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At least 145 records · Page 8Linked to original sources
PubMed1997

Schizophrenia in the genetic isolate of Finland.

We compared the features of schizophrenia in the homogeneous population of Finland (population about 5,000,000) and in an internal isolate in northeastern Finland inhabited in the 1680s by a small group of founders (current population about 18,000) in a register-based epidemiological study. We identified all cases with a diagnosis of schizophrenia in Finland born between 1940-1969 using three national computerized registers and found a total of 267 schizophrenia patients in the internal isolate and 29,124 in Finland. The lifetime prevalence was 2.21% in the internal isolate and 1.21% in Finland, respectively. The age-corrected lifetime risk was 3.2% in the internal isolate and 1.1% in the whole country. The risk of schizophrenia to siblings in the internal isolate was 6.4% (95% confidence interval 0.052, 0.078), 9.1% (95% CI 0.062, 0.130), and 6.8% (95% CI 0.028, 0.135) given 1, 2, or 3 affected siblings, and for all Finland 4.2% (95% CI 0.036, 0.043), 6.4% (95% CI 0.058, 0.071), and 8.7% (95% CI 0.068, 0.107) given 1, 2, or 3, affected siblings, respectively. The mean number of children in schizophrenia families and thus the number of families having at least two affected individuals were clearly higher in the isolate (24.9% vs 9.2%). We did not find any other epidemiological features differing between these two regions. It seems that the family material collected from the internal isolate is a representative subsample from the entire country and hopefully it enables easier identification of at least some predisposing genes for schizophrenia due to its unique population structure.

Adult↗
PubMed2004

Genetic diversity shown in Trichoderma biocontrol isolates.

Genetic variability within 69 biocontrol isolates of Trichoderma, obtained from different geographical locations and culture collections and selected as biocontrol agents, was studied. Sequence data, obtained from the ITS1 region of rDNA and a fragment of the translation elongation factor 1 (tef1) gene, were used in a phylogenetic analysis. Phylograms showing similar topologies were generated using alignments containing the ITS1 region or a portion of the tef1 gene. 21 distinct ITS1 sequence types and 17 distinct tef1 sequence types were identified among the 69 isolates. More than 50% of the potential biocontrol strains were grouped within Trichoderma sect. Pachybasium; of these, 81% were grouped within the cluster that included the ex-type strains of T. harzianum and T. inhamatum, and 16% were grouped with T. virens. Within T. sect. Trichoderma, which included 36% of the 69 strains, 56% were grouped with T. asperellum, and 24% with T. viride, T. atroviride or T. koningii. Only 10% of the strains studied were located in T. sect. Longibrachiatum.

Base Sequence↗
PubMed2006

Genome-wide linkage scan of schizophrenia: a cross-isolate study.

Genetic isolates are exceptional resources for the detection of susceptibility genes for complex diseases because of the potential reduction in genetic and clinical heterogeneity. However, the outcome of these mapping efforts is dependent upon the demographic history of a given isolated population, with the most significant factors being a constant population size, the number of generations since founding, and the pathogenic loci and their allele frequencies among founders. Here we employed a cross-isolate genome-wide multipoint linkage study design using uniform genetic and clinical methods in four Daghestan ethnically and demographically diverse isolates with an aggregation of schizophrenia. Our previous population-genetics study showed that Daghestan has an extremely high genetic diversity between ethnic populations and a low genetic diversity within them. The isolates selected for this study include some with more than 200 and some with fewer than 100 generations of demographical history since their founding. Updated clinical data using DSM-IV criteria showed between-isolate differences in aggregation of distinct types of schizophrenia: one of the isolates had a predominant aggregation of disorganized schizophrenia, while the other three had predominantly paranoid schizophrenia. The summarized cross-isolate results indicated prominent within and between-isolate differences in clinical and genetic heterogeneity: the most ancient isolates have roughly twofold fewer incidences of distinct clinical phenotypes and fewer linked genomic regions compared to the demographically younger isolates, which exhibit higher clinical and genetic heterogeneity. Affected individuals in the demographically ancient isolate of ethnic Dargins (No. 6022) who suffered from disorganized schizophrenia showed the highest linkage evidence at 17p11-p12 (LOD=3.73), while isolates with a predominant aggregation of paranoid schizophrenia (Nos. 6005, 6011, and 6034) showed the highest linkage evidence at 22q11 (LOD=3.0 and 4.4). The unified clinical, genomic, and statistical design we used enabled us to separate the linked and unlinked pedigrees in an unbiased fashion for each genomic location. Overall maximized heterogeneity lod scores for the combined pedigrees ranging from 3.5 to 8.7 were found at 2p24, 10q26, 11q23, 12q24, 17p11-p12, 22q11, and 22q13. The cross-isolate homogeneity in linkage patterns may be ascribed to an identical-by-descent "metahaplotype" block with pathogenic loci derived from the Daghestan ethnic groups' common ancestral metapopulation, while the cross-isolate differences may reflect differences in gene drift and recombination events in the history of local isolates. The results obtained support the notion that mapping genes of any complex disease (e.g., schizophrenia) in demographically older genetic isolates may be more time and cost effective in comparison with demographically younger isolates, especially in genetically heterogeneous outbred populations, due to higher clinical and genetic homogeneity of the primary isolates. A study at higher genotyping density across the regions of interest and fluorescence in situ hybridization analyses are currently underway.

Chromosome Mapping↗
PubMed2003

Oral clefts and syndromic forms of tooth agenesis as models for genetics of isolated tooth agenesis.

Genetic defects responsible for tooth agenesis are only now beginning to be uncovered. MSX1 and PAX9 have been associated with tooth agenesis in mice and humans, but interestingly for humans, these genes are associated with specific missing teeth. Mouse models also show that specific genes contribute to the development of specific types of teeth. A precise description of the phenotype specifying which teeth are missing has become fundamental. Mendelian segregation can be identified in families with tooth agenesis, but heterogenous or multiple genes may be responsible for the development of specific types of teeth agenesis in humans. Data from animal models are still very complex, and the human embryology is still poorly understood. Oral clefts and syndromic forms of tooth agenesis may be the best models for isolated tooth agenesis. In the future, a precise description of the missing teeth in syndromes involving tooth agenesis may be useful.

Animals↗
PubMed2000

Genetic variability within the VP1 coding region of echovirus type 30 isolates.

Genetic relationships of the prototype Bastianni strain of 1958 and of 13 echovirus type 30 (ECV30) isolates associated with meningitis cases in Germany during a period from 1966 to 1997 were investigated using direct sequencing of amplicons derived from a part of the capsid protein VP1 gene. Sequences were aligned both with each other and with known sequences of other type 30 echovirus strains. Phylogenetic analysis indicated that isolates investigated in this work fell into at least three genetic clusters apart from the prototype Bastianni strain. This suggests that genetically distinct groups of ECV30 variants have developed over time.

Amino Acid Sequence↗
PubMedDate not supplied

Polymorphism and genetic evolution in an isolate in the Antilles: Saint-Barthélémy.

St Barthélémy, a small island near Guadaloupe, has been isolated since the eighteenth century. The population is made up of two geographical isolates, genetically separated. In each, the inbreeding level is increasing on account of random genetic drift, which is reinforced by village endogamy, equivalent to a kind of spouse selection. Consanguinity between spouses has been analysed to give an estimate of the contributions of random genetic drift and spouse choice to total inbreeding. A second estimate to inbreeding can be obtained from the variation in observed gene frequencies. The two estimates obtained are of the same order, 0.6-1.0%, and are comparable with those still observed in isolated villages of the French Pyrenees.

Alleles↗
PubMed2002

Construction and evaluation of plasmid vectors optimized for constitutive and regulated gene expression in Burkholderia cepacia complex isolates.

Genetic studies with Burkholderia cepacia complex isolates are hampered by the limited availability of cloning vectors and by the inherent resistance of these isolates to the most common antibiotics used for genetic selection. Also, some of the promoters widely employed for gene expression in Escherichia coli are inefficient in B. cepacia. In this study, we have utilized the backbone of the vector pME6000, a derivative of the pBBR1 plasmid that was originally isolated from Bordetella bronchiseptica, to construct a set of vectors useful for gene expression in B. cepacia. These vectors contain either the constitutive promoter of the S7 ribosomal protein gene from Burkholderia sp. strain LB400 or the arabinose-inducible P(BAD) promoter from E. coli. Promoter sequences were placed immediately upstream of multiple cloning sites in combination with the minimal sequence of pME6000 required for plasmid maintenance and mobilization. The functionality of both vectors was assessed by cloning the enhanced green fluorescent protein gene (e-gfp) and determining the levels of enhanced green fluorescent protein expression and fluorescence emission for a variety of clinical and environmental isolates of the B. cepacia complex. We also demonstrate that B. cepacia carrying these constructs can readily be detected intracellularly by fluorescence microscopy following the infection of Acanthamoeba polyphaga.

Burkholderia cepacia↗
PubMed1975

Genetic analysis of adenovirus type 2. I. Isolation and genetic characterization of temperature-sensitive mutants.

Temperature-sensitive mutants which replicate normally at 33 C but poorly at 39 C were isolated from nitrosoguanidine- or nitrous acid-mutagenized adenovirus 2 by (i) testing the cytopathic effect or inclusion body-forming capacity of random plaque isolates, or (ii) reduced plaque enlargement upon shifting from 33 to 39 C. Thirty-six mutants were isolated with 33 C/39 C plaque ratios varying from 20 to 10-5. Some of these mutants could be arranged into 13 groups by the complementation test. By means of recombination analysis a provisional linear genetic map was constructed.

Adenoviridae↗
PubMed2006

Restless legs syndrome: epidemiological and clinicogenetic study in a South Tyrolean population isolate.

Genetic contributions to restless legs syndrome (RLS) have been consistently recognized from population and family studies. To determine the clinical and genetic features of RLS in a population isolate and explore linkage to three previously described susceptibility loci on chromosomes 12q, 14q, and 9p, respectively, an isolated population in the South Tyrolean Alps was identified and 530 adults participated in the study. Using a two-step strategy, 47 patients with idiopathic RLS were ascertained. The prevalence in the population was 8.9%. Twenty-eight patients (59.6%) had at least one affected first-degree relative and were classified as hereditary cases. In a single extended pedigree, linkage to known RLS loci was investigated specifying autosomal dominant and recessive models; parametric and nonparametric multipoint linkage scores were computed. None of the calculated linkage scores was suggestive of linkage between RLS and any of the three investigated loci. This study was conducted in a population isolate providing for a homogeneous genetic and environmental background. The absence of a suggestive linkage signal at the three known RLS susceptibility loci is indicative of further locus heterogeneity of this frequent disorder and encourages further studies to unveil the genetic causes of RLS.

Adult↗
PubMed1994

CHO.K1 cell mutants sensitive to active oxygen-generating agents. I. Isolation and genetic studies.

Nine mutants isolated from CHO.K1 cells with increased sensitivity to the lethal effect of plumbagin (PG), a powerful superoxide generator, were classified into five groups, A-E, according to their sensitivity to PG and methyl viologen (MV). Two mutants of group B (Pa13 and Pb4) were sensitive to both drugs, and two mutants of group C (Pa14 and Pa15) were moderately sensitive to PG and extremely sensitive to MV. To mitomycin C (MMC) these mutants showed cross-sensitivity; especially Pa13 and Pb4 (group B) were highly sensitive to MMC. Genetic complementation analyses of these four mutants were carried out using MV sensitivity. Sensitivity group B was divided into two complementation group, I and II. Pa14 and Pa15 belonged to the same complementation group III. These four mutants were also classified into three complementation groups for MMC sensitivity. Because Pa13 and Pb4 were also sensitive to cis-diamminedichloroplatinum(II), they may have a defect in the repair of DNA crosslinks induced by these agents. A complementation group IV (Pa2 and Pa8) was also suggested based on the studies of MMC sensitivity.

Animals↗
PubMed2006

Eukaryotic microbes, species recognition and the geographic limits of species: examples from the kingdom Fungi.

The claim that eukaryotic micro-organisms have global geographic ranges, constituting a significant departure from the situation with macro-organisms, has been supported by studies of morphological species from protistan kingdoms. Here, we examine this claim by reviewing examples from another kingdom of eukaryotic microbes, the Fungi. We show that inferred geographic range of a fungal species depends upon the method of species recognition. While some fungal species defined by morphology show global geographic ranges, when fungal species are defined by phylogenetic species recognition they are typically shown to harbour several to many endemic species. We advance two non-exclusive reasons to explain the perceived difference between the size of geographic ranges of microscopic and macroscopic eukaryotic species when morphological methods of species recognition are used. These reasons are that microbial organisms generally have fewer morphological characters, and that the rate of morphological change will be slower for organisms with less elaborate development and fewer cells. Both of these reasons result in fewer discriminatory morphological differences between recently diverged lineages. The rate of genetic change, moreover, is similar for both large and small organisms, which helps to explain why phylogenetic species of large and small organisms show a more similar distribution of geographic ranges. As a consequence of the different rates in fungi of genetic and morphological changes, genetic isolation precedes a recognizable morphological change. The final step in speciation, reproductive isolation, also follows genetic isolation and may precede morphological change.

Classification↗
PubMed1996

Phylogenetic analysis of hepatitis D viruses indicating a new genotype I subgroup among African isolates.

Genetic analysis was performed on 13 hepatitis D virus (HDV) isolates from Ethiopia, Somalia, Jordan, Kuwait, Bulgaria, Moldavia, and Sweden. The complete nucleotide sequence and genomic organization are described for the first time for two African HDV isolates. Phylogenetic analysis showed all the African isolates to be intrarelated and to form a novel group within HDV genotype I; the suggested designation for this group is IC. The genetic distance to previously described type I isolates was about 0.15. The HDV genotype I isolates (total of 22 examined) phylogenetically formed three clusters, each of them corresponding to certain geographic regions; the "western" group consisted of six HDV isolates from western Europe and the United States plus one from Kuwait; the "eastern" group consisted of two isolates from Moldavia and one each from Bulgaria, Nauru, mainland China, and Taiwan; and the "African-Middle East" group consisted of six HDV isolates from Ethiopia and one from Somalia, Jordan, and Lebanon.

Adolescent↗