BRCA1 transcriptionally regulates genes associated with the basal-like phenotype in breast cancer

Expression profiling of BRCA1-deficient tumours has identified a pattern of gene expression similar to basal-like breast tumours. In this study, we examine whether a BRCA1-dependent transcriptional mechanism may underpin the link between BRCA1 and basal-like phenotype. In methods section, the mRNA and protein were harvested from a number of BRCA1 mutant and wild-type breast cancer cell lines and from matched isogenic controls. Microarray-based expression profiling was used to identify potential BRCA1-regulated transcripts. These gene targets were then validated (by in silico analysis of tumour samples) by real-time PCR and Western blot analysis. Chromatin immunoprecipitation (ChIP) assays were used to confirm recruitment of BRCA1 to specific promoters. In results, we demonstrate that functional BRCA1 represses the expression of cytokeratins 5(KRT5) and 17(KRT17) and p-Cadherin (CDH3) in HCC1937 and T47D breast cancer cell lines at both mRNA and protein level. ChIP assays demonstrate that BRCA1 is recruited to the promoters of KRT5, KRT17 and CDH3, and re-ChIP assays confirm that BRCA1 is recruited independently to form c-Myc and Sp1 complexes on the CDH3 promoter. We show that siRNA-mediated inhibition of endogenous c-Myc (and not Sp1) results in a marked increase in CDH3 expression analogous to that observed following the inhibition of endogenous BRCA1. The data provided suggest a model whereby BRCA1 and c-Myc form a repressor complex on the promoters of specific basal genes and represent a potential mechanism to explain the observed overexpression of key basal markers in BRCA1-deficient tumours.

The schizophrenia phenotype in 22q11 deletion syndrome

Objective: This study investigated the schizophrenia phenotype in 24 subjects with 22q11 deletion syndrome (22qDS) and schizophrenia (22qDS-schizophrenia), a rare but relatively homogenous genetic subtype of schizophrenia associated with a microdeletion on chromosome 22. Individuals with 22qDS are at genetically high risk for schizophrenia.

Transonic Aeroelastic Stability Predictions Under the Influence of Structural Variability

Flutter prediction as currently practiced is almost always deterministic in nature, based on a single structural model that is assumed to represent a fleet of aircraft. However, it is also recognized that there can be significant structural variability, even for different flights of the same aircraft. The safety factor used for flutter clearance is in part meant to account for this variability. Simulation tools can, however, represent the consequences of structural variability in the flutter predictions, providing extra information that could be useful in planning physical tests and assessing risk. The main problem arising for this type of calculation when using high-fidelity tools based on computational fluid dynamics is the computational cost. The current paper uses an eigenvalue-based stability method together with Euler-level aerodynamics and different methods for propagating structural variability to stability predictions. The propagation methods are Monte Carlo, perturbation, and interval analysis. The feasibility of this type of analysis is demonstrated. Results are presented for the Goland wing and a generic fighter configuration.

On how structural model variability influence transonic aeroelasticity stability.

This paper considers the ways in which structural model parameter variability can in?uence aeroelastic stability. Previous work on formulating the stability calculation (with the Euler equations providing the aerodynamic predictions) is exploited to use Monte Carlo, Interval and Perturbation calculations to allow this question to be investigated. Three routes are identi?ed. The ?rst involves variable normal mode frequencies only. The second involves normal mode frequencies and mode shapes. Finally, the third, in addition to normal mode frequencies and mode shapes, also includes their in?uence on the static equilibrium. Previous work has suggested only considering route 1, which allows signi?cant gains in computational e?ciency if reduced order models can be built for the aerodynamics. However, results in the current paper show that neglecting route 2 can give misleading results for the ?utter onset prediction.

BRCA1 transcriptionally regulates genes associated with the basal breast cancer phenotype

Background Ten to twenty per cent of breast tumours exhibit a basallike genetic profile and these tumours carry a poor prognosis. Breast tumours which contain germline mutations for BRCA1 commonly exhibit a molecular profile similar to basal breast tumours. BRCA1 is a tumour suppressor gene which is mutated in up to 5–10% of breast cancer cases and is involved in multiple cellular processes including DNA damage control, cell cycle checkpoint control, apoptosis, ubiquitination and transcriptional regulation.

Methods Microarray-based profiling was carried out using the HCC1937EV and HCC1937BR breast cancer cell lines. Basal gene and protein expression levels were analysed by qRT-PCR and western blotting. ChIP analyses were performed and demonstrated that BRCA1 regulates basal gene expression through a transcriptional mechanism involving c-myc.

Results We have previously carried out microarray-based expression profiling to examine differences in gene expression when BRCA1 is reconstituted in BRCA1 mutated HCC1937 breast cancer cells. We observed that p-cadherin and the cytokeratin 5 and cytokeratin 17 genes, which are strongly correlated with the basal phenotype, are differentially expressed when BRCA1 is reconstituted. In addition, qRT-PCR and ChIP analysis of BRCA1 reconstituted cells show that BRCA1 represses the expression of these basal genes by a transcriptional mechanism. Furthermore, abrogation of endogenous BRCA1 protein in the T47D cell line using siRNA results in reexpression of these basal genes, suggesting that BRCA1 expression levels may be important in basal gene expression. We have also demonstrated that BRCA1 is physically associated with the promoter regions of basal genes through an association with c-myc. Consequently, we have confirmed that siRNA inhibition of c-myc in T47D cells results in re-expression of these genes.

Conclusions Our results suggest that BRCA1 is involved in the transcriptional regulation of genes associated with the basal phenotype and that BRCA1 controls basal gene expression through a transcriptional mechanism involving c-myc. Further work is now concentrating on defining the relationship between BRCA1 and basal gene expression and how this may affect clinical responses to breast cancer chemotherapy.

Microsatellite loci for Euglossa annectans (Hymenoptera: Apidae) and their variability in other orchid bees

Orchid or euglossine bees are conspicuous Hymenoptera of the Neotropics, where they pollinate numerous plants, including orchids. Allozyme-based analyses have suggested that their populations suffer from inbreeding, as evidenced by so-called diploid male production. We have developed nine polymorphic microsatellite loci for the widespread Euglossa annectans, with observed heterozygosities ranging from 0.143 to 0.952 and between 2 and 9 alleles per species. These loci will be useful for analysis of relatedness, population genetic structure and diploid male production in this and related species.

Characterization of 14 polymorphic microsatellite loci for the facultatively eusocial sweat bee Halictus rubicundus (Hymenoptera, Halictidae) and their variability in related species

Sweat bees display considerable variation in social organization and a few species, such as Halictus rubicundus, are even facultatively eusocial. Fourteen polymorphic, unlinked microsatellite loci were isolated from H. rubicundus and characterized in 45 females. The number of alleles per locus ranged from two to 18 (mean 10.1), observed heterozygosity ranged from 0.24 to 0.98 (mean 0.71) and expected heterozygosity ranged from 0.24 to 0.98 (mean 0.70). Six or more loci cross-amplified in four other sweat bees. These loci will be useful for the study of social evolution and population genetic structure in H. rubicundus and many other sweat bees.

Temporal Variability in Predator-Prey Relationships of a Forest Floor Food Web

Connectance webs represent the standard data description in food web ecology, but their usefulness is often limited in understanding the patterns and processes within ecosystems. Increasingly, efforts have been made to incorporate additional, biologically meaningful, data into food web descriptions, including the construction of food webs using data describing the body size and abundance of each species. Here, data from a terrestrial forest floor food web, sampled seasonally over a 1-year period, were analysed to investigate (i) how stable the body size abundance and predator prey relationships of an ecosystem are through time and (ii) whether there are system-specific differences in body size abundance and predator prey relationships between ecosystem types.

Limbal stem cell deficiency and ocular phenotype in ectrodactyly-ectodermal dysplasia-clefting syndrome caused by p63 mutations

Objective: To describe the ocular phenotype in patients with ectrodactyly-ectodermal dysplasia-clefting (EEC) syndrome (MIM#604292) and to determine the pathogenic basis of visual morbidity. Design: Retrospective case series. Participants: Nineteen families (23 patients) affected by EEC syndrome from the United Kingdom, Ireland, and Italy. Methods: General medical examination to fulfill the diagnostic criteria for EEC syndrome and determine the phenotypic severity. Mutational analysis of p63 was performed by polymerase chain reaction-based bidirectional Sanger sequencing. All patients with EEC syndrome underwent a complete ophthalmic examination and ocular surface assessment. Limbal stem cell deficiency (LSCD) was diagnosed clinically on the basis of corneal conjunctivalization and anatomy of the limbal palisades of Vogt. Impression cytology using immunofluorescent antibodies was performed in 1 individual. Histologic and immunohistochemical analyses were performed on a corneal button and corneal pannus from 2 EEC patients. Main Outcome Measures: The EEC syndrome phenotypic severity (EEC score), best-corrected Snellen visual acuity (decimal fraction), slit-lamp biomicroscopy, tear function index, tear breakup time, LSCD, p63 DNA sequence variants, impression cytology, and corneal histopathology. Results: Eleven heterozygous missense mutations in the DNA binding domain of p63 were identified in all patients with EEC syndrome. All patients had ocular involvement and the commonest was an anomaly of the meibomian glands and lacrimal drainage system defects. The major cause of visual morbidity was progressive LSCD, which was detected in 61% (14/23). Limbal stem cell deficiency was related to advancing age and caused a progressive keratopathy, resulting in a dense vascularized corneal pannus, and eventually leading to visual impairment. Histologic analysis and impression cytology confirmed LSCD. Conclusions: Heterozygous p63 mutations cause the EEC syndrome and result in visual impairment owing to progressive LSCD. There was no relationship of limbal stem cell failure with the severity of EEC syndrome, as classified by the EEC score, or the underlying molecular defect in p63. Financial Disclosure(s): The authors have no proprietary or commercial interest in any of the materials discussed in this article. © 2012 American Academy of Ophthalmology.

Interhemispheric gradient of atmospheric radiocarbon reveals natural variability of Southern Ocean winds

Tree ring Delta C-14 data (Reimer et al., 2004; McCormac et al., 2004) indicate that atmospheric Delta C-14 varied on multi-decadal to centennial timescales, in both hemispheres, over the period between AD 950 and 1830. The Northern and Southern Hemispheric Delta C-14 records display similar variability, but from the data alone is it not clear whether these variations are driven by the production of C-14 in the stratosphere (Stuiver and Quay, 1980) or by perturbations to exchanges between carbon reservoirs (Siegenthaler et al., 1980). As the sea-air flux of (CO2)-C-14 has a clear maximum in the open ocean regions of the Southern Ocean, relatively modest perturbations to the winds over this region drive significant perturbations to the interhemispheric gradient. In this study, model simulations are used to show that Southern Ocean winds are likely a main driver of the observed variability in the interhemispheric gradient over AD 950-1830, and further, that this variability may be larger than the Southern Ocean wind trends that have been reported for recent decades (notably 1980-2004). This interpretation also implies that there may have been a significant weakening of the winds over the Southern Ocean within a few decades of AD 1375, associated with the transition between the Medieval Climate Anomaly and the Little Ice Age. The driving forces that could have produced such a shift in the winds at the Medieval Climate Anomaly to Little Ice Age transition remain unknown. Our process-focused suite of perturbation experiments with models raises the possibility that the current generation of coupled climate and earth system models may underestimate the natural background multi-decadal- to centennial-timescale variations in the winds over the Southern Ocean.

How Structural Model Variability Influences Transonic Aeroelastic Stability

This paper considers the ways in which structural model parameter variability can influence aeroelastic stability. Previous work on formulating the stability calculation (with the Euler equations providing the aerodynamic predictions) is exploited to use Monte Carlo, interval, and perturbation calculations to allow this question to be investigated. Three routes are identified. The first involves variable normal-mode frequencies only. The second involves normal-mode frequencies and shapes. Finally, the third, in addition to normal-mode frequencies and shapes, also includes their influence on the static equilibrium. Previous work has suggested only considering the first route, which allows significant gains in computational efficiency if reduced-order models can be built for the aerodynamics. However, results in the current paper show that neglecting the mode-shape variation can give misleading results for the flutter-onset prediction, complicating the development of reduced aerodynamic models for variability analysis.