Differential Phenotypic Expression Research Articles

Epigenetic study of the differential phenotypic expression of a hypertrophic cardiomyopathy-related pathological variant at MYBPC3 in a cohort of monozygotic twins

Abstract Introduction Hypertrophic cardiomyopathy (HCM) is a inherited cardiac disease with a variable penetrance and expressivity. Epigenetics orchestrates the interplay between the environment and the molecular changes that lead to the development of the pathological phenotype. It is of great interest to identify the changes that determine the magnitude of left ventricular hypertrophy (LVH) in patients carrying a given pathogenic variant. Methods In this work, we used peripheral blood samples from a cohort of three homozygous twin pairs carrying the p.Gly263Ter pathogenic variant at MYBPC3 gene to suppress the underlying genetic effect and isolate the role of DNA methylation in its divergent phenotypic expressivity. Results We found a poorer life-style and a more anxious personality among the more severely affected patients. Using a pair-matched model corrected by cell type proportions, a total of 2486 differentially methylated positions (DMP) were extracted with moderate but proportional methylation changes to the LVH of the patients. DMP were enriched in functional regions controlled by repressor histone marks (H3K27me3, H3K9me3) and tended to colocalise forming differentially methylated regions (DMR) across genes mainly related to homophilic surface adhesion molecules and Ca2+ transport. Strikingly, many affected genes were found to be involved in LVH development, such as PLSCR2, ELMO3, TRIM68, HOXA5, UCN3, PCDHGA3, PAX8-AS1, suggesting that the analysis of blood samples could be able to recapitulate alterations at cardiac tissue level. Furthermore, the relationship of the observed changes with the development of the pathology was successfully validated with an external cohort of peripheral blood samples from healthy patients. Further studies are needed to validate the observed changes at cardiac tissue and to verify their causal role. Conclusions In this cohort of monozygotic twins we were able to identify promising epigenetic peripheral blood changes that relate to the expressivity of the HCM. Anxious personalities and lifestyle divergences could lie behind our findings. DNA methylation changes tend to locate at key positions related to cell-to-cell communication and Ca2+ metabolism, as well as at other loci already described to regulate LVH and stress.

Applying a geometric morphometric surface semilandmark-based approach for assessing sexual dimorphism in cranial bones

Traditionally, sex estimation in human skulls has been carried out applying non-metric and inter-landmark distance approaches. Such estimation has substantially improved with the introduction of geometric morphometric semilandmark-based registration, representing a useful tool for capturing the complex morphology of 3D surfaces, particularly in human skulls. Taking in account these improvements, the main purpose of this study is to show the benefits of these techniques for assessing by means of a quantitative, hypothesis testing approach the differential phenotypic expression of sexual dimorphism in human cranial traits, using the frontal bone, the mastoid process of the temporal bone, and the zygomatic bone as proxies. According to our main results: i) accuracy and precision of sex estimation is higher when the shape variable is included in the analysis than when it is not, ii) numerical classification tends to be more accurate in males than in females for both shape and size components of sexual dimorphism, and iii) a single trait or two traits in combination would be more successful in sex classification than the three traits taken as a whole. The introduction in the present study of a surface semilandmark-based approach for quantitatively assessing sexual dimorphism in human skull considerably improves the capture of sexual dimorphic signatures, corroborating the importance of the information carried by the surface of the frontal bone, mastoid process, and zygomatic bone. Our results suggest that shape and size components should be considered as relevant factors in making a differential, bone- dependent sex assessment in human crania.

Impact of Nax genes for Na+ exclusion from leaves on bread wheat yield on saline soils

AbstractWheat production in many countries is threatened by climate change and rising sea levels causing increases in salt‐water intrusion in low‐lying coastal areas. Large areas of the coastal zone of Bangladesh remain fallow during the dry season primarily due to salinity. It is estimated that 0.86 million hectares of land currently under fallow in the dry season would be suitable for wheat production using varieties with enhanced salt tolerance. This study investigated the impact of salt tolerance Nax genes (Na+ exclusion) on the grain yield of bread wheat grown on saline soils in southern Bangladesh. Nax1 and Nax2 genes were separately crossed into two Bangladeshi bread wheat varieties, BARI Gom 25 and BARI Gom 26, through conventional crossing with marker‐assisted selection. The key outcome was strong evidence that both Nax genes have the capacity to lower leaf Na+ concentration in locally adapted bread wheat and consequently deliver improved yields in challenging field environments in southern Bangladesh with moderate to high salinity. The genetic backgrounds of the adapted varieties played a significant role in the expression of these genes. There was a differential response in the phenotypic expression of Nax genes to reduce leaf Na+ levels between the two local varieties selected as recurrent parents and the resultant variation in yield. The average reduction in leaf Na+ concentrations from the third backcrossed lines in the BARI Gom 25 background was about twice that of lines in the BARI Gom 26 background. These same lines typically yielded between 10% and 20% higher than BARI Gom 25 on moderate to high salinity sites, whereas the backcrossed lines in the BARI Gom 26 background yielded similarly to their recurrent parent at these same sites. The contrast in the differential phenotypic expression of the Nax genes evident in the two recurrent parents represented in this study highlights the importance of crossing salt tolerance Nax genes into a range of locally adapted high‐yielding genetic backgrounds to identify the greatest potential for improvement in salt tolerance.

An insight into genetics of congenital heart defects associated with Down syndrome

Down syndrome is the most frequent live born human aneuploidy. Down syndrome is characterized by a set of phenotypically identified dysmorphism and various congenital malformations of which congenital heart defects is seen in about 50% of all cases. Atrio-ventricular Septal Defect is the most common form of congenital heart defect observed in Down syndrome. However, the exact molecular cause underlying the incidence of congenital heart defects and its differential phenotypic expression in DS are still not perfectly understood. In this review we have brought together findings from different studies and discussed multiple perspectives of the genetics of congenital cardiac defects in trisomy 21 background, viz., the contributions of triplicated dosage of chromosome 21 genes along with the effect of mutations in non- chromosome 21 disomic genes. Further, the roles of copy number variation and microRNAs have been discussed. We have also tried to shed light on the role of folate metabolism gene polymorphisms on congenital cardiac anomalies observed in Down syndrome. Lastly, we summarized the role of genes from different signaling pathways involved in cardiogenesis and also the recent developments in understanding of Down syndrome associated congenital heart defect from the studies on mice models. This review provides an overview regarding current state-of-art of knowledge related to Down syndrome associated congenital heart defects based on what have been discovered so far in this domain and hints at what prospect of research lies in this field in the future.

Improving the identification of haploid maize seeds using convolutional neural networks

AbstractA critical step toward the success of the doubled haploid (DH) technique is the haploid identification within induction crosses. The R1‐nj marker is the principal mechanism employed in this task enabling the selection of haploids at the seed stage. Although it seems easy to identify haploid seeds, this task is performed manually by visual classification, which becomes an inefficient process in terms of time and labor. Also, differential phenotypic expression of the R1‐nj marker results in high rates of false positives among haploid seeds. For the first time, an image‐based convolutional neural network (CNN) was trained to identify true positives among putative haploid seeds. The experiment was conducted using 3,000 maize (Zea mays L.) seeds from induction crosses classified as haploid (1,000), diploid (1,000), and inhibited (1,000) class. Images were taken from each seed, and then seeds were planted in the field to confirm their ploidy. For putative haploids (R1‐nj phenotype), the classification accuracy on average was 94.39%, 97.07% for the haploid class, and 91.71% for the diploid class. However, the CNN model was unable to distinguish true haploid seeds among the putative haploid class, which indicates that CNN did not recognize different patterns between them. Finally, we provided a highly accurate and trained CNN model to the scientific community to classify haploid maize seeds via R1‐nj, which can support maize breeders to optimize DH pipelines, mainly for small breeding programs with limited resources.

Differential phenotypic expression of a novel PDHA1 mutation in a female monozygotic twin pair

Pyruvate dehydrogenase complex (PDC) deficiency caused by mutations in the X-linked PDHA1 gene has a broad clinical presentation, and the pattern of X-chromosome inactivation has been proposed as a major factor contributing to its variable expressivity in heterozygous females. Here, we report the first set of monozygotic twin females with PDC deficiency, caused by a novel, de novo heterozygous missense mutation in exon 11 of PDHA1 (NM_000284.3: c.1100A>T). Both twins presented in infancy with a similar clinical phenotype including developmental delay, episodes of hypotonia or encephalopathy, epilepsy, and slowly progressive motor impairment due to pyramidal, extrapyramidal, and cerebellar involvement. However, they exhibited clear differences in disease severity that correlated well with residual PDC activities (approximately 60% and 20% of mean control values, respectively) and levels of immunoreactive E1α subunit in cultured skin fibroblasts. To address whether the observed clinical and biochemical differences could be explained by the pattern of X-chromosome inactivation, we undertook an androgen receptor assay in peripheral blood. In the less severely affected twin, a significant bias in the relative activity of the two X chromosomes with a ratio of approximately 75:25 was detected, while the ratio was close to 50:50 in the other twin. Although it may be difficult to extrapolate these results to other tissues, our observation provides further support to the hypothesis that the pattern of X-chromosome inactivation may influence the phenotypic expression of the same mutation in heterozygous females and broadens the clinical and genetic spectrum of PDC deficiency.

Binding of Free and Immune Complex-Associated Hepatitis C Virus to Erythrocytes Is Mediated by the Complement System.

Erythrocytes bind circulating immune complexes (ICs) and facilitate IC clearance from the circulation. Chronic hepatitis C virus (HCV) infection is associated with IC-related disorders. In this study, we investigated the kinetics and mechanism of HCV and HCV-IC binding to and dissociation from erythrocytes. Cell culture-produced HCV was mixed with erythrocytes from healthy blood donors, and erythrocyte-associated virus particles were quantified. Purified complement proteins, complement-depleted serum, and complement receptor antibodies were used to investigate complement-mediated HCV-erythrocyte binding. Purified HCV-specific immunoglobulin G (IgG) from a chronic HCV-infected patient was used to study complement-mediated HCV-IC/erythrocyte binding. Binding of HCV to erythrocytes increased 200- to 1,000-fold after adding complement active human serum in the absence of antibody. Opsonization of free HCV occurred within 10 minutes, and peak binding to erythrocytes was observed at 20-30 minutes. Complement protein C1 was required for binding, whereas C2, C3, and C4 significantly enhanced binding. Complement receptor 1 (CR1, CD35) antibodies blocked the binding of HCV to erythrocytes isolated from chronically infected HCV patients and healthy blood donors. HCV-ICs significantly enhanced complement-mediated binding to erythrocytes compared to unbound HCV. Dissociation of complement-opsonized HCV from erythrocytes depended on the presence of Factor I. HCV released by Factor I bound preferentially to CD19+ B cells compared to other leukocytes. Conclusion: These results demonstrate that complement mediates the binding of free and IC-associated HCV to CR1 on erythrocytes and provide a mechanistic rationale for investigating the differential phenotypic expression of HCV-IC-related disease.

Increased Innate Lymphoid Cells in Periodontal Tissue of the Murine Model of Periodontitis: The Role of AMP-Activated Protein Kinase and Relevance for the Human Condition.

Innate lymphoid cells (ILCs) are master regulators of immune and inflammatory responses, but their own regulatory mechanisms and functional roles of their subtypes (i.e., ILC1s–ILC3s) remain largely unresolved. Interestingly, AMP-activated protein kinase (AMPK), influences inflammatory responses, but its role in modulation of ILCs is not known. Periodontitis is a prevalent disorder with impairment of immune and inflammatory responses contributing importantly to its pathogenesis; however, neither the role of ILCs nor AMPK has been explored in this condition. We tested the hypotheses that (a) periodontitis increases ILCs and expression of relevant cytokines thereby contributing to inflammation and (b) knockdown of AMPK worsens indices of periodontitis in association with further increases in subtypes of ILCs and cytokine expression. The studies utilized wild-type (WT) and AMPK knockout (KO) mice, subjected to ligature-induced periodontitis or sham operation, in association with the use of micro-CT for assessment of bone loss, immunogold electron microscopy to show presence of ILCs in periodontal tissues, flow cytometry for quantitative assessment of subtypes of ILCs and RT-polymerase chain reaction analyses to measure mRNA expression of several relevant cytokines. The results for the first time show (a) presence of each subtype of ILCs in periodontal tissues of sham control and periodontitis animals, (b) that periodontitis is associated with increased frequencies of ILC1s–ILC3s with the effect more marked for ILC2s and differential phenotypic marker expression for ILC3s, (c) that AMPK KO mice display exacerbation of indices of periodontitis in association with further increases in the frequency of subtypes of ILCs with persistence of ILC2s effect, and (d) that periodontitis increased mRNA for interleukin (IL)-33, but not IL-5 or IL-13, in WT mice but expression of these cytokines was markedly increased in AMPK KO mice with periodontitis. Subsequently, we showed that human periodontitis is associated with increases in each ILCs subtype with the effect more marked for ILC2s and that mRNA expressions for IL-33 and IL-5 are markedly greater for sites affected by periodontitis than healthy sites. Collectively, these novel observations indicate a pivotal role for ILCs in pathogenesis of periodontitis and that AMPK is a regulator of their phenotype expression in this condition.

Promise and Reality of Genomics: Link to Schizophrenia Involves Lots of Unknowns

Back to table of contents Previous article Next article Clinical and Research NewsFull AccessPromise and Reality of Genomics: Link to Schizophrenia Involves Lots of UnknownsMark MoranMark MoranSearch for more papers by this authorPublished Online:15 May 2017https://doi.org/10.1176/appi.pn.2017.5a1AbstractHundreds of possible gene mutations may act alone or with each other to determine phenotypic expression of schizophrenia.Better treatments for schizophrenia rely on a more complete understanding of how genetic mutations alter the activity of neural circuits in patients with the disease. NIMH Director Joshua Gordon, M.D., says extremely large study cohorts are necessary to help prioritize targets for genetic research in schizophrenia. That’s the message National Institute of Mental Health (NIMH) Director Joshua Gordon, M.D., delivered to researchers and clinicians during a plenary lecture at the International Congress of Schizophrenia Research in San Diego in March. Gordon said the path forward for genomics and schizophrenia, though promising, is extraordinarily daunting: hundreds of potential gene mutations act through the same complex chain—genes to molecules to cells to circuits to behavior—resulting in a diversity of possible phenotypes. This wide range of phenotypes accounts for what has traditionally been called the “heterogeneity” of schizophrenia. “There is the promise of genetics, and there is the reality,” Gordon said at the meeting. “The reality is that there are hundreds of genes that contribute to subsyndromal or syndromal schizophrenia, and each one of these mutations has a very small effect size. There is a lot of biology [between the mutation and the phenotypic expression of disease] that we don’t understand. When you throw in environmental influences, it makes the complexity picture completely non-linear.”Gordon gave an example of how genetics contribute to understanding the differential phenotypic expression of schizophrenia based on his own work at Columbia University and the New York Psychiatric Institute prior to his becoming director of NIMH. He and colleagues focused on the 22q11 microdeletion, a tiny mutation in a portion of chromosome 22 known to be associated with schizophrenia and cognitive deficits. They found that mice bred with the 22q11 microdeletion took longer to learn a working memory task than those that did not have the mutation. Additional analyses suggested that the working memory impairments in the mice appear to be due to disrupted communication between the hippocampus and the prefrontal cortex, where spatial information is encoded in memory. Even further, Gordon and his long-time collaborator Joseph Gogos, M.D., Ph.D., were able to elucidate neurochemical abnormalities in the development of axons (the threadlike fibers from a neuron that transmit information to another neuron), which appear to account for disrupted communication between the hippocampus and prefrontal cortex. Gordon said this work illustrates how genetic mutations and the various behavioral phenotypes associated with schizophrenia can be linked to offer a more complete understanding of the neurobiology of the disorder. In this case, one phenotypic expression (impaired working memory) is associated with a genetic mutation (22q11) that is linked to cells and neural networks specifically associated with disrupted communication of information between two brain structures (the hippocampus and prefrontal cortex). Yet as elegant as it appears, Gordon said it almost certainly oversimplifies the true picture of what happens in schizophrenia. “The bigger problem is that it represents only a portion of what we know about schizophrenia genetics,” Gordon said, with hundreds of other possible gene mutations that may act alone or in concert with each other to determine phenotypic expression. What is necessary and what Gordon said he and other researchers hope to find is “critical convergence” of research findings—“where some significant amount of schizophrenia is explained by one common convergent pathophysiology.” For that, he said, it will be necessary to collect data on extremely large population cohorts to link genomics to phenotypes. That’s an enormous undertaking. Gordon said he has appointed the Workgroup on Genomics of the National Advisory Mental Health Council and charged it with answering the following questions: What are the best strategies for prioritizing genetic signals/genes for functional analyses?What are the best experimental and computational tools for investigating genetic risk factors?How can NIMH leverage diverse population-based cohorts to enable large-scale genomic discovery?How should dimensional phenotypes be used to further elucidate the genetic architecture of mental disorders?In the meantime, Gordon suggested the way forward toward better treatment of patients with schizophrenia is to leverage developing integrated care networks to make the treatments that exist—antipsychotic medication and evidence-based psychosocial therapies—available to patients in primary care. “But I deeply believe that in order to truly transform the efficacy of drug treatment for schizophrenia we need to understand the neurobiology of the disease,” he said. ■ ISSUES NewArchived

Phenotypic characteristics and comparative proteomics of Staphylococcus aureus strains with different vancomycin-resistance levels

Reduced vancomycin susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) is a worldwide problem. Unfortunately, its genetic marker and molecular mechanisms remained unknown. This study investigated differential phenotypic characteristic and protein expression profiles among three groups of MRSA isolates, including vancomycin-susceptible S. aureus (VSSA), heterogeneous vancomycin-intermediate S. aureus (hVISA) and vancomycin-intermediate S. aureus (VISA) (n = 7 isolates/group). Phenotypic characteristic revealed significant greater number of isolates with non-spreading colony in VISA as compared to both VSSA and hVISA groups. 2-DE followed by nanoLC-MS/MS analyses revealed increased glyceraldehyde 3-phosphate dehydrogenase (GAPDH) in both hVISA and VISA, whereas 50S ribosomal protein L14 (RplN) and DNA-binding protein II (Hup) were increased only in VISA. The non-spreading colony and GAPDH level of MRSA may be used as the markers for differentiation of VSSA, hVISA and VISA.

Differential phenotypic and genetic expression of defence compounds in a plant-herbivore interaction along elevation.

Elevation gradients impose large differences in abiotic and biotic conditions over short distances, in turn, likely driving differences in gene expression more than would genetic variation per se, as natural selection and drift are less likely to fix alleles at such a narrow spatial scale. As elevation increases, the pressure exerted on plants by herbivores and on arthropod herbivores by predators decreases, and organisms spanning the elevation gradient are thus expected to show lower levels of defence at high elevation. The alternative hypothesis, based on the optimal defence theory, is that defence allocation should be higher in low-resource habitats such as those at high elevation, due to higher costs associated with tissue replacement. In this study, we analyse variation with elevation in (i) defence compound content in the plant Lotus corniculatus and (ii) gene expression associated with defence against predators in the specific phytophagous moth, Zygaena filipendulae. Both species produce cyanogenic glycosides (CNglcs) such as lotaustralin and linamarin as defence mechanisms, with the moth, in addition, being able to sequester CNglcs from its host plant. Specifically, we tested the assumption that the defence-associated phenotype in plants and the gene expression in the insect herbivore should covary between low- and high-elevation environments. We found that L. corniculatus accumulated more CNglcs at high elevation, a result in agreement with the optimal defence theory. By contrast, we found that the levels of expression in the defence genes of Z. filipendulae larvae were not related to the CNglc content of their host plant. Overall, expression levels were not correlated with elevation either, with the exception of the UGT33A1 gene, which showed a marginally significant trend towards higher expression at high elevation when using a simple statistical framework. These results suggest that the defence phenotype of plants against herbivores, and subsequent herbivore sequestration machineries and de novo production, are based on a complex network of interactions.

Morphological variation of Cosmos bipinnatus (Asteraceae) and its relation to abiotic variables in central Mexico

Morphological variability can lead to serious taxonomic problems in species with wide distribution ranges. Although morphological variability is partly due to ontogenetic programming, abiotic variables can also exert a significant effect on micro- and macromorphological characters. In this paper, we studied the morphological variability (43 characters) of Cosmos bipinnatus associated to different vegetation types in central Mexico. We searched for significant correlations between the overall morphology of C. bipinnatus and abiotic variables such as altitude and soil parameters (pH, organic matter content, NH4, NO3, PO4, total N and total P content). We also analyzed the Simplified Relative Distance Plasticity Index (RDPIs). Locality had a significant effect in all but three morphological characters measured. Also, 71.43 % of the characters had a significant correlation with at least one abiotic variable. PO4 content was significantly correlated with paleae characters, while pH had a significant effect in ligule coloration. Discriminant function analysis revealed that C. bipinnatus individuals collected at grasslands and Pinus forests form separate clusters, while individuals collected at scrubs and Quercus forests showed considerable overlap. The RDPIs across all sites showed very low levels of plasticity in almost all characters. Some abiotic variables (altitude, soil NH4 and PO4 content, and soil pH) largely contribute to the differential phenotypic expression of C. bipinnatus in central Mexico. However, we found that the number of external phyllaries, the trichome length, and the petiole area can be considered diagnostic traits of C. bipinnatus as they did not show differences within and between collected sites. We hypothesize that the low levels of plasticity found in C. bipinnatus across sites is due to the high tolerance of the species to different environmental conditions.

Characterization of the DNA Methylome during Human B-Cell Differentiation

Introduction: Modulation of the DNA methylation landscape during cell differentiation is a well-established phenomenon. The B-cell lineage represents a paradigmatic cellular model to study the dynamic epigenome during cell development and specification because major B-cell maturation stages are well defined and display differential phenotypic and gene expression features. Furthermore, different B-cell subpopulations show different proliferation abilities, microenvironmental influences and life spans, providing a window of opportunity to study the epigenome in the context of multiple processes.Methods: We performed whole-genome bisulfite sequencing (WGBS), high-density methylation microarrays and gene expression profiling of ten purified human B-cell subpopulations spanning the entire differentiation program, ranging from uncommitted progenitors to terminally-differentiated plasma cells.Results: The results of both WGBS and methylation microarrays indicate that B-cell ontogenesis involves an extensive and gradual reconfiguration of the DNA methylome. We uncovered that non-CpG methylation at CpApC trinucleotides is present in progenitor cells and disappears upon B-cell commitment independently of CpG demethylation. CpG methylation, in contrast, changed extensively during the entire B-cell maturation program, with one quarter of all measured CpGs showing dynamic methylation. B-cell enhancers suffered more extensive methylation changes than promoter regions, especially in the early differentiation steps up to the germinal center B-cell (gcBC) stage, and their demethylation seemed to be mediated by binding of lineage-specific transcription factors. Enhancers with dynamic methylation were related to genes involved in a large B-cell network that showed high gene expression variability throughout differentiation. In highly proliferative gcBCs, we observed a shift of dynamic methylation from regulatory towards non-functional elements; gcBCs start to undergo global demethylation of late-replicating heterochromatic regions and methylation of polycomb-repressed regions. This signature becomes particularly extensive in long-lived memory B cells and plasma cells, indicating that these changes start in highly proliferative cells and then accumulate in non-proliferative cells with extended lifespan.Conclusion: Our epigenomic analysis of the B-cell differentiation program extends our knowledge on how the DNA methylome is modulated during cell specification and maturation and offers a resource for researchers in the field, both at global and single gene levels. DisclosuresNo relevant conflicts of interest to declare.

Linking transcriptomic and genomic variation to growth in brook charr hybrids (Salvelinus fontinalis, Mitchill)

Hybridization can lead to phenotypic differences arising from changes in gene expression patterns or new allele combinations. Variation in gene expression is thought to be controlled by differences in transcription regulation of parental alleles, either through cis- or trans-regulatory elements. A previous study among brook charr hybrids from different populations (Rupert, Laval, and domestic) showing distinct length at age during early life stages also revealed different patterns in transcription regulation inheritance of transcript abundance. In the present study, transcript abundance using RNA-sequencing and quantitative real-time PCR, single-nucleotide polymorphism (SNP) genotypes and allelic imbalance were assessed in order to understand the molecular mechanisms underlying the observed transcriptomic and differences in length at age among domestic × Rupert hybrids and Laval × domestic hybrids. We found 198 differentially expressed genes between the two hybrid crosses, and allelic imbalance could be analyzed for 69 of them. Among these 69 genes, 36 genes exhibited cis-acting regulatory effects in both of the two crosses, thus confirming the prevalent role of cis-acting regulatory elements in the regulation of differentially expressed genes among intraspecific hybrids. In addition, we detected a significant association between SNP genotypes of three genes and length at age. Our study is thus one of the few that have highlighted some of the molecular mechanisms potentially involved in the differential phenotypic expression in intraspecific hybrids for nonmodel species.

Self-compatibility Evaluation in Almond: Strategies, Achievements, and Failures

Several approaches have been used in evaluating self-compatibility in almond. These include fruit set after self-pollination and bagging, pollen tube growth, and the more recent Sf allele identification by molecular markers and gene sequencing. However, none of these methods have given fully reliable results because they all show advantages and limitations. Pollen contamination may distort pollination results as well as inaccuracies during fruit setting operations. Factors other than self-compatibility such as inbreeding may affect fruit set and pollen tube growth. Detection of S alleles by RNase activity and polymerase chain reaction analysis by consensus primers has not always been conclusive. The differential phenotypic expression of the Sfa and the Sfi alleles has revealed that the presence of the Sf allele is not the only requirement for self-compatibility expression in almond. As a consequence, the coding region of the Sf allele may not be the sole factor involved in that expression, which may be caused by modifier genes outside this region. Missequencing of alleles has also created confusion for allele identification. Thus, self-compatibility evaluation in almond must involve a better knowledge of the plant material as a whole, and not only of its genotype. All factors involved in setting a commercial crop in conditions of solid plantings of a single cultivar must be put together to evaluate almond self-compatibility. This approach is fundamental for the understanding of self-compatibility in almond and for the evaluation of the new selections in a breeding program.

Organ-Associated Muscles in <I>Aedes albopictus</I> (Diptera: Culicidae) Respond Differentially to Sindbis Virus

Differential host cell responses to the alphavirus Sindbis were observed in visceral muscles of the adult female mosquito Aedes albopictus. Following intrathoracic inoculation with SIN, muscles associated with the midgut, hindgut, and ovary resulted in clearance, persistence, and refractoriness to virus, respectively. Prominent sarcomeres characteristic of myofilaments were identified in muscles associated with these three organs by phalloidin labeling of actin, confirming these cells as muscle. The location of virus antigen mimicked the distribution of actin in both mid- and hindgut-associated muscles. Furthermore, these myofilaments remained intact following virus clearance from midgut muscles and during virus persistence in hindgut muscles. Changes in the temporal onset of virus antigen following high titer inoculum compared with standard titer inoculum was observed in anterior midgut muscles, but not in muscles associated with the posterior midgut or hindgut. Muscle bundles closely approximated the gut surface, while a wispy association was displayed at the ovary surface. Prominent ultrastructural differences were observed in the basal lamina attached to the gut compared with the ovary. Additionally, ultrastructural evidence for virus-associated pathology was observed in gut-associated muscles and gut epithelium. Visceral muscles, all composed of the same tissue type, but associated to three different organs in the insect abdomen, responded differentially to Sindbis. We speculate that variations in structure, function or physiology and ultrastructure inherent to insect host cells or organs interactions reflect the complicated milieu of the organism and contribute to differential virus phenotypic expression in muscle cells.

Gibberellins regulate lateral root formation in Populus through interactions with auxin and other hormones.

The role of gibberellins (GAs) in regulation of lateral root development is poorly understood. We show that GA-deficient (35S:PcGA2ox1) and GA-insensitive (35S:rgl1) transgenic Populus exhibited increased lateral root proliferation and elongation under in vitro and greenhouse conditions, and these effects were reversed by exogenous GA treatment. In addition, RNA interference suppression of two poplar GA 2-oxidases predominantly expressed in roots also decreased lateral root formation. GAs negatively affected lateral root formation by inhibiting lateral root primordium initiation. A whole-genome microarray analysis of root development in GA-modified transgenic plants revealed 2069 genes with significantly altered expression. The expression of 1178 genes, including genes that promote cell proliferation, growth, and cell wall loosening, corresponded to the phenotypic severity of the root traits when transgenic events with differential phenotypic expression were compared. The array data and direct hormone measurements suggested crosstalk of GA signaling with other hormone pathways, including auxin and abscisic acid. Transgenic modification of a differentially expressed gene encoding an auxin efflux carrier suggests that GA modulation of lateral root development is at least partly imparted by polar auxin transport modification. These results suggest a mechanism for GA-regulated modulation of lateral root proliferation associated with regulation of plant allometry during the stress response.

A differential phenotypic expression of a divergent spindle mutation in interspecific Brachiaria hybrids

Several mutations are known to alter the normal progression of meiosis and can be correlated with defects in microtubule distribution. The dv mutation affects the spindle organization and chromosomes do not converge into focused poles. Two Brachiaria hybrids presented the phenotypic expressions of dv mutation but exhibited many more details in the second division. Bivalents were distantly positioned and spread over a large metaphase plate and failed to converge into focused poles. Depending on the distance of chromosomes at the poles, telophase I nuclei were elongated or the chromosomes were grouped into various micronuclei of different sizes in each cell. The first cytokinesis occurred. However, when there were micronuclei, a second cytokinesis immediately took place dividing the prophase II meiocytes into three or four cells. In each meiocyte, meiosis progressed to the second division. Slightly elongated nuclei or micronuclei were recorded in telophase II. After a third cytokinesis, hexads or octads were formed. Pollen grains of different sizes were generated. One of these hybrids presented a higher frequency of abnormal cells than when previously analyzed. The fate of these hybrids as genitors or as candidates for cultivars in the Brachiaria breeding program is discussed.

Sexually dimorphic changes in the amygdala in relation to delusional beliefs in first episode psychosis

Background Few attempts have been made to examine the relationship between amygdala abnormalities and specific symptoms in psychosis. The present study explored the relationship between amygdala morphology and mood congruent and mood incongruent delusional beliefs. Methods Amygdala volumes were measured in 43 patients presenting with delusional beliefs in the context of their first episode of psychosis and 43 healthy volunteers matched for age and gender. Results Left-greater-than-right-asymmetry of the amygdala varied as a function of gender and mood congruence of delusional beliefs, due to asymmetrical enlargement of the left amygdala in women presenting with predominantly mood incongruent delusions. However, there was no difference in amygdala volumes across groups. Conclusions Amygdala abnormalities in women may be associated with aberrant emotional processing that could contribute to the development of mood incongruent delusional beliefs. Sexually dimorphic changes in the amygdala may contribute to differential phenotypic illness expression in men and women.

Aberrant Low Expression Level of Bovine β-Lactoglobulin Is Associated with a C to A Transversion in the BLG Promoter Region

β-Lactoglobulin (β-LG) is the major whey protein in cow's milk. It is well established that the predominant 2 genetic variants, β-LG A and B, are differentially expressed. Extensive investigation of the genetic variation in the promoter region of the BLG gene revealed the existence of specific haplotypes associated with the A and B variants, respectively. However, the genetic basis for the differential expression of BLG A and B alleles is still elusive. We have previously reported a quantitative β-LG B variant, characterized by a very low β-LG protein expression level. Here, we report that the corresponding BLG allele (BLG B*) shows a correspondingly low mRNA expression level. Comparative DNA sequencing of 7,670 bp of the BLG B* allele and the established BLG B allele revealed a unique difference of a C to A transversion at position 215 bp upstream of the translation initiation site (g.-215C>A). This mutation segregated perfectly with the differential phenotypic expression in a paternal half-sib family and could be confirmed in 2 independent cases. The sequence of the BLG B allele in the region of the mutation is highly conserved among 4 related ruminant species. The site of the mutation corresponds to a putative consensus-binding sequence for the transcription factors c-Rel and Elk-1 as predicted by searching the TRANSFAC database. The β-LG B* site might be relevant in the natural production of milk of low β-LG content.