk of skin cancer. This condition is characterized by an abnormal susceptibility to specific related human papillomavirus genotypes, including the oncogenic HPV5. Epidermodysplasia verruciformis is usually considered as an autosomal recessive disease. We recently mapped a susceptibility locus for epidermodysplasia verruciformis (EV1) to chromosome 17qter within the 1 cM interval between markers D17S939 and D17S802. We report here the genotyping for 10 microsatellite markers spanning 29 cM around EV1 in two consanguineous epidermodysplasia verruciformis families from Colombia (C2) and France (F1) comprising five patients and two patients, respectively. Using homozygosity mapping, linkage with 17qter markers was observed for family C2 only. Multipoint linkage analysis yielded maximum multipoint LOD-score values above 10 between markers D17S1839 and D17S802 encompassing the EV1 locus. A genome-wide search performed in family F1 yielded evidence for linkage between epidermodysplasia verruciformis and the chromosomal 2p marker D2S365. Nine additional microsatellite markers spanning 15 cM in this region were analyzed. Assuming an autosomal recessive inheritance with a complete penetrance, the expected maximum two-point LOD-score value of 1.8 was obtained for three markers and multipoint linkage analysis yielded a maximum LOD-score value of 3. 51 between markers D2S2144 and D2S392. Haplotype analysis allowed to map a candidate region for a second epidermodysplasia verruciformis susceptibility locus (EV2) within the 8 cM interval between markers D2S171 and D2S2347 of the 2p21-p24 region. In contrast, linkage with 2p markers was excluded for family C2 and for the three families in which we mapped EV1 previously. The disclosure of two susceptibility loci for epidermodysplasia verruciformis provides evidence for a nonallelic heterogeneity in this disease.

Adolescent↗
PubMed1999

A susceptibility locus for epidermodysplasia verruciformis, an abnormal predisposition to infection with the oncogenic human papillomavirus type 5, maps to chromosome 17qter in a region containing a psoriasis locus.

Epidermodysplasia verruciformis (EV) is a rare genodermatosis characterized by an abnormal susceptibility to infection with a specific group of related human papillomavirus (HPV) genotypes, including the oncogenic HPV5 associated with the skin carcinomas developing in about half of EV patients. EV is usually considered as an autosomal recessive condition. Taking EV as a model to identify a locus underlying the susceptibility to HPV infections, we performed a genome-wide search for linkage with 255 microsatellite genetic markers in three consanguineous EV families comprising six patients, using the homozygosity mapping approach. Homozygosity restricted to affected individuals was observed for a marker of chromosome 17q (D17S784) in two families and a marker about 17 centiMorgan (cM) distal (D17S1807) in the third family. Ten additional microsatellite markers spanning 29 cM in this region were analyzed. Two-point lod score values greater than 3 were obtained for four markers and multipoint linkage analysis yielded a maximum lod score of 10.17 between markers D17S939 and D17S802. Recombination events observed in two families allowed a candidate region for the EV susceptibility locus to be mapped to the 1 cM region defined by these two markers. The EV locus (named EV1) is included in the 17qter region recently found to contain a dominant locus for the susceptibility to familial psoriasis. It has been shown that patients suffering from psoriasis are likely to constitute the reservoir of HPV5. It is thus tempting to speculate that distinct defects affecting the same gene may be involved in the two skin conditions.

Chromosome Mapping↗
PubMed1997

A cottontail rabbit papillomavirus strain (CRPVb) with strikingly divergent E6 and E7 oncoproteins: An insight in the evolution of papillomaviruses.

We previously observed that warts induced by an isolate of cottontail rabbit papillomavirus (CRPV) showed incomplete instead of systemic regression in some domestic rabbits. We report that the viral isolate contained, as a major component, a CRPV strain (CRPVb) showing an unexpectedly high divergence in the E6 and E7 open reading frames (ORFs), compared to the prototype CRPVa present in the isolate as a minor component. The E6 and E7 oncoproteins of CRPVa and -b disclosed only 87.5% identical amino acids and differed in size by three and two amino acids, respectively. This divergence involved (i) a great number (4.4%) of nucleotide substitutions and a high rate (83.3%) of nonsynonymous mutations; (ii) mutations changing the E6 and E7 stop codons; and (iii) in-frame sequence insertions in the E6 ORF (18 nucleotides) and downstream of the mutated E7 stop codon (6 nucleotides), both likely to result from a duplication of adjacent sequences. These extensive differences could account for distinct biological and antigenic properties. Strikingly, only four (0.8%) amino acids of the L1 major capsid protein were variable. Thus, it seems likely that sequence duplications and mutations affecting stop codons exert a strong selection pressure on the fixation of nonsynonymous mutations and that phylogenetic calculations based only on point mutations may misevaluate the time scale of the evolution of papillomaviruses.

Amino Acid Sequence↗
PubMed1996

Mechanisms of transcriptional activation of the promoter of the rainbow trout prolactin gene by GHF1/Pit1 and glucocorticoid.

The transcription factor GHF1/Pit1, required for the expression of the prolactin (PRL) and other pituitary-specific genes, is highly conserved from fish to mammals but the mechanisms by which it activates transcription are poorly understood. The activity of the promoter (-627/+15 region) of the rainbow trout PRL (tPRL) gene fused to the luciferase reporter gene was studied using GHF1-expressing rat pituitary GC cells. Nuclear extracts of GC cells produced five GHF1-specific footprints in the tPRL promoter, with the position of the two most proximal ones being highly conserved in trout and mammalian GHF1-regulated genes. Deletional and mutational analyses of the tPRL promoter showed that the most proximal GHF1 site alone is sufficient to confer sub-maximal GHF1-dependent transcriptional activity and that a glucocorticoid response element-like motif mediates dexamethasone stimulation. It is suggested that GHF1 molecules bound to different sites of the tPRL promoter cannot interact simultaneously with the transcriptional apparatus. Moreover, GHF1 and the ligand-bound glucocorticoid receptor tethered to their cognate elements in the promoter could cooperate to enhance transcription by interacting simultaneously with different members of the basal transcriptional complex.

Animals↗
PubMed1996

HLA control in the progression of human papillomavirus infections.

Cellular immunity is likely to be of major importance for the clearance of inapparent or overt infections caused by human papillomaviruses (HPVs). The highly polymorphic class I or class II human leukocyte antigen (HLA) molecules present HPV-derived peptides to cytotoxic (CD8+) or helper (CD4+) T lymphocytes bearing specific receptors and condition the immune responsiveness to HPV infections. Recent data point to a role of an altered expression of HLA molecules in the persistence of HPV-induced cervical premalignant lesions and their progression towards invasive carcinoma. Furthermore positive of negative associations of certain HLA alleles or haplotypes with cutaneous of cervical neoplasias have been found. These observations may have important implications in the design of therapy or vaccines aimed at eradicating cervical cancer.

Animals↗