Developmental genomics reaches new heights.
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The objectives of this study were to develop a rapid method for sex determination for several mammalian species using polymerase chain reaction (PCR) and to use this method to determine whether there is a significant developmental difference in spherical diameter between male and female d-10 or -11 porcine embryos. The PCR system was developed and verified using genomic DNA from pigs of known sex, then it was tested with genomic DNA from several other mammalian species. Sex is determined by amplification of two genes in a single reaction. The presence or absence of a region of the Sry (sex-determining region Y) gene determines sex, and amplification of the Zfy (male) or Zfx (female) genes acts as a positive control for PCR. Sex determination was successful for all animals tested, including pigs, cattle, sheep, goats, llamas, horses, humans, baboons, dogs, cats, rats, and mice. A total of 209 embryos were collected from 21 crossbred gilts on d 10 or 11 of gestation, and their diameters were measured. No significant difference in embryo diameter was detected between male and female embryos, indicating that sexual dimorphism in embryonic growth in pigs does not occur before the period of rapid embryo elongation. The present sexing technique using PCR is rapid (approximately 6 h from receipt of embryos to results), and it may be useful for examining the effects of sex on any trait of interest in early porcine embryos and embryos from several other mammals.
OBJECTIVE: To evaluate and implement rapid molecular diagnostic techniques for the detection of foot and mouth disease virus (FMDV) suitable for use in Australia. DESIGN: Two PCR TaqMan assays targeted to the FMDV internal ribosome entry site or the 3D polymerase coding region for the rapid detection of FMDV were evaluated using non-infectious materials to determine the test most appropriate for implementation as part of Australia's national preparedness for the rapid detection and diagnosis of FMD outbreaks. RESULTS: Two published tests (PCR TaqMan assays targeted to the FMDV IRES region or the FMDV 3D polymerase coding region) were evaluated for their ability to detect FMDV genetic material in non-infectious FMDV ELISA antigen stocks held at Australian Animal Health Laboratory. Both tests were able to detect FMDV genetic material from strains O1 Manisa, O-3039, A22, A24, A Malaysia, C, Asia 1 and SAT 1, 2 and 3. With the exception of Asia 1, the TaqMan assay targeted to the FMD 3D polymerase coding region had Ct values equal to or lower than for the TaqMan assay targeted to the IRES region suggesting that this test may provide broader serotype detection and sensitivity. However, the TaqMan assay directed to the FMDV IRES is the only one to date to have undergone substantial evaluation using clinical samples collected during an outbreak. The greatest differences observed were for O-3039, SAT 1, and 3. CONCLUSION: Given the ease of setting up both tests, AAHL currently runs both tests on highly suspect FMD investigations to provide independent confirmation of the absence of FMDV because the tests are focused on two independent regions of the FMDV genome. These tests add substantially to Australia's preparedness for FMD diagnosis complementing the already well-established virus isolation and antigen capture ELISA tests for index case diagnosis of FMD in Australia.
We are developing a genetic map of the dog based partly upon markers contained within known genes. In order to facilitate the development of these markers, we have used polymerase chain reaction (PCR) primers designed to conserved regions of genes that have been sequenced in at least two species. We have refined the method for designing primers to maximize the number that produce successful amplifications across as many mammalian species as possible. We report the development of primer sets for 11 loci in detail: CFTR, COL10A1, CSFIR, CYP1A1, DCN1, FES, GHR, GLB1, PKLR, PVALB, and RB1. We also report an additional 75 primer sets in the appendices. The PCR products were sequenced to show that the primers amplify the expected canine genes. These primer sets thus define a class of gene-specific sequence-tagged sites (STSs). There are a number of uses for these STSs, including the rapid development of various linkage tools and the rapid testing of genomic and cDNA libraries for the presence of their corresponding genes. Six of the eleven gene targets reported in detail have been proposed to serve as "anchored reference loci" for the development of mammalian genetic maps [O'Brien, S. J., et al., Nat. Genet. 3:103, 1993]. The primer sets should cover a significant portion of the canine genome for the development of a linkage map. In order to determine how useful these primer sets would be for the other genome projects, we tested the 11 primer sets on the DNA from species representing five mammalian orders. Eighty-four percent of the gene-species combinations amplified successfully. We have named these primer sets "universal mammalian sequence-tagged sites" because they should be useful for many mammalian genome projects.
Chromosome 4 introgression in Timor hybrid-derived Coffea arabica is established, but the robustness of accession prioritization and the relative strength of cultivated-introgressed differentiation across the canephora-derived (sgC) and eugenioides-derived (sgE) subgenomes remained unclear under explicit subgenome filtering. We reanalyzed public genomic resources from 44 coffee accessions using strict contig-level subgenome filtering, Arabica-only population-structure analysis, SNP-panel sensitivity testing, genome-wide differentiation scans, permutation testing, and direct sequence alignment. Population structure and accession rankings were stable across marker densities and random seeds, and the same six introgressed references were retained throughout. Chromosome 4 ranked first in both subgenomes, with a strong sgC signal and a markedly weaker sgE signal; independent baseline-panel permutation tests supported both chromosome 4-associated signals. Direct alignment supported correspondence to the expected chromosome 4 pseudomolecules while showing incomplete source coverage and unresolved exact boundaries. Alignment-supported blocks contained 88 sgC and 62 sgE provisional defense-, signaling-, and regulatory-associated annotations. These results provide a genome-wide, quantitatively validated framework for prioritizing introgressed germplasm and candidate chromosome 4 regions for phenotype-linked coffee research without implying equivalent introgression, exact liftover, or causal resistance genes.
BACKGROUND: Proposed testing of large plasma pools with genome amplification technology (GAT) for detection of transfusion-transmissible viruses may have unanticipated complications not associated with individual unit testing. One such potential complication, the effect of dilution resulting from pool formation, was the subject of the present study. STUDY DESIGN AND METHODS: Specimens from three plasma donor HIV type 1 (HIV-1) seroconversion panels were tested with a quantitative HIV-1 RNA GAT assay (lower detection limit, 400 copies). GAT results were compared to HIV-1 p24 antigen and anti-HIV-1/2 enzyme immunoassay results. Effects of dilution on the detection of GAT-positive panel specimens were assessed by terminal dilution with pooled volunteer-donor EDTA plasma samples. RESULTS: Low HIV-1 RNA copy numbers (755 and 890 copies/0.1-mL input) that were detectable in two individual plasma specimens before HIV-1 p24 antigen were subsequently undetectable by GAT upon dilution with an equal volume of nonreactive plasma from a single donor. HIV-1 RNA at higher copy numbers (15,500 copies/0.1-mL input) in an HIV-1 p24 antigen-reactive and anti-HIV-1/2-nonreactive specimen was undetectable when diluted to 1-in-50 (1-in-50). Terminal dilution of seven HIV-1 RNA-containing plasma panel specimens indicated a proportional loss of HIV-1 RNA detectability with increasing dilution. CONCLUSION: GAT for detection of HIV-1 RNA in individual specimens was more sensitive than other HIV markers. For pooled plasma testing, GAT-independent constraints, such as effects of dilution, may preclude the use of GAT detection as a replacement for individual unit testing with HIV serologic assays.
The specific features of genome domains lacking distinct boundaries are considered. These domains cannot be mapped by testing extended genome regions for nuclease sensitivity and thereby differ from structural domains determined at the level of DNA folding in chromatin. Yet they possess the properties of typical functional domains, containing a gene or several coordinated genes along with a complex of cis-regulatory elements, which control these genes. Domains with vague boundaries may be mapped with certain structural tests, e.g., by assessing histone acetylation or the distribution of tissue-specific DNase I-hypersensitive sites through extended genome regions. The mechanisms are described in detail that regulate the function of genes in domains with vague boundaries, including overlapping domains with genes differing in tissue specificity of expression.
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Rhesus (Rh) and Kell blood group immunisations are the most frequent causes of haemolytic disease of the newborn. Recently, the molecular bases of the Rh and Kell antigens have been elucidated. Subsequently, specific polymerase chain reactions (PCRs) could be developed to determine the RhD, RhC/Rhc and RhE/Rhe genotypes as well as the KI genotype (from the Kell blood group) with genomic DNA. The tests were applied to genomically determine the foetal Rh and Kell blood groups with DNA obtained from amniotic fluid cells. The genotypes obtained were compared with the Rh phenotypes established by cord blood red cell serology. The PCRs to determine the RhD, Rhc, RhE and Rhe and KI genotypes were found to be reliable. The test for RhC however, resulted in false-positive C genotypes. Indeed, more than half of the subsequently tested C-negative Negroid donors were false-positive with the DNA test. Thus, except for RhC, it is possible to reliably determine the Rh and KI genotypes of a foetus with DNA isolated from amniotic fluid cells. Amniocentesis, however, carries a risk for the pregnancy and therefore the tests will only be justified in pregnant women in whom an antibody has been detected and the father of the foetus is heterozygous for the specific antigen. Recently foetal RhD genotypes were determined in foetal DNA circulating in the plasma of RhD-negative pregnant women. This could eventually lead to the introduction of assays with which the foetal blood group can be determined without any risk to the foetus.
INTRODUCTION: Varenicline is an α4β2 nicotinic acetylcholine receptor partial agonist with the highest therapeutic efficacy of any pharmacological smoking cessation aid and a 12-month cessation rate of 26%. Genetic variation may be associated with varenicline response, but to date, no genome-wide association studies of varenicline response have been published. METHODS: In this study, we investigated the genetic contribution to varenicline effectiveness using two electronic health record-derived phenotypes. We defined short-term varenicline effectiveness (SVE) and long-term varenicline effectiveness (LVE) by assessing smoking status at 3 and 12 months, respectively, after initiating varenicline treatment. In Stage 1, comprising five European cohort studies, we tested genome-wide associations with SVE (1405 cases, 2074 controls) and LVE (1576 cases, 2555 controls), defining sentinel variants (the most strongly associated variant within 1 Mb) with p-value < 5 × 10-6 to follow up in Stage 2. In Stage 2, we tested association between sentinel variants and comparable smoking cessation endpoints in varenicline randomized controlled trials. We subsequently meta-analyzed Stages 1 and 2. RESULTS: No variants reached genome-wide significance in the meta-analysis. In Stage 1, 10 sentinel variants were associated with SVE and five with LVE at a suggestive significance threshold (p-value < 5 × 10-6); none of these sentinels were previously implicated in varenicline-aided smoking cessation or in genetic studies of smoking behavior. CONCLUSIONS: We provide initial insights into the biological underpinnings of varenicline-aided smoking cessation, through implicating genes involved in various processes, including gene expression, cilium assembly, and early-stage development. IMPLICATIONS: Leveraging electronic health records, we undertook the largest genetic study of varenicline-aided smoking cessation to date, and the only such study to test genome-wide associations. We showed distinct genetic variants associated (p-value < 5 × 10-6) with varenicline-aided smoking cessation which implicate diverse cellular functions, including transcriptional regulation, RNA modification, and cilium assembly. These provide insights which, if independently corroborated, will improve understanding of varenicline response. The growing availability of biobank resources with genetic and varenicline response data will provide future opportunities for larger studies using the approach we developed.
MOTIVATION: The identification of signatures of positive selection can provide important insights into recent evolutionary history in human populations. Current methods mostly rely on allele frequency determination or focus on one or a small number of candidate chromosomal regions per study. With the availability of large-scale genotype data, efficient approaches for an unbiased whole genome scan are becoming necessary. METHODS: We have developed a new method, the whole genome long-range haplotype test (WGLRH), which uses genome-wide distributions to test for recent positive selection. Adapted from the long-range haplotype (LRH) test, the WGLRH test uses patterns of linkage disequilibrium (LD) to identify regions with extremely low historic recombination. Common haplotypes with significantly longer than expected ranges of LD given their frequencies are identified as putative signatures of recent positive selection. In addition, we have also determined the ancestral alleles of SNPs by genotyping chimpanzee and gorilla DNA, and have identified SNPs where the non-ancestral alleles have risen to extremely high frequencies in human populations, termed 'flipped SNPs'. Combining the haplotype test and the flipped SNPs determination, the WGLRH test serves as an unbiased genome-wide screen for regions under putative selection, and is potentially applicable to the study of other human populations. RESULTS: Using WGLRH and high-density oligonucleotide arrays interrogating 116 204 SNPs, we rapidly identified putative regions of positive selection in three populations (Asian, Caucasian, African-American), and extended these observations to a fourth population, Yoruba, with data obtained from the International HapMap consortium. We mapped significant regions to annotated genes. While some regions overlap with genes previously suggested to be under positive selection, many of the genes have not been previously implicated in natural selection and offer intriguing possibilities for further study. AVAILABILITY: the programs for the WGLRH algorithm are freely available and can be downloaded at http://www.affymetrix.com/support/supplement/WGLRH_program.zip.
Gene dosage variations occur in many diseases. In cancer, deletions and copy number increases contribute to alterations in the expression of tumour-suppressor genes and oncogenes, respectively. Developmental abnormalities, such as Down, Prader Willi, Angelman and Cri du Chat syndromes, result from gain or loss of one copy of a chromosome or chromosomal region. Thus, detection and mapping of copy number abnormalities provide an approach for associating aberrations with disease phenotype and for localizing critical genes. Comparative genomic hybridization (CGH) was developed for genome-wide analysis of DNA sequence copy number in a single experiment. In CGH, differentially labelled total genomic DNA from a 'test' and a 'reference' cell population are cohybridized to normal metaphase chromosomes, using blocking DNA to suppress signals from repetitive sequences. The resulting ratio of the fluorescence intensities at a location on the 'cytogenetic map', provided by the chromosomes, is approximately proportional to the ratio of the copy numbers of the corresponding DNA sequences in the test and reference genomes. CGH has been broadly applied to human and mouse malignancies. The use of metaphase chromosomes, however, limits detection of events involving small regions (of less than 20 Mb) of the genome, resolution of closely spaced aberrations and linking ratio changes to genomic/genetic markers. Therefore, more laborious locus-by-locus techniques have been required for higher resolution studies. Hybridization to an array of mapped sequences instead of metaphase chromosomes could overcome the limitations of conventional CGH (ref. 6) if adequate performance could be achieved. Copy number would be related to the test/reference fluorescence ratio on the array targets, and genomic resolution could be determined by the map distance between the targets, or by the length of the cloned DNA segments. We describe here our implementation of array CGH. We demonstrate its ability to measure copy number with high precision in the human genome, and to analyse clinical specimens by obtaining new information on chromosome 20 aberrations in breast cancer.
MOTIVATION: The recent rapid rise in the availability of whole genome DNA sequence data has led to bottlenecks in their complete analysis. Specifically, there is a need for software tools that will allow mining of gene and putative gene data at a whole genome level. These new tools will complement the current set already in use for studying specific aspects of individual genes and putative genes in detail. A key software challenge is to make them user-friendly, without losing their flexibility and capability for use in research. RESULTS: The creation of GeneOrder-a web-based interactive, computational tool-allows researchers to compare the order of genes in two genomes. It has been tested on full genome sequence data for viruses, mitochondria and chloroplasts that were obtained from the NCBI GenBank database. It is accessible at http://www.bif.atcc.org/GENEOrder/index.html. GeneOrder prepares the comparison in table form, listing the order of similar genes. Hyperlinks are provided from this output; these lead to the 'Protein Coding Regions' in the NCBI database.