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PubMed2004

Genetic variation in radiation-induced expression phenotypes.

Studies have demonstrated that natural variation in the expression level of genes at baseline is extensive, and the determinants of this variation can be mapped by a genetic-linkage approach. In this study, we used lymphoblastoid cells to explore the variation in radiation-induced transcriptional changes. We found that, among normal individuals, there is extensive variation in transcriptional response to radiation exposure. By studying monozygotic twins, we demonstrated that there is evidence of a heritable component to this variation. The postradiation variation in the expression level of several genes, including the ferredoxin reductase gene (FDXR) and the cyclin-dependent kinase inhibitor 1A gene (CDKN1A), is significantly greater (P<.001) among twin pairs than within twin pairs. The induction of FDXR by radiation showed a bimodal distribution. Our findings have important implications for understanding the genetic basis of radiation response, which has remained largely unknown due to the lack of family material needed for genetic studies. Our approach, which uses expression phenotypes in cell lines, allows us to expose cells from family members to radiation. Similar study design can be applied to dissect the genetic basis of other complex human traits.

Cell Cycle Proteins↗
PubMed1993

Association between genetic variation at the porphobilinogen deaminase gene and schizophrenia.

There is growing evidence that some genetic predisposition is important in the etiology of schizophrenia. We have sought to implicate a major gene by performing a candidate gene association study comparing the allele frequencies of seven restriction fragment length polymorphisms (RFLPs) at six loci in both a psychiatrically normal control group (N = 51) and an affected (schizophrenia or schizoaffective disorder) group (N = 55). Each group comprised Caucasians of northern European origin. The candidate areas (D5S39, D5S78, dopamine receptor D2 (DRD2), D11S29, porphobilinogen deaminase (PBGD), and D11S84) were selected on the basis of prior cytogenetic findings in schizophrenics, linkage studies, and/or implicated gene products. The presence of a polymorphic ApaLI site within the PBGD gene showed a significant association with the presence of illness (P = 0.02). The relative risk of possessing the allele with the ApaLI site was 2.10. No significant association was found with any of the six other RFLPs. Our data suggests that either the PBGD gene itself or an unknown gene linked to and/or in linkage disequilibrium with the PBGD locus predisposes some individuals to schizophrenia. Independent replication of these findings will be required to determine their relevance to schizophrenia.

Adolescent↗
PubMed2004

Effect of genetic variation on the thermal stability of human serum albumin.

Reversible thermal denaturation of 33 genetic variants of human serum albumin (HSA) appeared to be a two-state process when studied by circular dichroism (CD). Fourteen single-residue variants have Tm values (midpoint of denaturation) higher than, and nine have Tm values lower than, their endogenous, wild-type counterpart. Nine single-residue variants have DeltaHv values (van't Hoff enthalpy) higher than, and 14 have DeltaHv values lower than, normal albumin. All types of combinations of positive and negative DeltaTm values and Delta(DeltaHv) values were found. Good linear correlations between mutation-induced changes of alpha-helical content and Delta(DeltaHv) values, but not DeltaTm values, were found especially for the variants mutated in domains I and III. The effect of altered chain length and glycosylation on Tm and DeltaHv was also studied. For all variants, no clear relationship was found between the changes in the thermodynamic parameters and the type of substitution, changes in protein charge or hydrophobicity. However, the protein changes taking place in domain I have a rather uniform effect (almost all of the nine variants have positive DeltaTm values and negative Delta(DeltaHv) values, i.e., they denature more easily than normal albumin but they do so at a higher temperature). The present results can be of both protein chemical relevance and of clinical interest, because they could be useful when designing stable, recombinant HSAs for clinical applications.

Circular Dichroism↗
PubMed2003

Support for genetic variation in neuregulin 1 and susceptibility to schizophrenia.

Recently, it has been reported that genetic variants around the gene neuregulin 1 are associated with schizophrenia in an Icelandic sample. Of particular interest was the presence of a single-risk haplotype that was significantly over-represented in schizophrenic individuals compared to controls (15.4 : 7.5%, P=6.7 x 10(-6)). We have attempted to replicate this result in our large collection of 573 schizophrenia cases and 618 controls. We found that the risk haplotype was more common in cases than controls (9.5 : 7.5%; P=0.04), and especially in our subset of 141 cases with a family history of schizophrenia (11.6%; P=0.019). Our results therefore replicate the Icelandic findings in an out-bred Northern European population, although they suggest that the risk conferred by the haplotype is small.

Adult↗
PubMed1993

Genetic variation and phylogenetic relationships among worldwide collections of the Russian wheat aphid, Diuraphis noxia (Mordvilko), inferred from allozyme and RAPD-PCR markers.

Genetic analyses were conducted on Diuraphis noxia (Mordvilko) populations collected from wheat, barley and other grasses from various countries throughout the world. These collections had been found to contain clones that differed in virulence from various cultivars, cuticular hydrocarbon profiles and life cycle characters. Discrete genetic markers analysed in this study included allozymes and arbitrary regions of the genome amplified by the polymerase chain reaction (RAPD-PCR). In all, 23 enzymes were evaluated; 17 of these enzymes representing 20 isozyme loci, were judged suitable for allozyme analysis. Polymorphisms were detected at three (15 per cent) loci: beta-esterase (beta-EST), phosphoglucose isomerase (PGI), and 6-phosphogluconate dehydrogenase (6-PGDH). The average expected heterozygosity amongst these loci was 4.9 per cent in the worldwide collection. Allozyme variation was absent within most populations, particularly within those countries where the species was recently introduced. Much greater genetic variation was detected when populations were analysed with RAPD-PCR. Populations were analysed with 69 polymorphic bands amplified by seven primers. All populations could be distinguished with this method. Cluster analyses indicated strong similarities between U.S.A. populations and collections from South Africa, Mexico, France and Turkey. The most variation was detected among populations from the Middle East and southern Russia.

Animals↗
PubMedDate not supplied

A first assessment of genetic variation in Welwitschia mirabilis Hook.

Welwitschia mirabilis is a monotypic member of the family Welwitchiaceae which, along with Ephedra and Gnetum species, comprises the gymnospermous order Gnetales. While the monophyly of this order is now widely accepted, the relationship of the Gnetales to other seed plants is still contentious. Despite the unique phylogenetic position of W. mirabilis and its extraordinary physiological and anatomical adaptations, little is known about the plant's phylogeny or its current distribution in isolated locations throughout the Namib Desert. As a preliminary step in the design of an more extensive phylogeographic study, we analyzed 37 random amplified polymorphic DNA (RAPD) loci from 59 plants distributed among five sites separated by distances of 6-440 km. Cluster analysis and analysis of molecular variance (AMOVA) revealed significant levels of variation within and between populations and little evidence of inbreeding. Genetic differences between populations reflect the geographic distances separating them. Three of the populations formed discernable genetic clusters, suggesting that little gene flow occurs between populations separated by > or = 18 km. In contrast, gene flow is occurring between two populations separated by only 6 km, supporting previous observations that pollen dispersal is primarily local and that seeds are not readily wind-born over the large distances separating most W. mirabilis populations. As a working hypothesis, we propose that W. mirabilis had a continuous distribution across its current range as much as 105 million years ago, and that as a consequence of subsequent drying trends and physical disturbance, populations became progressively isolated, accounting for their current distribution.

Biological Evolution↗
PubMed1996

Antigenic and genetic variation of the HN protein of mumps virus strains.

The relationships between different strains of mumps virus were established by determination of the sequence of the HN gene. They closely resemble those established from other portions of the genome, suggesting that the viruses are not recombinants over the areas examined. The relationships were consistent with those established by reaction with monoclonal antibodies raised against the Urabe strain, which has a similar antigenic structure to previously studied laboratory strains, and largely consistent with the specificity of the serological response of naturally infected or vaccinated human subjects.

Amino Acid Sequence↗
PubMed2000

Genetic variation in in-vitro cytokine-induced production of nitric oxide by murine peritoneal macrophages.

Quantitative aspects of the in-vitro interferon (IFN)-gamma-induced nitric oxide (NO) production by peritoneal macrophages of eight inbred strains of mice were investigated. Animals employed in the study can be assorted into three phenotype categories: high, moderate, and low NO-responders. Concentration of nitrites in the 24-h supernatants of cells stimulated with recombinant murine IFN-gamma (25 U/ml) reached the following values (mean +/- SEM; in microM): C57BL/10 (33.7+/-1.88) = C57BL/6 (32.1+/-2.10) > SIL (24.0+/-1.55) > CBA/J (18.1+/-1.79) = C3H/HeN (18.0+/-1.10) > DBA/2 (11.4+/-1.16) = DBA/1 (11.0+/-1.20) = Balb/c (11.0+/-1.16). Approximately 80% of the total variation was found to be controlled by genetic factors. No association between the extent of NO formation and variation in the constitutive expression of macrophage IFN-gamma receptor was observed. Similar magnitude of inter-strain differences was sustained after enhanced NO-stimulation of the cells with IFN-gamma + tumour necrosis factor (TNF)-alpha, but only high (strains BL/10, BL/6, SJL, CBA/J, C3H/HeN) and low (DBA/1, DBA/2, Balb/c) NO-responder phenotypes were detected after the triple cytokine cocktail composed of IFN-gamma + TNF-alpha + interleukin (IL)-10. The strain differences remained unchanged after the supplementation of culture medium with L-arginine or tetrahydrobipopterin. Genetically governed differences in IFN-gamma-induced NO production have been found to be tightly associated with differential expression of inducible nitric oxide synthase mRNA. Possible implications of the findings for various fields of NO biomedical research are discussed.

Animals↗
PubMed1973

Genetic variation in a gradient of environmental variability: marine bivalvia (Mollusca).

Six bivalve mollusk species were sampled for genetic variability at two enzyme synthesizing loci. The effective number of alleles and absolute number of alleles decreased with depth of burial within the sediment, intertidally, and with depth of water, subtidally. It is proposed that environmental variability regulates genetic variability at these two loci.

Alleles↗
PubMed1990

Genetic variation of alpha-2-HS-glycoprotein in the Kyushu district of Japan: description of three new rare variants.

The genetic polymorphism of alpha 2-HS-glycoprotein (AHSG) was studied in the Kyushu district of Japan using polyacrylamide gel isoelectric focusing, followed by immunoblotting. Three new rare variants were observed and designated AHSG*16, AHSG*17 and AHSG*18, tentatively. The frequencies of the polymorphic genes AHSG*1 and AHSG*2 were similar to those in other areas of Japan.

Fibronectins↗
PubMed2026

Deep soil layers show the most pronounced genetic variation in wheat root length.

Wheat is one of the most important cereals worldwide, yet significant gaps remain in our understanding of genetic variability in root traits, especially those associated with deeper rooting that support resource acquisition in challenging environments. Root traits are typically controlled by many genes with small effects and often display low heritability. Our aim was to develop a statistical approach to analyse root variation across soil depth and to determine where genetic differences in root intensity are most detectable. An experiment was conducted at the RadiMax semi-field facility, which is designed to measure deep root systems. Five years of phenotypic data recorded each June produced observations from 1500 rows. Each row captured root intensity across the soil profile from 0.6 m to 2.6 m, enabling detailed analysis of vertical root distribution. Across the five years, 513 winter wheat cultivars were grown in the facility, and among those 409 were genotyped with SNP chips. Depth-resolved regression models with random coefficients were used to quantify genetic and non-genetic variation in root intensity across soil depths, while accounting for spatial variation between rows. Random variation within rows was found to be constant across depths. The models showed that genetic variance for cumulative root intensity increased substantially below 1.1 m, with the deepest layers exhibiting the largest differences between wheat lines. Narrow-sense heritability of point measurements peaked at approximately 1.5 m ([Formula: see text]).

Genetic variability↗
PubMed1979

A review of research on genetic variation in physiological characteristics related to performance in dairy cattle.

Genetic influence on physiological characteristics ranges from single gene effects on amino acid substitutions in alternative forms of proteins to quantitative genetic effects on the amounts of enzymes and hormones. The number of loci involved in the control of quantitative variation in physiologically important substances is not known. A number of marker genes that affect blood antigens, serum and milk proteins, and enzymes have been identified in dairy cattle. However, relatively little is known about genetic effects on quantitative physiological traits in dairy cattle. Much more is known about the genetic control of hormones in laboratory animals. About 25% of the variation in milk production of dairy cows results from genetic differences. We need more studies of genetic influences on the various physiological and biochemical processes involved in the secretion of milk to reveal the mechanisms by which genetics influences the quantity and quality of milk produced by individual cows.

Animals↗
PubMed1994

Genetic variation at pig plasma protein locus PLP1 and its assignment to chromosome 5.

A new genetic polymorphism of an unidentified plasma protein (PLP1) in pigs was described by using a method of two-dimensional gel electrophoresis and protein staining. Two codominant alleles, with frequencies of 0.83 and 0.17, were found in the Swedish Yorkshire breed. The PLP1 marker was typed in a three-generation pedigree and tested for linkage against a set of 128 markers. The PLP1 locus showed significant LOD score values with three different microsatellite markers (S0092, DAGK and S0005), previously assigned to chromosome 5.

Animals↗
PubMed2005

Loss of genetic variation in geographically marginal populations of Atriplex tatarica (Chenopodiaceae).

BACKGROUND AND AIMS: Genetic variability was estimated for Atriplex tatarica from 25 populations in the Czech Republic. Since its north-western range margin is in central Europe, a relationship between marginality and low within-population genetic diversity was tested in accordance with the Central-Marginal Model. METHODS: Population genetic diversity was expressed by assessing patterns of variation at 13 putatively neutral allozyme loci (comprising 30 putative alleles) within and between 25 natural populations of A. tatarica along a north-west-south-east transect in the Czech Republic. KEY RESULTS: Atriplex tatarica is a species of human-made habitats with a mixed mating system and wide geographic distribution. Overall, A. tatarica displayed moderate levels of genetic diversity in comparison with other herbaceous plants. The percentage of loci that were polymorphic was 47.1%, with average values of 1.55, 0.151 and 0.155 for the average number of alleles per polymorphic locus (A), observed heterozygosity (Ho) and expected heterozygosity (He), respectively. There was only weak evidence of inbreeding within populations (FIS=0.031) and significant population differentiation (FST=0.214). Analysis of the data provides no evidence for isolation-by-distance for the whole study area. However, Mantel tests were highly significant for the marginal Bohemian region and non-significant for the central Moravian region. While northern populations of A. tatarica showed significantly lower allelic richness (A=1.462) than populations from the southern part of the study area (A=1.615), they did not differ in observed heterozygosity (Ho), gene diversity (HS), inbreeding within populations (FIS) or population differentiation (FST), despite generally lower values of particular genetic measurements in the marginal region. CONCLUSIONS: Genetic diversity, with the exception of allelic richness, was not significantly lower at the margins of the species' range. This, therefore, provides only weak support for the predictions of the Central-Marginal Model.

Chenopodiaceae↗