Linkage arrangement in the vitellogenin gene family of Xenopus laevis as revealed by gene segregation analysis.

Using restriction fragment length polymorphism (RFLP) we have analyzed the segregation of alleles of the different vitellogenin genes of Xenopus laevis. The results demonstrate that the four genes whose expression is controlled by oestrogen, form two linkage groups. The genes A1, A2 and B1 are linked genetically whereas the fourth gene, the gene B2, segregates independently. The possible origin of this unexpected arrangement is discussed.

Pattern of attack of a galling insect reveals an unexpected preference-performance linkage on medium-sized resources

Pattern of attack of a galling insect reveals an unexpected preference-performance linkage on medium-sized resources. The Plant Vigor Hypothesis (PVH) predicts oviposition preference and higher offspring performance on longer and fast-growing shoots, and although several studies have tested its predictions, long-term studies concerning the patterns of host selection by galling species are still lacking. The PVH was tested in this study using Bauhinia brevipes (Fabaceae) as the host of a leaf gall midge, Asphondylia microcapillata (Diptera, Cecidomyiidae) during three consecutive years. Shoots were collected from the same 80 plants between 2001 and 2003 and shoot length, number of healthy and galled leaves, gall number, and mortality factors were recorded. Nearly 600 galls were found on the 5,800 shoots collected. Medium-sized shoots supported from 46 to 70% of all galls, with greater gall survival rate in 2002 and 2003. A decrease in parasitism rate coupled with an increase in gall predation lead to a constant similar gall survivorship rate in all years (x = 22.7%). Although gall abundance varied among years (122 in 2001, 114 in 2002 and 359 in 2003) preference for longer shoots was not observed because the percentage of galled shoots and galled leaves were higher on medium shoot length classes in all years. The observed distribution of gall abundance and galled shoots were always greater than the expected distribution on medium shoot length classes. These findings do not support the PVH, and show that A. microcapillata can maximize the female preference and larval performance on medium-sized shoots of B. brevipes.

Generación de cursos virtuales adaptativos en SCORM e IMS-LD

The use of virtual learning environments it’s more and more frequent in all education levels. However, this increasing use of such environments also implies that the different stages now used in the processes of teaching-learning need to be considered. Student users in a virtual learning environment are faced, not only to the problems related to acquire the knowledge of their course, but also to technological problems as information overloading, getting used to web surfing, computer use, etc. One way to minimize the impact caused by heterogeneity existing in virtual learning environments is to adapt several aspects to the specific characteristics from the user and his context. From this point of view, this work shows a model for an integral user that has been used to generate a virtual course that can interoperate between ELearning platforms. This course has been created using the SCORM reference model and the IMSLD specification

Evidence against close linkage of the loci for fraXq of Martin-Bell syndrome and for factor IX.

Linkage between the loci for fraXq of Martin-Bell syndrome and factor IX was studied in nine families exhibiting this syndrome by means of a restriction fragment length polymorphism at the factor IX locus. Computer analysis of the data indicates there to be no evidence for close linkage between the syndrome and the factor IX locus.

First-generation linkage map for the European tree frog (Hyla arborea) with utility in congeneric species.

BACKGROUND: Western Palearctic tree frogs (Hyla arborea group) represent a strong potential for evolutionary and conservation genetic research, so far underexploited due to limited molecular resources. New microsatellite markers have recently been developed for Hyla arborea, with high cross-species utility across the entire circum-Mediterranean radiation. Here we conduct sibship analyses to map available markers for use in future population genetic applications. FINDINGS: We characterized eight linkage groups, including one sex-linked, all showing drastically reduced recombination in males compared to females, as previously documented in this species. Mapping of the new 15 markers to the ~200 My diverged Xenopus tropicalis genome suggests a generally conserved synteny with only one confirmed major chromosome rearrangement. CONCLUSIONS: The new microsatellites are representative of several chromosomes of H. arborea that are likely to be conserved across closely-related species. Our linkage map provides an important resource for genetic research in European Hylids, notably for studies of speciation, genome evolution and conservation.

A linkage map of spring turnip rape based on RFLP and RAPD markers

Selostus: RAPD- ja RFLP-markkereista koostuva rypsin kytkentäkartta

A genomewide linkage study on suicidality in major depressive disorder confirms evidence for linkage to 2p12.

Suicidal behavior is commonly associated with depression. Twin studies indicate that both suicidality and major depressive disorder (MDD) are heritable. However, epidemiological evidence suggests that the inheritance of suicidality is likely to be independent of the underlying psychiatric disorder, implying a distinct genetic contribution to suicidality. We conducted a genomewide linkage search aiming to detect genomic loci that may harbor susceptibility genes contributing to risk for suicidality in recurrent MDD. Affected sibling pair (ASP) variance components analysis was performed using the Depression Network cohort of 971 ASPs. The quantitative trait measuring suicidality as a broad phenotype, encompassing ideation and suicide attempts, was established from Schedules for Clinical Assessment in Neuropsychiatry interview items. We examined 1,060 genotyped microsatellite markers with an average spacing of 3.3 cM. Empirical thresholds for linkage evidence were set by whole-genome simulations (LOD = 2.71 for genomewide significance, 1.71 for suggestive linkage). No genomewide significant findings were found. Marker D3S1234 on 3p14 achieved suggestive linkage and yielded a maximum LOD of 1.853 (P = 0.0017), loci 9p24.3 and 18q22-q23 achieved LOD scores >1.5. We found some support for linkage to 2p12 (LOD = 1.2, P = 0.0087) which was previously implicated in linkage studies of suicidality. Our follow-up meta-analysis of five studies showed strong linkage to this region (P = 2 × 10(-6) ). In conclusion, this study analyzed suicidality as a continuous trait in MDD. We found modest evidence for linkage on 3p14. Our meta-analysis supports previous evidence of linkage to suicidality on 2p12. Some candidate genes in these regions may plausibly be implicated in suicidality.

Suggestive linkage to chromosome 1q for bone mineral apparent density in Brazilian sister adolescents.

OBJECTIVE: To investigate linkage to chromosome 1q and 11q region for lumbar spine, femoral neck and total body BMD and volumetric BMD in Brazilian sister adolescents aged 10-20-year-old and 57 mothers. METHODS: We evaluated 161 sister pairs (n=329) aged 10-20 years old and 57 of their mothers in this study. Physical traits and lifestyle factors were collected as covariates for lumbar spine (LS), femoral neck (FN) and total body (TB) BMD and bone mineral apparent density (BMAD). We selected nine microsatellite markers in chromosome 1q region (spanning nearly 33cM) and eight in chromosome 11q region (spanning nearly 34cM) to perform linkage analysis. RESULTS: The highest LOD score values obtained from our data were in sister pairs LS BMAD analysis. Their values were: 1.32 (P<0.006), 2.61 (P<0.0002) and 2.44 (P<0.0004) in D1S218, D1S2640 and D1S2623 markers, respectively. No significant LOD score was found with LS and FN BMD/BMAD in chromosome 11q region. Only TB BMD showed significant linkage higher than 1.0 for chromosome 11q region in the markers D11S4191 and D11S937. DISCUSSION/CONCLUSIONS: Our results provided suggestive linkage for LS BMAD at D1S2640 marker in adolescent sister pairs and suggest a possible candidate gene (LHX4) related to adolescent LS BMAD in this region. These results reinforce chromosome 1q21-23 as a candidate region to harbor one or more bone formation/maintenance gene. In the other hand, it did not repeat for chromosome 11q12-13 in our population.

Etude clinique et analyse de liaison au locus 3q28 de deux familles suisses avec atrophie optique dominante de Kjer (OPA1) [Clinical study and genetic 3q28 locus linkage in 2 Swiss families with Kjer dominant optic atrophy (OPA1)]

METHODS: We examined 20 patients from 2 unrelated Swiss families to describe their clinical phenotype. In addition, a linkage analysis was performed in an attempt to confirm the reported genetic homogeneity of this condition as well as to refine its genomic localization. RESULTS: Two point analysis provided a cumulative LOD-score of 3.03 with marker D3S 2305. The absence of recombination precluded further refinement of the disease interval. CONCLUSIONS: Our data confirm the genetic homogeneity and the extreme variability of expression, occasionally mimicking low tension glaucoma.

Genetic linkage maps of 'Pêra' sweet orange and 'Cravo' mandarin with RAPD markers

The objective of this work was to construct linkage maps of 'Pêra' sweet orange [Citrus sinensis (L.) Osbeck] and 'Cravo' mandarin (Citrus reticulata Blanco) using RAPD markers and the pseudo-testcross strategy. The parents were chosen according to the resistance/susceptibility to citrus variegate chlorosis (CVC). The segregation of 176 markers was analyzed in 94 progeny of F1 hybrids, which were obtained from controlled crossings. The linkage map of 'Pêra' sweet orange had 117 markers defined by 12 linkage groups, which spanned 612.1 cM. Only six markers could not be linked to the linkage group and 48.7% of the markers showed segregation distortion. The linkage map of 'Cravo' mandarin had 51 markers defined by 12 linkage groups, which spanned 353.3 cM. Only two markers did not link to the groups and 15.7% showed segregation distortion. The construction of linkage maps is relevant to future mapping studies of the inheritance of CVC, citrus canker and leprosis.

Mutation screening of the urocortin gene: identification of new single nucleotide polymorphisms and association studies with obesity in French Caucasians.

A linkage between obesity-related phenotypes and the 2p21-23 locus has been reported previously. The urocortin (UCN) gene resides at this interval, and its protein decreases appetite behavior, suggesting that UCN may be a candidate gene for susceptibility to obesity. We localized the UCN gene by radiation hybrid mapping, and the surrounding markers were genotyped in a collection of French families. Evidence for linkage was shown between the marker D2S165 and leptin levels (LOD score, 1.34; P = 0.006) and between D2S2247 and the z-score of body mass index (LOD score, 1.829; P = 0.0019). The gene was screened for SNPs in 96 obese patients. Four new variants were established. Two single nucleotide polymorphisms were located in the promoter (-535 A-->G, -286 G-->A), one in intron 1 (+31 C-->G), and one in the 3'-untranslated region (+34 C-->T). Association studies in cohorts of 722 unrelated obese and 381 control subjects and transmission disequilibrium tests, performed for the two frequent promoter polymorphisms, in 120 families (894 individuals) showed that no association was present between these variants and obesity, obesity-related phenotypes, and diabetes. Thus, our analyses of the genetic variations of the UCN gene suggest that, at least in French Caucasians, they do not represent a major cause of obesity.

Population specific and up to date cardiovascular risk charts can be efficiently obtained with record linkage of routine and observational data.

BACKGROUND: Only few countries have cohorts enabling specific and up-to-date cardiovascular disease (CVD) risk estimation. Individual risk assessment based on study samples that differ too much from the target population could jeopardize the benefit of risk charts in general practice. Our aim was to provide up-to-date and valid CVD risk estimation for a Swiss population using a novel record linkage approach. METHODS: Anonymous record linkage was used to follow-up (for mortality, until 2008) 9,853 men and women aged 25-74 years who participated in the Swiss MONICA (MONItoring of trends and determinants in CVD) study of 1983-92. The linkage success was 97.8%, loss to follow-up 1990-2000 was 4.7%. Based on the ESC SCORE methodology (Weibull regression), we used age, sex, blood pressure, smoking, and cholesterol to generate three models. We compared the 1) original SCORE model with a 2) recalibrated and a 3) new model using the Brier score (BS) and cross-validation. RESULTS: Based on the cross-validated BS, the new model (BS = 14107×10(-6)) was somewhat more appropriate for risk estimation than the original (BS = 14190×10(-6)) and the recalibrated (BS = 14172×10(-6)) model. Particularly at younger age, derived absolute risks were consistently lower than those from the original and the recalibrated model which was mainly due to a smaller impact of total cholesterol. CONCLUSION: Using record linkage of observational and routine data is an efficient procedure to obtain valid and up-to-date CVD risk estimates for a specific population.

Ultra-Deep Pyrosequencing Detects Conserved Genomic Sites and Quantifies Linkage of Drug-Resistant Amino Acid Changes in the Hepatitis B Virus Genome

Selection of amino acid substitutions associated with resistance to nucleos(t)ide-analog (NA) therapy in the hepatitis B virus (HBV) reverse transcriptase (RT) and their combination in a single viral genome complicates treatment of chronic HBV infection and may affect the overlapping surface coding region. In this study, the variability of an overlapping polymerase-surface region, critical for NA resistance, is investigated before treatment and under antiviral therapy, with assessment of NA-resistant amino acid changes simultaneously occurring in the same genome (linkage analysis) and their influence on the surface coding region.

High-density linkage maps fail to detect any genetic component to sex determination in a Rana temporaria family.

Sex chromosome differentiation in Rana temporaria varies strikingly among populations or families: whereas some males display well-differentiated Y haplotypes at microsatellite markers on linkage group 2 (LG2 ), others are genetically undistinguishable from females. We analysed with RADseq markers one family from a Swiss lowland population with no differentiated sex chromosomes, and where sibship analyses had failed to detect any association between the phenotypic sex of progeny and parental haplotypes. Offspring were reared in a common tank in outdoor conditions and sexed at the froglet stage. We could map a total of 2177 SNPs (1123 in the mother, 1054 in the father), recovering in both adults 13 linkage groups (= chromosome pairs) that were strongly syntenic to Xenopus tropicalis despite > 200 My divergence. Sexes differed strikingly in the localization of crossovers, which were uniformly distributed in the female but limited to chromosome ends in the male. None of the 2177 markers showed significant association with offspring sex. Considering the very high power of our analysis, we conclude that sex determination was not genetic in this family; which factors determined sex remain to be investigated.