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PubMed2026

Panmixia in a Widespread Butterfly: High Dispersal and Ecological Generalism Buffer Against Landscape Fragmentation.

Habitat fragmentation is widely expected to reduce population connectivity and increase genetic differentiation, although the strength of these effects depends on species-specific traits such as dispersal ability. Here, we investigated the population genetic structure of the cosmopolitan butterfly, Pieris rapae L. (Lepidoptera: Pieridae), across western Germany using genome-wide single-nucleotide polymorphism (SNP) data. To analyze the effects of landscape structure on genetic connectivity, we applied a paired study design comprising four landscape pairs, each consisting of a highly intensified, modern agricultural landscape and a more heterogeneous, traditional landscape. Our results revealed no evidence of genetic differentiation. Pairwise FST values were close to zero; we detected no isolation by distance, and clustering analyses supported a single genetic population. No meaningful associations between genetic variation and environmental variables were detected, with landscape effects explaining less than 0.4% of genomic variation. Consequently, we found no evidence for stronger genetic structuring in modern compared to more connected traditional landscapes. Our results suggest that extensive habitat fragmentation does not necessarily translate into reduced genetic connectivity in highly mobile, generalist species. In P. rapae , high dispersal ability and ecological generalism appear to buffer against the genetic consequences of landscape modification, resulting in panmictic population structure even across strongly contrasting agricultural landscapes.

Pieris rapae↗
PubMed1992

Yeast SNF/SWI transcriptional activators and the SPT/SIN chromatin connection.

Genetic studies of many diversely regulated genes in the yeast Saccharomyces cerevisiae have identified two groups of genes with global functions in transcription. The first group comprises five SNF and SWI genes required for transcriptional activation. The other group, containing SPT and SIN genes, was identified by suppressor analysis and includes genes that encode histones. Recent evidence suggests that these SNF/SWI and SPT/SIN genes control transcription via effects on chromatin. SNF2/SWI2 sequence homologues have been identified in many organisms, suggesting that the SNF/SWI and SPT/SIN functions are conserved throughout eukaryotes.

Biological Evolution↗
PubMed2002

Mode of delivery and asthma -- is there a connection?

Genetic factors cannot explain the recent rapid increase in the incidence of atopic diseases. The phenomenon has been explained by environmental factors, and there are data for and against the hypothesis that a decline in the pressure of microbial stimulation early in life could be behind the allergy epidemic. Changes have also occurred in maternity care, among them a rise in the caesarean section rate, which could diminish initial microbial exposure and thereby alter T helper 1 cell/T helper-2 cell development and affect the risk of developing atopy. In this study, we sought to establish whether mode of delivery does influence the development of atopic asthma. Finnish 1987 Medical Birth Register (n = 59,927 live births) information was linked between several national health registers to obtain information on asthma and mode of delivery in children registered. The data were adjusted for maternal age, previous deliveries, child's sex, and birth size. Atopy was evaluated in the second study (Turku Birth Cohort), which involved 219 children born by vaginal delivery (n = 106) or caesarean section (n = 113); history of atopic symptoms was established by questionnaire and a clinical examination was conducted, including skin prick testing and determination of total and allergen-specific IgE in serum. The register study showed the cumulative incidence of asthma at the age of seven to be significantly higher in children born by caesarean section (4.2%) than in those vaginally delivered (3.3%), the adjusted odds ratio (OR) for confounding variables being 1.21 (1.08-1.36), p < 0.01. In the second study, significantly more positive allergy tests were reported in questionnaires in the caesarean (22%) than in the vaginal delivery group (11%), OR 2.22 (1.06-4.64), p < 0.01, and a trend toward more positive skin prick reactions was documented at clinical examination; 41% versus 29%, OR 1.31 (0.65-2.65), p = 0.11. In conclusion, these results suggest that caesarean section delivery may be associated with an increased prevalence of atopic asthma.

Asthma↗
PubMed2006

Elevation and connectivity define genetic refugia for mountain sheep as climate warms.

Global warming is predicted to affect the evolutionary potential of natural populations. We assessed genetic diversity of 25 populations of desert bighorn sheep (Ovis canadensis nelsoni) in southeastern California, where temperatures have increased and precipitation has decreased during the 20th century. Populations in low-elevation habitats had lower genetic diversity, presumably reflecting more fluctuations in population sizes and founder effects. Higher-elevation habitats acted as reservoirs of genetic diversity. However, genetic diversity was also affected by population connectivity, which has been disrupted by human development. Restoring population connectivity may be necessary to buffer the effects of climate change on this desert-adapted ungulate.

Alleles↗
PubMed2003

Functional and effective frontotemporal connectivity and genetic risk for schizophrenia.

BACKGROUND: Functional neuroimaging and electrophysiologic studies have found disturbed frontotemporal interaction in schizophrenia. We sought to determine whether abnormalities of frontotemporal connectivity are trait markers of genetic risk for schizophrenia. METHODS: We investigated 64 schizophrenia patients, 79 of their clinically unaffected siblings, and 88 unrelated normal controls with an auditory oddball electroencephalogram (EEG) evoked potential paradigm. We measured: 1) frontotemporal event-related EEG-coherence (i.e. a measure of functional connectivity); and 2) we performed structural equation modeling of the effective connectivity between the frontal P300 and temporoparietal P300-amplitude. RESULTS: Schizophrenic patients and their siblings showed a reduction of frontotemporal coherence. At peak activation during the P300 time-window, a negative ("inhibitory") frontotemporal path coefficient was found in normal controls, whereas a positive coefficient was seen in schizophrenic patients with siblings being intermediate. Intra-class correlations between sib-pairs and relative risk estimates of the applied connectivity measures were non-significant. Topographic correlation matrix analyses suggested that the altered functional and effective frontotemporal connectivity indirectly reflect regional abnormalities of increased activation variance. CONCLUSIONS: Impaired interaction of the frontotemporal macro-circuit indirectly reflects genetically determined abnormalities of frontal and temporoparietal microcircuits. The reasons why frontotemporal connectivity appears to be a poor predictor of genetic risk for schizophrenia are discussed.

Adult↗
PubMed2002

The phylogeography and connectivity of the latitudinally widespread scleractinian coral Plesiastrea versipora in the Western Pacific.

Whereas terrestrial animal populations might show genetic connectivity within a continent, marine species, such as hermatypic corals, may have connectivity stretching to all corners of the planet. We quantified the genetic variability within and among populations of the widespread scleractinian coral, Plesiastrea versipora along the eastern Australian seaboard (4145 km) and the Ryukyu Archipelago (Japan, 681 km) using sequences of internal transcribed spacers (ITS1-2) from ribosomal DNA. Geographic patterns in genetic variability were deduced from a nested clade analysis (NCA) performed on a parsimony network haplotype. This analysis allowed the establishment of geographical associations in the distribution of haplotypes within the network cladogram, therefore allowing us to deduce phylogeographical patterns based under models of restricted gene flow, fragmentation and range expansion. No significant structure was found among Ryukyu Archipelago populations. The lack of an association between the positions of haplotypes in the cladogram with geographical location of these populations may be accounted for by a high level of gene flow of P. versipora within this region, probably due to the strong Kuroshio Current. In contrast, strong geographical associations were apparent among populations of P. versipora along the south-east coast of Australia. This pattern of restricted genetic connectivity among populations of P. versipora on the eastern seaboard of Australia seems to be associated with the present surface ocean current (the East Australian Current) on this side of the south-western Pacific Ocean.

Animals↗
PubMed2026

Shared genetic architecture of obesity and gastroesophageal reflux disease.

Obesity is identified as a risk factor of gastroesophageal reflux disease (GERD). This study aims to elucidate the shared genetic architecture of obesity-related phenotypes and GERD. Based on the publicly available genome-wide association studies' datasets, this genome-wide pleiotropic association study was conducted with various genetic approaches (including linkage disequilibrium score regression, high-definition likelihood inference for genetic correlations, pleiotropic analysis under composite null hypothesis, Functional Mapping and Annotation, Bayesian colocalization, summary-based Mendelian randomization, and multi-marker analysis of genomic annotation analysis) sequentially to unravel the genetic associations from single-nucleotide polymorphism to gene levels, and to reveal the underlying shared genetic architecture between obesity-related phenotypes and GERD. This study discovered shared genetic mechanisms between GERD and several obesity-related phenotypes, including arm fat percentage (left), arm fat percentage (right), leg fat percentage (left), leg fat percentage (right), trunk fat percentage, waist-to-hip ratio, and body mass index. Significant genetic correlations were observed by linkage disequilibrium score regression and high-definition likelihood inference for genetic correlations, with multiple associated pleiotropic loci and their mapped genes identified by pleiotropic analysis under composite null hypothesis, Functional Mapping and Annotation, Bayesian colocalization, summary-based Mendelian randomization, and multi-marker analysis of genomic annotation analysis. Additionally, several brain tissues were identified to be linked to both obesity and GERD by multi-marker analysis of genomic annotation. This research provided strong evidence of genetic correlations and brought novel insights into the underlying genetic connections and shared genetic architectures of obesity and GERD.

Humans↗
PubMed2026

Diversity and population connectivity of members of the family Eunicidae inhabiting deep-water corals in the North Atlantic.

Eunicid polychaetes are often found in association with Cold Water Corals (CWCs), even establishing symbiotic relationships, such as those described between Desmophyllum pertusum and Eunice norvegica. While genetic connectivity of CWCs across the North Atlantic has been widely studied, little is known about their associated fauna in this regard. Here, we present a study combining a focused analysis of the genetic and genomic connectivity of E. norvegica with a regional assessment of the distribution and evolutionary relationships of three CWC-associated eunicid species from the Cantabrian Sea and the North of the United Kingdom (190-1,230&#xa0;m depth). An integrative approach using genetic (16S, COI and 18S), morphological and ecological data allowed the identification of the eunicids studied, with new records of Eunice cf. nicidioformis and Leodice cf. antarctica in the Cantabrian Sea, as well as previously undocumented associations with CWC species. In addition, RADseq data contributed to the delimitation of the closely related species E. norvegica and Eunice philocorallia. Moreover, the genetic connectivity of E. norvegica was studied trough a RADseq (1,067 neutral SNPs) approach. Our results indicate a single panmictic population across approximately 2,000&#xa0;km, suggesting that oceanographic currents facilitate passive dispersal of E. norvegica lecithotrophic larvae, aided by coral host stepping-stones. The connectivity patterns observed for E. norvegica mirror those of D. pertusum, on which the worm is ecologically dependent. Our study highlights the importance of using integrated genetic, morphological and ecological data to characterise and delineate understudied CWC-associated species and improve our understanding of their dispersal capabilities and genetic connectivity to inform future conservation recommendations.

Animals↗
PubMed2026

Fine-Scale Landscape Genomics Show Asymmetric Patterns of Gene Flow for the Invasive Mosquito Aedes albopictus.

Mosquito-borne viruses like dengue, Zika, and chikungunya pose increasing health risks in the United States due to the expanding range of Aedes albopictus, a highly invasive mosquito species that now has a global distribution. Aedes albopictus thrive in artificial containers associated with anthropogenic land use, allowing populations to reach high numbers in urban and suburban environments. While the global spread of Ae. albopictus has been well characterized, the effects of heterogeneous urban landscapes on dispersal and gene flow at fine spatial scales remain unclear. This study analyzed the genetic connectivity of Aedes albopictus populations collected in Wake County, North Carolina in 2018. We used single nucleotide polymorphisms (SNP) data from double-digest restriction-enzyme associated DNA sequencing (ddRADseq) and examined genetic connectivity through principal component analysis (PCA) and genetic network analysis. We then evaluated migration and source-sink dynamics using a Bayesian approach for SNP data (BA3-SNP). We found little evidence of genetic clustering or isolated populations of Ae. albopictus in Wake County, suggesting high gene flow between sites. Migration analysis demonstrated asymmetric gene flow from rural to urban regions within Wake County, with greater gene flow occurring between and within urban regions. These findings suggest that the pattern of gene flow of Ae. albopictus populations within local metropolitan areas may involve urban city centers serving as genetic sinks and surrounding suburban and rural regions serving as sources. This study highlights how heterogeneous landscapes shape mosquito population connectivity and migration at fine spatial scales, which is critical for informing vector control and public health intervention strategies.

Aedes albopictus↗
PubMed2004

Molecular evolution in large genetic networks: does connectivity equal constraint?

Genetic networks show a broad-tailed distribution of the number of interaction partners per protein, which is consistent with a power-law. It has been proposed that such broad-tailed distributions are observed because they confer robustness against mutations to the network. We evaluate this hypothesis for two genetic networks, that of the E. coli core intermediary metabolism and that of the yeast protein-interaction network. Specifically, we test the hypothesis through one of its key predictions: highly connected proteins should be more important to the cell and, thus, subject to more severe selective and evolutionary constraints. We find, however, that no correlation between highly connected proteins and evolutionary rate exists in the E. coli metabolic network and that there is only a weak correlation in the yeast protein-interaction network. Furthermore, we show that the observed correlation is function-specific within the protein-interaction network: only genes involved in the cell cycle and transcription show significant correlations. Our work sheds light on conflicting results by previous researchers by comparing data from multiple types of protein-interaction datasets and by using a closely related species as a reference taxon. The finding that highly connected proteins can tolerate just as many amino acid substitutions as other proteins leads us to conclude that power-laws in cellular networks do not reflect selection for mutational robustness.

Energy Metabolism↗
PubMed2026

High connectivity and genetic diversity in the Endangered endemic white-spotted sand bass 'camotillo' (Paralabrax albomaculatus) within the Gal&#xe1;pagos Marine Reserve.

BACKGROUND: Paralabrax albomaculatus, known as the camotillo or white-spotted sand bass, is a finfish endemic to the Gal&#xe1;pagos Islands. An important species in the artisanal fishery, P. albomaculatus has undergone heavy population declines in recent decades, and is categorised as Endangered by the IUCN. Despite its socio-economic importance and endemic status, nothing is currently known about the population structure of the species, impeding evidence-based fisheries management. In this study, we use microsatellite markers to investigate its population structure and genetic diversity over the east, south and west of the Gal&#xe1;pagos archipelago. RESULTS: We found evidence of high connectivity across the archipelago, with the species constituting a single population. We also found that genetic diversity was high, despite fishing pressure and recorded ongoing population declines. CONCLUSIONS: Our results suggest that P. albomaculatus should be managed as a single fishery stock across the Gal&#xe1;pagos. As a single-population species and fishery, managers should also be aware that P. albomaculatus is inherently vulnerable to perturbation as recruitment from other populations is not possible in the event of population decline. However, high genetic diversity gives cause for cautious optimism regarding the genetic capacity for resilience of the population to novel environmental stressors. These results should aid in the implementation of a species-specific management plan for this Gal&#xe1;pagos endemic.

Animals↗
PubMed2000

Genetics advances and learning disability.

BACKGROUND: Medicine is rapidly becoming molecular medicine, and little escapes the grasp of modern genetics. Most disorders associated with learning disability have at least a genetic component influencing their expression; in many disorders, disturbances of genetic mechanisms play a pivotal role. AIMS: Dynamic mutations, imprinting mechanisms and gene-dosage effects are explained with reference to genetic disorders that lead to learning disability. METHOD: A review of recent important studies in the genetics of learning disability. RESULTS: A host of new genetic connections to conditions associated with learning disability have been made. CONCLUSIONS: A basic understanding of these genetic connections is important for all learning disability psychiatrists if they are to follow the rapid changes--already beginning to influence our practice--that hold immense promise for the future.

Angelman Syndrome↗
PubMed2005

Genetic analysis connects SLX5 and SLX8 to the SUMO pathway in Saccharomyces cerevisiae.

MOT1 encodes an essential ATPase that functions as a general transcriptional regulator in vivo by modulating TATA-binding protein (TBP) DNA-binding activity. Although MOT1 was originally identified both biochemically and in several genetic screens as a transcriptional repressor, a combination of subsequent genetic, chromatin immunoprecipitation, and microarray analysis suggested that MOT1 might also have an additional role in vivo as a transcriptional activator. To better understand the role(s) of MOT1 in vivo, we selected for genomic suppressors of a mot1 temperature-sensitive mutation. This selection identified mutations in SPT15 (TBP) and BUR6, both of which are clearly linked with MOT1 at the functional level. The vast majority of the suppressor mutations, however, unexpectedly occurred in six genes that encode known components of the SUMO pathway and in two other genes with unknown functions, SLX5 and SLX8. Additional results presented here, including extensive synthetic lethality observed between slx5delta and slx8delta and SUMO pathway mutations, suggest that SLX5 and SLX8 are new components or regulators of the SUMO pathway and that SUMO modification might have a general role in transcriptional regulation as part of the TBP regulatory network.

Adenosine Triphosphatases↗
PubMed1990

[A genetic correlational analysis of the behavioral and physiological characteristics of spontaneously hypertensive rats (SHR)].

The SHR rats differ from normotensive WKY rats in a number of behavioral and physiological traits. In order to determine causal or accidental nature of relationships between these traits and hypertension, their correlations with arterial pressure level in the 2nd generation of SHR x WKY hybrids (F2), were studied. A positive correlation of body mass and characteristics of potassium appetite with a level of blood pressure corresponding to interstrain differences between SHR and WKY rats was found in F2 population showing genetic connection of these traits with hypertension. The negative correlation in F2 between open-field activity and arterial pressure was opposite to interstrain differences and environmental correlation (within parental strains and F1 hybrids). It seemed to be caused by prevalence of environmental correlation or of accidental fixation of this trait in SHR strain over the genetic connection found in F2 hybrids.

Animals↗
PubMed2005

Nonequilibrium conditions following landscape rearrangement: the relative contribution of past and current hydrological landscapes on the genetic structure of a stream-dwelling fish.

Interpreting patterns of population structure in nature is often challenging, especially in dynamic landscapes where population genetic connectivity evolves over time. In this study, we document the absence of migration-drift equilibrium in a stream-dwelling euryhaline fish resulting from past fine-scale drainage rearrangements and evaluate the relative contribution of past and current hydrological landscapes on observed population structure. Based on allelic variation at nine microsatellite loci, genetic relationships among 12 populations of brook charr, Salvelinus fontinalis, from Gros Morne National Park of Canada (GMNP, Newfoundland, Canada) did not reflect current stream hierarchical structure. In addition, we observed no correlation between population differentiation and contemporary landscape features (waterway distance and sums of altitudinal differences). Instead, population relationships were consistent with historical hydrological structure predicted a priori based on geomorphological and biogeographical evidences. Also, population differentiation was strongly correlated with inferred historical landscape features. Contemporary barriers have apparently preserved the signature of past genetic connectivity by constraining gene flow. Based on the relationships between population differentiation and current and past landscape features at various spatial scales, we suggest that brook charr genetic diversity in GMNP is mostly the result of small distance migrations at the time of colonization and subsequent differentiation through drift. This study highlights the potential of approaching landscapes from a combination of contemporary and historical perspectives when interpreting nonequilibrium population structures resulting from landscape rearrangement.

Animals↗
PubMed1993

A 1.5-megabase yeast artificial chromosome contig from human chromosome 10q11.2 connecting three genetic loci (RET, D10S94, and D10S102) closely linked to the MEN2A locus.

The genetic loci RET, D10S94, and D10S102 from human chromosome 10q11.2 are very closely linked to a locus responsible for the multiple endocrine neoplasia type 2 (MEN2A and MEN2B) and medullary thyroid carcinoma (MTC1) familial cancer syndromes. We have constructed a 1.5-megabase contig consisting of six genomic yeast artificial chromosome clones which include these loci and define their physical order. A critical crossover event has been identified within the map interval; this event places the MEN2A locus centromeric to D10S102 and defines the orientation of the physical map on the chromosome. The orientation of the contig and order of the markers are centromere-RET-D10S94-D10S102-telomere. In addition, a microsatellite repeat polymorphism with a heterozygosity of 71% at the RET locus and a restriction fragment length polymorphism with a heterozygosity of 42% detected by a lambda clone from the D10S94 locus have been developed for high-resolution genetic linkage mapping and predictive diagnostic testing. These data place three important markers on a contiguous physical map, narrow the MEN2 disease locus interval, and provide a framework for further candidate gene identification efforts. Placement of these genetic loci along a clone-based map and continued expansion of the contig will also facilitate efforts to determine the relationship of physical to genetic distance near the centromeres of human chromosomes.

Base Sequence↗
PubMed1993

Physical mapping and YAC-cloning connects four genetically distinct 4qter loci (D4S163, D4S139, D4F35S1 and D4F104S1) in the FSHD gene-region.

We have constructed a long-range restriction map of the region on chromosome 4q that contains the gene for facioscapulohumeral muscular dystrophy (FSHD). This region contains the linkage group cen ... D4S163-D4S139-D4F35S1-D4F104S1-FSHD ... 4qter, which spans a genetic distance of about 5 cM. Pulse field gel electrophoresis (PFGE) mapping indicated that these loci span a region not more than 1 Mb. STSs were developed for several of these loci, which served to isolate four overlapping yeast artificial chromosomes (YACs). These YACs confirmed the PFGE map and have allowed us to generate a more detailed restriction map using cosmid contig mapping. The physical distances were smaller than was expected on the basis of the genetic map. Two potential HTF islands have been detected within the cloned region. One HTF island maps about 100 kb centromeric from the tandem repeats involved in the FSHD mutation, whereas the other maps within these tandem repeats.

Base Sequence↗